explanation blue bibcodes open ADS page with paths to full text
Author name code: chaplin
ADS astronomy entries on 2022-09-14
author:"Chaplin, William J."
---------------------------------------------------------
Title: Unexpected solar-cycle variation of acoustic mode power in
Sun-as-a-star observations
Authors: Howe, Rachel; Chaplin, W. J.; Elsworth, Y. P.; Hale, S. J.;
Nielsen, M. B.
2022MNRAS.514.3821H Altcode: 2022arXiv220515655H; 2022MNRAS.tmp.1518H
We examine the solar-cycle variation of the power in the low-degree
helioseismic modes by looking at binned power spectra from 45 yr of
observations with the Birmingham Solar Oscillations Network, which
provides a more robust estimate of the mode power than that obtained
by peak fitting. The solar-cycle variation of acoustic mode power in
the 5-min band is clearly seen. Unusually, even though Cycle 24 was
substantially weaker in terms of surface magnetic activity than Cycle
23, the reduction in mode power at solar maximum is very similar
for the two cycles, suggesting that the relationship between mode
power and magnetic activity is more complex than has previously been
thought. This is in contrast to the mode frequencies, which show a
strong correlation with activity with only subtle differences in the
response across different solar cycles.
---------------------------------------------------------
Title: Solar-like oscillations and ellipsoidal variations in TESS
observations of the binary 12 Boötis
Authors: Ball, Warrick H.; Miglio, Andrea; Chaplin, William J.;
Stassun, Keivan G.; García, Rafael; González-Cuesta, Lucia; Mathur,
Savita; Appourchaux, Thierry; Benomar, Othman; Buzasi, Derek L.;
Jiang, Chen; Kayhan, Cenk; Örtel, Sibel; Orhan, Zeynep Çelik;
Yıldız, Mutlu; Ong, J. M. Joel; Basu, Sarbani
2022MNRAS.tmp.2121B Altcode: 2022arXiv220802302B
Binary stars in which oscillations can be studied in either or both
components can provide powerful constraints on our understanding
of stellar physics. The bright binary 12 Boötis (12 Boo) is a
particularly promising system because the primary is roughly 60 per
cent brighter than the secondary despite being only a few per cent
more massive. Both stars have substantial surface convection zones
and are therefore, presumably, solar-like oscillators. We report
here the first detection of solar-like oscillations and ellipsoidal
variations in the TESS light curve of 12 Boo. Though the solar-like
oscillations are not clear enough to unambiguously measure individual
mode frequencies, we combine global asteroseismic parameters and a
precise fit to the spectral energy distribution (SED) to provide new
constraints on the properties of the system that are several times more
precise than values in the literature. The SED fit alone provides new
effective temperatures, luminosities and radii of 6115 ± 45 K, 7.531
± 0.110 L<SUB>⊙</SUB> and 2.450 ± 0.045 R<SUB>⊙</SUB> for 12 Boo
A and 6200 ± 60 K, 4.692 ± 0.095 L<SUB>⊙</SUB> and 1.901 ± 0.045
R<SUB>⊙</SUB> for 12 Boo B. When combined with our asteroseismic
constraints on 12 Boo A, we obtain an age of $2.67^{+0.12}_{-0.16}\,
\mathrm{Gyr}$, which is consistent with that of 12 Boo B.
---------------------------------------------------------
Title: A probabilistic method for detecting solar-like oscillations
using meaningful prior information. Application to TESS 2-minute
photometry
Authors: Nielsen, M. B.; Hatt, E.; Chaplin, W. J.; Ball, W. H.;
Davies, G. R.
2022A&A...663A..51N Altcode: 2022arXiv220309404N
Context. Current and future space-based observatories such as the
Transiting Exoplanet Survey Satellite (TESS) and PLATO are set to
provide an enormous amount of new data on oscillating stars, and
in particular stars that oscillate similar to the Sun. Solar-like
oscillators constitute the majority of known oscillating stars and so
automated analysis methods are becoming an ever increasing necessity to
make as much use of these data as possible. <BR /> Aims: Here we aim
to construct an algorithm that can automatically determine if a given
time series of photometric measurements shows evidence of solar-like
oscillations. The algorithm is aimed at analyzing data from the TESS
mission and the future PLATO mission, and in particular stars in
the main-sequence and subgiant evolutionary stages. <BR /> Methods:
The algorithm first tests the range of observable frequencies in the
power spectrum of a TESS light curve for an excess that is consistent
with that expected from solar-like oscillations. In addition, the
algorithm tests if a repeating pattern of oscillation frequencies is
present in the time series, and whether it is consistent with the large
separation seen in solar-like oscillators. Both methods use scaling
relations and observations which were established and obtained during
the CoRoT, Kepler, and K2 missions. <BR /> Results: Using a set of
test data consisting of visually confirmed solar-like oscillators and
nonoscillators observed by TESS, we find that the proposed algorithm can
attain a 94.7% true positive (TP) rate and a 8.2% false positive (FP)
rate at peak accuracy. However, by applying stricter selection criteria,
the FP rate can be reduced to ≈ 2%, while retaining an 80% TP rate.
---------------------------------------------------------
Title: ET White Paper: To Find the First Earth 2.0
Authors: Ge, Jian; Zhang, Hui; Zang, Weicheng; Deng, Hongping; Mao,
Shude; Xie, Ji-Wei; Liu, Hui-Gen; Zhou, Ji-Lin; Willis, Kevin; Huang,
Chelsea; Howell, Steve B.; Feng, Fabo; Zhu, Jiapeng; Yao, Xinyu; Liu,
Beibei; Aizawa, Masataka; Zhu, Wei; Li, Ya-Ping; Ma, Bo; Ye, Quanzhi;
Yu, Jie; Xiang, Maosheng; Yu, Cong; Liu, Shangfei; Yang, Ming; Wang,
Mu-Tian; Shi, Xian; Fang, Tong; Zong, Weikai; Liu, Jinzhong; Zhang, Yu;
Zhang, Liyun; El-Badry, Kareem; Shen, Rongfeng; Tam, Pak-Hin Thomas;
Hu, Zhecheng; Yang, Yanlv; Zou, Yuan-Chuan; Wu, Jia-Li; Lei, Wei-Hua;
Wei, Jun-Jie; Wu, Xue-Feng; Sun, Tian-Rui; Wang, Fa-Yin; Zhang,
Bin-Bin; Xu, Dong; Yang, Yuan-Pei; Li, Wen-Xiong; Xiang, Dan-Feng;
Wang, Xiaofeng; Wang, Tinggui; Zhang, Bing; Jia, Peng; Yuan, Haibo;
Zhang, Jinghua; Xuesong Wang, Sharon; Gan, Tianjun; Wang, Wei; Zhao,
Yinan; Liu, Yujuan; Wei, Chuanxin; Kang, Yanwu; Yang, Baoyu; Qi, Chao;
Liu, Xiaohua; Zhang, Quan; Zhu, Yuji; Zhou, Dan; Zhang, Congcong;
Yu, Yong; Zhang, Yongshuai; Li, Yan; Tang, Zhenghong; Wang, Chaoyan;
Wang, Fengtao; Li, Wei; Cheng, Pengfei; Shen, Chao; Li, Baopeng; Pan,
Yue; Yang, Sen; Gao, Wei; Song, Zongxi; Wang, Jian; Zhang, Hongfei;
Chen, Cheng; Wang, Hui; Zhang, Jun; Wang, Zhiyue; Zeng, Feng; Zheng,
Zhenhao; Zhu, Jie; Guo, Yingfan; Zhang, Yihao; Li, Yudong; Wen, Lin;
Feng, Jie; Chen, Wen; Chen, Kun; Han, Xingbo; Yang, Yingquan; Wang,
Haoyu; Duan, Xuliang; Huang, Jiangjiang; Liang, Hong; Bi, Shaolan; Gai,
Ning; Ge, Zhishuai; Guo, Zhao; Huang, Yang; Li, Gang; Li, Haining;
Li, Tanda; Yuxi; Lu; Rix, Hans-Walter; Shi, Jianrong; Song, Fen;
Tang, Yanke; Ting, Yuan-Sen; Wu, Tao; Wu, Yaqian; Yang, Taozhi; Yin,
Qing-Zhu; Gould, Andrew; Lee, Chung-Uk; Dong, Subo; Yee, Jennifer C.;
Shvartzvald, Yossi; Yang, Hongjing; Kuang, Renkun; Zhang, Jiyuan;
Liao, Shilong; Qi, Zhaoxiang; Yang, Jun; Zhang, Ruisheng; Jiang, Chen;
Ou, Jian-Wen; Li, Yaguang; Beck, Paul; Bedding, Timothy R.; Campante,
Tiago L.; Chaplin, William J.; Christensen-Dalsgaard, Jørgen; García,
Rafael A.; Gaulme, Patrick; Gizon, Laurent; Hekker, Saskia; Huber,
Daniel; Khanna, Shourya; Li, Yan; Mathur, Savita; Miglio, Andrea;
Mosser, Benoît; Ong, J. M. Joel; Santos, Ângela R. G.; Stello,
Dennis; Bowman, Dominic M.; Lares-Martiz, Mariel; Murphy, Simon; Niu,
Jia-Shu; Ma, Xiao-Yu; Molnár, László; Fu, Jian-Ning; De Cat, Peter;
Su, Jie; consortium, the ET
2022arXiv220606693G Altcode:
We propose to develop a wide-field and ultra-high-precision photometric
survey mission, temporarily named "Earth 2.0 (ET)". This mission is
designed to measure, for the first time, the occurrence rate and the
orbital distributions of Earth-sized planets. ET consists of seven
30cm telescopes, to be launched to the Earth-Sun's L2 point. Six
of these are transit telescopes with a field of view of 500 square
degrees. Staring in the direction that encompasses the original Kepler
field for four continuous years, this monitoring will return tens of
thousands of transiting planets, including the elusive Earth twins
orbiting solar-type stars. The seventh telescope is a 30cm microlensing
telescope that will monitor an area of 4 square degrees toward the
galactic bulge. This, combined with simultaneous ground-based KMTNet
observations, will measure masses for hundreds of long-period and
free-floating planets. Together, the transit and the microlensing
telescopes will revolutionize our understandings of terrestrial
planets across a large swath of orbital distances and free space. In
addition, the survey data will also facilitate studies in the fields
of asteroseismology, Galactic archeology, time-domain sciences, and
black holes in binaries.
---------------------------------------------------------
Title: Stellar dating using chemical clocks and Bayesian inference
Authors: Moya, A.; Sarro, L. M.; Delgado-Mena, E.; Chaplin, W. J.;
Adibekyan, V.; Blanco-Cuaresma, S.
2022A&A...660A..15M Altcode: 2022arXiv220105228M
Context. Dating stars is a major challenge with a deep impact on many
astrophysical fields. One of the most promising techniques for this is
using chemical abundances. Recent space- and ground-based facilities
have improved the quantity of stars with accurate observations. This
has opened the door for using Bayesian inference tools to maximise
the information we can extract from them. <BR /> Aims: Our aim is
to present accurate and reliable stellar age estimates of FGK stars
using chemical abundances and stellar parameters. <BR /> Methods:
We used one of the most flexible Bayesian inference techniques
(hierarchical Bayesian models) to exceed current possibilities in
the use of chemical abundances for stellar dating. Our model is a
data-driven model. We used a training set that has been presented
in the literature with ages estimated with isochrones and accurate
stellar abundances and general characteristics. The core of the model
is a prescription of certain abundance ratios as linear combinations of
stellar properties including age. We gathered four different testing
sets to assess the accuracy, precision, and limits of our model. We
also trained a model using chemical abundances alone. <BR /> Results:
We found that our age estimates and those coming from asteroseismology,
other accurate sources, and also with ten Gaia benchmark stars agree
well. The mean absolute difference of our estimates compared with
those used as reference is 0.9 Ga, with a mean difference of 0.01
Ga. When using open clusters, we reached a very good agreement for
Hyades, NGC 2632, Ruprecht 147, and IC 4651. We also found outliers
that are a reflection of chemical peculiarities and/or stars at the
limit of the validity ranges of the training set. The model that only
uses chemical abundances shows slightly worse mean absolute difference
(1.18 Ga) and mean difference (−0.12 Ga).
---------------------------------------------------------
Title: The K2 Galactic Archaeology Program Data Release 3:
Age-abundance Patterns in C1-C8 and C10-C18
Authors: Zinn, Joel C.; Stello, Dennis; Elsworth, Yvonne; García,
Rafael A.; Kallinger, Thomas; Mathur, Savita; Mosser, Benoît; Hon,
Marc; Bugnet, Lisa; Jones, Caitlin; Reyes, Claudia; Sharma, Sanjib;
Schönrich, Ralph; Warfield, Jack T.; Luger, Rodrigo; Vanderburg,
Andrew; Kobayashi, Chiaki; Pinsonneault, Marc H.; Johnson, Jennifer A.;
Huber, Daniel; Buder, Sven; Joyce, Meridith; Bland-Hawthorn, Joss;
Casagrande, Luca; Lewis, Geraint F.; Miglio, Andrea; Nordlander,
Thomas; Davies, Guy R.; Silva, Gayandhi De; Chaplin, William J.;
Silva Aguirre, Victor
2022ApJ...926..191Z Altcode: 2021arXiv210805455Z
We present the third and final data release of the K2 Galactic
Archaeology Program (K2 GAP) for Campaigns C1-C8 and C10-C18. We
provide asteroseismic radius and mass coefficients, κ <SUB> R </SUB>
and κ <SUB> M </SUB>, for ~19,000 red giant stars, which translate
directly to radius and mass given a temperature. As such, K2 GAP
DR3 represents the largest asteroseismic sample in the literature
to date. K2 GAP DR3 stellar parameters are calibrated to be on an
absolute parallactic scale based on Gaia DR2, with red giant branch
and red clump evolutionary state classifications provided via a
machine-learning approach. Combining these stellar parameters with
GALAH DR3 spectroscopy, we determine asteroseismic ages with precisions
of ~20%-30% and compare age-abundance relations to Galactic chemical
evolution models among both low- and high-α populations for α, light,
iron-peak, and neutron-capture elements. We confirm recent indications
in the literature of both increased Ba production at late Galactic times
as well as significant contributions to r-process enrichment from prompt
sources associated with, e.g., core-collapse supernovae. With an eye
toward other Galactic archeology applications, we characterize K2 GAP
DR3 uncertainties and completeness using injection tests, suggesting
that K2 GAP DR3 is largely unbiased in mass/age, with uncertainties of
2.9% (stat.) ± 0.1% (syst.) and 6.7% (stat.) ± 0.3% (syst.) in κ
<SUB> R </SUB> and κ <SUB> M </SUB> for red giant branch stars and
4.7% (stat.) ± 0.3% (syst.) and 11% (stat.) ± 0.9% (syst.) for red
clump stars. We also identify percent-level asteroseismic systematics,
which are likely related to the time baseline of the underlying data,
and which therefore should be considered in TESS asteroseismic analysis.
---------------------------------------------------------
Title: A 20 Second Cadence View of Solar-type Stars and Their Planets
with TESS: Asteroseismology of Solar Analogs and a Recharacterization
of π Men c
Authors: Huber, Daniel; White, Timothy R.; Metcalfe, Travis S.;
Chontos, Ashley; Fausnaugh, Michael M.; Ho, Cynthia S. K.; Van Eylen,
Vincent; Ball, Warrick H.; Basu, Sarbani; Bedding, Timothy R.; Benomar,
Othman; Bossini, Diego; Breton, Sylvain; Buzasi, Derek L.; Campante,
Tiago L.; Chaplin, William J.; Christensen-Dalsgaard, Jørgen; Cunha,
Margarida S.; Deal, Morgan; García, Rafael A.; García Muñoz,
Antonio; Gehan, Charlotte; González-Cuesta, Lucía; Jiang, Chen;
Kayhan, Cenk; Kjeldsen, Hans; Lundkvist, Mia S.; Mathis, Stéphane;
Mathur, Savita; Monteiro, Mário J. P. F. G.; Nsamba, Benard; Ong,
Jia Mian Joel; Pakštienė, Erika; Serenelli, Aldo M.; Silva Aguirre,
Victor; Stassun, Keivan G.; Stello, Dennis; Norgaard Stilling,
Sissel; Lykke Winther, Mark; Wu, Tao; Barclay, Thomas; Daylan, Tansu;
Günther, Maximilian N.; Hermes, J. J.; Jenkins, Jon M.; Latham,
David W.; Levine, Alan M.; Ricker, George R.; Seager, Sara; Shporer,
Avi; Twicken, Joseph D.; Vanderspek, Roland K.; Winn, Joshua N.
2022AJ....163...79H Altcode: 2021arXiv210809109H
We present an analysis of the first 20 second cadence light curves
obtained by the TESS space telescope during its extended mission. We
find improved precision of 20 second data compared to 2 minute data for
bright stars when binned to the same cadence (≍10%-25% better for T
≲ 8 mag, reaching equal precision at T ≍ 13 mag), consistent with
pre-flight expectations based on differences in cosmic-ray mitigation
algorithms. We present two results enabled by this improvement. First,
we use 20 second data to detect oscillations in three solar analogs
(γ Pav, ζ Tuc, and π Men) and use asteroseismology to measure their
radii, masses, densities, and ages to ≍1%, ≍3%, ≍1%, and ≍20%
respectively, including systematic errors. Combining our asteroseismic
ages with chromospheric activity measurements, we find evidence that the
spread in the activity-age relation is linked to stellar mass and thus
the depth of the convection zone. Second, we combine 20 second data and
published radial velocities to recharacterize π Men c, which is now the
closest transiting exoplanet for which detailed asteroseismology of the
host star is possible. We show that π Men c is located at the upper
edge of the planet radius valley for its orbital period, confirming
that it has likely retained a volatile atmosphere and that the
"asteroseismic radius valley" remains devoid of planets. Our analysis
favors a low eccentricity for π Men c (<0.1 at 68% confidence),
suggesting efficient tidal dissipation (Q/k <SUB>2,1</SUB> ≲ 2400)
if it formed via high-eccentricity migration. Combined, these early
results demonstrate the strong potential of TESS 20 second cadence
data for stellar astrophysics and exoplanet science.
---------------------------------------------------------
Title: VizieR Online Data Catalog: APF radial velocity follow up of
{iota} Draconis (Hill+, 2021)
Authors: Hill, M. L.; Kane, S. R.; Campante, T. L.; Li, Z.; Dalba,
P. A.; Brandt, T. D.; White, T. R.; Pope, B. J. S.; Stassun, K. G.;
Fulton, B. J.; Corsaro, E.; Li, T.; Ong, J. M. J.; Bedding, T. R.;
Bossini, D.; Buzasi, D. L.; Chaplin, W. J.; Cunha, M. S.; Garcia,
R. A.; Breton, S. N.; Hon, M.; Huber, D.; Jiang, C.; Kayhan, C.;
Kuszlewicz, J. S.; Mathur, S.; Serenelli, A.; Stello, D.
2022yCat..51620211H Altcode:
456 radial velocity observations were obtained by the Levy spectrometer
on the Automated Planet Finder (APF) at Lick Observatory from 2018
February to 2021 February. <P />(1 data file).
---------------------------------------------------------
Title: TESS Asteroseismology of α Mensae: Benchmark Ages for a G7
Dwarf and Its M Dwarf Companion
Authors: Chontos, Ashley; Huber, Daniel; Berger, Travis A.; Kjeldsen,
Hans; Serenelli, Aldo M.; Silva Aguirre, Victor; Ball, Warrick H.;
Basu, Sarbani; Bedding, Timothy R.; Chaplin, William J.; Claytor,
Zachary R.; Corsaro, Enrico; Garcia, Rafael A.; Howell, Steve B.;
Lundkvist, Mia S.; Mathur, Savita; Metcalfe, Travis S.; Nielsen,
Martin B.; Mian Joel Ong, Jia; Çelik Orhan, Zeynep; Örtel, Sibel;
Salama, Maissa; Stassun, Keivan G.; Townsend, R. H. D.; van Saders,
Jennifer L.; Winther, Mark; Yildiz, Mutlu; Butler, R. Paul; Tinney,
C. G.; Wittenmyer, Robert A.
2021ApJ...922..229C Altcode: 2020arXiv201210797C
Asteroseismology of bright stars has become increasingly important as
a method to determine the fundamental properties (in particular ages)
of stars. The Kepler Space Telescope initiated a revolution by detecting
oscillations in more than 500 main-sequence and subgiant stars. However,
most Kepler stars are faint and therefore have limited constraints
from independent methods such as long-baseline interferometry. Here
we present the discovery of solar-like oscillations in α Men
A, a naked-eye (V = 5.1) G7 dwarf in TESS's southern continuous
viewing zone. Using a combination of astrometry, spectroscopy, and
asteroseismology, we precisely characterize the solar analog α Men A
(T <SUB>eff</SUB> = 5569 ± 62 K, R <SUB>⋆</SUB> = 0.960 ± 0.016 R
<SUB>⊙</SUB>, M <SUB>⋆</SUB> = 0.964 ± 0.045 M <SUB>⊙</SUB>). To
characterize the fully convective M dwarf companion, we derive
empirical relations to estimate mass, radius, and temperature given
the absolute Gaia magnitude and metallicity, yielding M <SUB>⋆</SUB>
= 0.169 ± 0.006 M <SUB>⊙</SUB>, R <SUB>⋆</SUB> = 0.19 ± 0.01 R
<SUB>⊙</SUB>, and T <SUB>eff</SUB> = 3054 ± 44 K. Our asteroseismic
age of 6.2 ± 1.4 (stat) ± 0.6 (sys) Gyr for the primary places α
Men B within a small population of M dwarfs with precisely measured
ages. We combined multiple ground-based spectroscopy surveys to reveal
an activity cycle of P = 13.1 ± 1.1 yr for α Men A, a period similar
to that observed in the Sun. We used different gyrochronology models
with the asteroseismic age to estimate a rotation period of ~30 days
for the primary. Alpha Men A is now the closest (d = 10 pc) solar
analog with a precise asteroseismic age from space-based photometry,
making it a prime target for next-generation direct-imaging missions
searching for true Earth analogs.
---------------------------------------------------------
Title: PLATO hare-and-hounds exercise: asteroseismic model fitting
of main-sequence solar-like pulsators
Authors: Cunha, M. S.; Roxburgh, I. W.; Aguirre Børsen-Koch, V.;
Ball, W. H.; Basu, S.; Chaplin, W. J.; Goupil, M. -J.; Nsamba,
B.; Ong, J.; Reese, D. R.; Verma, K.; Belkacem, K.; Campante, T.;
Christensen-Dalsgaard, J.; Clara, M. T.; Deheuvels, S.; Monteiro,
M. J. P. F. G.; Noll, A.; Ouazzani, R. M.; Rørsted, J. L.; Stokholm,
A.; Winther, M. L.
2021MNRAS.508.5864C Altcode: 2021MNRAS.tmp.2643C; 2021arXiv211003332C
Asteroseismology is a powerful tool to infer fundamental stellar
properties. The use of these asteroseismic-inferred properties in a
growing number of astrophysical contexts makes it vital to understand
their accuracy. Consequently, we performed a hare-and-hounds exercise
where the hares simulated data for six artificial main-sequence stars
and the hounds inferred their properties based on different inference
procedures. To mimic a pipeline such as that planned for the PLATO
mission, all hounds used the same model grid. Some stars were simulated
using the physics adopted in the grid, others a different one. The
maximum relative differences found (in absolute value) between the
inferred and true values of the mass, radius, and age were 4.32, 1.33,
and 11.25 per cent, respectively. The largest systematic differences in
radius and age were found for a star simulated assuming gravitational
settling, not accounted for in the model grid, with biases of -0.88
per cent (radius) and 8.66 per cent (age). For the mass, the most
significant bias (-3.16 per cent) was found for a star with a helium
enrichment ratio outside the grid range. Moreover, an ~7 per cent
dispersion in age was found when adopting different prescriptions
for the surface corrections or shifting the classical observations
by ±1σ. The choice of the relative weight given to the classical
and seismic constraints also impacted significantly the accuracy and
precision of the results. Interestingly, only a few frequencies were
required to achieve accurate results on the mass and radius. For the
age the same was true when at least one l = 2 mode was considered.
---------------------------------------------------------
Title: Asteroseismology of iota Draconis and Discovery of an
Additional Long-period Companion
Authors: Hill, Michelle L.; Kane, Stephen R.; Campante, Tiago L.; Li,
Zhexing; Dalba, Paul A.; Brandt, Timothy D.; White, Timothy R.; Pope,
Benjamin J. S.; Stassun, Keivan G.; Fulton, Benjamin J.; Corsaro,
Enrico; Li, Tanda; Ong, J. M. Joel; Bedding, Timothy R.; Bossini,
Diego; Buzasi, Derek L.; Chaplin, William J.; Cunha, Margarida S.;
García, Rafael A.; Breton, Sylvain N.; Hon, Marc; Huber, Daniel;
Jiang, Chen; Kayhan, Cenk; Kuszlewicz, James S.; Mathur, Savita;
Serenelli, Aldo; Stello, Dennis
2021AJ....162..211H Altcode: 2021arXiv210713583H
Giant stars as known exoplanet hosts are relatively rare due to
the potential challenges in acquiring precision radial velocities
and the small predicted transit depths. However, these giant host
stars are also some of the brightest in the sky and so enable high
signal-to-noise ratio follow-up measurements. Here, we report on new
observations of the bright (V ~ 3.3) giant star ι Draconis (ι Dra),
known to host a planet in a highly eccentric ~511 day period orbit. TESS
observations of the star over 137 days reveal asteroseismic signatures,
allowing us to constrain the stellar radius, mass, and age to ~2%,
~6%, and ~28%, respectively. We present the results of continued
radial-velocity monitoring of the star using the Automated Planet
Finder over several orbits of the planet. We provide more precise
planet parameters of the known planet and, through the combination of
our radial-velocity measurements with Hipparcos and Gaia astrometry,
we discover an additional long-period companion with an orbital period
of $\sim {68}_{-36}^{+60}$ yr. Mass predictions from our analysis
place this substellar companion on the border of the planet and brown
dwarf regimes. The bright nature of the star combined with the revised
orbital architecture of the system provides an opportunity to study
planetary orbital dynamics that evolve as the star moves into the
giant phase of its evolution.
---------------------------------------------------------
Title: Hierarchically modelling Kepler dwarfs and subgiants to
improve inference of stellar properties with asteroseismology
Authors: Lyttle, Alexander J.; Davies, Guy R.; Li, Tanda; Carboneau,
Lindsey M.; Leung, Ho-Hin; Westwood, Harry; Chaplin, William J.;
Hall, Oliver J.; Huber, Daniel; Nielsen, Martin B.; Basu, Sarbani;
García, Rafael A.
2021MNRAS.505.2427L Altcode: 2021arXiv210504482L; 2021MNRAS.tmp.1343L
With recent advances in modelling stars using high-precision
asteroseismology, the systematic effects associated with our assumptions
of stellar helium abundance (Y) and the mixing-length theory parameter
(α<SUB>MLT</SUB>) are becoming more important. We apply a new method
to improve the inference of stellar parameters for a sample of Kepler
dwarfs and subgiants across a narrow mass range ($0.8 \lt M \lt 1.2\,
\rm M_\odot$). In this method, we include a statistical treatment of Y
and the α<SUB>MLT</SUB>. We develop a hierarchical Bayesian model to
encode information about the distribution of Y and α<SUB>MLT</SUB>
in the population, fitting a linear helium enrichment law including
an intrinsic spread around this relation and normal distribution
in α<SUB>MLT</SUB>. We test various levels of pooling parameters,
with and without solar data as a calibrator. When including the Sun
as a star, we find the gradient for the enrichment law, $\Delta Y /
\Delta Z = 1.05\substack{+0.28\-0.25}$ and the mean α<SUB>MLT</SUB>
in the population, $\mu _\alpha = 1.90\substack{+0.10\-0.09}$. While
accounting for the uncertainty in Y and α<SUB>MLT</SUB>, we are still
able to report statistical uncertainties of 2.5 per cent in mass, 1.2
per cent in radius, and 12 per cent in age. Our method can also be
applied to larger samples that will lead to improved constraints on
both the population level inference and the star-by-star fundamental
parameters.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Oscillations in red giants from
TESS data (Silva+, 2020)
Authors: Silva Aguirre, V.; Stello, D.; Stokholm, A.; Mosumgaard,
J. R.; Ball, W. H.; Basu, S.; Bossini, D.; Bugnet, L.; Buzasi, D.;
Campante, T. L.; Carboneau, L.; Chaplin, W. J.; Corsaro, E.; Davies,
G. R.; Elsworth, Y.; Garcia, R. A.; Gaulme, P.; Hall, O. J.; Handberg,
R.; Hon, M.; Kallinger, T.; Kang, L.; Lund, M. N.; Mathur, S.; Mints,
A.; Mosser, B.; Celik Orhan, Z.; Rodrigues, T. S.; Vrard, M.; Yildiz,
M.; Zinn, J. C.; Ortel, S.; Beck, P. G.; Bell, K. J.; Guo, Z.; Jiang,
C.; Kuszlewicz, J. S.; Kuehn, C. A.; Li, T.; Lundkvist, M. S.;
Pinsonneault, M.; Tayar, J.; Cunha, M. S.; Hekker, S.; Huber, D.;
Miglio, A.; Monteiro, M. J. P. F. G.; Slumstrup, D.; Winther, M. L.;
Angelou, G.; Benomar, O.; Bodi, A.; de Moura, B. L.; Deheuvels, S.;
Derekas, A.; di Mauro, M. P.; Dupret, M. -A.; Jimenez, A.; Lebreton,
Y.; Matthews, J.; Nardetto, N.; Do Nascimento, J. D.; Pereira, F.;
Rodriguez Diaz, L. F.; Serenelli, A. M.; Spitoni, E.; Stonkute, E.;
Suarez, J. C.; Szabo, R.; van Eylen, V.; Ventura, R.; Verma, K.;
Weiss, A.; Wu, T.; Barclay, T.; Christensen-Dalsgaard, J.; Jenkins,
J. M.; Kjeldsen, H.; Ricker, G. R.; Seager, S.; Vanderspek, R.
2021yCat..18899034S Altcode:
Since the onset of the "space revolution" of high-precision high-cadence
photometry, asteroseismology has been demonstrated as a powerful tool
for informing Galactic archeology investigations. The launch of the
NASA Transiting Exoplanet Survey Satellite (TESS) mission has enabled
seismic-based inferences to go full sky-providing a clear advantage for
large ensemble studies of the different Milky Way components. Here we
demonstrate its potential for investigating the Galaxy by carrying out
the first asteroseismic ensemble study of red giant stars observed by
TESS. We use a sample of 25 stars for which we measure their global
asteroseimic observables and estimate their fundamental stellar
properties, such as radius, mass, and age. Significant improvements
are seen in the uncertainties of our estimates when combining seismic
observables from TESS with astrometric measurements from the Gaia
mission compared to when the seismology and astrometry are applied
separately. Specifically, when combined we show that stellar radii can
be determined to a precision of a few percent, masses to 5%-10%, and
ages to the 20% level. This is comparable to the precision typically
obtained using end-of-mission Kepler data. <P />(1 data file).
---------------------------------------------------------
Title: Asteroseismology of the Red-giant Hosts KOI-3886 and iota
Draconis
Authors: Campante, Tiago L.; Li, Tanda; Ong, J. M. Joel; Corsaro,
Enrico; Hill, Michelle L.; Lillo-Box, Jorge; Bedding, Timothy R.;
Bossini, Diego; Brandt, Timothy D.; Breton, Sylvain N.; Buzasi,
Derek L.; Chaplin, William J.; Cunha, Margarida S.; García, Rafael
A.; Hon, Marc; Huber, Daniel; Jiang, Chen; Kane, Stephen R.; Kayhan,
Cenk; Kuszlewicz, James S.; Mathur, Savita; Pereira, Filipe; Santos,
Nuno C.; Serenelli, Aldo; Stello, Dennis
2021tsc2.confE..84C Altcode:
Kepler asteroseismology has played an important role in the
characterization of host stars and their planetary systems. Target
selection biases, however, meant that this synergy would remain
mostly confined to main-sequence stars. The advent of TESS has since
lifted this restriction, enabling the systematic search for transiting
planets around seismic giants, as well as revisiting previously known
evolved hosts using asteroseismology. Here, we present the detailed
asteroseismic modeling of two high-luminosity red-giant branch
hosts, KOI-3886 and iota Draconis. KOI-3886, observed by Kepler
over 4 years and later by TESS over 1 sector, has been a longtime
candidate host. iota Draconis, observed by TESS over 5 sectors,
is known to host a planet in a highly eccentric orbit. The precise
(~ 6%) seismic mass derived for iota Draconis was combined with new
radial-velocity observations to detect an additional long-period
companion. Regarding KOI-3886, asteroseismology was key in helping
reveal the planet candidate as a false positive and reinterpreting the
system as an eclipsing brown dwarf in a hierarchical triple with two
evolved stars. This brings to light the importance of asteroseismology
in the study of planetary orbital dynamics off the main sequence and
its lesser known role in candidate vetting.
---------------------------------------------------------
Title: Haydn
Authors: Miglio, Andrea; Girardi, Léo; Grundahl, Frank; Mosser,
Benoit; Bastian, Nate; Bragaglia, Angela; Brogaard, Karsten; Buldgen,
Gaël; Chantereau, William; Chaplin, William; Chiappini, Cristina;
Dupret, Marc-Antoine; Eggenberger, Patrick; Gieles, Mark; Izzard,
Robert; Kawata, Daisuke; Karoff, Christoffer; Lagarde, Nadège;
Mackereth, Ted; Magrin, Demetrio; Meynet, Georges; Michel, Eric;
Montalbán, Josefina; Nascimbeni, Valerio; Noels, Arlette; Piotto,
Giampaolo; Ragazzoni, Roberto; Soszyński, Igor; Tolstoy, Eline;
Toonen, Silvia; Triaud, Amaury; Vincenzo, Fiorenzo
2021ExA....51..963M Altcode: 2021ExA...tmp...21M; 2019arXiv190805129M
In the last decade, the Kepler and CoRoT space-photometry missions have
demonstrated the potential of asteroseismology as a novel, versatile
and powerful tool to perform exquisite tests of stellar physics, and to
enable precise and accurate characterisations of stellar properties,
with impact on both exoplanetary and Galactic astrophysics. Based
on our improved understanding of the strengths and limitations of
such a tool, we argue for a new small/medium space mission dedicated
to gathering high-precision, high-cadence, long photometric series
in dense stellar fields. Such a mission will lead to breakthroughs
in stellar astrophysics, especially in the metal poor regime, will
elucidate the evolution and formation of open and globular clusters,
and aid our understanding of the assembly history and chemodynamics
of the Milky Way's bulge and a few nearby dwarf galaxies.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Dwarf stars asteroseismic rotation
rates (Hall+, 2021)
Authors: Hall, O. J.; Davies, G. R.; van Saders, J.; Nielsen, M. B.;
Lund, M. N.; Chaplin, W. J.; Garcia, R. A.; Amard, L.; Breimann,
A. A.; Khan, S.; See, V.; Tayar, J.
2021yCatp061000501H Altcode:
Parameters for the 94 stars for which seismic rotation rates
were obtained in the paper. Temperatures (Teff), age, mass,
metallicity ([Fe/H]) and surface gravity (log(g)) are adopted from
the LEGACY (L, Lund et al., 2017ApJ...835..172L, Silva Aguirre
et al., 2017ApJ...836..173S) and 'Kages' (K, Silva Aguirre et al.,
2015MNRAS.452.2127S, Davies et al., 2016MNRAS.456.2183D) catalogues, as
listed in the Source column. Projected splitting (ν<SUB>s</SUB>sin(i)),
inclination angle (i) and asteroseismic rotation (P) are from the
paper. Uncertainties were taken using the 15.9th and 84.1st percentiles
of posterior distributions on the parameters, which are frequently
asymmetrical in linear space. Reported values are the median of the
posterior distributions. For parameters with no direct posterior samples
(e.g. rotation) the full posterior samples were transformed before
taking the summary statistics. The stellar type denotes whether a star
is roughly classified as belonging to the main sequence (MS), Sub-Giants
(SG) or 'hot' stars (H). <P />The flags indicate the following: 0;
no issues, used in the gyrochronology analysis. 1; has either a number
of effective samples neff<1000 for the asteroseismic splitting, or
Gelman-Rubin convergence metric of R>1.1, indicating that rotation
measurements for these stars are less robust than those with a flag of
0. 2; was found to strongly disagree with multiple literature values,
excluded from the gyrochronology analysis. 3; fell outside the model
range of the stellar models, and were therefore not used in the
gyrochronology analysis. <P />(1 data file).
---------------------------------------------------------
Title: Impact of magnetic activity on inferred stellar properties
of main-sequence Sun-like stars
Authors: Thomas, Alexandra E. L.; Chaplin, William J.; Basu, Sarbani;
Rendle, Ben; Davies, Guy; Miglio, Andrea
2021MNRAS.502.5808T Altcode: 2021MNRAS.tmp..387T; 2021arXiv210202566T
The oscillation frequencies observed in Sun-like stars are susceptible
to being shifted by magnetic activity effects. The measured shifts
depend on a complex relationship involving the mode type, the
field strength, and spatial distribution of activity, as well as the
inclination angle of the star. Evidence of these shifts is also present
in frequency separation ratios that are often used when inferring
global properties of stars in order to avoid surface effects. However,
one assumption when using frequency ratios for this purpose is that
there are no near-surface perturbations that are non-spherically
symmetric. In this work, we studied the impact on inferred stellar
properties when using frequency ratios that are influenced by
non-homogeneous activity distributions. We generate several sets of
artificial oscillation frequencies with various amounts of shift and
determine stellar properties using two separate pipelines. We find
that for asteroseismic observations of Sun-like targets we can expect
magnetic activity to affect mode frequencies that will bias the results
from stellar modelling analysis. Although for most stellar properties
this offset should be small, typically less than 0.5 per cent in mass,
estimates of age and central hydrogen content can have an error of
up to 5 per cent and 3 per cent, respectively. We expect a larger
frequency shift and therefore larger bias for more active stars. We
also warn that for stars with very high or low inclination angles,
the response of modes to activity is more easily observable in the
separation ratios and hence will incur a larger bias.
---------------------------------------------------------
Title: Orbital misalignment of the super-Earth π Men c with the
spin of its star
Authors: Kunovac Hodžić, Vedad; Triaud, Amaury H. M. J.; Cegla,
Heather M.; Chaplin, William J.; Davies, Guy R.
2021MNRAS.502.2893K Altcode: 2021MNRAS.tmp..280H; 2020arXiv200711564K
Planet-planet scattering events can leave an observable trace of
a planet's migration history in the form of orbital misalignment
with respect to the stellar spin axis, which is measurable
from spectroscopic time-series taken during transit. We present
high-resolution spectroscopic transits observed with ESPRESSO of
the close-in super-Earth π Men c. The system also contains an outer
giant planet on a wide, eccentric orbit, recently found to be inclined
with respect to the inner planetary orbit. These characteristics are
reminiscent of past dynamical interactions. We successfully retrieve
the planet-occulted light during transit, and find evidence that
the orbit of π Men c is moderately misaligned with the stellar
spin axis with λ = - 24${_{.}^{\circ}}$0 ± 4${_{.}^{\circ}}$1
($\psi = {26{_{.}^{\circ}} 9}^{+5{_{.}^{\circ}}8 }_{-4{_{.}^{\circ}}7
}$). This is consistent with the super-Earth π Men c having followed a
high-eccentricity migration followed by tidal circularization, and hints
that super-Earths can form at large distances from their star. We also
detect clear signatures of solar-like oscillations within our ESPRESSO
radial velocity time series, where we reach a radial velocity precision
of ~20 cm s<SUP>-1</SUP>. We model the oscillations using Gaussian
processes (GPs) and retrieve a frequency of maximum oscillation,
$\nu _\mathrm{max}{} = 2771^{+65}_{-60}\, \mu \mathrm{Hz}$. These
oscillations make it challenging to detect the Rossiter-McLaughlin
effect using traditional methods. We are, however, successful using
the reloaded Rossiter-McLaughlin approach. Finally, in the appendix,
we also present physical parameters and ephemerides for π Men c from
a GP transit analysis of the full Transiting Exoplanet Survey Satellite
Cycle 1 data.
---------------------------------------------------------
Title: Prospects for Galactic and stellar astrophysics with
asteroseismology of giant stars in the TESS continuous viewing zones
and beyond
Authors: Mackereth, J. Ted; Miglio, Andrea; Elsworth, Yvonne; Mosser,
Benoit; Mathur, Savita; Garcia, Rafael A.; Nardiello, Domenico;
Hall, Oliver J.; Vrard, Mathieu; Ball, Warrick H.; Basu, Sarbani;
Beaton, Rachael L.; Beck, Paul G.; Bergemann, Maria; Bossini, Diego;
Casagrande, Luca; Campante, Tiago L.; Chaplin, William J.; Chiappini,
Cristina; Girardi, Léo; Jørgensen, Andreas Christ Sølvsten; Khan,
Saniya; Montalbán, Josefina; Nielsen, Martin B.; Pinsonneault, Marc
H.; Rodrigues, Thaíse S.; Serenelli, Aldo; Silva Aguirre, Victor;
Stello, Dennis; Tayar, Jamie; Teske, Johanna; van Saders, Jennifer L.;
Willett, Emma
2021MNRAS.502.1947M Altcode: 2020arXiv201200140M; 2021MNRAS.tmp..131M
The NASA Transiting Exoplanet Survey Satellite (NASA-TESS) mission
presents a treasure trove for understanding the stars it observes
and the Milky Way, in which they reside. We present a first look at
the prospects for Galactic and stellar astrophysics by performing
initial asteroseismic analyses of bright (G < 11) red giant stars
in the TESS southern continuous viewing zone (SCVZ). Using three
independent pipelines, we detect ν<SUB>max</SUB> and Δν in 41 per
cent of the 15 405 star parent sample (6388 stars), with consistency
at a level of $\sim \! 2{{\ \rm per\ cent}}$ in ν<SUB>max</SUB>
and $\sim \! 5{{\ \rm per\ cent}}$ in Δν. Based on this, we
predict that seismology will be attainable for ~3 × 10<SUP>5</SUP>
giants across the whole sky and at least 10<SUP>4</SUP> giants with
≥1 yr of observations in the TESS-CVZs, subject to improvements in
analysis and data reduction techniques. The best quality TESS-CVZ data,
for 5574 stars where pipelines returned consistent results, provide
high-quality power spectra across a number of stellar evolutionary
states. This makes possible studies of, for example, the asymptotic
giant branch bump. Furthermore, we demonstrate that mixed ℓ = 1 modes
and rotational splitting are cleanly observed in the 1-yr data set. By
combining TESS-CVZ data with TESS-HERMES, SkyMapper, APOGEE, and Gaia,
we demonstrate its strong potential for Galactic archaeology studies,
providing good age precision and accuracy that reproduces well the age
of high [α/Fe] stars and relationships between mass and kinematics
from previous studies based on e.g. Kepler. Better quality astrometry
and simpler target selection than the Kepler sample makes this data
ideal for studies of the local star formation history and evolution
of the Galactic disc. These results provide a strong case for detailed
spectroscopic follow-up in the CVZs to complement that which has been
(or will be) collected by current surveys.
---------------------------------------------------------
Title: Lifetimes and rotation within the solar mean magnetic field
Authors: Ross, Eddie; Chaplin, William J.; Hale, Steven J.; Howe,
Rachel; Elsworth, Yvonne P.; Davies, Guy R.; Nielsen, Martin Bo
2021MNRAS.502.5603R Altcode: 2021MNRAS.tmp..426C; 2021MNRAS.tmp..495R; 2021arXiv210204743R
We have used very high-cadence (sub-minute) observations of the solar
mean magnetic field (SMMF) from the Birmingham Solar Oscillations
Network (BiSON) to investigate the morphology of the SMMF. The
observations span a period from 1992 to 2012, and the high-cadence
observations allowed the exploration of the power spectrum up to
frequencies in the mHz range. The power spectrum contains several broad
peaks from a rotationally modulated (RM) component, whose linewidths
allowed us to measure, for the first time, the lifetime of the RM
source. There is an additional broadband, background component in the
power spectrum which we have shown is an artefact of power aliasing
due to the low fill of the data. The sidereal rotation period of the RM
component was measured as 25.23 ± 0.11 d and suggests that the signal
is sensitive to a time-averaged latitude of ∼12°. We have also
shown the RM lifetime to be 139.6 ± 18.5 d. This provides evidence
to suggest that the RM component of the SMMF is connected to magnetic
flux concentrations (MFCs) and active regions (ARs) of magnetic flux,
based both on its lifetime and location on the solar disc.
---------------------------------------------------------
Title: TOI-257b (HD 19916b): a warm sub-saturn orbiting an evolved
F-type star
Authors: Addison, Brett C.; Wright, Duncan J.; Nicholson, Belinda
A.; Cale, Bryson; Mocnik, Teo; Huber, Daniel; Plavchan, Peter;
Wittenmyer, Robert A.; Vanderburg, Andrew; Chaplin, William J.;
Chontos, Ashley; Clark, Jake T.; Eastman, Jason D.; Ziegler, Carl;
Brahm, Rafael; Carter, Bradley D.; Clerte, Mathieu; Espinoza, Néstor;
Horner, Jonathan; Bentley, John; Jordán, Andrés; Kane, Stephen R.;
Kielkopf, John F.; Laychock, Emilie; Mengel, Matthew W.; Okumura,
Jack; Stassun, Keivan G.; Bedding, Timothy R.; Bowler, Brendan
P.; Burnelis, Andrius; Blanco-Cuaresma, Sergi; Collins, Michaela;
Crossfield, Ian; Davis, Allen B.; Evensberget, Dag; Heitzmann, Alexis;
Howell, Steve B.; Law, Nicholas; Mann, Andrew W.; Marsden, Stephen
C.; Matson, Rachel A.; O'Connor, James H.; Shporer, Avi; Stevens,
Catherine; Tinney, C. G.; Tylor, Christopher; Wang, Songhu; Zhang,
Hui; Henning, Thomas; Kossakowski, Diana; Ricker, George; Sarkis,
Paula; Schlecker, Martin; Torres, Pascal; Vanderspek, Roland; Latham,
David W.; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Mireles,
Ismael; Rowden, Pam; Pepper, Joshua; Daylan, Tansu; Schlieder, Joshua
E.; Collins, Karen A.; Collins, Kevin I.; Tan, Thiam-Guan; Ball,
Warrick H.; Basu, Sarbani; Buzasi, Derek L.; Campante, Tiago L.;
Corsaro, Enrico; González-Cuesta, L.; Davies, Guy R.; de Almeida,
Leandro; do Nascimento, Jose-Dias, Jr.; García, Rafael A.; Guo,
Zhao; Handberg, Rasmus; Hekker, Saskia; Hey, Daniel R.; Kallinger,
Thomas; Kawaler, Steven D.; Kayhan, Cenk; Kuszlewicz, James S.; Lund,
Mikkel N.; Lyttle, Alexander; Mathur, Savita; Miglio, Andrea; Mosser,
Benoit; Nielsen, Martin B.; Serenelli, Aldo M.; Aguirre, Victor Silva;
Themeßl, Nathalie
2021MNRAS.502.3704A Altcode: 2020arXiv200107345A; 2020MNRAS.tmp.3757A
We report the discovery of a warm sub-Saturn, TOI-257b (HD 19916b),
based on data from NASA's Transiting Exoplanet Survey Satellite
(TESS). The transit signal was detected by TESS and confirmed to
be of planetary origin based on radial velocity observations. An
analysis of the TESS photometry, the MINERVA-Australis, FEROS, and
HARPS radial velocities, and the asteroseismic data of the stellar
oscillations reveals that TOI-257b has a mass of M<SUB>P</SUB> = 0.138
± 0.023 $\rm {M_J}$ (43.9 ± 7.3 $\, M_{\rm \oplus}$ ), a radius of
R<SUB>P</SUB> = 0.639 ± 0.013 $\rm {R_J}$ (7.16 ± 0.15 $\, \mathrm{
R}_{\rm \oplus}$ ), bulk density of $0.65^{+0.12}_{-0.11}$ (cgs),
and period $18.38818^{+0.00085}_{-0.00084}$ $\rm {days}$ . TOI-257b
orbits a bright (V = 7.612 mag) somewhat evolved late F-type star
with M<SUB>*</SUB> = 1.390 ± 0.046 $\rm {M_{sun}}$ , R<SUB>*</SUB>
= 1.888 ± 0.033 $\rm {R_{sun}}$ , T<SUB>eff</SUB> = 6075 ± 90 $\rm
{K}$ , and vsin i = 11.3 ± 0.5 km s<SUP>-1</SUP>. Additionally, we
find hints for a second non-transiting sub-Saturn mass planet on a
∼71 day orbit using the radial velocity data. This system joins the
ranks of a small number of exoplanet host stars (∼100) that have
been characterized with asteroseismology. Warm sub-Saturns are rare
in the known sample of exoplanets, and thus the discovery of TOI-257b
is important in the context of future work studying the formation and
migration history of similar planetary systems.
---------------------------------------------------------
Title: Haiku CS20.5 - Weakened magnetic braking supported by
asteroseismic rotation
Authors: Hall, O. J.; Davies, G. R.; van Saders, J.; Nielsen, M. B.;
Lund, M. N.; Chaplin, W. J.; Garcia, R. A.; Amard, L.; Breimann,
A. A.; Khan, S.; See, V.; Tayar, J.
2021csss.confE..70H Altcode:
Studies using asteroseismic ages and rotation rates from star-spot
rotation have indicated that standard age-rotation relations may
break down roughly half-way through the main sequence lifetime, a
phenomenon referred to as weakened magnetic braking. While rotation
rates from spots can be difficult to determine for older, less active
stars, rotational splitting of asteroseismic oscillation frequencies
can provide rotation rates for both active and quiescent stars,
and so can confirm whether this effect really takes place on the
main sequence. In this talk, I'll show how we obtained asteroseismic
rotation rates of 91 main sequence stars showing high signal-to-noise
modes of oscillation. Using these new rotation rates, along with
effective temperatures, metallicities and seismic masses and ages,
we built a hierarchical Bayesian mixture model that showed that our
new ensemble more closely agreed with weakened magnetic braking,
over a standard rotational evolution scenario.
---------------------------------------------------------
Title: VizieR Online Data Catalog: 117 exoplanets in habitable zone
with Kepler DR25 (Bryson+, 2021)
Authors: Bryson, S.; Kunimoto, M.; Kopparapu, R. K.; Coughlin, J. L.;
Borucki, W. J.; Koch, D.; Aguirre, V. S.; Allen, C.; Barentsen, G.;
Batalha, N. M.; Berger, T.; Boss, A.; Buchhave, L. A.; Burke, C. J.;
Caldwell, D. A.; Campbell, J. R.; Catanzarite, J.; Chandrasekaran,
H.; Chaplin, W. J.; Christiansen, J. L.; Christensen-Dalsgaard,
J.; Ciardi, D. R.; Clarke, B. D.; Cochran, W. D.; Dotson, J. L.;
Doyle, L. R.; Duarte, E. S.; Dunham, E. W.; Dupree, A. K.; Endl, M.;
Fanson, J. L.; Ford, E. B.; Fujieh, M.; Gautier, T. N., III; Geary,
J. C.; Gilliland, R. L.; Girouard, F. R.; Gould, A.; Haas, M. R.;
Henze, C. E.; Holman, M. J.; Howard, A. W.; Howell, S. B.; Huber,
D.; Hunter, R. C.; Jenkins, J. M.; Kjeldsen, H.; Kolodziejczak, J.;
Larson, K.; Latham, D. W.; Li, J.; Mathur, S.; Meibom, S.; Middour,
C.; Morris, R. L.; Morton, T. D.; Mullally, F.; Mullally, S. E.;
Pletcher, D.; Prsa, A.; Quinn, S. N.; Quintana, E. V.; Ragozzine,
D.; Ramirez, S. V.; Sanderfer, D. T.; Sasselov, D.; Seader, S. E.;
Shabram, M.; Shporer, A.; Smith, J. C.; Steffen, J. H.; Still, M.;
Torres, G.; Troeltzsch, J.; Twicken, J. D.; Uddin, A. K.; van Cleve,
J. E.; Voss, J.; Weiss, L. M.; Welsh, W. F.; Wohler, B.; Zamudio, K. A.
2021yCat..51610036B Altcode:
We present the occurrence rates for rocky planets in the habitable
zones (HZs) of main-sequence dwarf stars based on the Kepler DR25
planet candidate catalog and Gaia-based stellar properties. We
provide the first analysis in terms of star-dependent instellation
flux, which allows us to track HZ planets. We define {eta}{Earth}
as the HZ occurrence of planets with radii between 0.5 and 1.5
R{Earth} orbiting stars with effective temperatures between 4800
and 6300K. We find that {eta}{Earth} for the conservative HZ is
between 0.37<SUB>-0.21</SUB><SUP>+0.48</SUP> (errors reflect 68%
credible intervals) and 0.60<SUB>-0.36</SUB><SUP>+0.90</SUP>
planets per star, while the optimistic HZ occurrence
is between 0.58<SUB>-0.33</SUB><SUP>+0.73</SUP> and
0.88<SUB>-0.51</SUB><SUP>+1.28</SUP> planets per star. These
bounds reflect two extreme assumptions about the extrapolation of
completeness beyond orbital periods where DR25 completeness data are
available. The large uncertainties are due to the small number of
detected small HZ planets. We find similar occurrence rates between
using Poisson likelihood Bayesian analysis and using Approximate
Bayesian Computation. Our results are corrected for catalog completeness
and reliability. Both completeness and the planet occurrence rate are
dependent on stellar effective temperature. We also present occurrence
rates for various stellar populations and planet size ranges. We
estimate with 95% confidence that, on average, the nearest HZ planet
around G and K dwarfs is ~6pc away and there are ~4 HZ rocky planets
around G and K dwarfs within 10pc of the Sun. <P />(1 data file).
---------------------------------------------------------
Title: Poster CS20.5 - Weakened magnetic braking supported by
asteroseismic rotation
Authors: Hall, Oliver James; Davies, G. R.; van Saders, J.; Nielsen,
M. B.; Lund, M. N.; Chaplin, W. J.; Garcia, R. A.; Amard, L.; Breimann,
A. A.; Khan, S.; See, V.; Tayar, J.
2021csss.confE..69H Altcode:
Studies using asteroseismic ages and rotation rates from star-spot
rotation have indicated that standard age-rotation relations may
break down roughly half-way through the main sequence lifetime, a
phenomenon referred to as weakened magnetic braking. While rotation
rates from spots can be difficult to determine for older, less active
stars, rotational splitting of asteroseismic oscillation frequencies
can provide rotation rates for both active and quiescent stars,
and so can confirm whether this effect really takes place on the
main sequence. In this talk, I'll show how we obtained asteroseismic
rotation rates of 91 main sequence stars showing high signal-to-noise
modes of oscillation. Using these new rotation rates, along with
effective temperatures, metallicities and seismic masses and ages,
we built a hierarchical Bayesian mixture model that showed that our
new ensemble more closely agreed with weakened magnetic braking,
over a standard rotational evolution scenario.
---------------------------------------------------------
Title: VizieR Online Data Catalog: K2 GAP DR2: campaigns 4, 6 &
7 (Zinn+, 2020)
Authors: Zinn, J. C.; Stello, D.; Elsworth, Y.; Garcia, R. A.;
Kallinger, T.; Mathur, S.; Mosser, B.; Bugnet, L.; Jones, C.; Hon, M.;
Sharma, S.; Schonrich, R.; Warfield, J. T.; Luger, R.; Pinsonneault,
M. H.; Johnson, J. A.; Huber, D.; Silva Aguirre, V.; Chaplin, W. J.;
Davies, G. R.; Miglio, A.
2021yCat..22510023Z Altcode:
In the context of the Galactic Archaeology Program (GAP; Stello+
2015ApJ...809L...3S), analyses of the Kepler K2 campaigns presented
here were prioritized due to their coverage of the sky: the Galactic
center (C7; 2015 Oct-Dec), the Galactic anticenter (C4; 2015 Feb-Apr),
and out of the Galactic plane (C6; 2015 Jul-Sep). <P />(3 data files).
---------------------------------------------------------
Title: PBjam: A Python Package for Automating Asteroseismology of
Solar-like Oscillators
Authors: Nielsen, M. B.; Davies, G. R.; Ball, W. H.; Lyttle, A. J.;
Li, T.; Hall, O. J.; Chaplin, W. J.; Gaulme, P.; Carboneau, L.; Ong,
J. M. J.; García, R. A.; Mosser, B.; Roxburgh, I. W.; Corsaro, E.;
Benomar, O.; Moya, A.; Lund, M. N.
2021AJ....161...62N Altcode: 2020arXiv201200580N
Asteroseismology is an exceptional tool for studying stars using the
properties of observed modes of oscillation. So far the process of
performing an asteroseismic analysis of a star has remained somewhat
esoteric and inaccessible to nonexperts. In this software paper
we describe PBjam, an open-source Python package for analyzing
the frequency spectra of solar-like oscillators in a simple but
principled and automated way. The aim of PBjam is to provide a set of
easy-to-use tools to extract information about the radial and quadropole
oscillations in stars that oscillate like the Sun, which may then be
used to infer bulk properties such as stellar mass, radius, age, or even
structure. Asteroseismology and its data analysis methods are becoming
increasingly important as space-based photometric observatories are
producing a wealth of new data, allowing asteroseismology to be applied
in a wide range of contexts such as exoplanet, stellar structure and
evolution, and Galactic population studies. * Release 1.0.0 Zenodo,
doi:10.5281/zenodo.4300079.
---------------------------------------------------------
Title: Science Extraction from TESS Observations of Known Exoplanet
Hosts
Authors: Kane, Stephen R.; Bean, Jacob L.; Campante, Tiago L.;
Dalba, Paul A.; Fetherolf, Tara; Mocnik, Teo; Ostberg, Colby; Pepper,
Joshua; Simpson, Emilie R.; Turnbull, Margaret C.; Ricker, George R.;
Vanderspek, Roland; Latham, David W.; Seager, Sara; Winn, Joshua N.;
Jenkins, Jon M.; Huber, Daniel; Chaplin, William J.
2021PASP..133a4402K Altcode: 2020arXiv201015164K
The transit method of exoplanet discovery and characterization
has enabled numerous breakthroughs in exoplanetary science. These
include measurements of planetary radii, mass-radius relationships,
stellar obliquities, bulk density constraints on interior models, and
transmission spectroscopy as a means to study planetary atmospheres. The
Transiting Exoplanet Survey Satellite (TESS) has added to the exoplanet
inventory by observing a significant fraction of the celestial sphere,
including many stars already known to host exoplanets. Here we describe
the science extraction from TESS observations of known exoplanet hosts
during the primary mission. These include transit detection of known
exoplanets, discovery of additional exoplanets, detection of phase
signatures and secondary eclipses, transit ephemeris refinement,
and asteroseismology as a means to improve stellar and planetary
parameters. We provide the statistics of TESS known host observations
during Cycle 1 and 2, and present several examples of TESS photometry
for known host stars observed with a long baseline. We outline the
major discoveries from observations of known hosts during the primary
mission. Finally, we describe the case for further observations of
known exoplanet hosts during the TESS extended mission and the expected
science yield.
---------------------------------------------------------
Title: The Occurrence of Rocky Habitable-zone Planets around
Solar-like Stars from Kepler Data
Authors: Bryson, Steve; Kunimoto, Michelle; Kopparapu, Ravi K.;
Coughlin, Jeffrey L.; Borucki, William J.; Koch, David; Aguirre,
Victor Silva; Allen, Christopher; Barentsen, Geert; Batalha, Natalie
M.; Berger, Travis; Boss, Alan; Buchhave, Lars A.; Burke, Christopher
J.; Caldwell, Douglas A.; Campbell, Jennifer R.; Catanzarite, Joseph;
Chandrasekaran, Hema; Chaplin, William J.; Christiansen, Jessie L.;
Christensen-Dalsgaard, Jørgen; Ciardi, David R.; Clarke, Bruce D.;
Cochran, William D.; Dotson, Jessie L.; Doyle, Laurance R.; Duarte,
Eduardo Seperuelo; Dunham, Edward W.; Dupree, Andrea K.; Endl, Michael;
Fanson, James L.; Ford, Eric B.; Fujieh, Maura; Gautier, Thomas N.,
III; Geary, John C.; Gilliland, Ronald L.; Girouard, Forrest R.; Gould,
Alan; Haas, Michael R.; Henze, Christopher E.; Holman, Matthew J.;
Howard, Andrew W.; Howell, Steve B.; Huber, Daniel; Hunter, Roger C.;
Jenkins, Jon M.; Kjeldsen, Hans; Kolodziejczak, Jeffery; Larson,
Kipp; Latham, David W.; Li, Jie; Mathur, Savita; Meibom, Søren;
Middour, Chris; Morris, Robert L.; Morton, Timothy D.; Mullally,
Fergal; Mullally, Susan E.; Pletcher, David; Prsa, Andrej; Quinn,
Samuel N.; Quintana, Elisa V.; Ragozzine, Darin; Ramirez, Solange V.;
Sanderfer, Dwight T.; Sasselov, Dimitar; Seader, Shawn E.; Shabram,
Megan; Shporer, Avi; Smith, Jeffrey C.; Steffen, Jason H.; Still,
Martin; Torres, Guillermo; Troeltzsch, John; Twicken, Joseph D.;
Uddin, Akm Kamal; Van Cleve, Jeffrey E.; Voss, Janice; Weiss, Lauren
M.; Welsh, William F.; Wohler, Bill; Zamudio, Khadeejah A.
2021AJ....161...36B Altcode: 2020arXiv201014812B
We present the occurrence rates for rocky planets in the habitable
zones (HZs) of main-sequence dwarf stars based on the Kepler DR25
planet candidate catalog and Gaia-based stellar properties. We provide
the first analysis in terms of star-dependent instellation flux,
which allows us to track HZ planets. We define η<SUB>⊕</SUB>
as the HZ occurrence of planets with radii between 0.5 and 1.5
R<SUB>⊕</SUB> orbiting stars with effective temperatures between
4800 and 6300 K. We find that η<SUB>⊕</SUB> for the conservative
HZ is between ${0.37}_{-0.21}^{+0.48}$ (errors reflect 68% credible
intervals) and ${0.60}_{-0.36}^{+0.90}$ planets per star, while the
optimistic HZ occurrence is between ${0.58}_{-0.33}^{+0.73}$ and
${0.88}_{-0.51}^{+1.28}$ planets per star. These bounds reflect two
extreme assumptions about the extrapolation of completeness beyond
orbital periods where DR25 completeness data are available. The
large uncertainties are due to the small number of detected
small HZ planets. We find similar occurrence rates between using
Poisson likelihood Bayesian analysis and using Approximate Bayesian
Computation. Our results are corrected for catalog completeness and
reliability. Both completeness and the planet occurrence rate are
dependent on stellar effective temperature. We also present occurrence
rates for various stellar populations and planet size ranges. We
estimate with 95% confidence that, on average, the nearest HZ planet
around G and K dwarfs is ∼6 pc away and there are ∼4 HZ rocky
planets around G and K dwarfs within 10 pc of the Sun.
---------------------------------------------------------
Title: Chronologically dating the early assembly of the Milky Way
Authors: Montalbán, Josefina; Mackereth, J. Ted; Miglio, Andrea;
Vincenzo, Fiorenzo; Chiappini, Cristina; Buldgen, Gael; Mosser,
Benoît; Noels, Arlette; Scuflaire, Richard; Vrard, Mathieu; Willett,
Emma; Davies, Guy R.; Hall, Oliver J.; Nielsen, Martin Bo; Khan,
Saniya; Rendle, Ben M.; van Rossem, Walter E.; Ferguson, Jason W.;
Chaplin, William J.
2021NatAs...5..640M Altcode: 2021NatAs.tmp...90M; 2020arXiv200601783M
The standard cosmological model predicts that galaxies
are built through hierarchical assembly on cosmological
timescales<SUP>1,2</SUP>. The Milky Way, like other disk galaxies,
underwent violent mergers and accretion of small satellite galaxies
in its early history. Owing to Gaia Data Release 2<SUP>3</SUP>
and spectroscopic surveys<SUP>4</SUP>, the stellar remnants of such
mergers have been identified<SUP>5-7</SUP>. The chronological dating
of such events is crucial to uncover the formation and evolution
of the Galaxy at high redshift, but it has so far been challenging
due to difficulties in obtaining precise ages for these oldest
stars. Here we combine asteroseismology—the study of stellar
oscillations—with kinematics and chemical abundances to estimate
precise stellar ages (~11%) for a sample of stars observed by the
Kepler space mission<SUP>8</SUP>. Crucially, this sample includes
not only some of the oldest stars that were formed inside the
Galaxy but also stars formed externally and subsequently accreted
onto the Milky Way. Leveraging this resolution in age, we provide
compelling evidence in favour of models in which the Galaxy had
already formed a substantial population of its stars (which now reside
mainly in its thick disk) before the infall of the satellite galaxy
Gaia-Enceladus/Sausage<SUP>5,6</SUP> around 10 billion years ago.
---------------------------------------------------------
Title: Age dissection of the Milky Way discs: Red giants in the
Kepler field
Authors: Miglio, A.; Chiappini, C.; Mackereth, J. T.; Davies, G. R.;
Brogaard, K.; Casagrande, L.; Chaplin, W. J.; Girardi, L.; Kawata,
D.; Khan, S.; Izzard, R.; Montalbán, J.; Mosser, B.; Vincenzo, F.;
Bossini, D.; Noels, A.; Rodrigues, T.; Valentini, M.; Mandel, I.
2021A&A...645A..85M Altcode: 2020arXiv200414806M
Ensemble studies of red-giant stars with exquisite asteroseismic
(Kepler), spectroscopic (APOGEE), and astrometric (Gaia) constraints
offer a novel opportunity to recast and address long-standing questions
concerning the evolution of stars and of the Galaxy. Here, we infer
masses and ages for nearly 5400 giants with available Kepler light
curves and APOGEE spectra using the code PARAM, and discuss some
of the systematics that may affect the accuracy of the inferred
stellar properties. We then present patterns in mass, evolutionary
state, age, chemical abundance, and orbital parameters that we deem
robust against the systematic uncertainties explored. First, we
look at age-chemical-abundances ([Fe/H] and [α/Fe]) relations. We
find a dearth of young, metal-rich ([Fe/H] > 0.2) stars, and the
existence of a significant population of old (8-9 Gyr), low-[α/Fe],
super-solar metallicity stars, reminiscent of the age and metallicity
of the well-studied open cluster NGC 6791. The age-chemo-kinematic
properties of these stars indicate that efficient radial migration
happens in the thin disc. We find that ages and masses of the nearly
400 α-element-rich red-giant-branch (RGB) stars in our sample
are compatible with those of an old (∼11 Gyr), nearly coeval,
chemical-thick disc population. Using a statistical model, we show that
the width of the observed age distribution is dominated by the random
uncertainties on age, and that the spread of the inferred intrinsic age
distribution is such that 95% of the population was born within ∼1.5
Gyr. Moreover, we find a difference in the vertical velocity dispersion
between low- and high-[α/Fe] populations. This discontinuity,
together with the chemical one in the [α/Fe] versus [Fe/H] diagram,
and with the inferred age distributions, not only confirms the different
chemo-dynamical histories of the chemical-thick and thin discs, but it
is also suggestive of a halt in the star formation (quenching) after the
formation of the chemical-thick disc. We then exploit the almost coeval
α-rich population to gain insight into processes that may have altered
the mass of a star along its evolution, which are key to improving the
mapping of the current, observed, stellar mass to the initial mass and
thus to the age. Comparing the mass distribution of stars on the lower
RGB (R < 11 R<SUB>⊙</SUB>) with those in the red clump (RC), we
find evidence for a mean integrated RGB mass loss ⟨ΔM⟩ = 0.10 ±
0.02 M<SUB>⊙</SUB>. Finally, we find that the occurrence of massive (M
≳ 1.1 M<SUB>⊙</SUB>) α-rich stars is of the order of 5% on the RGB,
and significantly higher in the RC, supporting the scenario in which
most of these stars had undergone an interaction with a companion. <P
/>Table C.1 is only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/645/A85">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/645/A85</A>
---------------------------------------------------------
Title: A next generation upgraded observing platform for the automated
Birmingham Solar Oscillations Network (BiSON)
Authors: Hale, S J; Chaplin, W J; Davies, G R; Elsworth, Y P
2021arXiv210110205H Altcode:
The Birmingham Solar Oscillations Network (BiSON) is a collection
of ground-based automated telescopes observing oscillations of the
Sun. The network has been operating since the early 1990s. We present
development work on a prototype next generation observation platform,
BiSON:NG, based almost entirely on inexpensive off-the-shelf components,
and where the footprint is reduced to a size that can be inexpensively
installed on the roof of an existing building. Continuous development
is essential in ensuring that automated networks such as BiSON are
well placed to observe the next solar cycle and beyond.
---------------------------------------------------------
Title: Weakened magnetic braking supported by asteroseismic rotation
rates of Kepler dwarfs
Authors: Hall, Oliver J.; Davies, Guy R.; van Saders, Jennifer;
Nielsen, Martin B.; Lund, Mikkel N.; Chaplin, William J.; García,
Rafael A.; Amard, Louis; Breimann, Angela A.; Khan, Saniya; See,
Victor; Tayar, Jamie
2021NatAs...5..707H Altcode: 2021NatAs.tmp...71H; 2021arXiv210410919H
Studies using asteroseismic ages and rotation rates from star-spot
rotation have indicated that standard age-rotation relations may break
down roughly half way through the main sequence lifetime, a phenomenon
referred to as weakened magnetic braking. Although rotation rates from
spots can be difficult to determine for older, less active stars,
rotational splitting of asteroseismic oscillation frequencies can
provide rotation rates for both active and quiescent stars, and so can
confirm whether this effect really takes place on the main sequence. We
obtained asteroseismic rotation rates of 91 main sequence stars showing
high signal-to-noise modes of oscillation. Using these new rotation
rates, along with effective temperatures, metallicities and seismic
masses and ages, we built a hierarchical Bayesian mixture model to
determine whether the ensemble more closely agreed with a standard
rotational evolution scenario, or one where weakened magnetic braking
takes place. The weakened magnetic braking scenario was found to be
98.4% more likely for our stellar ensemble, adding to the growing body
of evidence for this stage of stellar rotational evolution. This work
presents a large catalogue of seismic rotation rates for stars on the
main sequence, which opens up possibilities for more detailed ensemble
analysis of rotational evolution with Kepler.
---------------------------------------------------------
Title: The K2 Galactic Archaeology Program Data Release 2:
Asteroseismic Results from Campaigns 4, 6, and 7
Authors: Zinn, Joel C.; Stello, Dennis; Elsworth, Yvonne; García,
Rafael A.; Kallinger, Thomas; Mathur, Savita; Mosser, Benoît; Bugnet,
Lisa; Jones, Caitlin; Hon, Marc; Sharma, Sanjib; Schönrich, Ralph;
Warfield, Jack T.; Luger, Rodrigo; Pinsonneault, Marc H.; Johnson,
Jennifer A.; Huber, Daniel; Silva Aguirre, Victor; Chaplin, William
J.; Davies, Guy R.; Miglio, Andrea
2020ApJS..251...23Z Altcode: 2020arXiv201204051Z
Studies of Galactic structure and evolution have benefited enormously
from Gaia kinematic information, though additional, intrinsic
stellar parameters like age are required to best constrain Galactic
models. Asteroseismology is the most precise method of providing
such information for field star populations en masse, but existing
samples for the most part have been limited to a few narrow fields
of view by the CoRoT and Kepler missions. In an effort to provide
well-characterized stellar parameters across a wide range in Galactic
position, we present the second data release of red giant asteroseismic
parameters for the K2 Galactic Archaeology Program (GAP). We provide
${\nu }_{\max }$ and ${\rm{\Delta }}\nu $ based on six independent
pipeline analyses; first-ascent red giant branch (RGB) and red clump
(RC) evolutionary state classifications from machine learning;
and ready-to-use radius and mass coefficients, κ<SUB>R</SUB> and
κ<SUB>M</SUB>, which, when appropriately multiplied by a solar-scaled
effective temperature factor, yield physical stellar radii and
masses. In total, we report 4395 radius and mass coefficients, with
typical uncertainties of 3.3% (stat.) ± 1% (syst.) for κ<SUB>R</SUB>
and 7.7% (stat.) ± 2% (syst.) for κ<SUB>M</SUB> among RGB stars, and
5.0% (stat.) ± 1% (syst.) for κ<SUB>R</SUB> and 10.5% (stat.) ± 2%
(syst.) for κ<SUB>M</SUB> among RC stars. We verify that the sample
is nearly complete—except for a dearth of stars with ${\nu }_{\max
}\lesssim 10\mbox{--}20\,\mu \mathrm{Hz}$ —by comparing to Galactic
models and visual inspection. Our asteroseismic radii agree with radii
derived from Gaia Data Release 2 parallaxes to within 2.2% ± 0.3%
for RGB stars and 2.0% ± 0.6% for RC stars.
---------------------------------------------------------
Title: A next generation upgraded observing platform for the automated
Birmingham Solar Oscillations Network (BiSON)
Authors: Hale, S. J.; Chaplin, W. J.; Davies, G. R.; Elsworth, Y. P.
2020SPIE11452E..22H Altcode:
The Birmingham Solar Oscillations Network (BiSON) is a collection
of ground-based automated telescopes observing oscillations of the
Sun. The network has been operating since the early 1990s. We present
development work on a prototype next generation observation platform,
BiSON:NG, based almost entirely on inexpensive offthe-shelf components,
and where the footprint is reduced to a size that can be inexpensively
installed on the roof of an existing building. Continuous development
is essential in ensuring that automated networks such as BiSON are
well placed to observe the next solar cycle and beyond.
---------------------------------------------------------
Title: From solar-like to mira stars: a unifying description of
stellar pulsators in the presence of stochastic noise
Authors: Cunha, M. S.; Avelino, P. P.; Chaplin, W. J.
2020MNRAS.499.4687C Altcode: 2020arXiv200909873C; 2020MNRAS.tmp.2755C
We discuss and characterize the power spectral density properties of a
model aimed at describing pulsations in stars from the main-sequence
to the asymptotic giant branch. We show that the predicted limit
of the power spectral density for a pulsation mode in the presence
of stochastic noise is always well approximated by a Lorentzian
function. While in stars predominantly stochastically driven the
width of the Lorentzian is defined by the mode lifetime, in stars
where the driving is predominately coherent the width is defined by the
amplitude of the stochastic perturbations. In stars where both drivings
are comparable, the width is defined by both these parameters and is
smaller than that expected from pure stochastic driving. We illustrate
our model through numerical simulations and propose a well-defined
classification of stars into predominantly stochastic (solar-like)
and predominately coherent (classic) pulsators. We apply the model
to the study of the Mira variable U Per, and the semiregular variable
L2 Pup and, following our classification, conclude that they are both
classical pulsators. Our model provides a natural explanation for the
change in behaviour of the pulsation amplitude-period relation noted
in several earlier works. Moreover, our study of L2 Pup enables us to
test the scaling relation between the mode line width and effective
temperature, confirming that an exponential scaling reproduces well
the data all the way from the main sequence to the asymptotic giant
branch, down to temperatures about 1000 K below what has been tested
in previous studies.
---------------------------------------------------------
Title: Robust asteroseismic properties of the bright planet host
HD 38529
Authors: Ball, Warrick H.; Chaplin, William J.; Nielsen, Martin B.;
González-Cuesta, Lucia; Mathur, Savita; Santos, Ângela R. G.;
García, Rafael; Buzasi, Derek; Mosser, Benoît; Deal, Morgan;
Stokholm, Amalie; Mosumgaard, Jakob Rørsted; Silva Aguirre, Victor;
Nsamba, Benard; Campante, Tiago; Cunha, Margarida S.; Ong, Joel; Basu,
Sarbani; Örtel, Sibel; Çelik Orhan, Z.; Yıldız, Mutlu; Stassun,
Keivan; Kane, Stephen R.; Huber, Daniel
2020MNRAS.499.6084B Altcode: 2020arXiv201007323B; 2020MNRAS.tmp.3009B
The Transiting Exoplanet Survey Satellite (TESS) is recording
short-cadence, high duty-cycle timeseries across most of the sky, which
presents the opportunity to detect and study oscillations in interesting
stars, in particular planet hosts. We have detected and analysed
solar-like oscillations in the bright G4 subgiant HD 38529, which
hosts an inner, roughly Jupiter-mass planet on a $14.3\, \mathrm{d}$
orbit and an outer, low-mass brown dwarf on a $2136\, \mathrm{d}$
orbit. We combine results from multiple stellar modelling teams to
produce robust asteroseismic estimates of the star's properties,
including its mass $M=1.48\pm 0.04\, \mathrm{M}_\odot {}$, radius
$R=2.68\pm 0.03\, \mathrm{R}_\odot {}$, and age $t=3.07\pm 0.39\,
\mathrm{Gyr}{}$. Our results confirm that HD 38529 has a mass near
the higher end of the range that can be found in the literature and
also demonstrate that precise stellar properties can be measured given
shorter timeseries than produced by CoRoT, Kepler, or K2.
---------------------------------------------------------
Title: A Layered Approach to Robust Determination of Asteroseismic
Parameters
Authors: Elsworth, Yvonne; Themeßl, Nathalie; Hekker, Saskia;
Chaplin, William
2020RNAAS...4..177E Altcode:
We describe here a layered approach to the robust determination of
the broad characteristics of the asteroseismic signal from red-giant
stars. No single stringent test can exclude all false results. The
use of multiple, weak tests not only provides robust results but also
avoids over-constraining the parameter space.
---------------------------------------------------------
Title: The TESS light curve of AI Phoenicis
Authors: Maxted, P. F. L.; Gaulme, Patrick; Graczyk, D.; Hełminiak,
K. G.; Johnston, C.; Orosz, Jerome A.; Prša, Andrej; Southworth, John;
Torres, Guillermo; Davies, Guy R.; Ball, Warrick; Chaplin, William J.
2020MNRAS.498..332M Altcode: 2020arXiv200309295M; 2020MNRAS.tmp.1795M
Accurate masses and radii for normal stars derived from observations
of detached eclipsing binary stars are of fundamental importance for
testing stellar models and may be useful for calibrating free parameters
in these model if the masses and radii are sufficiently precise and
accurate. We aim to measure precise masses and radii for the stars
in the bright eclipsing binary AI Phe, and to quantify the level of
systematic error in these estimates. We use several different methods
to model the Transiting Exoplanet Survey Satellite (TESS) light curve
of AI Phe combined with spectroscopic orbits from multiple sources
to estimate precisely the stellar masses and radii together with
robust error estimates. We find that the agreement between different
methods for the light-curve analysis is very good but some methods
underestimate the errors on the model parameters. The semi-amplitudes
of the spectroscopic orbits derived from spectra obtained with modern
échelle spectrographs are consistent to within 0.1 per cent. The masses
of the stars in AI Phe are $M_1 = 1.1938 \pm 0.0008\, \rm M_{\odot }$
and $M_2 = 1.2438 \pm 0.0008\, \rm M_{\odot }$ , and the radii are $R_1
= 1.8050 \pm 0.0022\, \rm R_{\odot }$ and $R_2 = 2.9332 \pm 0.0023\,
\rm R_{\odot }$ . We conclude that it is possible to measure accurate
masses and radii for stars in bright eclipsing binary stars to a
precision of 0.2 per cent or better using photometry from TESS and
spectroscopy obtained with modern échelle spectrographs. We provide
recommendations for publishing masses and radii of eclipsing binary
stars at this level of precision.
---------------------------------------------------------
Title: TESS asteroseismology of the known planet host star
λ<SUP>2</SUP> Fornacis
Authors: Nielsen, M. B.; Ball, W. H.; Standing, M. R.; Triaud,
A. H. M. J.; Buzasi, D.; Carboneau, L.; Stassun, K. G.; Kane, S. R.;
Chaplin, W. J.; Bellinger, E. P.; Mosser, B.; Roxburgh, I. W.; Çelik
Orhan, Z.; Yıldız, M.; Örtel, S.; Vrard, M.; Mazumdar, A.; Ranadive,
P.; Deal, M.; Davies, G. R.; Campante, T. L.; García, R. A.; Mathur,
S.; González-Cuesta, L.; Serenelli, A.
2020A&A...641A..25N Altcode: 2020arXiv200700497N
Context. The Transiting Exoplanet Survey Satellite (TESS) is observing
bright known planet-host stars across almost the entire sky. These
stars have been subject to extensive ground-based observations,
providing a large number of radial velocity measurements. <BR />
Aims: The objective of this work is to use the new TESS photometric
observations to characterize the star <ASTROBJ>λ2 Fornacis</ASTROBJ>,
and following this to update the parameters of the orbiting planet
<ASTROBJ>λ2 For b</ASTROBJ>. <BR /> Methods: We measured the
frequencies of the p-mode oscillations in <ASTROBJ>λ2 For</ASTROBJ>,
and in combination with non-seismic parameters estimated the stellar
fundamental properties using stellar models. Using the revised
stellar properties and a time series of archival radial velocities
from the UCLES, HIRES and HARPS instruments spanning almost 20 years,
we refit the orbit of λ<SUP>2</SUP> For b and searched the residual
radial velocities for remaining variability. <BR /> Results: We find
that λ<SUP>2</SUP> For has a mass of 1.16 ± 0.03 M<SUB>⊙</SUB>
and a radius of 1.63 ± 0.04 R<SUB>⊙</SUB>, with an age of 6.3 ±
0.9 Gyr. This and the updated radial velocity measurements suggest a
mass of λ<SUP>2</SUP> For b of 16.8<SUB>-1.3</SUB><SUP>+1.2</SUP>
M<SUB>⊕</SUB>, which is ∼5M<SUB>⊕</SUB> less than literature
estimates. We also detect an additional periodicity at 33 days in the
radial velocity measurements, which is likely due to the rotation of the
host star. <BR /> Conclusions: While previous literature estimates of
the properties of λ<SUP>2</SUP> For are ambiguous, the asteroseismic
measurements place the star firmly at the early stage of its subgiant
evolutionary phase. Typically only short time series of photometric
data are available from TESS, but by using asteroseismology it is still
possible to provide tight constraints on the properties of bright
stars that until now have only been observed from the ground. This
prompts a reexamination of archival radial velocity data that have
been accumulated in the past few decades in order to update the
characteristics of the planet hosting systems observed by TESS for
which asteroseismology is possible.
---------------------------------------------------------
Title: VizieR Online Data Catalog: RAVE 6th data release (Steinmetz+,
2020)
Authors: Steinmetz, M.; Matijevic, G.; Enke, H.; Zwitter, T.; Guiglion,
G.; McMillan, P. J.; Kordopatis, G.; Valentini, M.; Chiappini, C.;
Casagrande, L.; Wojno, J.; Anguiano, B.; Bienayme, O.; Bijaoui,
A.; Binney, J.; Burton, D.; Cass, P.; de Laverny, P.; Fiegert, K.;
Freeman, K.; Fulbright, J. P.; Gibson, B. K.; Gilmore, G.; Grebel,
E. K.; Helmi, A.; Kunder, A.; Munari, U.; Navarro, J. F.; Parker, Q.;
Ruchti, G. R.; Recio-Blanco, A.; Reid, W.; Seabroke, G. M.; Siviero,
A.; Siebert, A.; Stupar, M.; Watson, F.; Williams, M. E. K.; Wyse,
R. F. G.; Anders, F.; Antoja, T.; Birko, D.; Bland-Hawthorn, J.;
Bossini, D.; Garcia, R. A.; Carrillo, I.; Chaplin, W. J.; Elsworth,
Y.; Famaey, B.; Gerhard, O.; Jofre, P.; Just, A.; Mathur, S.; Miglio,
A.; Minchev, I.; Monari, G.; Mosser, B.; Ritter, A.; Rodrigues, T. S.;
Scholz, R. -D.; Sharma, S.; Sysoliatina, K.
2020yCat.3283....0S Altcode:
The Radial Velocity Experiment (RAVE) is a magnitude-limited
(9<I<12) spectroscopic survey of Galactic stars randomly
selected in the southern hemisphere. The RAVE medium resolution
spectra (R~7500) cover the Ca-triplet region (8410-8795Å) and span
the complete time frame from the start of RAVE observations on 12
April 2003 to their completion on 4 April 2013. Wavelength-calibrated
and flux-normalized spectra for 518387 observations of 451783 unique
stars are presented. The final data release 6 consists of spectra,
error spectra, spectral classification, derived radial velocities,
and cross matches with other relevant catalogs. <P />Further data
products are using a suite of advanced reduction pipelines focusing on
stellar atmospheric parameters, in particular purely spectroscopically
derived stellar atmospheric parameters (Teff, logg, and the overall
metallicity), enhanced stellar parameters inferred via a Bayesian
pipeline using Gaia DR2 astrometric priors, and asteroseismically
calibrated stellar parameters for giant stars based on asteroseismic
observations for 699 K2 stars. In addition, we provide abundances of
the elements Fe, Al, and Ni, as well as an overall [alpha/Fe] ratio
obtained using a new pipeline based on the GAUGUIN optimization method
that is able to deal with variable signal-to-noise ratios. The Rave DR6
catalogs are cross matched with relevant astrometric and photometric
catalogs, and are complemented by orbital parameters and effective
temperatures based on the infrared flux method. <P />(22 data files).
---------------------------------------------------------
Title: The Evolution of Rotation and Magnetic Activity in 94 Aqr Aa
from Asteroseismology with TESS
Authors: Metcalfe, Travis S.; van Saders, Jennifer L.; Basu, Sarbani;
Buzasi, Derek; Chaplin, William J.; Egeland, Ricky; Garcia, Rafael
A.; Gaulme, Patrick; Huber, Daniel; Reinhold, Timo; Schunker, Hannah;
Stassun, Keivan G.; Appourchaux, Thierry; Ball, Warrick H.; Bedding,
Timothy R.; Deheuvels, Sébastien; González-Cuesta, Lucía; Handberg,
Rasmus; Jiménez, Antonio; Kjeldsen, Hans; Li, Tanda; Lund, Mikkel N.;
Mathur, Savita; Mosser, Benoit; Nielsen, Martin B.; Noll, Anthony;
Çelik Orhan, Zeynep; Örtel, Sibel; Santos, Ângela R. G.; Yildiz,
Mutlu; Baliunas, Sallie; Soon, Willie
2020ApJ...900..154M Altcode: 2020arXiv200712755M
Most previous efforts to calibrate how rotation and magnetic activity
depend on stellar age and mass have relied on observations of clusters,
where isochrones from stellar evolution models are used to determine the
properties of the ensemble. Asteroseismology employs similar models to
measure the properties of an individual star by matching its normal
modes of oscillation, yielding the stellar age and mass with high
precision. We use 27 days of photometry from the Transiting Exoplanet
Survey Satellite to characterize solar-like oscillations in the G8
subgiant of the 94 Aqr triple system. The resulting stellar properties,
when combined with a reanalysis of 35 yr of activity measurements
from the Mount Wilson HK project, allow us to probe the evolution of
rotation and magnetic activity in the system. The asteroseismic age
of the subgiant agrees with a stellar isochrone fit, but the rotation
period is much shorter than expected from standard models of angular
momentum evolution. We conclude that weakened magnetic braking may be
needed to reproduce the stellar properties, and that evolved subgiants
in the hydrogen shell-burning phase can reinvigorate large-scale dynamo
action and briefly sustain magnetic activity cycles before ascending
the red giant branch.
---------------------------------------------------------
Title: The Sixth Data Release of the Radial Velocity Experiment
(RAVE). I. Survey Description, Spectra, and Radial Velocities
Authors: Steinmetz, Matthias; Matijevič, Gal; Enke, Harry; Zwitter,
Tomaž; Guiglion, Guillaume; McMillan, Paul J.; Kordopatis, Georges;
Valentini, Marica; Chiappini, Cristina; Casagrande, Luca; Wojno,
Jennifer; Anguiano, Borja; Bienaymé, Olivier; Bijaoui, Albert;
Binney, James; Burton, Donna; Cass, Paul; de Laverny, Patrick;
Fiegert, Kristin; Freeman, Kenneth; Fulbright, Jon P.; Gibson,
Brad K.; Gilmore, Gerard; Grebel, Eva K.; Helmi, Amina; Kunder,
Andrea; Munari, Ulisse; Navarro, Julio F.; Parker, Quentin; Ruchti,
Gregory R.; Recio-Blanco, Alejandra; Reid, Warren; Seabroke, George
M.; Siviero, Alessandro; Siebert, Arnaud; Stupar, Milorad; Watson,
Fred; Williams, Mary E. K.; Wyse, Rosemary F. G.; Anders, Friedrich;
Antoja, Teresa; Birko, Danijela; Bland-Hawthorn, Joss; Bossini, Diego;
García, Rafael A.; Carrillo, Ismael; Chaplin, William J.; Elsworth,
Yvonne; Famaey, Benoit; Gerhard, Ortwin; Jofre, Paula; Just, Andreas;
Mathur, Savita; Miglio, Andrea; Minchev, Ivan; Monari, Giacomo; Mosser,
Benoit; Ritter, Andreas; Rodrigues, Thaise S.; Scholz, Ralf-Dieter;
Sharma, Sanjib; Sysoliatina, Kseniia; RAVE Collaboration
2020AJ....160...82S Altcode: 2020arXiv200204377S
The Radial Velocity Experiment (RAVE) is a magnitude-limited (9 <
I < 12) spectroscopic survey of Galactic stars randomly selected
in Earth's southern hemisphere. The RAVE medium-resolution spectra
(R ∼ 7500) cover the Ca-triplet region (8410-8795 Å). The sixth and
final data release (DR6) is based on 518,387 observations of 451,783
unique stars. RAVE observations were taken between 2003 April 12 and
2013 April 4. Here we present the genesis, setup, and data reduction
of RAVE as well as wavelength-calibrated and flux-normalized spectra
and error spectra for all observations in RAVE DR6. Furthermore, we
present derived spectral classification and radial velocities for the
RAVE targets, complemented by cross-matches with Gaia DR2 and other
relevant catalogs. A comparison between internal error estimates,
variances derived from stars with more than one observing epoch, and
a comparison with radial velocities of Gaia DR2 reveals consistently
that 68% of the objects have a velocity accuracy better than 1.4
km s<SUP>-1</SUP>, while 95% of the objects have radial velocities
better than 4.0 km s<SUP>-1</SUP>. Stellar atmospheric parameters,
abundances and distances are presented in a subsequent publication. The
data can be accessed via the RAVE website (http://rave-survey.org)
or the Vizier database.
---------------------------------------------------------
Title: The Sixth Data Release of the Radial Velocity Experiment
(RAVE). II. Stellar Atmospheric Parameters, Chemical Abundances,
and Distances
Authors: Steinmetz, Matthias; Guiglion, Guillaume; McMillan, Paul J.;
Matijevič, Gal; Enke, Harry; Kordopatis, Georges; Zwitter, Tomaž;
Valentini, Marica; Chiappini, Cristina; Casagrande, Luca; Wojno,
Jennifer; Anguiano, Borja; Bienaymé, Olivier; Bijaoui, Albert;
Binney, James; Burton, Donna; Cass, Paul; de Laverny, Patrick;
Fiegert, Kristin; Freeman, Kenneth; Fulbright, Jon P.; Gibson,
Brad K.; Gilmore, Gerard; Grebel, Eva K.; Helmi, Amina; Kunder,
Andrea; Munari, Ulisse; Navarro, Julio F.; Parker, Quentin; Ruchti,
Gregory R.; Recio-Blanco, Alejandra; Reid, Warren; Seabroke, George
M.; Siviero, Alessandro; Siebert, Arnaud; Stupar, Milorad; Watson,
Fred; Williams, Mary E. K.; Wyse, Rosemary F. G.; Anders, Friedrich;
Antoja, Teresa; Birko, Danijela; Bland-Hawthorn, Joss; Bossini, Diego;
García, Rafael A.; Carrillo, Ismael; Chaplin, William J.; Elsworth,
Yvonne; Famaey, Benoit; Gerhard, Ortwin; Jofre, Paula; Just, Andreas;
Mathur, Savita; Miglio, Andrea; Minchev, Ivan; Monari, Giacomo; Mosser,
Benoit; Ritter, Andreas; Rodrigues, Thaise S.; Scholz, Ralf-Dieter;
Sharma, Sanjib; Sysoliatina, Kseniia; RAVE Collaboration
2020AJ....160...83S Altcode: 2020arXiv200204512S
We present part 2 of the sixth and final Data Release (DR6) of the
Radial Velocity Experiment (RAVE), a magnitude-limited ( $9\lt I\lt 12$
) spectroscopic survey of Galactic stars randomly selected in Earth's
southern hemisphere. The RAVE medium-resolution spectra (R ∼ 7500)
cover the Ca triplet region (8410-8795 Å) and span the complete time
frame from the start of RAVE observations on 2003 April 12 to their
completion on 2013 April 4. In the second of two publications, we
present the data products derived from 518,387 observations of 451,783
unique stars using a suite of advanced reduction pipelines focusing on
stellar atmospheric parameters, in particular purely spectroscopically
derived stellar atmospheric parameters ( ${T}_{\mathrm{eff}}$ ,
$\mathrm{log}g$ , and the overall metallicity), enhanced stellar
atmospheric parameters inferred via a Bayesian pipeline using Gaia DR2
astrometric priors, and asteroseismically calibrated stellar atmospheric
parameters for giant stars based on asteroseismic observations for
699 K2 stars. In addition, we provide abundances of the elements Fe,
Al, and Ni, as well as an overall [α/Fe] ratio obtained using a
new pipeline based on the GAUGUIN optimization method that is able
to deal with variable signal-to-noise ratios. The RAVE DR6 catalogs
are cross-matched with relevant astrometric and photometric catalogs,
and are complemented by orbital parameters and effective temperatures
based on the infrared flux method. The data can be accessed via the
RAVE website (http://rave-survey.org) or the Vizier database.
---------------------------------------------------------
Title: The 16th Data Release of the Sloan Digital Sky Surveys:
First Release from the APOGEE-2 Southern Survey and Full Release of
eBOSS Spectra
Authors: Ahumada, Romina; Prieto, Carlos Allende; Almeida, Andrés;
Anders, Friedrich; Anderson, Scott F.; Andrews, Brett H.; Anguiano,
Borja; Arcodia, Riccardo; Armengaud, Eric; Aubert, Marie; Avila,
Santiago; Avila-Reese, Vladimir; Badenes, Carles; Balland, Christophe;
Barger, Kat; Barrera-Ballesteros, Jorge K.; Basu, Sarbani; Bautista,
Julian; Beaton, Rachael L.; Beers, Timothy C.; Benavides, B. Izamar
T.; Bender, Chad F.; Bernardi, Mariangela; Bershady, Matthew; Beutler,
Florian; Bidin, Christian Moni; Bird, Jonathan; Bizyaev, Dmitry; Blanc,
Guillermo A.; Blanton, Michael R.; Boquien, Médéric; Borissova,
Jura; Bovy, Jo; Brandt, W. N.; Brinkmann, Jonathan; Brownstein, Joel
R.; Bundy, Kevin; Bureau, Martin; Burgasser, Adam; Burtin, Etienne;
Cano-Díaz, Mariana; Capasso, Raffaella; Cappellari, Michele;
Carrera, Ricardo; Chabanier, Solène; Chaplin, William; Chapman,
Michael; Cherinka, Brian; Chiappini, Cristina; Doohyun Choi, Peter;
Chojnowski, S. Drew; Chung, Haeun; Clerc, Nicolas; Coffey, Damien;
Comerford, Julia M.; Comparat, Johan; da Costa, Luiz; Cousinou,
Marie-Claude; Covey, Kevin; Crane, Jeffrey D.; Cunha, Katia; Ilha,
Gabriele da Silva; Dai, Yu Sophia; Damsted, Sanna B.; Darling,
Jeremy; Davidson, James W., Jr.; Davies, Roger; Dawson, Kyle; De,
Nikhil; de la Macorra, Axel; De Lee, Nathan; Queiroz, Anna Bárbara
de Andrade; Deconto Machado, Alice; de la Torre, Sylvain; Dell'Agli,
Flavia; du Mas des Bourboux, Hélion; Diamond-Stanic, Aleksandar M.;
Dillon, Sean; Donor, John; Drory, Niv; Duckworth, Chris; Dwelly,
Tom; Ebelke, Garrett; Eftekharzadeh, Sarah; Davis Eigenbrot, Arthur;
Elsworth, Yvonne P.; Eracleous, Mike; Erfanianfar, Ghazaleh; Escoffier,
Stephanie; Fan, Xiaohui; Farr, Emily; Fernández-Trincado, José G.;
Feuillet, Diane; Finoguenov, Alexis; Fofie, Patricia; Fraser-McKelvie,
Amelia; Frinchaboy, Peter M.; Fromenteau, Sebastien; Fu, Hai; Galbany,
Lluís; Garcia, Rafael A.; García-Hernández, D. A.; Oehmichen,
Luis Alberto Garma; Ge, Junqiang; Maia, Marcio Antonio Geimba;
Geisler, Doug; Gelfand, Joseph; Goddy, Julian; Gonzalez-Perez,
Violeta; Grabowski, Kathleen; Green, Paul; Grier, Catherine J.; Guo,
Hong; Guy, Julien; Harding, Paul; Hasselquist, Sten; Hawken, Adam
James; Hayes, Christian R.; Hearty, Fred; Hekker, S.; Hogg, David
W.; Holtzman, Jon A.; Horta, Danny; Hou, Jiamin; Hsieh, Bau-Ching;
Huber, Daniel; Hunt, Jason A. S.; Chitham, J. Ider; Imig, Julie;
Jaber, Mariana; Angel, Camilo Eduardo Jimenez; Johnson, Jennifer A.;
Jones, Amy M.; Jönsson, Henrik; Jullo, Eric; Kim, Yerim; Kinemuchi,
Karen; Kirkpatrick, Charles C., IV; Kite, George W.; Klaene, Mark;
Kneib, Jean-Paul; Kollmeier, Juna A.; Kong, Hui; Kounkel, Marina;
Krishnarao, Dhanesh; Lacerna, Ivan; Lan, Ting-Wen; Lane, Richard R.;
Law, David R.; Le Goff, Jean-Marc; Leung, Henry W.; Lewis, Hannah; Li,
Cheng; Lian, Jianhui; Lin, Lihwai; Long, Dan; Longa-Peña, Penélope;
Lundgren, Britt; Lyke, Brad W.; Ted Mackereth, J.; MacLeod, Chelsea
L.; Majewski, Steven R.; Manchado, Arturo; Maraston, Claudia; Martini,
Paul; Masseron, Thomas; Masters, Karen L.; Mathur, Savita; McDermid,
Richard M.; Merloni, Andrea; Merrifield, Michael; Mészáros, Szabolcs;
Miglio, Andrea; Minniti, Dante; Minsley, Rebecca; Miyaji, Takamitsu;
Mohammad, Faizan Gohar; Mosser, Benoit; Mueller, Eva-Maria; Muna,
Demitri; Muñoz-Gutiérrez, Andrea; Myers, Adam D.; Nadathur,
Seshadri; Nair, Preethi; Nandra, Kirpal; do Nascimento, Janaina
Correa; Nevin, Rebecca Jean; Newman, Jeffrey A.; Nidever, David L.;
Nitschelm, Christian; Noterdaeme, Pasquier; O'Connell, Julia E.;
Olmstead, Matthew D.; Oravetz, Daniel; Oravetz, Audrey; Osorio,
Yeisson; Pace, Zachary J.; Padilla, Nelson; Palanque-Delabrouille,
Nathalie; Palicio, Pedro A.; Pan, Hsi-An; Pan, Kaike; Parker, James;
Paviot, Romain; Peirani, Sebastien; Ramŕez, Karla Peña; Penny,
Samantha; Percival, Will J.; Perez-Fournon, Ismael; Pérez-Ràfols,
Ignasi; Petitjean, Patrick; Pieri, Matthew M.; Pinsonneault, Marc;
Poovelil, Vijith Jacob; Povick, Joshua Tyler; Prakash, Abhishek;
Price-Whelan, Adrian M.; Raddick, M. Jordan; Raichoor, Anand; Ray,
Amy; Rembold, Sandro Barboza; Rezaie, Mehdi; Riffel, Rogemar A.;
Riffel, Rogério; Rix, Hans-Walter; Robin, Annie C.; Roman-Lopes,
A.; Román-Zúñiga, Carlos; Rose, Benjamin; Ross, Ashley J.; Rossi,
Graziano; Rowlands, Kate; Rubin, Kate H. R.; Salvato, Mara; Sánchez,
Ariel G.; Sánchez-Menguiano, Laura; Sánchez-Gallego, José R.;
Sayres, Conor; Schaefer, Adam; Schiavon, Ricardo P.; Schimoia,
Jaderson S.; Schlafly, Edward; Schlegel, David; Schneider, Donald P.;
Schultheis, Mathias; Schwope, Axel; Seo, Hee-Jong; Serenelli, Aldo;
Shafieloo, Arman; Shamsi, Shoaib Jamal; Shao, Zhengyi; Shen, Shiyin;
Shetrone, Matthew; Shirley, Raphael; Aguirre, Víctor Silva; Simon,
Joshua D.; Skrutskie, M. F.; Slosar, Anže; Smethurst, Rebecca;
Sobeck, Jennifer; Sodi, Bernardo Cervantes; Souto, Diogo; Stark,
David V.; Stassun, Keivan G.; Steinmetz, Matthias; Stello, Dennis;
Stermer, Julianna; Storchi-Bergmann, Thaisa; Streblyanska, Alina;
Stringfellow, Guy S.; Stutz, Amelia; Suárez, Genaro; Sun, Jing;
Taghizadeh-Popp, Manuchehr; Talbot, Michael S.; Tayar, Jamie; Thakar,
Aniruddha R.; Theriault, Riley; Thomas, Daniel; Thomas, Zak C.;
Tinker, Jeremy; Tojeiro, Rita; Toledo, Hector Hernandez; Tremonti,
Christy A.; Troup, Nicholas W.; Tuttle, Sarah; Unda-Sanzana, Eduardo;
Valentini, Marica; Vargas-González, Jaime; Vargas-Magaña, Mariana;
Vázquez-Mata, Jose Antonio; Vivek, M.; Wake, David; Wang, Yuting;
Weaver, Benjamin Alan; Weijmans, Anne-Marie; Wild, Vivienne; Wilson,
John C.; Wilson, Robert F.; Wolthuis, Nathan; Wood-Vasey, W. M.; Yan,
Renbin; Yang, Meng; Yèche, Christophe; Zamora, Olga; Zarrouk, Pauline;
Zasowski, Gail; Zhang, Kai; Zhao, Cheng; Zhao, Gongbo; Zheng, Zheng;
Zheng, Zheng; Zhu, Guangtun; Zou, Hu
2020ApJS..249....3A Altcode: 2019arXiv191202905A
This paper documents the 16th data release (DR16) from the Sloan
Digital Sky Surveys (SDSS), the fourth and penultimate from the
fourth phase (SDSS-IV). This is the first release of data from the
Southern Hemisphere survey of the Apache Point Observatory Galactic
Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also
included. DR16 is also notable as the final data release for the main
cosmological program of the Extended Baryon Oscillation Spectroscopic
Survey (eBOSS), and all raw and reduced spectra from that project are
released here. DR16 also includes all the data from the Time Domain
Spectroscopic Survey and new data from the SPectroscopic IDentification
of ERosita Survey programs, both of which were co-observed on eBOSS
plates. DR16 has no new data from the Mapping Nearby Galaxies at
Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library
"MaStar"). We also preview future SDSS-V operations (due to start in
2020), and summarize plans for the final SDSS-IV data release (DR17).
---------------------------------------------------------
Title: TESS Asteroseismic Analysis of the Known Exoplanet Host Star
HD 222076
Authors: Jiang, Chen; Bedding, Timothy R.; Stassun, Keivan G.; Veras,
Dimitri; Corsaro, Enrico; Buzasi, Derek L.; Mikołajczyk, Przemysław;
Zhang, Qian-sheng; Ou, Jian-wen; Campante, Tiago L.; Rodrigues,
Thaíise S.; Nsamba, Benard; Bossini, Diego; Kane, Stephen R.; Ong,
Jia Mian Joel; Yıldız, Mutlu; Çelik Orhan, Zeynep; Örtel, Sibel;
Wu, Tao; Zhang, Xinyi; Li, Tanda; Basu, Sarbani; Cunha, Margarida S.;
Christensen-Dalsgaard, Jørgen; Chaplin, William J.
2020ApJ...896...65J Altcode: 2020arXiv200500272J
The Transiting Exoplanet Survey Satellite (TESS) is an all-sky
survey mission aiming to search for exoplanets that transit bright
stars. The high-quality photometric data of TESS are excellent
for the asteroseismic study of solar-like stars. In this work, we
present an asteroseismic analysis of the red-giant star HD 222076
hosting a long-period (2.4 yr) giant planet discovered through radial
velocities. Solar-like oscillations of HD 222076 are detected around
203 μHz by TESS for the first time. Asteroseismic modeling, using
global asteroseismic parameters as inputs, yields a determination
of the stellar mass ( ${M}_{\star }=1.12\pm 0.12\,{M}_{\odot }$ ),
radius ( ${R}_{\star }=4.34\pm 0.21\,{R}_{\odot }$ ), and age (7.4 ±
2.7 Gyr), with precisions greatly improved from previous studies. The
period spacing of the dipolar mixed modes extracted from the observed
power spectrum reveals that the star is on the red-giant branch burning
hydrogen in a shell surrounding the core. We find that the planet will
not escape the tidal pull of the star and will be engulfed into it
within about 800 Myr, before the tip of the red-giant branch is reached.
---------------------------------------------------------
Title: VizieR Online Data Catalog: APOGEE-2 data from DR16 (Majewski+,
2017)
Authors: Majewski, S. R.; Schiavon, R. P.; Frinchaboy, P. M.;
Allende Prieto, C.; Barkhouser, R.; Bizyaev, D.; Blank, B.; Brunner,
S.; Burton, A.; Carrera, R.; Chojnowski, S. D.; Cunha, K.; Epstein,
C.; Fitzgerald, G.; Garcia Perez, A. E.; Hearty, F. R.; Henderson,
C.; Holtzman, J. A.; Johnson, J. A.; Lam, C. R.; Lawler, J. E.;
Maseman, P.; Meszaros, S.; Nelson, M.; Nguyen, D. C.; Nidever, D. L.;
Pinsonneault, M.; Shetrone, M.; Smee, S.; Smith, V. V.; Stolberg, T.;
Skrutskie, M. F.; Walker, E.; Wilson, J. C.; Zasowski, G.; Anders,
F.; Basu, S.; Beland, S.; Blanton, M. R.; Bovy, J.; Brownstein, J. R.;
Carlberg, J.; Chaplin, W.; Chiappini, C.; Eisenstein, D. J.; Elsworth,
Y.; Feuillet, D.; Fleming, S. W.; Galbraith-Frew, J.; Garcia, R. A.;
Garcia-Hernandez, D. A.; Gillespie, B. A.; Girardi, L.; Gunn, J. E.;
Hasselquist, S.; Hayden, M. R.; Hekker, S.; Ivans, I.; Kinemuchi,
K.; Klaene, M.; Mahadevan, S.; Mathur, S.; Mosser, B.; Muna, D.;
Munn, J. A.; Nichol, R. C.; O'Connell, R. W.; Parejko, J. K.; Robin,
A. C.; Rocha-Pinto, H.; Schultheis, M.; Serenelli, A. M.; Shane, N.;
Silva Aguirre, E. V.; Sob Eck, J. S.; Thompson, B.; Troup, N. W.;
Weinberg, D. H.; Zamora, O.
2020yCat..51540094M Altcode:
The second generation of the Apache Point Observatory Galactic Evolution
Experiment (APOGEE-2) observes the "archaeological" record embedded
in hundreds of thousands of stars to explore the assembly history and
evolution of the Milky Way Galaxy. <P />APOGEE-2 maps the dynamical
and chemical patterns of Milky Way stars with data from the 1-meter
NMSU Telescope and the 2.5-meter Sloan Foundation Telescope at the
Apache Point Observatory in New Mexico (APOGEE-2N), and the 2.5-meter
du Pont Telescope at Las Campanas Observatory in Chile (APOGEE-2S). <P
/>(2 data files).
---------------------------------------------------------
Title: VizieR Online Data Catalog: APOGEE-2 data from DR16 (Majewski+,
2017)
Authors: Majewski, S. R.; Schiavon, R. P.; Frinchaboy, P. M.;
Allende Prieto, C.; Barkhouser, R.; Bizyaev, D.; Blank, B.; Brunner,
S.; Burton, A.; Carrera, R.; Chojnowski, S. D.; Cunha, K.; Epstein,
C.; Fitzgerald, G.; Garcia Perez, A. E.; Hearty, F. R.; Henderson,
C.; Holtzman, J. A.; Johnson, J. A.; Lam, C. R.; Lawler, J. E.;
Maseman, P.; Meszaros, S.; Nelson, M.; Nguyen, D. C.; Nidever, D. L.;
Pinsonneault, M.; Shetrone, M.; Smee, S.; Smith, V. V.; Stolberg, T.;
Skrutskie, M. F.; Walker, E.; Wilson, J. C.; Zasowski, G.; Anders,
F.; Basu, S.; Beland, S.; Blanton, M. R.; Bovy, J.; Brownstein, J. R.;
Carlberg, J.; Chaplin, W.; Chiappini, C.; Eisenstein, D. J.; Elsworth,
Y.; Feuillet, D.; Fleming, S. W.; Galbraith-Frew, J.; Garcia, R. A.;
Garcia-Hernandez, D. A.; Gillespie, B. A.; Girardi, L.; Gunn, J. E.;
Hasselquist, S.; Hayden, M. R.; Hekker, S.; Ivans, I.; Kinemuchi,
K.; Klaene, M.; Mahadevan, S.; Mathur, S.; Mosser, B.; Muna, D.;
Munn, J. A.; Nichol, R. C.; O'Connell, R. W.; Parejko, J. K.; Robin,
A. C.; Rocha-Pinto, H.; Schultheis, M.; Serenelli, A. M.; Shane, N.;
Silva Aguirre, E. V.; Sob Eck, J. S.; Thompson, B.; Troup, N. W.;
Weinberg, D. H.; Zamora, O.
2020yCat.3284....0M Altcode:
The second generation of the Apache Point Observatory Galactic Evolution
Experiment (APOGEE-2) observes the "archaeological" record embedded
in hundreds of thousands of stars to explore the assembly history and
evolution of the Milky Way Galaxy. <P />APOGEE-2 maps the dynamical
and chemical patterns of Milky Way stars with data from the 1-meter
NMSU Telescope and the 2.5-meter Sloan Foundation Telescope at the
Apache Point Observatory in New Mexico (APOGEE-2N), and the 2.5-meter
du Pont Telescope at Las Campanas Observatory in Chile (APOGEE-2S). <P
/>(2 data files).
---------------------------------------------------------
Title: Very regular high-frequency pulsation modes in young
intermediate-mass stars
Authors: Bedding, Timothy R.; Murphy, Simon J.; Hey, Daniel R.; Huber,
Daniel; Li, Tanda; Smalley, Barry; Stello, Dennis; White, Timothy R.;
Ball, Warrick H.; Chaplin, William J.; Colman, Isabel L.; Fuller,
Jim; Gaidos, Eric; Harbeck, Daniel R.; Hermes, J. J.; Holdsworth,
Daniel L.; Li, Gang; Li, Yaguang; Mann, Andrew W.; Reese, Daniel R.;
Sekaran, Sanjay; Yu, Jie; Antoci, Victoria; Bergmann, Christoph;
Brown, Timothy M.; Howard, Andrew W.; Ireland, Michael J.; Isaacson,
Howard; Jenkins, Jon M.; Kjeldsen, Hans; McCully, Curtis; Rabus,
Markus; Rains, Adam D.; Ricker, George R.; Tinney, Christopher G.;
Vanderspek, Roland K.
2020Natur.581..147B Altcode: 2020arXiv200506157B
Asteroseismology probes the internal structures of stars by using
their natural pulsation frequencies<SUP>1</SUP>. It relies on
identifying sequences of pulsation modes that can be compared with
theoretical models, which has been done successfully for many classes
of pulsators, including low-mass solar-type stars<SUP>2</SUP>,
red giants<SUP>3</SUP>, high-mass stars<SUP>4</SUP> and white
dwarfs<SUP>5</SUP>. However, a large group of pulsating stars of
intermediate mass—the so-called δ Scuti stars—have rich pulsation
spectra for which systematic mode identification has not hitherto been
possible<SUP>6,7</SUP>. This arises because only a seemingly random
subset of possible modes are excited and because rapid rotation tends
to spoil regular patterns<SUP>8-10</SUP>. Here we report the detection
of remarkably regular sequences of high-frequency pulsation modes in
60 intermediate-mass main-sequence stars, which enables definitive mode
identification. The space motions of some of these stars indicate that
they are members of known associations of young stars, as confirmed
by modelling of their pulsation spectra.
---------------------------------------------------------
Title: Measurement of Atmospheric Scintillation during a Period of
Saharan Dust (Calima) at Observatorio del Teide, Iz∼ana, Tenerife,
and the Impact on Photometric Exposure Times
Authors: Hale, S. J.; Chaplin, W. J.; Davies, G. R.; Elsworth, Y. P.;
Howe, R.; Pallé, P. L.
2020PASP..132c4501H Altcode:
We present scintillation noise profiles captured at the
Observatorio del Teide, Izaña, Tenerife, over a one-week period
in 2017 September. Contemporaneous data from the Birmingham Solar
Oscillations Network (BiSON) and the Stellar Activity (STELLA)
robotic telescopes provides estimates of daily atmospheric extinction
allowing the scintillation noise to be placed within the context of
overall atmospheric conditions. We discuss the results both in terms
of the impact on BiSON spectrophotometer design, and for astronomical
observations more generally. We find that scintillation noise power
reduces by half at about 5 Hz, and is reduced to one tenth between
20 and 30 Hz even during periods of mild Calima, where visibility is
reduced due to high concentrations of mineral dust in the atmosphere. We
show that the common accepted exposure time of <10 ms for limiting
the effect of scintillation noise in ground based photometry may be
increased, and that depending on the application there may be little
benefit to achieving exposure times shorter than 50 ms, relaxing
constraints on detector gain and bandwidth.
---------------------------------------------------------
Title: Solar cycle variation of ν<SUB>max</SUB> in helioseismic
data and its implications for asteroseismology
Authors: Howe, Rachel; Chaplin, William J.; Basu, Sarbani; Ball,
Warrick H.; Davies, Guy R.; Elsworth, Yvonne; Hale, Steven J.; Miglio,
Andrea; Nielsen, Martin Bo; Viani, Lucas S.
2020MNRAS.493L..49H Altcode: 2020MNRAS.tmpL...4H; 2020arXiv200110949C; 2020arXiv200110949H
The frequency, ν<SUB>max</SUB>, at which the envelope of pulsation
power peaks for solar-like oscillators is an important quantity in
asteroseismology. We measure ν<SUB>max</SUB> for the Sun using 25
yr of Sun-as-a-star Doppler velocity observations with the Birmingham
Solar-Oscillations Network (BiSON), by fitting a simple model to binned
power spectra of the data. We also apply the fit to Sun-as-a-star
Doppler velocity data from Global Oscillation Network Group and Global
Oscillations at Low Frequency, and photometry data from VIRGO/SPM
on the ESA/NASA SOHO spacecraft. We discover a weak but nevertheless
significant positive correlation of the solar ν<SUB>max</SUB> with
solar activity. The uncovered shift between low and high activity,
of ∼eq 25 μ Hz, translates to an uncertainty of 0.8 per cent in
radius and 2.4 per cent in mass, based on direct use of asteroseismic
scaling relations calibrated to the Sun. The mean ν<SUB>max</SUB>
in the different data sets is also clearly offset in frequency. Our
results flag the need for caution when using ν<SUB>max</SUB> in
asteroseismology.
---------------------------------------------------------
Title: Modelling stochastic signatures in classical pulsators
Authors: Avelino, P. P.; Cunha, M. S.; Chaplin, W. J.
2020MNRAS.492.4477A Altcode: 2020arXiv200104558A; 2020MNRAS.tmp..118A
We consider the impact of stochastic perturbations on otherwise
coherent oscillations of classical pulsators. The resulting dynamics
are modelled by a driven damped harmonic oscillator subject to
either an external or an internal forcing and white noise velocity
perturbations. We characterize the phase and relative amplitude
variations using analytical and numerical tools. When the forcing is
internal the phase variation displays a random walk behaviour and a red
noise power spectrum with a ragged erratic appearance. We determine
the dependence of the root mean square phase and relative amplitude
variations (σ<SUB>Δφ</SUB> and σ<SUB>ΔA/A</SUB>, respectively)
on the amplitude of the stochastic perturbations, the damping constant
η, and the total observation time t<SUB>obs</SUB> for this case,
under the assumption that the relative amplitude variations remain
small, showing that σ<SUB>Δφ</SUB> increases with t_obs^{1/2}
becoming much larger than σ<SUB>ΔA/A</SUB> for t<SUB>obs</SUB>
≫ η<SUP>-1</SUP>. In the case of an external forcing the phase and
relative amplitude variations remain of the same order, independent
of the observing time. In the case of an internal forcing, we find
that σ<SUB>Δφ</SUB> does not depend on η. Hence, the damping time
cannot be inferred from fitting the power of the signal, as done for
solar-like pulsators, but the amplitude of the stochastic perturbations
may be constrained from the observations. Our results imply that,
given sufficient time, the variation of the phase associated with the
stochastic perturbations in internally driven classical pulsators will
become sufficiently large to be probed observationally.
---------------------------------------------------------
Title: Detection and Characterization of Oscillating Red Giants:
First Results from the TESS Satellite
Authors: Silva Aguirre, Víctor; Stello, Dennis; Stokholm, Amalie;
Mosumgaard, Jakob R.; Ball, Warrick H.; Basu, Sarbani; Bossini, Diego;
Bugnet, Lisa; Buzasi, Derek; Campante, Tiago L.; Carboneau, Lindsey;
Chaplin, William J.; Corsaro, Enrico; Davies, Guy R.; Elsworth, Yvonne;
García, Rafael A.; Gaulme, Patrick; Hall, Oliver J.; Handberg,
Rasmus; Hon, Marc; Kallinger, Thomas; Kang, Liu; Lund, Mikkel N.;
Mathur, Savita; Mints, Alexey; Mosser, Benoit; Çelik Orhan, Zeynep;
Rodrigues, Thaíse S.; Vrard, Mathieu; Yıldız, Mutlu; Zinn, Joel C.;
Örtel, Sibel; Beck, Paul G.; Bell, Keaton J.; Guo, Zhao; Jiang, Chen;
Kuszlewicz, James S.; Kuehn, Charles A.; Li, Tanda; Lundkvist, Mia S.;
Pinsonneault, Marc; Tayar, Jamie; Cunha, Margarida S.; Hekker, Saskia;
Huber, Daniel; Miglio, Andrea; F. G. Monteiro, Mario J. P.; Slumstrup,
Ditte; Winther, Mark L.; Angelou, George; Benomar, Othman; Bódi,
Attila; De Moura, Bruno L.; Deheuvels, Sébastien; Derekas, Aliz; Di
Mauro, Maria Pia; Dupret, Marc-Antoine; Jiménez, Antonio; Lebreton,
Yveline; Matthews, Jaymie; Nardetto, Nicolas; do Nascimento, Jose D.,
Jr.; Pereira, Filipe; Rodríguez Díaz, Luisa F.; Serenelli, Aldo M.;
Spitoni, Emanuele; Stonkutė, Edita; Suárez, Juan Carlos; Szabó,
Robert; Van Eylen, Vincent; Ventura, Rita; Verma, Kuldeep; Weiss,
Achim; Wu, Tao; Barclay, Thomas; Christensen-Dalsgaard, Jørgen;
Jenkins, Jon M.; Kjeldsen, Hans; Ricker, George R.; Seager, Sara;
Vanderspek, Roland
2020ApJ...889L..34S Altcode: 2019arXiv191207604S; 2020ApJ...889L..34A
Since the onset of the "space revolution" of high-precision high-cadence
photometry, asteroseismology has been demonstrated as a powerful tool
for informing Galactic archeology investigations. The launch of the
NASA Transiting Exoplanet Survey Satellite (TESS) mission has enabled
seismic-based inferences to go full sky—providing a clear advantage
for large ensemble studies of the different Milky Way components. Here
we demonstrate its potential for investigating the Galaxy by carrying
out the first asteroseismic ensemble study of red giant stars observed
by TESS. We use a sample of 25 stars for which we measure their
global asteroseimic observables and estimate their fundamental stellar
properties, such as radius, mass, and age. Significant improvements
are seen in the uncertainties of our estimates when combining seismic
observables from TESS with astrometric measurements from the Gaia
mission compared to when the seismology and astrometry are applied
separately. Specifically, when combined we show that stellar radii can
be determined to a precision of a few percent, masses to 5%-10%, and
ages to the 20% level. This is comparable to the precision typically
obtained using end-of-mission Kepler data.
---------------------------------------------------------
Title: Modelling the response of potassium vapour in resonance
scattering spectroscopy
Authors: Hale, S J; Chaplin, W J; Davies, G R; Elsworth, Y P
2020arXiv200204546H Altcode:
Resonance scattering techniques are often used to study the properties
of atoms and molecules. The Birmingham Solar Oscillations Network
(BiSON) makes use of Resonance Scattering Spectroscopy by applying
the known properties of potassium vapour to achieve ultra-precise
Doppler velocity observations of oscillations of the Sun. We present
a model of the resonance scattering properties of potassium vapour
which can be used to determine the ideal operating vapour temperature
and detector parameters within a spectrophotometer. The model is
validated against a typical BiSON vapour cell using a tunable diode
laser, where the model is fitted to observed absorption profiles at
a range of temperatures. Finally we demonstrate using the model to
determine the effects of varying scattering detector aperture size,
and vapour temperature, and again validate against observed scattering
profiles. Such information is essential when designing the next
generation of BiSON spectrophotometers (BiSON:NG), where the aim is
to make use of off-the-shelf components to simplify and miniaturise
the instrumentation as much as practical.
---------------------------------------------------------
Title: Michael Thompson's Legacy in Solar and Stellar Physics
Authors: Chaplin, William J.
2020ASSP...57....3C Altcode:
Professor Michael J. Thompson died on 15 October 2018. Michael made
long-lasting contributions to the international research community as
both a research pioneer in the field of solar and stellar astrophysics
and as an administrator who held major leadership positions in the UK
and the USA. In this review we summarize his outstanding contributions
to research.
---------------------------------------------------------
Title: Age dating of an early Milky Way merger via asteroseismology
of the naked-eye star ν Indi
Authors: Chaplin, William J.; Serenelli, Aldo M.; Miglio, Andrea;
Morel, Thierry; Mackereth, J. Ted; Vincenzo, Fiorenzo; Kjeldsen, Hans;
Basu, Sarbani; Ball, Warrick H.; Stokholm, Amalie; Verma, Kuldeep;
Mosumgaard, Jakob Rørsted; Silva Aguirre, Victor; Mazumdar, Anwesh;
Ranadive, Pritesh; Antia, H. M.; Lebreton, Yveline; Ong, Joel;
Appourchaux, Thierry; Bedding, Timothy R.; Christensen-Dalsgaard,
Jørgen; Creevey, Orlagh; García, Rafael A.; Handberg, Rasmus; Huber,
Daniel; Kawaler, Steven D.; Lund, Mikkel N.; Metcalfe, Travis S.;
Stassun, Keivan G.; Bazot, Michäel; Beck, Paul G.; Bell, Keaton J.;
Bergemann, Maria; Buzasi, Derek L.; Benomar, Othman; Bossini, Diego;
Bugnet, Lisa; Campante, Tiago L.; Orhan, Zeynep çelik; Corsaro,
Enrico; González-Cuesta, Lucía; Davies, Guy R.; Di Mauro, Maria
Pia; Egeland, Ricky; Elsworth, Yvonne P.; Gaulme, Patrick; Ghasemi,
Hamed; Guo, Zhao; Hall, Oliver J.; Hasanzadeh, Amir; Hekker, Saskia;
Howe, Rachel; Jenkins, Jon M.; Jiménez, Antonio; Kiefer, René;
Kuszlewicz, James S.; Kallinger, Thomas; Latham, David W.; Lundkvist,
Mia S.; Mathur, Savita; Montalbán, Josefina; Mosser, Benoit; Bedón,
Andres Moya; Nielsen, Martin Bo; Örtel, Sibel; Rendle, Ben M.; Ricker,
George R.; Rodrigues, Thaíse S.; Roxburgh, Ian W.; Safari, Hossein;
Schofield, Mathew; Seager, Sara; Smalley, Barry; Stello, Dennis;
Szabó, Róbert; Tayar, Jamie; Themeßl, Nathalie; Thomas, Alexandra
E. L.; Vanderspek, Roland K.; van Rossem, Walter E.; Vrard, Mathieu;
Weiss, Achim; White, Timothy R.; Winn, Joshua N.; Yıldız, Mutlu
2020NatAs...4..382C Altcode: 2020NatAs.tmp....7C; 2020arXiv200104653C
Over the course of its history, the Milky Way has ingested multiple
smaller satellite galaxies<SUP>1</SUP>. Although these accreted
stellar populations can be forensically identified as kinematically
distinct structures within the Galaxy, it is difficult in general
to date precisely the age at which any one merger occurred. Recent
results have revealed a population of stars that were accreted via the
collision of a dwarf galaxy, called Gaia-Enceladus<SUP>1</SUP>, leading
to substantial pollution of the chemical and dynamical properties of
the Milky Way. Here we identify the very bright, naked-eye star ν
Indi as an indicator of the age of the early in situ population of
the Galaxy. We combine asteroseismic, spectroscopic, astrometric and
kinematic observations to show that this metal-poor, alpha-element-rich
star was an indigenous member of the halo, and we measure its age
to be 11.0 ±0.7 ? (stat) ±0.8 ? (sys) billion years. The star
bears hallmarks consistent with having been kinematically heated by
the Gaia-Enceladus collision. Its age implies that the earliest the
merger could have begun was 11.6 and 13.2 billion years ago, at 68%
and 95% confidence, respectively. Computations based on hierarchical
cosmological models slightly reduce the above limits.
---------------------------------------------------------
Title: The K2 Galactic Caps Project - going beyond the Kepler field
and ageing the Galactic disc
Authors: Rendle, B. M.; Miglio, A.; Chiappini, C.; Valentini, M.;
Davies, G. R.; Mosser, B.; Elsworth, Y.; García, R. A.; Mathur, S.;
Jofré, P.; Worley, C. C.; Casagrande, L.; Girardi, L.; Lund, M. N.;
Feuillet, D. K.; Gavel, A.; Magrini, L.; Khan, S.; Rodrigues, T. S.;
Johnson, J. A.; Cunha, K.; Lane, R. L.; Nitschelm, C.; Chaplin, W. J.
2019MNRAS.490.4465R Altcode: 2019MNRAS.tmp.2643R; 2019arXiv190607489R
Analyses of data from spectroscopic and astrometric surveys have led
to conflicting results concerning the vertical characteristics of
the Milky Way. Ages are often used to provide clarity, but typical
uncertainties of >40 per cent from photometry restrict the validity
of the inferences made. Using the Kepler APOKASC sample for context,
we explore the global population trends of two K2 campaign fields
(3 and 6), which extend further vertically out of the Galactic plane
than APOKASC. We analyse the properties of red giant stars utilizing
three asteroseismic data analysis methods to cross-check and validate
detections. The Bayesian inference tool PARAM is used to determine
the stellar masses, radii, and ages. Evidence of a pronounced red
giant branch bump and an [α/Fe] dependence on the position of the red
clump is observed from the K2 fields radius distribution. Two peaks
in the age distribution centred at ∼5 and ∼12 Gyr are found using
a sample with σ<SUB>age</SUB> < 35 per cent. In comparison with
Kepler, we find the older peak to be more prominent for K2. This age
bimodality is also observed based on a chemical selection of low-[α/Fe]
(≤0.1) and high-[α/Fe] (>0.1) stars. As a function of vertical
distance from the Galactic mid-plane (|Z|), the age distribution shows
a transition from a young to old stellar population with increasing
|Z| for the K2 fields. Further coverage of campaign targets with
high-resolution spectroscopy is required to increase the yield of
precise ages achievable with asteroseismology.
---------------------------------------------------------
Title: Measurement of atmospheric scintillation during a period of
Saharan dust (Calima) at Observatorio del Teide, Izaña, Tenerife,
and the impact on photometric exposure times
Authors: Hale, S J; Chaplin, W J; Davies, G R; Elsworth, Y P; Howe,
R; Pallé, P L
2019arXiv191212237H Altcode:
We present scintillation noise profiles captured at the Observatorio
del Teide, Izaña, Tenerife, over a one-week period in September
2017. Contemporaneous data from the Birmingham Solar Oscillations
Network (BiSON) and the Stellar Activity (STELLA) robotic telescopes
provides estimates of daily atmospheric extinction allowing the
scintillation noise to be placed within the context of overall
atmospheric conditions. We discuss the results both in terms of
the impact on BiSON spectrophotometer design, and for astronomical
observations more generally. We find that scintillation noise power
reduces by half at about~\SI{5}{\hertz}, and is reduced to one tenth
between~\SIrange{20}{30}{\hertz} even during periods of mild Calima,
where visibility is reduced due to high concentrations of mineral
dust in the atmosphere. We show that the common accepted exposure time
of~\SI{<10}{\milli\second} for limiting the effect of scintillation
noise in ground based photometry may be increased, and that depending
on the application there may be little benefit to achieving exposure
times shorter than~\SI{50}{\milli\second}, relaxing constraints on
detector gain and bandwidth.
---------------------------------------------------------
Title: Asteroseismology of the Multiplanet System K2-93
Authors: Lund, Mikkel N.; Knudstrup, Emil; Silva Aguirre, Víctor;
Basu, Sarbani; Chontos, Ashley; Von Essen, Carolina; Chaplin, William
J.; Bieryla, Allyson; Casagrande, Luca; Vanderburg, Andrew; Huber,
Daniel; Kane, Stephen R.; Albrecht, Simon; Latham, David W.; Davies,
Guy R.; Becker, Juliette C.; Rodriguez, Joseph E.
2019AJ....158..248L Altcode: 2019arXiv191107519L
We revisit the analysis of the bright multiplanet system K2-93,
discovered with data taken by the K2 mission. This system contains five
identified planets ranging in size from sub-Neptune to Jupiter size. The
K2 data available at the discovery of the system only showed single
transits for the three outer planets, which allowed weak constraints to
be put on their periods. As these planets are interesting candidates for
future atmospheric studies, a better characterization of the host star
and tighter constraints on their orbital periods are essential. Using
new data from the K2 mission taken after the discovery of the system,
we perform an asteroseismic characterization of the host star. We are
able to place strong constraints on the stellar parameters and obtain
a value for the stellar mass of {1.22}<SUB>-0.02</SUB><SUP>+0.03</SUP>
{M}<SUB>⊙ </SUB>, a stellar radius of 1.30 ± 0.01 R <SUB>⊙</SUB>,
and an age of {2.07}<SUB>-0.27</SUB><SUP>+0.36</SUP> Gyr. Put together
with the additional transits identified for two of the three outer
planets, we constrain the orbital periods of the outer planets and
provide updated estimates for the stellar reflex velocities induced
by the planets.
---------------------------------------------------------
Title: TESS Asteroseismology of the Known Red-giant Host Stars HD
212771 and HD 203949
Authors: Campante, Tiago L.; Corsaro, Enrico; Lund, Mikkel N.; Mosser,
Benoît; Serenelli, Aldo; Veras, Dimitri; Adibekyan, Vardan; Antia,
H. M.; Ball, Warrick; Basu, Sarbani; Bedding, Timothy R.; Bossini,
Diego; Davies, Guy R.; Delgado Mena, Elisa; García, Rafael A.;
Handberg, Rasmus; Hon, Marc; Kane, Stephen R.; Kawaler, Steven
D.; Kuszlewicz, James S.; Lucas, Miles; Mathur, Savita; Nardetto,
Nicolas; Nielsen, Martin B.; Pinsonneault, Marc H.; Reffert, Sabine;
Silva Aguirre, Víctor; Stassun, Keivan G.; Stello, Dennis; Stock,
Stephan; Vrard, Mathieu; Yıldız, Mutlu; Chaplin, William J.; Huber,
Daniel; Bean, Jacob L.; Çelik Orhan, Zeynep; Cunha, Margarida S.;
Christensen-Dalsgaard, Jørgen; Kjeldsen, Hans; Metcalfe, Travis S.;
Miglio, Andrea; Monteiro, Mário J. P. F. G.; Nsamba, Benard; Örtel,
Sibel; Pereira, Filipe; Sousa, Sérgio G.; Tsantaki, Maria; Turnbull,
Margaret C.
2019ApJ...885...31C Altcode: 2019arXiv190905961C
The Transiting Exoplanet Survey Satellite (TESS) is performing a near
all-sky survey for planets that transit bright stars. In addition, its
excellent photometric precision enables asteroseismology of solar-type
and red-giant stars, which exhibit convection-driven, solar-like
oscillations. Simulations predict that TESS will detect solar-like
oscillations in nearly 100 stars already known to host planets. In this
paper, we present an asteroseismic analysis of the known red-giant host
stars HD 212771 and HD 203949, both systems having a long-period planet
detected through radial velocities. These are the first detections of
oscillations in previously known exoplanet-host stars by TESS, further
showcasing the mission’s potential to conduct asteroseismology of
red-giant stars. We estimate the fundamental properties of both stars
through a grid-based modeling approach that uses global asteroseismic
parameters as input. We discuss the evolutionary state of HD 203949 in
depth and note the large discrepancy between its asteroseismic mass
(M <SUB>*</SUB> = 1.23 ± 0.15 M <SUB>⊙</SUB> if on the red-giant
branch or M <SUB>*</SUB> = 1.00 ± 0.16 M <SUB>⊙</SUB> if in the
clump) and the mass quoted in the discovery paper (M <SUB>*</SUB>
= 2.1 ± 0.1 M <SUB>⊙</SUB>), implying a change >30% in the
planet’s mass. Assuming HD 203949 to be in the clump, we investigate
the planet’s past orbital evolution and discuss how it could have
avoided engulfment at the tip of the red-giant branch. Finally, HD
212771 was observed by K2 during its Campaign 3, thus allowing for
a preliminary comparison of the asteroseismic performances of TESS
and K2. We estimate the ratio of the observed oscillation amplitudes
for this star to be {A}<SUB>\max </SUB><SUP>{TESS</SUP>}/{A}<SUB>\max
</SUB><SUP>K2</SUP>=0.75+/- 0.14, consistent with the expected ratio
of ∼0.85 due to the redder bandpass of TESS.
---------------------------------------------------------
Title: Dynamical heating across the Milky Way disc using APOGEE
and Gaia
Authors: Mackereth, J. Ted; Bovy, Jo; Leung, Henry W.; Schiavon,
Ricardo P.; Trick, Wilma H.; Chaplin, William J.; Cunha, Katia;
Feuillet, Diane K.; Majewski, Steven R.; Martig, Marie; Miglio, Andrea;
Nidever, David; Pinsonneault, Marc H.; Aguirre, Victor Silva; Sobeck,
Jennifer; Tayar, Jamie; Zasowski, Gail
2019MNRAS.489..176M Altcode: 2019arXiv190104502M
The kinematics of the Milky Way disc as a function of age are
well measured at the solar radius, but have not been studied
over a wider range of Galactocentric radii. Here, we measure the
kinematics of mono-age, mono-[Fe/H] populations in the low and high
[α/Fe] discs between 4 ≲ R ≲ 13 kpc and |z| ≲ 2 kpc using
65 719 stars in common between APOGEE DR14 and Gaia DR2 for which
we estimate ages using a Bayesian neural network model trained on
asteroseismic ages. We determine the vertical and radial velocity
dispersions, finding that the low and high [α/Fe] discs display
markedly different age-velocity dispersion relations (AVRs) and
shapes σ<SUB>z</SUB>/σ<SUB>R</SUB>. The high [α/Fe] disc has
roughly flat AVRs and constant σ<SUB>z</SUB>/σ<SUB>R</SUB> =
0.64 ± 0.04, whereas the low [α/Fe] disc has large variations in
this ratio that positively correlate with the mean orbital radius of
the population at fixed age. The high [α/Fe] disc component's flat
AVRs and constant σ<SUB>z</SUB>/σ<SUB>R</SUB> clearly indicate
an entirely different heating history. Outer disc populations also
have flatter radial AVRs than those in the inner disc, likely due to
the waning effect of spiral arms. Our detailed measurements of AVRs
and σ<SUB>z</SUB>/σ<SUB>R</SUB> across the disc indicate that low
[α/Fe], inner disc (R ≲ 10 kpc) stellar populations are likely
dynamically heated by both giant molecular clouds and spiral arms,
while the observed trends for outer disc populations require a
significant contribution from another heating mechanism such as
satellite perturbations. We also find that outer disc populations have
slightly positive mean vertical and radial velocities likely because
they are part of the warped disc.
---------------------------------------------------------
Title: Sensitivity of low-degree solar p modes to active and ephemeral
regions: frequency shifts back to the Maunder minimum
Authors: Chaplin, William J.; Howe, Rachel; Basu, Sarbani; Elsworth,
Yvonne; Milbourne, Timothy W.; Haywood, Raphaëlle D.; Davies, Guy R.;
Hale, Steven J.; Miglio, Andrea; Ross, Eddie
2019MNRAS.489L..86C Altcode: 2019arXiv190808755C
We explore the sensitivity of the frequencies of low-degree solar
p modes to near-surface magnetic flux on different spatial scales
and strengths, specifically to active regions with strong magnetic
fields and ephemeral regions with weak magnetic fields. We also
use model reconstructions from the literature to calculate average
frequency offsets back to the end of the Maunder minimum. We find
that the p-mode frequencies are at least 3 times less sensitive
(at 95 per cent confidence) to the ephemeral-region field than they
are to the active-region field. Frequency shifts between activity
cycle minima and maxima are controlled predominantly by the change
of active region flux. Frequency shifts at cycle minima (with respect
to a magnetically quiet Sun) are determined largely by the ephemeral
flux, and are estimated to have been 0.1 μ Hz or less over the last
few minima. We conclude that at epochs of cycle minimum, frequency
shifts due to near-surface magnetic activity are negligible compared
to the offsets between observed and model frequencies that arise from
inaccurate modelling of the near-surface layers (the so-called surface
term). The implication is that this will be the case for other Sun-like
stars with similar activity, which has implications for asteroseismic
modelling of stars.
---------------------------------------------------------
Title: Bayesian hierarchical inference of asteroseismic inclination
angles
Authors: Kuszlewicz, James S.; Chaplin, William J.; North, Thomas
S. H.; Farr, Will M.; Bell, Keaton J.; Davies, Guy R.; Campante,
Tiago L.; Hekker, Saskia
2019MNRAS.488..572K Altcode: 2019MNRAS.tmp.1650K; 2019arXiv190701565K; 2019MNRAS.tmp.1602K
The stellar inclination angle - the angle between the rotation axis
of a star and our line of sight - provides valuable information in
many different areas, from the characterization of the geometry of
exoplanetary and eclipsing binary systems to the formation and evolution
of those systems. We propose a method based on asteroseismology and
a Bayesian hierarchical scheme for extracting the inclination angle
of a single star. This hierarchical method therefore provides a means
to both accurately and robustly extract inclination angles from red
giant stars. We successfully apply this technique to an artificial
data set with an underlying isotropic inclination angle distribution
to verify the method. We also apply this technique to 123 red giant
stars observed with Kepler. We also show the need for a selection
function to account for possible population-level biases, which are
not present in individual star-by-star cases, in order to extend the
hierarchical method towards inferring underlying population inclination
angle distributions.
---------------------------------------------------------
Title: Signatures of Magnetic Activity: On the Relation between
Stellar Properties and p-mode Frequency Variations
Authors: Santos, A. R. G.; Campante, T. L.; Chaplin, W. J.; Cunha,
M. S.; van Saders, J. L.; Karoff, C.; Metcalfe, T. S.; Mathur, S.;
García, R. A.; Lund, M. N.; Kiefer, R.; Silva Aguirre, V.; Davies,
G. R.; Howe, R.; Elsworth, Y.
2019ApJ...883...65S Altcode: 2019arXiv190802897S
In the Sun, the properties of acoustic modes are sensitive to changes
in the magnetic activity. In particular, mode frequencies are observed
to increase with increasing activity level. Thanks to CoRoT and
Kepler, such variations have been found in other solar-type stars
and encode information on the activity-related changes in their
interiors. Thus, the unprecedented long-term Kepler photometric
observations provide a unique opportunity to study stellar activity
through asteroseismology. The goal of this work is to investigate
the dependencies of the observed mode frequency variations on
the stellar parameters and whether those are consistent with an
activity-related origin. We select the solar-type oscillators with
highest signal-to-noise ratio, in total, 75 targets. Using the temporal
frequency variations determined in Santos et al., we study the relation
between those variations and the fundamental stellar properties. We
also compare the observed frequency shifts with chromospheric and
photometric activity indexes, which are only available for a subset
of the sample. We find that frequency shifts increase with increasing
chromospheric activity, which is consistent with an activity-related
origin of the observed frequency shifts. Frequency shifts are also
found to increase with effective temperature, which is in agreement with
the theoretical predictions for the activity-related frequency shifts
by Metcalfe et al. Frequency shifts are largest for fast rotating
and young stars, which is consistent with those being more active
than slower rotators and older stars. Finally, we find evidence for
frequency shifts increasing with stellar metallicity.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Radial velocities and transit
times for KOI 4 (Chontos+, 2019)
Authors: Chontos, A.; Huber, D.; Latham, D. W.; Bieryla, A.; van
Eylen, V.; Bedding, T. R.; Berger, T.; Buchhave, L. A.; Campante,
T. L.; Chaplin, W. J.; Colman, I. L.; Coughlin, J. L.; Davies, G.;
Hirano, T.; Howard, A. W.; Isaacson, H.
2019yCat..51570192C Altcode:
Following the asteroseismic reclassification of the host star, we
initiated an intensive radial velocity (RV) follow-up program using
the Tillinghast Reflector Echelle Spectrograph (TRES), a fiber-fed
echelle spectrograph spanning the spectral range of 3900-9100 Å
with a resolving power of R~44000. We obtained 23 spectra with TRES
between UT 2009 November 8 and 2017 September 13 using the medium 2.3"
fiber. The spectra were reduced and extracted as outlined in Buchhave
et al. (2010, J/ApJ/720/1118). The average exposure time of ~1800 s,
corresponding to a mean signal-to-noise ratio (S/N) per resolution
element of ~53 at the peak of the continuum near the Mg b triplet at
519 nm. We used the strongest S/N spectrum as a template to derive
relative RVs by cross-correlating the remaining spectra order-by-order
against the template, which is given a relative velocity of 0 km/s,
by definition. <P />(2 data files).
---------------------------------------------------------
Title: New light on the Gaia DR2 parallax zero-point: influence of
the asteroseismic approach, in and beyond the Kepler field
Authors: Khan, S.; Miglio, A.; Mosser, B.; Arenou, F.; Belkacem, K.;
Brown, A. G. A.; Katz, D.; Casagrande, L.; Chaplin, W. J.; Davies,
G. R.; Rendle, B. M.; Rodrigues, T. S.; Bossini, D.; Cantat-Gaudin,
T.; Elsworth, Y. P.; Girardi, L.; North, T. S. H.; Vallenari, A.
2019A&A...628A..35K Altcode: 2019arXiv190405676K
The importance of studying the Gaia DR2 parallax zero-point by external
means was underlined by the articles that accompanied the release,
and initiated by several works making use of Cepheids, eclipsing
binaries, and asteroseismology. Despite a very efficient elimination
of basic-angle variations, a small fluctuation remains and shows up as
a small offset in the Gaia DR2 parallaxes. By combining astrometric,
asteroseismic, spectroscopic, and photometric constraints, we undertake
a new analysis of the Gaia parallax offset for nearly 3000 red-giant
branch (RGB) and 2200 red clump (RC) stars observed by Kepler, as
well as about 500 and 700 red giants (all either in the RGB or RC
phase) selected by the K2 Galactic Archaeology Program in campaigns
3 and 6. Engaging in a thorough comparison of the astrometric and
asteroseismic parallaxes, we are able to highlight the influence of
the asteroseismic method, and measure parallax offsets in the Kepler
field that are compatible with independent estimates from literature
and open clusters. Moreover, adding the K2 fields to our investigation
allows us to retrieve a clear illustration of the positional dependence
of the zero-point, in general agreement with the information provided
by quasars. Lastly, we initiate a two-step methodology to make progress
in the simultaneous calibration of the asteroseismic scaling relations
and of the Gaia DR2 parallax offset, which will greatly benefit from
the gain in precision with the third data release of Gaia.
---------------------------------------------------------
Title: VizieR Online Data Catalog: High-precision radial velocities
for HD 221416 (Huber+, 2019)
Authors: Huber, D.; Chaplin, W. J.; Chontos, A.; Kjeldsen, H.;
Christensen-Dalsgaard, J.; Bedding, T. R.; Ball, W.; Brahm, R.;
Espinoza, N.; Henning, T.; Jordan, A.; Sarkis, P.; Knudstrup, E.;
Albrecht, S.; Grundahl, F.; Andersen, M. F.; Palle, P. L.; Crossfield,
I.; Fulton, B.; Howard, A. W.; Isaacson, H. T.; Weiss, L. M.; Handberg,
R.; Lund, M. N.; Serenelli, A. M.; Rorsted Mosumgaard, J.; Stokholm,
A.; Bieryla, A.; Buchhave, L. A.; Latham, D. W.; Quinn, S. N.;
Gaidos, E.; Hirano, T.; Ricker, G. R.; Vanderspek, R. K.; Seager,
S.; Jenkins, J. M.; Winn, J. N.; Antia, H. M.; Appourchaux, T.; Basu,
S.; Bell, K. J.; Benomar, O.; Bonanno, A.; Buzasi, D. L.; Campante,
T. L.; Celik Orhan, Z.; Corsaro, E.; Cunha, M. S.; Davies, G. R.;
Deheuvels, S.; Grunblatt, S. K.; Hasanzadeh, A.; di Mauro, M. P.;
Garcia, R. A.; Gaulme, P.; Girardi, L.; Guzik, J. A.; Hon, M.; Jiang,
C.; Kallinger, T.; Kawaler, S. D.; Kuszlewicz, J. S.; Lebreton, Y.; Li,
T.; Lucas, M.; Lundkvist, M. S.; Mann, A. W.; Mathis, S.; Mathur, S.;
Mazumdar, A.; Metcalfe, T. S.; Miglio, A.; Monteiro, M. J. P. F. G.;
Mosser, B.; Noll, A.; Nsamba, B.; Ong, J. M. J.; Ortel, S.; Pereira,
F.; Ranadive, P.; Regulo, C.; Rodrigues, T. S.; Roxburgh, I. W.;
Aguirre, V. S.; Smalley, B.; Schofield, M.; Sousa, S. G.; Stassun,
K. G.; Stello, D.; Tayar, J.; White, T. R.; Verma, K.; Vrard, M.;
Yildiz, M.; Baker, D.; Bazot, M.; Beichmann, C.; Bergmann, C.;
Bugnet, L.; Cale, B.; Carlino, R.; Cartwright, S. M.; Christiansen,
J. L.; Ciardi, D. R.; Creevey, O.; Dittmann, J. A.; Do Nascimento,
J. -D., Jr.; van Eylen, V.; Furesz, G.; Gagne, J.; Gao, P.; Gazeas,
K.; Giddens, F.; Hall, O. J.; Hekker, S.; Ireland, M. J.; Latouf,
N.; Lebrun, D.; Levine, A. M.; Matzko, W.; Natinsky, E.; Page, E.;
Plavchan, P.; Mansouri-Samani, M.; McCauliff, S.; Mullally, S. E.;
Orenstein, B.; Soto, A. G.; Paegert, M.; van Saders, J. L.; Schnaible,
C.; Soderblom, D. R.; Szabo, R.; Tanner, A.; Tinney, C. G.; Teske,
J.; Thomas, A.; Trampedach, R.; Wright, D.; Yuan, T. T.; Zohrabi, F.
2019yCat..51570245H Altcode:
We obtained high-resolution spectra of HD 221416 using several
facilities within the TESS Follow-up Observation Program (TFOP),
including HIRES (Vogt et al. 1994SPIE.2198..362V) on the 10 m telescope
at Keck Observatory (Maunakea, Hawai'i); the Hertzsprung SONG Telescope
at Teide Observatory (Tenerife; Grundahl et al. 2017ApJ...836..142G);
HARPS (Mayor et al. 2003Msngr.114...20M), FEROS (Kaufer et
al. 1999Msngr..95....8K), Coralie (Queloz et al. 2001Msngr.105....1Q),
and FIDEOS (Vanzi et al. 2018MNRAS.477.5041V) on the MPG/ESO 3.6 m, 2.2
m, 1.2 m, and 1 m telescopes at La Silla Observatory (Chile); Veloce
(Gilbert et al. 2018SPIE10702E..0YG) on the 3.9 m Anglo-Australian
Telescope at Siding Spring Observatory (Australia); TRES (Furesz 2008,
PhD thesis Univ. Szeged) on the 1.5 m Tillinghast reflector at the
F. L. Whipple Observatory (Mt. Hopkins, Arizona); and iSHELL (Rayner
et al. 2012SPIE.8446E..2CR) on the NASA IRTF Telescope (Maunakea,
Hawai'i). All spectra used in this paper were obtained between 2018
November 11 and December 30 and have a minimum spectral resolution of
R~44000. <P />(1 data file).
---------------------------------------------------------
Title: KOI-3890: a high-mass-ratio asteroseismic red giant+M-dwarf
eclipsing binary undergoing heartbeat tidal interactions
Authors: Kuszlewicz, James S.; North, Thomas S. H.; Chaplin, William
J.; Bieryla, Allyson; Latham, David W.; Miglio, Andrea; Bell, Keaton
J.; Davies, Guy R.; Hekker, Saskia; Campante, Tiago L.; Deheuvels,
Sebastien; Lund, Mikkel N.
2019MNRAS.487...14K Altcode: 2019arXiv190500040K; 2019MNRAS.tmp.1136K
KOI-3890 is a highly eccentric, 153-d period eclipsing, single-lined
spectroscopic binary system containing a red giant star showing
solar-like oscillations alongside tidal interactions. The combination of
transit photometry, radial velocity observations, and asteroseismology
has enabled the detailed characterization of both the red giant primary
and the M-dwarf companion, along with the tidal interaction and the
geometry of the system. The stellar parameters of the red giant primary
are determined through the use of asteroseismology and grid-based
modelling to give a mass and radius of M_{\star }=1.04± 0.06 M_{⊙}
and R_{\star }=5.8± 0.2 R_{⊙}, respectively. When combined with
transit photometry, the M-dwarf companion is found to have a mass and
radius of M<SUB>c</SUB>=0.23± 0.01 M_{⊙} and R<SUB>c</SUB>=0.256±
0.007 R_{⊙}. Moreover, through asteroseismology we constrain the age
of the system through the red giant primary to be 9.1^{+2.4}_{-1.7}
Gyr. This provides a constraint on the age of the M-dwarf secondary,
which is difficult to do for other M-dwarf binary systems. In addition,
the asteroseismic analysis yields an estimate of the inclination angle
of the rotation axis of the red giant star of i=87.6^{+2.4}_{-1.2}
degrees. The obliquity of the system - the angle between the stellar
rotation axis and the angle normal to the orbital plane - is also
derived to give ψ =4.2^{+2.1}_{-4.2} degrees, showing that the system
is consistent with alignment. We observe no radius inflation in the
M-dwarf companion when compared to current low-mass stellar models.
---------------------------------------------------------
Title: Testing asteroseismology with Gaia DR2: hierarchical models
of the Red Clump
Authors: Hall, Oliver J.; Davies, Guy R.; Elsworth, Yvonne P.;
Miglio, Andrea; Bedding, Timothy R.; Brown, Anthony G. A.; Khan,
Saniya; Hawkins, Keith; García, Rafael A.; Chaplin, William J.;
North, Thomas S. H.
2019MNRAS.486.3569H Altcode: 2019MNRAS.tmp.1036H; 2019arXiv190407919H
Asteroseismology provides fundamental stellar parameters independent
of distance, but subject to systematics under calibration. Gaia DR2
has provided parallaxes for a billion stars, which are offset by a
parallax zero-point (ϖ<SUB>zp</SUB>). Red Clump (RC) stars have a
narrow spread in luminosity, thus functioning as standard candles to
calibrate these systematics. This work measures how the magnitude
and spread of the RC in the Kepler field are affected by changes
to temperature and scaling relations for seismology, and changes to
the parallax zero-point for Gaia. We use a sample of 5576 RC stars
classified through asteroseismology. We apply hierarchical Bayesian
latent variable models, finding the population-level properties of the
RC with seismology, and use those as priors on Gaia parallaxes to find
ϖ<SUB>zp</SUB>. We then find the position of the RC, using published
values for ϖ<SUB>zp</SUB>. We find a seismic temperature-insensitive
spread of the RC of {∼ }0.03 mag in the 2MASS K band and a larger and
slightly temperature-dependent spread of {∼ }0.13 mag in the Gaia
G band. This intrinsic dispersion in the K band provides a distance
precision of {∼ } 1{{ per cent}} for RC stars. Using Gaia data alone,
we find a mean zero-point of -41± 10 μ as. This offset yields RC
absolute magnitudes of -1.634 ± 0.018 in K and 0.546 ± 0.016 in
G. Obtaining these same values through seismology would require a
global temperature shift of {∼ }-70 K, which is compatible with
known systematics in spectroscopy.
---------------------------------------------------------
Title: Determining the Best Method of Calculating the Large Frequency
Separation For Stellar Models
Authors: Viani, Lucas S.; Basu, Sarbani; Corsaro, Enrico; Ball,
Warrick H.; Chaplin, William J.
2019ApJ...879...33V Altcode: 2019arXiv190508333V
Asteroseismology of solar-like oscillators often relies on the
comparisons between stellar models and stellar observations in order
to determine the properties of stars. The values of the global
seismic parameters, ν <SUB>max</SUB> (the frequency where the
smoothed amplitude of the oscillations peak) and Δν (the large
frequency separation), are frequently used in grid-based modeling
searches. However, the methods by which Δν is calculated from
observed data and how Δν is calculated from stellar models are not
the same. Typically for observed stars, especially for those with low
signal-to-noise data, Δν is calculated by taking the power spectrum
of a power spectrum, or with autocorrelation techniques. However, for
stellar models, the actual individual mode frequencies are calculated
and the average spacing between them directly determined. In this
work we try to determine the best way to combine model frequencies
in order to obtain Δν that can be compared with observations. For
this we use stars with high signal-to-noise observations from Kepler
as well as simulated Transiting Exoplanet Survey Satellite data of
Ball et al. We find that when determining Δν from individual mode
frequencies the best method is to use the ℓ = 0 modes with either
no weighting or with a Gaussian weighting around ν <SUB>max</SUB>.
---------------------------------------------------------
Title: Sounding stellar cycles with Kepler - III. Comparative analysis
of chromospheric, photometric, and asteroseismic variability
Authors: Karoff, C.; Metcalfe, T. S.; Montet, B. T.; Jannsen, N. E.;
Santos, A. R. G.; Nielsen, M. B.; Chaplin, W. J.
2019MNRAS.485.5096K Altcode: 2019arXiv190202172K; 2019MNRAS.tmp..751K
By combining ground-based spectrographic observations of variability in
the chromospheric emission from Sun-like stars with the variability seen
in their eigenmode frequencies, it is possible to relate the changes
observed at the surfaces of these stars to the changes taking place
in the interior. By further comparing this variability to changes in
the relative flux from the stars, one can obtain an expression for
how these activity indicators relate to the energy output from the
stars. Such studies become very pertinent when the variability can
be related to stellar cycles as they can then be used to improve our
understanding of the solar cycle and its effect on the energy output
from the Sun. Here, we present observations of chromospheric emission
in 20 Sun-like stars obtained over the course of the nominal 4 yr Kepler
mission. Even though 4 yr is too short to detect stellar equivalents of
the 11 yr solar cycle, observations from the Kepler mission can still
be used to analyse the variability of the different activity indicators
thereby obtaining information of the physical mechanism generating
the variability. The analysis reveals no strong correlation between
the different activity indicators, except in very few cases. We suggest
that this is due to the sparse sampling of our ground-based observations
on the one hand and that we are likely not tracing cyclic variability
on the other hand. We also discuss how to improve the situation.
---------------------------------------------------------
Title: A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered
by TESS
Authors: Huber, Daniel; Chaplin, William J.; Chontos, Ashley; Kjeldsen,
Hans; Christensen-Dalsgaard, Jørgen; Bedding, Timothy R.; Ball,
Warrick; Brahm, Rafael; Espinoza, Nestor; Henning, Thomas; Jordán,
Andrés; Sarkis, Paula; Knudstrup, Emil; Albrecht, Simon; Grundahl,
Frank; Fredslund Andersen, Mads; Pallé, Pere L.; Crossfield, Ian;
Fulton, Benjamin; Howard, Andrew W.; Isaacson, Howard T.; Weiss,
Lauren M.; Handberg, Rasmus; Lund, Mikkel N.; Serenelli, Aldo M.;
Rørsted Mosumgaard, Jakob; Stokholm, Amalie; Bieryla, Allyson;
Buchhave, Lars A.; Latham, David W.; Quinn, Samuel N.; Gaidos, Eric;
Hirano, Teruyuki; Ricker, George R.; Vanderspek, Roland K.; Seager,
Sara; Jenkins, Jon M.; Winn, Joshua N.; Antia, H. M.; Appourchaux,
Thierry; Basu, Sarbani; Bell, Keaton J.; Benomar, Othman; Bonanno,
Alfio; Buzasi, Derek L.; Campante, Tiago L.; Çelik Orhan, Z.; Corsaro,
Enrico; Cunha, Margarida S.; Davies, Guy R.; Deheuvels, Sebastien;
Grunblatt, Samuel K.; Hasanzadeh, Amir; Di Mauro, Maria Pia; García,
Rafael A.; Gaulme, Patrick; Girardi, Léo; Guzik, Joyce A.; Hon, Marc;
Jiang, Chen; Kallinger, Thomas; Kawaler, Steven D.; Kuszlewicz, James
S.; Lebreton, Yveline; Li, Tanda; Lucas, Miles; Lundkvist, Mia S.;
Mann, Andrew W.; Mathis, Stéphane; Mathur, Savita; Mazumdar, Anwesh;
Metcalfe, Travis S.; Miglio, Andrea; Monteiro, Mário J. P. F. G.;
Mosser, Benoit; Noll, Anthony; Nsamba, Benard; Ong, Jia Mian Joel;
Örtel, S.; Pereira, Filipe; Ranadive, Pritesh; Régulo, Clara;
Rodrigues, Thaíse S.; Roxburgh, Ian W.; Silva Aguirre, Victor;
Smalley, Barry; Schofield, Mathew; Sousa, Sérgio G.; Stassun,
Keivan G.; Stello, Dennis; Tayar, Jamie; White, Timothy R.; Verma,
Kuldeep; Vrard, Mathieu; Yıldız, M.; Baker, David; Bazot, Michaël;
Beichmann, Charles; Bergmann, Christoph; Bugnet, Lisa; Cale, Bryson;
Carlino, Roberto; Cartwright, Scott M.; Christiansen, Jessie L.;
Ciardi, David R.; Creevey, Orlagh; Dittmann, Jason A.; Do Nascimento,
Jose-Dias, Jr.; Van Eylen, Vincent; Fürész, Gabor; Gagné, Jonathan;
Gao, Peter; Gazeas, Kosmas; Giddens, Frank; Hall, Oliver J.; Hekker,
Saskia; Ireland, Michael J.; Latouf, Natasha; LeBrun, Danny; Levine,
Alan M.; Matzko, William; Natinsky, Eva; Page, Emma; Plavchan,
Peter; Mansouri-Samani, Masoud; McCauliff, Sean; Mullally, Susan E.;
Orenstein, Brendan; Garcia Soto, Aylin; Paegert, Martin; van Saders,
Jennifer L.; Schnaible, Chloe; Soderblom, David R.; Szabó, Róbert;
Tanner, Angelle; Tinney, C. G.; Teske, Johanna; Thomas, Alexandra;
Trampedach, Regner; Wright, Duncan; Yuan, Thomas T.; Zohrabi, Farzaneh
2019AJ....157..245H Altcode: 2019arXiv190101643H
We present the discovery of HD 221416 b, the first transiting planet
identified by the Transiting Exoplanet Survey Satellite (TESS) for
which asteroseismology of the host star is possible. HD 221416 b
(HIP 116158, TOI-197) is a bright (V = 8.2 mag), spectroscopically
classified subgiant that oscillates with an average frequency of
about 430 μHz and displays a clear signature of mixed modes. The
oscillation amplitude confirms that the redder TESS bandpass compared
to Kepler has a small effect on the oscillations, supporting the
expected yield of thousands of solar-like oscillators with TESS 2
minute cadence observations. Asteroseismic modeling yields a robust
determination of the host star radius (R <SUB>⋆</SUB> = 2.943 ±
0.064 R <SUB>⊙</SUB>), mass (M <SUB>⋆</SUB> = 1.212 ± 0.074 M
<SUB>⊙</SUB>), and age (4.9 ± 1.1 Gyr), and demonstrates that it has
just started ascending the red-giant branch. Combining asteroseismology
with transit modeling and radial-velocity observations, we show that
the planet is a “hot Saturn” (R <SUB>p</SUB> = 9.17 ± 0.33 R
<SUB>⊕</SUB>) with an orbital period of ∼14.3 days, irradiance
of F = 343 ± 24 F <SUB>⊕</SUB>, and moderate mass (M <SUB>p</SUB>
= 60.5 ± 5.7 M <SUB>⊕</SUB>) and density (ρ <SUB>p</SUB> = 0.431
± 0.062 g cm<SUP>-3</SUP>). The properties of HD 221416 b show that
the host-star metallicity-planet mass correlation found in sub-Saturns
(4-8 R <SUB>⊕</SUB>) does not extend to larger radii, indicating that
planets in the transition between sub-Saturns and Jupiters follow a
relatively narrow range of densities. With a density measured to ∼15%,
HD 221416 b is one of the best characterized Saturn-size planets to
date, augmenting the small number of known transiting planets around
evolved stars and demonstrating the power of TESS to characterize
exoplanets and their host stars using asteroseismology.
---------------------------------------------------------
Title: The Curious Case of KOI 4: Confirming Kepler’s First
Exoplanet Detection
Authors: Chontos, Ashley; Huber, Daniel; Latham, David W.; Bieryla,
Allyson; Van Eylen, Vincent; Bedding, Timothy R.; Berger, Travis;
Buchhave, Lars A.; Campante, Tiago L.; Chaplin, William J.; Colman,
Isabel L.; Coughlin, Jeff L.; Davies, Guy; Hirano, Teruyuki; Howard,
Andrew W.; Isaacson, Howard
2019AJ....157..192C Altcode: 2019arXiv190301591C
The discovery of thousands of planetary systems by Kepler has
demonstrated that planets are ubiquitous. However, a major challenge
has been the confirmation of Kepler planet candidates, many of which
still await confirmation. One of the most enigmatic examples is
KOI 4.01, Kepler’s first discovered planet candidate detection
(as KOI 1.01, 2.01, and 3.01 were known prior to launch). Here
we present the confirmation and characterization of KOI 4.01
(now Kepler-1658), using a combination of asteroseismology and
radial velocities. Kepler-1658 is a massive, evolved subgiant (M
<SUB>⋆</SUB> = 1.45 ± 0.06 M <SUB>⊙</SUB>, R <SUB>⋆</SUB> =
2.89 ± 0.12 R <SUB>⊙</SUB>) hosting a massive ({M}<SUB>{{p</SUB>}}
= 5.88 ± 0.47 {M}<SUB>{{J</SUB>}}, {R}<SUB>{{p</SUB>}} = 1.07
± 0.05 {R}<SUB>{{J</SUB>}}) hot Jupiter that orbits every 3.85
days. Kepler-1658 joins a small population of evolved hosts with
short-period (≤100 days) planets and is now the closest known planet
in terms of orbital period to an evolved star. Because of its uniqueness
and short orbital period, Kepler-1658 is a new benchmark system for
testing tidal dissipation and hot Jupiter formation theories. Using
all four years of the Kepler data, we constrain the orbital decay
rate to be \dot{P} ≤ -0.42 s yr<SUP>-1</SUP>, corresponding to a
strong observational limit of {Q}<SUB>\star </SUB><SUP>{\prime</SUP> }
≥ 4.826 × {10}<SUP>3</SUP> for the tidal quality factor in evolved
stars. With an effective temperature of {T}<SUB>eff</SUB>} ∼ 6200
K, Kepler-1658 sits close to the spin-orbit misalignment boundary
at ∼6250 K, making it a prime target for follow-up observations to
better constrain its obliquity and to provide insight into theories
for hot Jupiter formation and migration.
---------------------------------------------------------
Title: Asteroseismic constraints on active latitudes of solar-type
stars: HD 173701 has active bands at higher latitudes than the Sun
Authors: Thomas, Alexandra E. L.; Chaplin, William J.; Davies, Guy
R.; Howe, Rachel; Santos, Ángela R. G.; Elsworth, Yvonne; Miglio,
Andrea; Campante, Tiago; Cunha, Margarida S.
2019MNRAS.485.3857T Altcode: 2019arXiv190304998T; 2019MNRAS.tmp..736T
We present a new method for determining the location of active bands of
latitude on solar-type stars, which uses stellar-cycle-induced frequency
shifts of detectable solar-like oscillations. When near-surface
activity is distributed in a non-homogeneous manner, oscillation
modes of different angular degree and azimuthal order will have their
frequencies shifted by different amounts. We use this simple concept,
coupled to a model for the spatial distribution of the near-surface
activity, to develop two methods that use the frequency shifts to infer
minimum and maximum latitudes for the active bands. Our methods respond
to the range in latitude over which there is significant magnetic flux
present, over and above weak basal ephemeral flux levels. We verify
that we are able to draw accurate inferences in the solar case, using
Sun-as-a-star helioseismic data and artificial data. We then apply our
methods to Kepler data on the solar analogue HD 173701, and find that
its active bands straddle a much wider range in latitude than do the
bands on the Sun.
---------------------------------------------------------
Title: Stellar Physics and Galactic Archaeology using Asteroseismology
in the 2020's
Authors: Huber, Daniel; Basu, Sarbani; Beck, Paul; Bedding, Timothy R.;
Buzasi, Derek; Cantiello, Matteo; Chaplin, William J.; Christiansen,
Jessie L.; Cunha, Katia; Egeland, Ricky; Fuller, Jim; Garcia,
Rafael A.; Gies, Douglas R.; Guzik, Joyce; Hekker, Saskia; Hermes,
JJ; Jackiewicz, Jason; Johnson, Jennifer; Kawaler, Steve; Metcalfe,
Travis; Mosser, Benoit; Ness, Melissa; Pinsonneault, Marc; Piro,
Anthony L.; Aguirre, Victor Silva; Soderblom, David; Stassun, Keivan;
Tayar, Jamie; ten Brummelaar, Theo; Roettenbacher, Rachael; Trampedach,
Regner; van Belle, Gerard; van Saders, Jennifer; Stello, Dennis
2019BAAS...51c.488H Altcode: 2019astro2020T.488H; 2019arXiv190308188H
Asteroseismology is the only observational tool in astronomy that can
probe the interiors of stars, and is a benchmark method for deriving
fundamental properties of stars and exoplanets. In this white paper,
we describe key science questions and necessary facilities to continue
the asteroseismology revolution into the 2020's.
---------------------------------------------------------
Title: Filtering Solar-Like Oscillations for Exoplanet Detection in
Radial Velocity Observations
Authors: Chaplin, W. J.; Cegla, H. M.; Watson, C. A.; Davies, G. R.;
Ball, W. H.
2019AJ....157..163C Altcode: 2019arXiv190300657C
Cool main-sequence, subgiant, and red giant stars all show solar-like
oscillations, pulsations that are excited and intrinsically damped
by near-surface convection. Many overtones are typically excited
to observable amplitudes, giving a rich spectrum of detectable
modes. These modes provide a wealth of information on fundamental
stellar properties. However, the radial velocity (RV) shifts induced
by these oscillations can also be problematic when searching for
low-mass, long-period planets; this is because their amplitudes are
large enough to completely mask such minute planetary signals. Here we
show how fine-tuning exposure times to the stellar parameters can help
efficiently average out the solar-like, oscillation-induced shifts. To
reduce the oscillation signal to the RV precision commensurate
with an Earth analog, we find that for cool, low-mass stars (near
spectral type K), the necessary exposure times may be as short as ∼4
minutes, while for hotter, higher-mass stars (near spectral type F, or
slightly evolved), the required exposure times can be longer than 100
minutes. We provide guideline exposure durations required to suppress
the total observed amplitude due to oscillations to a level of 0.1 m
s<SUP>-1</SUP>, and a level corresponding to the Earth-analog reflex
amplitude for the star. Owing to the intrinsic stochastic variability
of the oscillations, we recommend in practice choosing short exposure
durations at the telescope and then averaging over those exposures
later, as guided by our predictions. To summarize, as we enter an
era of 0.1 m s<SUP>-1</SUP> instrumental precision, it is critical to
tailor our observing strategies to the stellar properties.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Masses and ages of 1059 HARPS-GTO
stars (Delgado Mena+, 2019)
Authors: Delgado Mena, E.; Moya, A.; Adibekyan, V.; Tsantaki, M.;
Gonzalez Hernandez, J. I.; Israelian, G.; Davies, G. R.; Chaplin,
W. J.; Sousa, S. G.; Ferreira, A.; Santos, N. C.
2019yCat..36240078D Altcode:
The baseline sample used in this work consist of 1111 FGK stars observed
within the context of the HARPS-GTO planet search programs (Mayor et
al., 2003Msngr.114...20M; Lo Curto et al., 2010, Cat. J/A+A/512/A48;
Santos et al., 2011, Cat. J/A+A/526/A112). The final spectra have
a resolution of R~115000 and high signal-to-noise ratio (45% of the
spectra have 100<S/N<300, 40% of the spectra have S/N>300 and
the mean S/N is 380). Precise stellar parameters for the full sample
of 1111 stars within the HARPS-GTO program were homogeneously derived
in Sousa et al. (2008, Cat. J/A+A/487/373, 2011a, Cat.J/A+A/526/A99,
2011b, Cat. J/A+A/533/A141). The parameters for cool stars were revised
by Tsantaki et al. (2013, Cat. J/A+A/555/A150) using a special list of
iron lines which was later applied to the full sample in Delgado Mena
et al. (2017, Cat. J/A+A/606/A94), also correcting the spectroscopic
gravities. From the 1111 stars in the original sample, the derivation of
parameters converged to a solution for 1059 of them. <P />(1 data file).
---------------------------------------------------------
Title: The Detailed Science Case for the Maunakea Spectroscopic
Explorer, 2019 edition
Authors: The MSE Science Team; Babusiaux, Carine; Bergemann, Maria;
Burgasser, Adam; Ellison, Sara; Haggard, Daryl; Huber, Daniel;
Kaplinghat, Manoj; Li, Ting; Marshall, Jennifer; Martell, Sarah;
McConnachie, Alan; Percival, Will; Robotham, Aaron; Shen, Yue;
Thirupathi, Sivarani; Tran, Kim-Vy; Yeche, Christophe; Yong, David;
Adibekyan, Vardan; Silva Aguirre, Victor; Angelou, George; Asplund,
Martin; Balogh, Michael; Banerjee, Projjwal; Bannister, Michele;
Barría, Daniela; Battaglia, Giuseppina; Bayo, Amelia; Bechtol,
Keith; Beck, Paul G.; Beers, Timothy C.; Bellinger, Earl P.; Berg,
Trystyn; Bestenlehner, Joachim M.; Bilicki, Maciej; Bitsch, Bertram;
Bland-Hawthorn, Joss; Bolton, Adam S.; Boselli, Alessandro; Bovy,
Jo; Bragaglia, Angela; Buzasi, Derek; Caffau, Elisabetta; Cami, Jan;
Carleton, Timothy; Casagrande, Luca; Cassisi, Santi; Catelan, Márcio;
Chang, Chihway; Cortese, Luca; Damjanov, Ivana; Davies, Luke J. M.;
de Grijs, Richard; de Rosa, Gisella; Deason, Alis; di Matteo, Paola;
Drlica-Wagner, Alex; Erkal, Denis; Escorza, Ana; Ferrarese, Laura;
Fleming, Scott W.; Font-Ribera, Andreu; Freeman, Ken; Gänsicke,
Boris T.; Gabdeev, Maksim; Gallagher, Sarah; Gandolfi, Davide; García,
Rafael A.; Gaulme, Patrick; Geha, Marla; Gennaro, Mario; Gieles, Mark;
Gilbert, Karoline; Gordon, Yjan; Goswami, Aruna; Greco, Johnny P.;
Grillmair, Carl; Guiglion, Guillaume; Hénault-Brunet, Vincent;
Hall, Patrick; Handler, Gerald; Hansen, Terese; Hathi, Nimish;
Hatzidimitriou, Despina; Haywood, Misha; Hernández Santisteban,
Juan V.; Hillenbrand, Lynne; Hopkins, Andrew M.; Howlett, Cullan;
Hudson, Michael J.; Ibata, Rodrigo; Ilić, Dragana; Jablonka,
Pascale; Ji, Alexander; Jiang, Linhua; Juneau, Stephanie; Karakas,
Amanda; Karinkuzhi, Drisya; Kim, Stacy Y.; Kong, Xu; Konstantopoulos,
Iraklis; Krogager, Jens-Kristian; Lagos, Claudia; Lallement, Rosine;
Laporte, Chervin; Lebreton, Yveline; Lee, Khee-Gan; Lewis, Geraint F.;
Lianou, Sophia; Liu, Xin; Lodieu, Nicolas; Loveday, Jon; Mészáros,
Szabolcs; Makler, Martin; Mao, Yao-Yuan; Marchesini, Danilo; Martin,
Nicolas; Mateo, Mario; Melis, Carl; Merle, Thibault; Miglio, Andrea;
Gohar Mohammad, Faizan; Molaverdikhani, Karan; Monier, Richard;
Morel, Thierry; Mosser, Benoit; Nataf, David; Necib, Lina; Neilson,
Hilding R.; Newman, Jeffrey A.; Nierenberg, A. M.; Nord, Brian;
Noterdaeme, Pasquier; O'Dea, Chris; Oshagh, Mahmoudreza; Pace, Andrew
B.; Palanque-Delabrouille, Nathalie; Pandey, Gajendra; Parker, Laura
C.; Pawlowski, Marcel S.; Peter, Annika H. G.; Petitjean, Patrick;
Petric, Andreea; Placco, Vinicius; Popović, Luka Č.; Price-Whelan,
Adrian M.; Prsa, Andrej; Ravindranath, Swara; Rich, R. Michael; Ruan,
John; Rybizki, Jan; Sakari, Charli; Sanderson, Robyn E.; Schiavon,
Ricardo; Schimd, Carlo; Serenelli, Aldo; Siebert, Arnaud; Siudek,
Malgorzata; Smiljanic, Rodolfo; Smith, Daniel; Sobeck, Jennifer;
Starkenburg, Else; Stello, Dennis; Szabó, Gyula M.; Szabo, Robert;
Taylor, Matthew A.; Thanjavur, Karun; Thomas, Guillaume; Tollerud,
Erik; Toonen, Silvia; Tremblay, Pier-Emmanuel; Tresse, Laurence;
Tsantaki, Maria; Valentini, Marica; Van Eck, Sophie; Variu, Andrei;
Venn, Kim; Villaver, Eva; Walker, Matthew G.; Wang, Yiping; Wang,
Yuting; Wilson, Michael J.; Wright, Nicolas; Xu, Siyi; Yildiz,
Mutlu; Zhang, Huawei; Zwintz, Konstanze; Anguiano, Borja; Bedell,
Megan; Chaplin, William; Collet, Remo; Cuillandre, Jean-Charles;
Duc, Pierre-Alain; Flagey, Nicolas; Hermes, JJ; Hill, Alexis;
Kamath, Devika; Laychak, Mary Beth; Małek, Katarzyna; Marley, Mark;
Sheinis, Andy; Simons, Doug; Sousa, Sérgio G.; Szeto, Kei; Ting,
Yuan-Sen; Vegetti, Simona; Wells, Lisa; Babas, Ferdinand; Bauman,
Steve; Bosselli, Alessandro; Côté, Pat; Colless, Matthew; Comparat,
Johan; Courtois, Helene; Crampton, David; Croom, Scott; Davies, Luke;
de Grijs, Richard; Denny, Kelly; Devost, Daniel; di Matteo, Paola;
Driver, Simon; Fernandez-Lorenzo, Mirian; Guhathakurta, Raja; Han,
Zhanwen; Higgs, Clare; Hill, Vanessa; Ho, Kevin; Hopkins, Andrew;
Hudson, Mike; Ibata, Rodrigo; Isani, Sidik; Jarvis, Matt; Johnson,
Andrew; Jullo, Eric; Kaiser, Nick; Kneib, Jean-Paul; Koda, Jun;
Koshy, George; Mignot, Shan; Murowinski, Rick; Newman, Jeff; Nusser,
Adi; Pancoast, Anna; Peng, Eric; Peroux, Celine; Pichon, Christophe;
Poggianti, Bianca; Richard, Johan; Salmon, Derrick; Seibert, Arnaud;
Shastri, Prajval; Smith, Dan; Sutaria, Firoza; Tao, Charling; Taylor,
Edwar; Tully, Brent; van Waerbeke, Ludovic; Vermeulen, Tom; Walker,
Matthew; Willis, Jon; Willot, Chris; Withington, Kanoa
2019arXiv190404907T Altcode:
(Abridged) The Maunakea Spectroscopic Explorer (MSE) is an end-to-end
science platform for the design, execution and scientific exploitation
of spectroscopic surveys. It will unveil the composition and dynamics
of the faint Universe and impact nearly every field of astrophysics
across all spatial scales, from individual stars to the largest scale
structures in the Universe. Major pillars in the science program for MSE
include (i) the ultimate Gaia follow-up facility for understanding the
chemistry and dynamics of the distant Milky Way, including the outer
disk and faint stellar halo at high spectral resolution (ii) galaxy
formation and evolution at cosmic noon, via the type of revolutionary
surveys that have occurred in the nearby Universe, but now conducted at
the peak of the star formation history of the Universe (iii) derivation
of the mass of the neutrino and insights into inflationary physics
through a cosmological redshift survey that probes a large volume of
the Universe with a high galaxy density. MSE is positioned to become
a critical hub in the emerging international network of front-line
astronomical facilities, with scientific capabilities that naturally
complement and extend the scientific power of Gaia, the Large Synoptic
Survey Telescope, the Square Kilometer Array, Euclid, WFIRST, the 30m
telescopes and many more.
---------------------------------------------------------
Title: New light on the Gaia DR2 parallax zero-point: influence of
the asteroseismic approach, in and beyond the Kepler field
Authors: Khan, Saniya; Miglio, Andrea; Mosser, Benoît; Arenou,
Frédéric; Belkacem, Kévin; Brown, Anthony G. A.; Katz, David;
Casagrande, Luca; Chaplin, William J.; Davies, Guy R.; Rendle, Ben
M.; Rodrigues, Thaíse S.; Bossini, Diego; Cantat-Gaudin, Tristan;
Elsworth, Yvonne P.; Girardi, Leo; North, Thomas S. H.; Vallenari,
Antonella
2019gaia.confE..13K Altcode:
The importance of studying the Gaia DR2 parallax zero-point by external
means was underlined by Lindegren et al. (2018), and initiated
by several works making use of Cepheids, eclipsing binaries, and
asteroseismology. Despite a very efficient elimination of basic-angle
variations, a small fluctuation remains and shows up as a small
offset in the Gaia DR2 parallaxes. <P />By combining astrometric,
asteroseismic, spectroscopic, and photometric constraints, we undertake
a new analysis of the Gaia parallax offset for nearly 3000 red-giant
branch (RGB) and 2200 red clump (RC) stars observed by Kepler, as well
as about 500 and 700 red giants (both RGB and RC) selected by the K2
Galactic Archaeology Program in campaigns 3 and 6. Engaging into a
thorough comparison of the astrometric and asteroseismic parallaxes,
we are able to highlight the influence of the asteroseismic method, and
measure parallax offsets in the Kepler field that are compatible with
independent estimates from literature and open clusters. <P />Moreover,
adding the K2 fields to our investigation allows us to retrieve a
clear illustration of the positional dependence of the zero-point,
in general agreement with the information provided by quasars. <P
/>Lastly, we initiate a two-step methodology to make progress in the
simultaneous calibration of the asteroseismic scaling relations and
of the Gaia DR2 parallax offset, which will greatly benefit from the
gain in precision with the third Data Release of Gaia.
---------------------------------------------------------
Title: Abundance to age ratios in the HARPS-GTO sample with Gaia
DR2. Chemical clocks for a range of [Fe/H]
Authors: Delgado Mena, E.; Moya, A.; Adibekyan, V.; Tsantaki, M.;
González Hernández, J. I.; Israelian, G.; Davies, G. R.; Chaplin,
W. J.; Sousa, S. G.; Ferreira, A. C. S.; Santos, N. C.
2019A&A...624A..78D Altcode: 2019arXiv190202127D; 2019A&A...624A..78M
<BR /> Aims: The purpose of this work is to evaluate how several
elements produced by different nucleosynthesis processes behave with
stellar age and provide empirical relations to derive stellar ages
from chemical abundances. <BR /> Methods: We derived different sets
of ages using Padova and Yonsei-Yale isochrones and HIPPARCOS and
Gaia parallaxes for a sample of more than 1000 FGK dwarf stars for
which he have high-resolution (R 115 000) and high-quality spectra
from the HARPS-GTO program. We analyzed the temporal evolution of
different abundance ratios to find the best chemical clocks. We
applied multivariable linear regressions to our sample of stars with
a small uncertainty on age to obtain empirical relations of age as
a function of stellar parameters and different chemical clocks. <BR
/> Results: We find that [α/Fe] ratio (average of Mg, Si, and Ti),
[O/Fe] and [Zn/Fe] are good age proxies with a lower dispersion than
the age-metallicity dispersion. Several abundance ratios present a
significant correlation with age for chemically separated thin disk
stars (i.e., low-α) but in the case of the chemically defined thick
disk stars (i.e., high-α) only the elements Mg, Si, Ca, and Ti II show
a clear correlation with age. We find that the thick disk stars are more
enriched in light-s elements than thin disk stars of similar age. The
maximum enrichment of s-process elements in the thin disk occurs in the
youngest stars which in turn have solar metallicity. The slopes of the
[X/Fe]-age relations are quite constant for O, Mg, Si, Ti, Zn, Sr, and
Eu regardless of the metallicity. However, this is not the case for Al,
Ca, Cu and most of the s-process elements, which display very different
trends depending on the metallicity. This demonstrates the limitations
of using simple linear relations based on certain abundance ratios to
obtain ages for stars of different metallicities. Finally, we show that
by using 3D relations with a chemical clock and two stellar parameters
(either T<SUB>eff</SUB>, [Fe/H] or stellar mass) we can explain up
to 89% of age variance in a star. A similar result is obtained when
using 2D relations with a chemical clock and one stellar parameter,
explaining up to a 87% of the variance. <BR /> Conclusions: The complete
understanding of how the chemical elements were produced and evolved in
the Galaxy requires the knowledge of stellar ages and precise chemical
abundances. We show how the temporal evolution of some chemical species
change with metallicity, with remarkable variations at super-solar
metallicities, which will help to better constrain the yields of
different nucleosynthesis processes along the history of the Galaxy. <P
/>Full Table 2 is only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A78">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A78</A>Based
on observations collected at the La Silla Observatory, ESO (Chile),
with the HARPS spectrograph at the 3.6 m ESO telescope (ESO runs ID
72.C-0488, 082.C-0212, and 085.C-0063).
---------------------------------------------------------
Title: VizieR Online Data Catalog: Mixing-length parameter for a
sample of KIC stars (Viani+, 2018)
Authors: Viani, L. S.; Basu, S.; J. O., J. M.; Bonaca, A.; Chaplin,
W. J.
2019yCat..18580028V Altcode:
Stellar models typically use the mixing-length approximation
as a way to implement convection in a simplified manner. While
conventionally the value of the mixing-length parameter, α, used is
the solar-calibrated value, many studies have shown that other values
of α are needed to properly model stars. This uncertainty in the
value of the mixing-length parameter is a major source of error in
stellar models and isochrones. Using asteroseismic data, we determine
the value of the mixing-length parameter required to properly model
a set of about 450 stars ranging in logg, Teff, and [Fe/H]. The
relationship between the value of α required and the properties of
the star is then investigated. For Eddington atmosphere, non-diffusion
models, we find that the value of α can be approximated by a linear
model, in the form of α/α<SUB>ȯ</SUB>=5.426-0.101, log(g)-1.071,
log(Teff)+0.437([Fe/H]). This process is repeated using a variety of
model physics, as well as compared with previous studies and results
from 3D convective simulations. <P />(1 data file).
---------------------------------------------------------
Title: The Asteroseismic Target List for Solar-like Oscillators
Observed in 2 minute Cadence with the Transiting Exoplanet Survey
Satellite
Authors: Schofield, Mathew; Chaplin, William J.; Huber, Daniel;
Campante, Tiago L.; Davies, Guy R.; Miglio, Andrea; Ball, Warrick
H.; Appourchaux, Thierry; Basu, Sarbani; Bedding, Timothy R.;
Christensen-Dalsgaard, Jørgen; Creevey, Orlagh; García, Rafael A.;
Handberg, Rasmus; Kawaler, Steven D.; Kjeldsen, Hans; Latham, David W.;
Lund, Mikkel N.; Metcalfe, Travis S.; Ricker, George R.; Serenelli,
Aldo; Silva Aguirre, Victor; Stello, Dennis; Vanderspek, Roland
2019ApJS..241...12S Altcode: 2019arXiv190110148S
We present the target list of solar-type stars to be observed in
short-cadence (2 minute) for asteroseismology by the NASA Transiting
Exoplanet Survey Satellite (TESS) during its 2 year nominal survey
mission. The solar-like Asteroseismic Target List (ATL) is comprised
of bright, cool main-sequence and subgiant stars and forms part of the
larger target list of the TESS Asteroseismic Science Consortium. The
ATL uses the Gaia Data Release 2 and the Extended Hipparcos Compilation
(XHIP) to derive fundamental stellar properties, to calculate detection
probabilities, and to produce a rank-ordered target list. We provide a
detailed description of how the ATL was produced and calculate expected
yields for solar-like oscillators based on the nominal photometric
performance by TESS. We also provide a publicly available source code
that can be used to reproduce the ATL, thereby enabling comparisons
of asteroseismic results from TESS with predictions from synthetic
stellar populations.
---------------------------------------------------------
Title: AIMS - a new tool for stellar parameter determinations using
asteroseismic constraints
Authors: Rendle, Ben M.; Buldgen, Gaël; Miglio, Andrea; Reese,
Daniel; Noels, Arlette; Davies, Guy R.; Campante, Tiago L.; Chaplin,
William J.; Lund, Mikkel N.; Kuszlewicz, James S.; Scott, Laura J. A.;
Scuflaire, Richard; Ball, Warrick H.; Smetana, Jiri; Nsamba, Benard
2019MNRAS.484..771R Altcode: 2019MNRAS.tmp...36R; 2019arXiv190102663R
A key aspect in the determination of stellar properties is the
comparison of observational constraints with predictions from stellar
models. Asteroseismic Inference on a Massive Scale (AIMS) is an open
source code that uses Bayesian statistics and a Markov Chain Monte
Carlo approach to find a representative set of models that reproduce a
given set of classical and asteroseismic constraints. These models are
obtained by interpolation on a pre-calculated grid, thereby increasing
computational efficiency. We test the accuracy of the different
operational modes within AIMS for grids of stellar models computed
with the Liège stellar evolution code (main sequence and red giants)
and compare the results to those from another asteroseismic analysis
pipeline, PARAM. Moreover, using artificial inputs generated from
models within the grid (assuming the models to be correct), we focus
on the impact on the precision of the code when considering different
combinations of observational constraints (individual mode frequencies,
period spacings, parallaxes, photospheric constraints,...). Our tests
show the absolute limitations of precision on parameter inferences using
synthetic data with AIMS, and the consistency of the code with expected
parameter uncertainty distributions. Interpolation testing highlights
the significance of the underlying physics to the analysis performance
of AIMS and provides caution as to the upper limits in parameter step
size. All tests demonstrate the flexibility and capability of AIMS
as an analysis tool and its potential to perform accurate ensemble
analysis with current and future asteroseismic data yields.
---------------------------------------------------------
Title: VizieR Online Data Catalog: APOKASC-2 catalog of Kepler
evolved stars (Pinsonneault+, 2018)
Authors: Pinsonneault, M. H.; Elsworth, Y. P.; Tayar, J.;
Serenelli, A.; Stello, D.; Zinn, J.; Mathur, S.; Garcia, R. A.;
Johnson, J. A.; Hekker, S.; Huber, D.; Kallinger, T.; Meszaros, S.;
Mosser, B.; Stassun, K.; Girardi, L.; Rodrigues, T. S.; Aguirre,
V. S.; An, D.; Basu, S.; Chaplin, W. J.; Corsaro, E.; Cunha, K.;
Garcia-Hernandez, D. A.; Holtzman, J.; Jonsson, H.; Shetrone, M.;
Smith, V. V.; Sobeck, J. S.; Stringfellow, G. S.; Zamora, O.; Beers,
T. C.; Fernandez-Trincado, J. G.; Frinchaboy, P. M.; Hearty, F. R.;
Nitschelm, C.
2019yCat..22390032P Altcode:
Our 6676 targets have high-resolution (R~22000) H-band spectra from
the Apache Point Observatory Galactic Evolution Experiment (APOGEE)
project (Majewski+ 2017AJ....154...94M), which were obtained during
the third Sloan Digital Sky Survey, hereafter SDSS-III (Eisenstein+
2011AJ....142...72E), and analyzed during the fourth Sloan Digital
Sky Survey, hereafter SDSS-IV (Blanton+ 2017AJ....154...28B). Our
asteroseismic data were obtained by the Kepler mission (Borucki+
2010Sci...327..977B), analyzed by members of the Kepler Asteroseismology
Science Consortium (KASC), and interpreted by the team using both
asteroseismic and spectroscopic data. <P />(2 data files).
---------------------------------------------------------
Title: The Behaviour of Galactic Cosmic-Ray Intensity During Solar
Activity Cycle 24
Authors: Ross, Eddie; Chaplin, William J.
2019SoPh..294....8R Altcode:
We have studied long-term variations of galactic cosmic-ray (GCR)
intensity in relation to the sunspot number (SSN) during the most
recent solar cycles. This study analyses the time lag between the GCR
intensity and SSN, and hysteresis plots of the GCR count rate against
SSN for Solar Cycles 20 - 23, to validate a methodology against
previous results in the literature, before applying the method to
provide a timely update on the behaviour of Cycle 24. Plots of SSN
versus GCR show a clear difference between the odd- and even-numbered
cycles. Linear and elliptical models have been fit to the data, with
the linear fit and elliptical model proving the more suitable model
for even- and odd-numbered solar-activity cycles, respectively, in
agreement with previous literature. Through the application of these
methods for Solar Cycle 24, it has been shown that Cycle 24 experienced
a lag of two to four months between the GCR intensity and SSN, and
this follows the trend of the preceding activity cycles, albeit with
a slightly longer lag than previous even-numbered cycles. It has been
shown through the hysteresis analysis that the linear fit is a better
representative model for Cycle 24, as the ellipse model does not show
a significant improvement, which is also in agreement with previous
even-numbered cycles.
---------------------------------------------------------
Title: Chapter 4 - Helioseismic Inferences on the Internal Structure
and Dynamics of the Sun
Authors: Basu, Sarbani; Chaplin, William J.
2019sgsp.book...87B Altcode:
Helioseismology has made it possible to peel back the outer layers of
the Sun to allow inferences to be made about its internal structure,
dynamics, and solar cycle-related changes. In this chapter, we introduce
helioseismic analyses, in particular inversion methods, and then
discuss knowledge that has been acquired through the application of
these analysis techniques to what is now an observational data archive
stretching back over a few solar cycles.
---------------------------------------------------------
Title: Combining multiple structural inversions to constrain the
solar modelling problem
Authors: Buldgen, G.; Salmon, S. J. A. J.; Noels, A.; Scuflaire,
R.; Montalban, J.; Baturin, V. A.; Eggenberger, P.; Gryaznov, V. K.;
Iosilevskiy, I. L.; Meynet, G.; Chaplin, W. J.; Miglio, A.; Oreshina,
A. V.; Richard, O.; Starostin, A. N.
2019A&A...621A..33B Altcode: 2018arXiv180908958B
Context. The Sun is the most studied of all stars, which serves as a
reference for all other observed stars in the Universe. Furthermore,
it also serves the role of a privileged laboratory of fundamental
physics and can help us better understand processes occuring in
conditions irreproducible on Earth. However, our understanding of our
star is currently lessened by the so-called solar modelling problem,
resulting from comparisons of theoretical solar models to helioseismic
constraints. These discrepancies can stem from various causes, such as
the radiative opacities, the equation of state as well as the mixing
of the chemical elements. <BR /> Aims: By analysing the potential of
combining information from multiple seismic inversions, our aim is
to help disentangle the origins of the solar modelling problem. <BR
/> Methods: We combined inversions of the adiabatic sound speed, an
entropy proxy and the Ledoux discriminant with other constraints such
as the position of the base of the convective zone and the photospheric
helium abundance. First, we tested various combinations of standard
ingredients available for solar modelling such as abundance tables,
equation of state, formalism for convection and diffusion and opacity
tables. Second, we studied the diagnostic potential of the inversions
on models including ad hoc modifications of the opacity profile and
additional mixing below the convective envelope. <BR /> Results: We
show that combining inversions provides stringent constraints on the
required modifications to the solar ingredients, far beyond what can
be achieved from sound speed inversions alone. We constrain the form
and amplitude of the opacity increase required in solar models and show
that a 15% increase at log T = 6.35 provides a significant improvement,
but is insufficient on its own. A more global increase in the opacity,
within the uncertainties of the current tables, coupled with a localized
additional mixing at the bottom of the convective zone provides the best
agreement for low-metallicity models. We show that high-metallicity
models do not satisfy all the inversion results. We conclude that the
solar modelling problem likely occurs from multiple small contributors,
as other ingredients such as the equation of state or the formalism of
convection can induce small but significant changes in the models and
that using phase shift analyses combined with our approach is the next
step for a better understanding of the inaccuracies of solar models
just below the convective envelope.
---------------------------------------------------------
Title: The behaviour of galactic cosmic ray intensity during solar
activity cycle 24
Authors: Ross, Eddie; Chaplin, William J.
2018arXiv181202125R Altcode:
We have studied long-term variations of galactic cosmic ray (GCR)
intensity in relation to the sunspot number (SSN) during the most
recent solar cycles. This study analyses the time-lag between the GCR
intensity and SSN, and hysteresis plots of the GCR count rate against
SSN for solar activity cycles 20-23 to validate a methodology against
previous results in the literature, before applying the method to
provide a timely update on the behaviour of cycle 24. Cross-plots
of SSN vs GCR show a clear difference between the odd-numbered and
even-numbered cycles. Linear and elliptical models have been fit to
the data with the linear fit and elliptical model proving the more
suitable model for even-numbered and odd-numbered solar activity
cycles respectively, in agreement with previous literature. Through
the application of these methods for the 24th solar activity cycle,
it has been shown that cycle 24 experienced a lag of 2-4 months and
follows the trend of the preceding activity cycles albeit with a
slightly longer lag than previous even-numbered cycles. It has been
shown through the hysteresis analysis that the linear fit is a better
representative model for cycle 24, as the ellipse model doesn't show
a significant improvement, which is also in agreement with previous
even-numbered cycles.
---------------------------------------------------------
Title: The Second APOKASC Catalog: The Empirical Approach
Authors: Pinsonneault, Marc H.; Elsworth, Yvonne P.; Tayar, Jamie;
Serenelli, Aldo; Stello, Dennis; Zinn, Joel; Mathur, Savita;
García, Rafael A.; Johnson, Jennifer A.; Hekker, Saskia; Huber,
Daniel; Kallinger, Thomas; Mészáros, Szabolcs; Mosser, Benoit;
Stassun, Keivan; Girardi, Léo; Rodrigues, Thaíse S.; Silva Aguirre,
Victor; An, Deokkeun; Basu, Sarbani; Chaplin, William J.; Corsaro,
Enrico; Cunha, Katia; García-Hernández, D. A.; Holtzman, Jon;
Jönsson, Henrik; Shetrone, Matthew; Smith, Verne V.; Sobeck,
Jennifer S.; Stringfellow, Guy S.; Zamora, Olga; Beers, Timothy C.;
Fernández-Trincado, J. G.; Frinchaboy, Peter M.; Hearty, Fred R.;
Nitschelm, Christian
2018ApJS..239...32P Altcode: 2018arXiv180409983P
We present a catalog of stellar properties for a large sample of
6676 evolved stars with Apache Point Observatory Galactic Evolution
Experiment spectroscopic parameters and Kepler asteroseismic
data analyzed using five independent techniques. Our data include
evolutionary state, surface gravity, mean density, mass, radius, age,
and the spectroscopic and asteroseismic measurements used to derive
them. We employ a new empirical approach for combining asteroseismic
measurements from different methods, calibrating the inferred stellar
parameters, and estimating uncertainties. With high statistical
significance, we find that asteroseismic parameters inferred from
the different pipelines have systematic offsets that are not removed
by accounting for differences in their solar reference values. We
include theoretically motivated corrections to the large frequency
spacing (Δν) scaling relation, and we calibrate the zero-point of
the frequency of the maximum power (ν <SUB>max</SUB>) relation to be
consistent with masses and radii for members of star clusters. For most
targets, the parameters returned by different pipelines are in much
better agreement than would be expected from the pipeline-predicted
random errors, but 22% of them had at least one method not return
a result and a much larger measurement dispersion. This supports
the usage of multiple analysis techniques for asteroseismic stellar
population studies. The measured dispersion in mass estimates for
fundamental calibrators is consistent with our error model, which
yields median random and systematic mass uncertainties for RGB stars
of order 4%. Median random and systematic mass uncertainties are at
the 9% and 8% level, respectively, for red clump stars.
---------------------------------------------------------
Title: A Synthetic Sample of Short-cadence Solar-like Oscillators
for TESS
Authors: Ball, Warrick H.; Chaplin, William J.; Schofield, Mathew;
Miglio, Andrea; Bossini, Diego; Davies, Guy R.; Girardi, Léo
2018ApJS..239...34B Altcode: 2018arXiv180909108B
NASA’s Transiting Exoplanet Survey Satellite (TESS) has begun a
two-year survey of most of the sky, which will include light curves
for thousands of solar-like oscillators sampled at a cadence of two
minutes. To prepare for this steady stream of data, we present a
mock catalog of light curves, designed to realistically mimic the
properties of the TESS sample. In the process, we also present the
first public release of the asteroFLAG Artificial DataSet Generator,
which simulates light curves of solar-like oscillators based on input
mode properties. The targets are drawn from a simulation of the Milky
Way’s populations and are selected in the same way as TESS’s true
Asteroseismic Target List. The light curves are produced by combining
stellar models, pulsation calculations and semi-empirical models
of solar-like oscillators. We describe the details of the catalog
and provide several examples. We provide pristine light curves to
which noise can be added easily. This mock catalog will be valuable
in testing asteroseismology pipelines for TESS and our methods can
be applied in preparation and planning for other observatories and
observing campaigns.
---------------------------------------------------------
Title: Stellar Surface Magneto-convection as a Source of Astrophysical
Noise. II. Center-to-limb Parameterization of Absorption Line Profiles
and Comparison to Observations
Authors: Cegla, H. M.; Watson, C. A.; Shelyag, S.; Chaplin, W. J.;
Davies, G. R.; Mathioudakis, M.; Palumbo, M. L., III; Saar, S. H.;
Haywood, R. D.
2018ApJ...866...55C Altcode: 2018arXiv180711423C
Manifestations of stellar activity (such as star-spots, plage/faculae,
and convective flows) are well-known to induce spectroscopic
signals often referred to as astrophysical noise by exoplanet
hunters. For example, setting an ultimate goal of detecting true
Earth analogs demands reaching radial velocity (RV) precisions of
∼9 cm s<SUP>-1</SUP>. While this is becoming technically feasible
with the latest generation of highly stabilized spectrographs, it
is astrophysical noise that sets the true fundamental barrier on
attainable RV precisions. In this paper, we parameterize the impact
of solar surface magneto-convection on absorption line profiles, and
extend the analysis from the solar disk center (Paper I) to the solar
limb. Off disk-center, the plasma flows orthogonal to the granule tops
begin to lie along the line of sight, and those parallel to the granule
tops are no longer completely aligned with the observer. Moreover, the
granulation is corrugated and the granules can block other granules, as
well as the intergranular lane components. Overall, the visible plasma
flows and geometry of the corrugated surface significantly impact the
resultant line profiles and induce center-to-limb variations in shape
and net position. We detail these herein, and compare to various solar
observations. We find our granulation parameterization can recreate
realistic line profiles and induced radial velocity shifts, across
the stellar disk, indicative of both those found in computationally
heavy radiative 3D magnetohydrodynamical simulations and empirical
solar observations.
---------------------------------------------------------
Title: Changes in the sensitivity of solar p-mode frequency shifts
to activity over three solar cycles
Authors: Howe, R.; Chaplin, W. J.; Davies, G. R.; Elsworth, Y.; Basu,
S.; Broomhall, A. -M.
2018MNRAS.480L..79H Altcode: 2018arXiv180701504H; 2018MNRAS.tmpL.128H
Low-degree solar p-mode observations from the long-lived Birmingham
Solar-Oscillations Network (BiSON) stretch back further than any other
single helioseismic data set. Results from BiSON have suggested that the
response of the mode frequency to solar activity levels may be different
in different cycles. In order to check whether such changes can also
be seen at higher degrees, we compare the response of medium-degree
solar p modes to activity levels across three solar cycles using data
from Big Bear Solar Observatory, Global Oscillation Network Group,
Michelson Doppler Imager, and Helioseismic and Magnetic Imager, by
examining the shifts in the mode frequencies and their sensitivity to
solar activity levels. We compare these shifts and sensitivities with
those from radial modes from BiSON. We find that the medium-degree data
show small but significant systematic differences between the cycles,
with solar Cycle 24 showing a frequency shift about 10 per cent larger
than Cycle 23 for the same change in activity as determined by the
10.7 cm radio flux. This may support the idea that there have been
changes in the magnetic properties of the shallow subsurface layers
of the Sun that have the strongest influence on the frequency shifts.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Temporal frequency shifts in 87
Kepler stars (Santos+, 2018)
Authors: Santos, A. R. G.; Campante, T. L.; Chaplin, W. J.; Cunha,
M. S.; Lund, M. N.; Kiefer, R.; Salabert, D.; Garcia, R. A.; Davies,
G. R.; Elsworth, Y.; Howe, R.
2018yCat..22370017S Altcode:
In the Sun, the frequencies of the acoustic modes are observed to
vary in phase with the magnetic activity level. These frequency
variations are expected to be common in solar-type stars and contain
information about the activity-related changes that take place in
their interiors. The unprecedented duration of Kepler photometric
time-series provides a unique opportunity to detect and characterize
stellar magnetic cycles through asteroseismology. In this work, we
analyze a sample of 87 solar-type stars, measuring their temporal
frequency shifts over segments of 90 days. For each segment, the
individual frequencies are obtained through a Bayesian peak-bagging
tool. The mean frequency shifts are then computed and compared with:
(1) those obtained from a cross-correlation method; (2) the variation
in the mode heights; (3) a photometric activity proxy; and (4)
the characteristic timescale of the granulation. For each star and
90-day sub-series, we provide mean frequency shifts, mode heights, and
characteristic timescales of the granulation. Interestingly, more than
60% of the stars show evidence for (quasi-)periodic variations in the
frequency shifts. In the majority of the cases, these variations are
accompanied by variations in other activity proxies. About 20% of the
stars show mode frequencies and heights varying approximately in phase,
in opposition to what is observed for the Sun. <P />(2 data files).
---------------------------------------------------------
Title: Synergy between asteroseismology and exoplanet science:
an outlook
Authors: Campante, Tiago L.; Barros, Susana C. C.; Demangeon, Olivier;
da Nóbrega, Hugo J.; Kuszlewicz, James S.; Pereira, Filipe; Chaplin,
William J.; Huber, Daniel
2018phos.confE..50C Altcode: 2018arXiv181206150C
Space-based asteroseismology has been playing an important role in
the characterization of exoplanet-host stars and their planetary
systems. The future looks even brighter, with space missions such
as NASA's TESS and ESA's PLATO ready to take on this legacy. In
this contribution, we provide an outlook on the synergy between
asteroseismology and exoplanet science, namely, on the prospect of
conducting a populational study of giant planets around oscillating
evolved stars with the TESS mission.
---------------------------------------------------------
Title: HD 89345: a bright oscillating star hosting a transiting warm
Saturn-sized planet observed by K2
Authors: Van Eylen, V.; Dai, F.; Mathur, S.; Gandolfi, D.; Albrecht,
S.; Fridlund, M.; García, R. A.; Guenther, E.; Hjorth, M.;
Justesen, A. B.; Livingston, J.; Lund, M. N.; Pérez Hernández,
F.; Prieto-Arranz, J.; Regulo, C.; Bugnet, L.; Everett, M. E.;
Hirano, T.; Nespral, D.; Nowak, G.; Palle, E.; Silva Aguirre, V.;
Trifonov, T.; Winn, J. N.; Barragán, O.; Beck, P. G.; Chaplin,
W. J.; Cochran, W. D.; Csizmadia, S.; Deeg, H.; Endl, M.; Heeren,
P.; Grziwa, S.; Hatzes, A. P.; Hidalgo, D.; Korth, J.; Mathis, S.;
Montañes Rodriguez, P.; Narita, N.; Patzold, M.; Persson, C. M.;
Rodler, F.; Smith, A. M. S.
2018MNRAS.478.4866V Altcode: 2018arXiv180501860V; 2018MNRAS.tmp.1339V
We report the discovery and characterization of HD 89345b (K2-234b;
EPIC 248777106b), a Saturn-sized planet orbiting a slightly evolved
star. HD 89345 is a bright star (V = 9.3 mag) observed by the K2 mission
with 1 min time sampling. It exhibits solar-like oscillations. We
conducted asteroseismology to determine the parameters of the star,
finding the mass and radius to be 1.12^{+0.04}_{-0.01} M_⊙ and
1.657^{+0.020}_{-0.004} R_⊙, respectively. The star appears to
have recently left the main sequence, based on the inferred age,
9.4^{+0.4}_{-1.3} Gyr, and the non-detection of mixed modes. The
star hosts a `warm Saturn' (P = 11.8 d, R<SUB>p</SUB> = 6.86 ± 0.14
R<SUB>⊕</SUB>). Radial-velocity follow-up observations performed with
the FIbre-fed Echelle Spectrograph, HARPS, and HARPS-N spectrographs
show that the planet has a mass of 35.7 ± 3.3 M<SUB>⊕</SUB>. The
data also show that the planet's orbit is eccentric (e ≈ 0.2). An
investigation of the rotational splitting of the oscillation frequencies
of the star yields no conclusive evidence on the stellar inclination
angle. We further obtained Rossiter-McLaughlin observations, which
result in a broad posterior of the stellar obliquity. The planet
seems to confirm to the same patterns that have been observed for
other sub-Saturns regarding planet mass and multiplicity, orbital
eccentricity, and stellar metallicity.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Kepler planetary cand. VIII. DR25
reliability (Thompson+, 2018)
Authors: Thompson, S. E.; Coughlin, J. L.; Hoffman, K.; Mullally,
F.; Christiansen, J. L.; Burke, C. J.; Bryson, S.; Batalha, N.; Haas,
M. R.; Catanzarite, J.; Rowe, J. F.; Barentsen, G.; Caldwell, D. A.;
Clarke, B. D.; Jenkins, J. M.; Li, J.; Latham, D. W.; Lissauer, J. J.;
Mathur, S.; Morris, R. L.; Seader, S. E.; Smith, J. C.; Klaus, T. C.;
Twicken, J. D.; van Cleve, J. E.; Wohler, B.; Akeson, R.; Ciardi,
D. R.; Cochran, W. D.; Henze, C. E.; Howell, S. B.; Huber, D.; Prsa,
A.; Ramirez, S. V.; Morton, T. D.; Barclay, T.; Campbell, J. R.;
Chaplin, W. J.; Charbonneau, D.; Christensen-Dalsgaard, J.; Dotson,
J. L.; Doyle, L.; Dunham, E. W.; Dupree, A. K.; Ford, E. B.; Geary,
J. C.; Girouard, F. R.; Isaacson, H.; Kjeldsen, H.; Quintana, E. V.;
Ragozzine, D.; Shabram, M.; Shporer, A.; Aguirre, V. S.; Steffen,
J. H.; Still, M.; Tenenbaum, P.; Welsh, W. F.; Wolfgang, A.; Zamudio,
K. A.; Koch, D. G.; Borucki, W. J.
2018yCat..22350038T Altcode:
We present the Kepler Object of Interest (KOI) catalog of transiting
exoplanets based on searching 4yr of Kepler time series photometry (Data
Release 25, Q1-Q17: Twicken+, 2016, J/AJ/152/158). The catalog contains
8054 KOIs, of which 4034 are planet candidates with periods between
0.25 and 632 days. Of these candidates, 219 are new, including two in
multiplanet systems (KOI-82.06 and KOI-2926.05) and 10 high-reliability,
terrestrial-size, habitable zone candidates. This catalog was created
using a tool called the Robovetter, which automatically vets the DR25
threshold crossing events (TCEs). The Robovetter also vetted simulated
data sets and measured how well it was able to separate TCEs caused by
noise from those caused by low signal-to-noise transits. We discuss
the Robovetter and the metrics it uses to sort TCEs. For orbital
periods less than 100 days the Robovetter completeness (the fraction
of simulated transits that are determined to be planet candidates)
across all observed stars is greater than 85%. For the same period
range, the catalog reliability (the fraction of candidates that are not
due to instrumental or stellar noise) is greater than 98%. However,
for low signal-to-noise candidates between 200 and 500 days around
FGK-dwarf stars, the Robovetter is 76.7% complete and the catalog is
50.5% reliable. <P />(6 data files).
---------------------------------------------------------
Title: Empirical Relations for the Accurate Estimation of Stellar
Masses and Radii
Authors: Moya, Andy; Zuccarino, Federico; Chaplin, William J.; Davies,
Guy R.
2018ApJS..237...21M Altcode: 2018arXiv180606574M
In this work, we have taken advantage of the most recent accurate
stellar characterizations carried out using asteroseismology, eclipsing
binaries and interferometry to evaluate a comprehensive set of empirical
relations for the estimation of stellar masses and radii. We have
gathered a total of 934 stars—of which around two-thirds are on
the main sequence—that are characterized with different levels of
precision, most of them having estimates of M, R, T <SUB>eff</SUB>, L,
g, ρ, and [Fe/H]. We have deliberately used a heterogeneous sample (in
terms of characterizing techniques and spectroscopic types) to reduce
the influence of possible biases coming from the observation, reduction,
and analysis methods used to obtain the stellar parameters. We have
studied a total of 576 linear combinations of T <SUB>eff</SUB>, L,
g, ρ, and [Fe/H] (and their logarithms) to be used as independent
variables to estimate M or R. We have used an error-in-variables
linear regression algorithm to extract the relations and to ensure
the fair treatment of the uncertainties. We present a total of 38
new or revised relations that have an adj-R <SUP>2</SUP> regression
statistic higher than 0.85, and a relative accuracy and precision
better than 10% for almost all the cases. The relations cover almost
all the possible combinations of observables, ensuring that, whatever
list of observables is available, there is at least one relation for
estimating the stellar mass and radius.
---------------------------------------------------------
Title: Signatures of Magnetic Activity in the Seismic Data of
Solar-type Stars Observed by Kepler
Authors: Santos, A. R. G.; Campante, T. L.; Chaplin, W. J.; Cunha,
M. S.; Lund, M. N.; Kiefer, R.; Salabert, D.; García, R. A.; Davies,
G. R.; Elsworth, Y.; Howe, R.
2018ApJS..237...17S Altcode: 2018arXiv180600136S
In the Sun, the frequencies of the acoustic modes are observed to
vary in phase with the magnetic activity level. These frequency
variations are expected to be common in solar-type stars and contain
information about the activity-related changes that take place in
their interiors. The unprecedented duration of Kepler photometric
time-series provides a unique opportunity to detect and characterize
stellar magnetic cycles through asteroseismology. In this work, we
analyze a sample of 87 solar-type stars, measuring their temporal
frequency shifts over segments of 90 days. For each segment, the
individual frequencies are obtained through a Bayesian peak-bagging
tool. The mean frequency shifts are then computed and compared with:
(1) those obtained from a cross-correlation method; (2) the variation
in the mode heights; (3) a photometric activity proxy; and (4)
the characteristic timescale of the granulation. For each star and
90-day sub-series, we provide mean frequency shifts, mode heights,
and characteristic timescales of the granulation. Interestingly, more
than 60% of the stars show evidence for (quasi-)periodic variations in
the frequency shifts. In the majority of the cases, these variations
are accompanied by variations in other activity proxies. About 20%
of the stars show mode frequencies and heights varying approximately
in phase, in opposition to what is observed for the Sun.
---------------------------------------------------------
Title: Signatures of Solar Cycle 25 in Subsurface Zonal Flows
Authors: Howe, R.; Hill, F.; Komm, R.; Chaplin, W. J.; Elsworth, Y.;
Davies, G. R.; Schou, J.; Thompson, M. J.
2018ApJ...862L...5H Altcode: 2018arXiv180702398H
The pattern of migrating zonal flow bands associated with the solar
cycle, known as the torsional oscillation, has been monitored with
continuous global helioseismic observations by the Global Oscillations
Network Group (GONG), together with those made by the Michelson
Doppler Imager (MDI) on board the Solar and Heliospheric Observatory
(SOHO) and its successor, the Helioseismic and Magnetic Imager (HMI)
on board the Solar Dynamics Observatory (SDO), since 1995, giving us
nearly two full solar cycles of observations. We report that the flows
now show traces of the mid-latitude acceleration that is expected to
become the main equatorward-moving branch of the zonal flow pattern for
Cycle 25. Based on the current position of this branch, we speculate
that the onset of widespread activity for Cycle 25 is unlikely to be
earlier than the middle of 2019.
---------------------------------------------------------
Title: Establishing the accuracy of asteroseismic mass and radius
estimates of giant stars - I. Three eclipsing systems at [Fe/H]
∼ -0.3 and the need for a large high-precision sample
Authors: Brogaard, K.; Hansen, C. J.; Miglio, A.; Slumstrup, D.;
Frandsen, S.; Jessen-Hansen, J.; Lund, M. N.; Bossini, D.; Thygesen,
A.; Davies, G. R.; Chaplin, W. J.; Arentoft, T.; Bruntt, H.; Grundahl,
F.; Handberg, R.
2018MNRAS.476.3729B Altcode: 2018arXiv180108167B; 2018MNRAS.tmp..262B
We aim to establish and improve the accuracy level of asteroseismic
estimates of mass, radius, and age of giant stars. This can be achieved
by measuring independent, accurate, and precise masses, radii, effective
temperatures and metallicities of long period eclipsing binary stars
with a red giant component that displays solar-like oscillations. We
measured precise properties of the three eclipsing binary systems
KIC 7037405, KIC 9540226, and KIC 9970396 and estimated their ages be
5.3 ± 0.5, 3.1 ± 0.6, and 4.8 ± 0.5 Gyr. The measurements of the
giant stars were compared to corresponding measurements of mass,
radius, and age using asteroseismic scaling relations and grid
modelling. We found that asteroseismic scaling relations without
corrections to Δν systematically overestimate the masses of the
three red giants by 11.7 per cent, 13.7 per cent, and 18.9 per cent,
respectively. However, by applying theoretical correction factors
f<SUB>Δν</SUB> according to Rodrigues et al. (2017), we reached
general agreement between dynamical and asteroseismic mass estimates,
and no indications of systematic differences at the precision level
of the asteroseismic measurements. The larger sample investigated
by Gaulme et al. (2016) showed a much more complicated situation,
where some stars show agreement between the dynamical and corrected
asteroseismic measures while others suggest significant overestimates
of the asteroseismic measures. We found no simple explanation for this,
but indications of several potential problems, some theoretical, others
observational. Therefore, an extension of the present precision study
to a larger sample of eclipsing systems is crucial for establishing
and improving the accuracy of asteroseismology of giant stars.
---------------------------------------------------------
Title: Investigating the Metallicity-Mixing-length Relation
Authors: Viani, Lucas S.; Basu, Sarbani; Ong J., M. Joel; Bonaca,
Ana; Chaplin, William J.
2018ApJ...858...28V Altcode: 2018arXiv180305924V
Stellar models typically use the mixing-length approximation
as a way to implement convection in a simplified manner. While
conventionally the value of the mixing-length parameter, α, used is
the solar-calibrated value, many studies have shown that other values
of α are needed to properly model stars. This uncertainty in the
value of the mixing-length parameter is a major source of error in
stellar models and isochrones. Using asteroseismic data, we determine
the value of the mixing-length parameter required to properly model
a set of about 450 stars ranging in log g, {T}<SUB>eff</SUB>}, and
[{Fe}/{{H}}]. The relationship between the value of α required
and the properties of the star is then investigated. For Eddington
atmosphere, non-diffusion models, we find that the value of α can
be approximated by a linear model, in the form of α /{α }<SUB>⊙
</SUB>=5.426{--}0.101 {log}(g)-1.071 {log}({T}<SUB>eff</SUB>})
+0.437([{Fe}/{{H}}]). This process is repeated using a variety of
model physics, as well as compared with previous studies and results
from 3D convective simulations.
---------------------------------------------------------
Title: Using asteroseismology to characterise exoplanet host stars
Authors: Lundkvist, Mia S.; Huber, Daniel; Silva Aguirre, Victor;
Chaplin, William J.
2018arXiv180402214L Altcode:
The last decade has seen a revolution in the field of asteroseismology
- the study of stellar pulsations. It has become a powerful method to
precisely characterise exoplanet host stars, and as a consequence also
the exoplanets themselves. This synergy between asteroseismology and
exoplanet science has flourished in large part due to space missions
such as $\textit{Kepler}$, which have provided high-quality data that
can be used for both types of studies. Perhaps the primary contribution
from asteroseismology to the research on transiting exoplanets is
the determination of very precise stellar radii that translate into
precise planetary radii, but asteroseismology has also proven useful
in constraining eccentricities of exoplanets as well as the dynamical
architecture of planetary systems. In this contribution, we introduce
some basic principles of asteroseismology and review current synergies
between the two fields.
---------------------------------------------------------
Title: Planetary Candidates Observed by Kepler. VIII. A Fully
Automated Catalog with Measured Completeness and Reliability Based
on Data Release 25
Authors: Thompson, Susan E.; Coughlin, Jeffrey L.; Hoffman, Kelsey;
Mullally, Fergal; Christiansen, Jessie L.; Burke, Christopher J.;
Bryson, Steve; Batalha, Natalie; Haas, Michael R.; Catanzarite,
Joseph; Rowe, Jason F.; Barentsen, Geert; Caldwell, Douglas A.;
Clarke, Bruce D.; Jenkins, Jon M.; Li, Jie; Latham, David W.; Lissauer,
Jack J.; Mathur, Savita; Morris, Robert L.; Seader, Shawn E.; Smith,
Jeffrey C.; Klaus, Todd C.; Twicken, Joseph D.; Van Cleve, Jeffrey
E.; Wohler, Bill; Akeson, Rachel; Ciardi, David R.; Cochran, William
D.; Henze, Christopher E.; Howell, Steve B.; Huber, Daniel; Prša,
Andrej; Ramírez, Solange V.; Morton, Timothy D.; Barclay, Thomas;
Campbell, Jennifer R.; Chaplin, William J.; Charbonneau, David;
Christensen-Dalsgaard, Jørgen; Dotson, Jessie L.; Doyle, Laurance;
Dunham, Edward W.; Dupree, Andrea K.; Ford, Eric B.; Geary, John C.;
Girouard, Forrest R.; Isaacson, Howard; Kjeldsen, Hans; Quintana, Elisa
V.; Ragozzine, Darin; Shabram, Megan; Shporer, Avi; Silva Aguirre,
Victor; Steffen, Jason H.; Still, Martin; Tenenbaum, Peter; Welsh,
William F.; Wolfgang, Angie; Zamudio, Khadeejah A.; Koch, David G.;
Borucki, William J.
2018ApJS..235...38T Altcode: 2017arXiv171006758T
We present the Kepler Object of Interest (KOI) catalog of transiting
exoplanets based on searching 4 yr of Kepler time series photometry
(Data Release 25, Q1-Q17). The catalog contains 8054 KOIs, of which
4034 are planet candidates with periods between 0.25 and 632 days. Of
these candidates, 219 are new, including two in multiplanet systems
(KOI-82.06 and KOI-2926.05) and 10 high-reliability, terrestrial-size,
habitable zone candidates. This catalog was created using a tool called
the Robovetter, which automatically vets the DR25 threshold crossing
events (TCEs). The Robovetter also vetted simulated data sets and
measured how well it was able to separate TCEs caused by noise from
those caused by low signal-to-noise transits. We discuss the Robovetter
and the metrics it uses to sort TCEs. For orbital periods less than 100
days the Robovetter completeness (the fraction of simulated transits
that are determined to be planet candidates) across all observed stars
is greater than 85%. For the same period range, the catalog reliability
(the fraction of candidates that are not due to instrumental or stellar
noise) is greater than 98%. However, for low signal-to-noise candidates
between 200 and 500 days around FGK-dwarf stars, the Robovetter is
76.7% complete and the catalog is 50.5% reliable. The KOI catalog,
the transit fits, and all of the simulated data used to characterize
this catalog are available at the NASA Exoplanet Archive.
---------------------------------------------------------
Title: VizieR Online Data Catalog: KIC star parallaxes from
asteroseismology vs Gaia (Huber+, 2017)
Authors: Huber, D.; Zinn, J.; Bojsen-Hansen, M.; Pinsonneault, M.;
Sahlholdt, C.; Serenelli, A.; Aguirre, V. S.; Stassun, K.; Stello,
D.; Tayar, J.; Bastien, F.; Bedding, T. R.; Buchhave, L. A.; Chaplin,
W. J.; Davies, G. R.; Garcia, R. A.; Latham, D. W.; Mathur, S.;
Mosser, B.; Sharma, S.
2018yCat..18440102H Altcode:
Our sample consists of dwarfs, subgiants, and red giants from the
APOGEE-Kepler Asteroseismic Science Consortium (APOKASC, Pinsonneault+
J/ApJS/215/19), supplemented with seismic detections using Kepler
short-cadence data from Chaplin+ (2014MNRAS.445..946C) and Huber+
(2013, J/ApJ/767/127). <P />(2 data files).
---------------------------------------------------------
Title: VizieR Online Data Catalog: APOKASC catalog of KIC dwarfs
and subgiants (Serenelli+, 2017)
Authors: Serenelli, A.; Johnson, J.; Huber, D.; Pinsonneault, M.;
Ball, W. H.; Tayar, J.; Aguirre, V. S.; Basu, S.; Troup, N.; Hekker,
S.; Kallinger, T.; Stello, D.; Davies, G. R.; Lund, M. N.; Mathur,
S.; Mosser, B.; Stassun, K. G.; Chaplin, W. J.; Elsworth, Y.; Garcia,
R. A.; Handberg, R.; Holtzman, J.; Hearty, F.; Garcia-Hernandez,
D. A.; Gaulme, P.; Zamora, O.
2018yCat..22330023S Altcode:
The catalog consists of stars with detected solar-like oscillations in
Kepler short-cadence data as reported in Chaplin+ (2011Sci...332..213C)
and with spectroscopic observations from the APOGEE-1 survey (Majewski+
2017AJ....154...94M). APOGEE spectra cover the H band, between
1.51 and 1.7um, at a resolution R=22500. <P />This work extends the
first APOKASC red giants catalog presented in Pinsonneault+ (2014,
J/ApJS/215/19) to include 415 dwarf and subgiant stars. It is based
on global seismic parameters Δν and ν<SUB>max</SUB> obtained from
Kepler short-cadence asteroseismic data with length of light curves
spanning from 30 up to 1055 days. <P />(3 data files).
---------------------------------------------------------
Title: Seismic signatures of magnetic activity in solar-type stars
observed by Kepler
Authors: Santos, A. R. G.; Campante, T. L.; Chaplin, W. J.; Cunha,
M. S.; Lund, M. N.; Kiefer, R.; Salabert, D.; García, R. A.; Davies,
G. R.; Elsworth, Y.; Howe, R.
2018IAUS..340..225S Altcode: 2018arXiv180604263S
The properties of the acoustic modes are sensitive to magnetic
activity. The unprecedented long-term Kepler photometry, thus, allows
stellar magnetic cycles to be studied through asteroseismology. We
search for signatures of magnetic cycles in the seismic data of Kepler
solar-type stars. We find evidence for periodic variations in the
acoustic properties of about half of the 87 analysed stars. In these
proceedings, we highlight the results obtained for two such stars,
namely KIC 8006161 and KIC 5184732.
---------------------------------------------------------
Title: Characterizing Host Stars Using Asteroseismology
Authors: Lundkvist, Mia Sloth; Huber, Daniel; Aguirre, Víctor Silva;
Chaplin, William J.
2018haex.bookE.177L Altcode:
The last decade has seen a revolution in the field of asteroseismology
- the study of stellar pulsations. It has become a powerful method to
precisely characterize exoplanet host stars and as a consequence also
the exoplanets themselves. This synergy between asteroseismology and
exoplanet science has flourished in large part due to space missions
such as Kepler, which have provided high-quality data that can be
used for both types of studies. Perhaps the primary contribution
from asteroseismology to the research on transiting exoplanets is
the determination of very precise stellar radii that translate into
precise planetary radii, but asteroseismology has also proven useful
in constraining eccentricities of exoplanets as well as the dynamical
architecture of planetary systems. In this chapter, we introduce some
basic principles of asteroseismology and review current synergies
between the two fields.
---------------------------------------------------------
Title: The Influence of Metallicity on Stellar Differential Rotation
and Magnetic Activity
Authors: Karoff, Christoffer; Metcalfe, Travis S.; Santos, Ângela
R. G.; Montet, Benjamin T.; Isaacson, Howard; Witzke, Veronika;
Shapiro, Alexander I.; Mathur, Savita; Davies, Guy R.; Lund, Mikkel N.;
Garcia, Rafael A.; Brun, Allan S.; Salabert, David; Avelino, Pedro P.;
van Saders, Jennifer; Egeland, Ricky; Cunha, Margarida S.; Campante,
Tiago L.; Chaplin, William J.; Krivova, Natalie; Solanki, Sami K.;
Stritzinger, Maximilian; Knudsen, Mads F.
2018ApJ...852...46K Altcode: 2017arXiv171107716K
Observations of Sun-like stars over the past half-century have improved
our understanding of how magnetic dynamos, like that responsible for the
11 yr solar cycle, change with rotation, mass, and age. Here we show
for the first time how metallicity can affect a stellar dynamo. Using
the most complete set of observations of a stellar cycle ever obtained
for a Sun-like star, we show how the solar analog HD 173701 exhibits
solar-like differential rotation and a 7.4 yr activity cycle. While
the duration of the cycle is comparable to that generated by the solar
dynamo, the amplitude of the brightness variability is substantially
stronger. The only significant difference between HD 173701 and the
Sun is its metallicity, which is twice the solar value. Therefore,
this provides a unique opportunity to study the effect of the
higher metallicity on the dynamo acting in this star and to obtain a
comprehensive understanding of the physical mechanisms responsible
for the observed photometric variability. The observations can be
explained by the higher metallicity of the star, which is predicted to
foster a deeper outer convection zone and a higher facular contrast,
resulting in stronger variability.
---------------------------------------------------------
Title: Empirically Calibrated Asteroseismic Masses and Radii for
Red Giants in the Kepler Fields
Authors: Pinsonneault, Marc; Elsworth, Yvonne; Silva Aguirre, Victor;
Chaplin, William J.; Garcia, Rafael A.; Hekker, Saskia; Holtzman,
Jon; Huber, Daniel; Johnson, Jennifer; Kallinger, Thomas; Mosser,
Benoit; Mathur, Savita; Serenelli, Aldo; Shetrone, Matthew; Stello,
Dennis; Tayar, Jamie; Zinn, Joel; APOGEE Team, KASC Team, APOKASC Team
2018AAS...23145013P Altcode:
We report on the joint asteroseismic and spectroscopic properties
of a sample of 6048 evolved stars in the fields originally observed
by the Kepler satellite. We use APOGEE spectroscopic data taken
from Data Release 13 of the Sloan Digital Sky Survey, combined with
asteroseismic data analyzed by members of the Kepler Asteroseismic
Science Consortium. With high statistical significance, the different
pipelines do not have relative zero points that are the same as the
solar values, and red clump stars do not have the same empirical
relative zero points as red giants. We employ theoretically motivated
corrections to the scaling relation for the large frequency spacing,
and adjust the zero point of the frequency of maximum power scaling
relation to be consistent with masses and radii for members of star
clusters. The scatter in calibrator masses is consistent with our error
estimation. Systematic and random mass errors are explicitly separated
and identified. The measurement scatter, and random uncertainties, are
three times larger for red giants where one or more technique failed to
return a value than for targets where all five methods could do so, and
this is a substantial fraction of the sample (20% of red giants and 25%
of red clump stars). Overall trends and future prospects are discussed.
---------------------------------------------------------
Title: Spatial incoherence of solar granulation: a global analysis
using BiSON 2B data
Authors: Lund, Mikkel N.; Chaplin, William J.; Hale, Steven J.;
Davies, Guy R.; Elsworth, Yvonne P.; Howe, Rachel
2017MNRAS.472.3256L Altcode: 2017arXiv170901329L
A poor understanding of the impact of convective turbulence in the
outer layers of the Sun and Sun-like stars challenges the advance
towards an improved understanding of their internal structure and
dynamics. Assessing and calibrating these effects is therefore of
great importance. Here, we study the spatial coherence of granulation
noise and oscillation modes in the Sun, with the aim of exploiting
any incoherence to beat down observed granulation noise, hence
improving the detection of low-frequency p modes. Using data from
the BiSON 2B instrument, we assess the coherence between different
atmospheric heights and between different surface regions. We find
that granulation noise from the different atmospheric heights probed
is largely incoherent; frequency regions dominated by oscillations
are almost fully coherent. We find a randomized phase difference for
the granulation noise, and a near zero difference for the evanescent
oscillations. A reduction of the incoherent granulation noise is shown
by application of the cross-spectrum.
---------------------------------------------------------
Title: The masses of retired A stars with asteroseismology: Kepler
and K2 observations of exoplanet hosts
Authors: North, Thomas S. H.; Campante, Tiago L.; Miglio, Andxsrea;
Davies, Guy R.; Grunblatt, Samuel K.; Huber, Daniel; Kuszlewicz,
James S.; Lund, Mikkel N.; Cooke, Benjamin F.; Chaplin, William J.
2017MNRAS.472.1866N Altcode: 2017arXiv170800716N
We investigate the masses of 'retired A stars' using asteroseismic
detections on seven low-luminosity red-giant and sub-giant stars
observed by the NASA Kepler and K2 missions. Our aim is to explore
whether masses derived from spectroscopy and isochrone fitting may have
been systematically overestimated. Our targets have all previously been
subject to long-term radial velocity observations to detect orbiting
bodies, and satisfy the criteria used by Johnson et al. to select
survey stars which may have had A-type (or early F-type) main-sequence
progenitors. The sample actually spans a somewhat wider range in mass,
from ≈ 1 M<SUB>⊙</SUB> up to ≈ 1.7 M<SUB>⊙</SUB>. Whilst for
five of the seven stars the reported discovery mass from spectroscopy
exceeds the mass estimated using asteroseismology, there is no strong
evidence for a significant, systematic bias across the sample. Moreover,
comparisons with other masses from the literature show that the absolute
scale of any differences is highly sensitive to the chosen reference
literature mass, with the scatter between different literature masses
significantly larger than reported error bars. We find that any mass
difference can be explained through use of different constraints during
the recovery process. We also conclude that underestimated uncertainties
on the input parameters can significantly bias the recovered stellar
masses, which may have contributed to the controversy on the mass
scale for retired A stars.
---------------------------------------------------------
Title: Seeing Double with K2: Testing Re-inflation with Two Remarkably
Similar Planets around Red Giant Branch Stars
Authors: Grunblatt, Samuel K.; Huber, Daniel; Gaidos, Eric; Lopez,
Eric D.; Howard, Andrew W.; Isaacson, Howard T.; Sinukoff, Evan;
Vanderburg, Andrew; Nofi, Larissa; Yu, Jie; North, Thomas S. H.;
Chaplin, William; Foreman-Mackey, Daniel; Petigura, Erik; Ansdell,
Megan; Weiss, Lauren; Fulton, Benjamin; Lin, Douglas N. C.
2017AJ....154..254G Altcode: 2017arXiv170605865G
Despite more than 20 years since the discovery of the first gas giant
planet with an anomalously large radius, the mechanism for planet
inflation remains unknown. Here, we report the discovery of K2-132b,
an inflated gas giant planet found with the NASA K2 Mission, and
a revised mass for another inflated planet, K2-97b. These planets
orbit on ≍9 day orbits around host stars that recently evolved
into red giants. We constrain the irradiation history of these
planets using models constrained by asteroseismology and Keck/High
Resolution Echelle Spectrometer spectroscopy and radial velocity
measurements. We measure planet radii of 1.31 ± 0.11 R<SUB>J</SUB>
and 1.30 ± 0.07 R<SUB>J</SUB>, respectively. These radii are typical
for planets receiving the current irradiation, but not the former,
zero age main-sequence irradiation of these planets. This suggests
that the current sizes of these planets are directly correlated to
their current irradiation. Our precise constraints of the masses
and radii of the stars and planets in these systems allow us to
constrain the planetary heating efficiency of both systems as 0.03
%<SUB>-0.02%</SUB><SUP>0.03%</SUP>. These results are consistent with
a planet re-inflation scenario, but suggest that the efficiency of
planet re-inflation may be lower than previously theorized. Finally,
we discuss the agreement within 10% of the stellar masses and radii,
and the planet masses, radii, and orbital periods of both systems,
and speculate that this may be due to selection bias in searching for
planets around evolved stars.
---------------------------------------------------------
Title: The First APOKASC Catalog of Kepler Dwarf and Subgiant Stars
Authors: Serenelli, Aldo; Johnson, Jennifer; Huber, Daniel;
Pinsonneault, Marc; Ball, Warrick H.; Tayar, Jamie; Silva Aguirre,
Victor; Basu, Sarbani; Troup, Nicholas; Hekker, Saskia; Kallinger,
Thomas; Stello, Dennis; Davies, Guy R.; Lund, Mikkel N.; Mathur,
Savita; Mosser, Benoit; Stassun, Keivan G.; Chaplin, William J.;
Elsworth, Yvonne; García, Rafael A.; Handberg, Rasmus; Holtzman, Jon;
Hearty, Fred; García-Hernández, D. A.; Gaulme, Patrick; Zamora, Olga
2017ApJS..233...23S Altcode: 2017arXiv171006858S
We present the first APOKASC catalog of spectroscopic and asteroseismic
data for dwarfs and subgiants. Asteroseismic data for our sample
of 415 objects have been obtained by the Kepler mission in short
(58.5 s) cadence, and light curves span from 30 up to more than 1000
days. The spectroscopic parameters are based on spectra taken as part
of the Apache Point Observatory Galactic Evolution Experiment and
correspond to Data Release 13 of the Sloan Digital Sky Survey. We
analyze our data using two independent {T}<SUB>{eff</SUB>} scales,
the spectroscopic values from DR13 and those derived from SDSS griz
photometry. We use the differences in our results arising from these
choices as a test of systematic temperature uncertainties and find
that they can lead to significant differences in the derived stellar
properties. Determinations of surface gravity ({log}g), mean density
(< ρ > ), radius (R), mass (M), and age (τ) for the whole sample
have been carried out by means of (stellar) grid-based modeling. We
have thoroughly assessed random and systematic error sources in the
spectroscopic and asteroseismic data, as well as in the grid-based
modeling determination of the stellar quantities provided in the
catalog. We provide stellar properties determined for each of the two
{T}<SUB>{eff</SUB>} scales. The median combined (random and systematic)
uncertainties are 2% (0.01 dex; {log}g), 3.4% (< ρ > ), 2.6%
(R), 5.1% (M), and 19% (τ) for the photometric {T}<SUB>{eff</SUB>}
scale and 2% ({log}g), 3.5% (< ρ > ), 2.7% (R), 6.3% (M), and 23%
(τ) for the spectroscopic scale. We present comparisons with stellar
quantities in the asteroseismic catalog by Chaplin et al. that highlight
the importance of having metallicity measurements for determining
stellar parameters accurately. Finally, we compare our results with
those coming from a variety of sources, including stellar radii
determined from TGAS parallaxes and asteroseismic analyses based on
individual frequencies. We find a very good agreement for all inferred
quantities. The latter comparison, in particular, gives strong support
to the determination of stellar quantities based on global seismology,
a relevant result for future missions such as TESS and PLATO.
---------------------------------------------------------
Title: VizieR Online Data Catalog: 61 main-sequence and subgiant
oscillations (Appourchaux+, 2012)
Authors: Appourchaux, T.; Chaplin, W. J.; Garcia, R. A.; Gruberbauer,
M.; Verner, G. A.; Antia, H. M.; Benomar, O.; Campante, T. L.; Davies,
G. R.; Deheuvels, S.; Handberg, R.; Hekker, S.; Howe, R.; Regulo,
C.; Salabert, D.; Bedding, T. R.; White, T. R.; Ballot, J.; Mathur,
S.; Silva Aguirre, V.; Elsworth, Y. P.; Basu, S.; Gilliland, R. L.;
Christensen-Dalsgaard, J.; Kjeldsen, H.; Uddin, K.; Stumpe, M. C.;
Barclay, T.
2017yCat..35430054A Altcode:
Kepler observations are obtained in two different operating
modes: long cadence (LC) and short cadence (SC) (Gilliland et al.,
2010ApJ...713L.160G; Jenkins et al., 2010ApJ...713L..87J). This work is
based on SC data. For the brightest stars (down to Kepler magnitude,
Kp~=12), SC observations can be obtained for a limited number of
stars (up to 512 at any given time) with a faster sampling cadence
of 58.84876s (Nyquist frequency of ~8.5mHz), which permits a more
precise transit timing and the performance of asteroseismology. Kepler
observations are divided into three-month-long quarters (Q). A subset
of 61 solar-type stars observed during quarters Q5-Q7 (March 22,
2010 to December 22, 2010) were chosen because they have oscillation
modes with high signal-to-noise ratios. This length of data gives a
frequency resolution of about 0.04uHz. <P />(2 data files).
---------------------------------------------------------
Title: Erratum: “Standing on the Shoulders of Dwarfs: The Kepler
Asteroseismic LEGACY Sample. I. Oscillation Mode Parameters”
(<A href="https://doi.org/10.3847/1538-4357/835/2/172">2017, ApJ,
835, 172</A>)
Authors: Lund, Mikkel N.; Silva Aguirre, Víctor; Davies, Guy R.;
Chaplin, William J.; Christensen-Dalsgaard, Jørgen; Houdek, Günter;
White, Timothy R.; Bedding, Timothy R.; Ball, Warrick H.; Huber,
Daniel; Antia, H. M.; Lebreton, Yveline; Latham, David W.; Handberg,
Rasmus; Verma, Kuldeep; Basu, Sarbani; Casagrande, Luca; Justesen,
Anders B.; Kjeldsen, Hans; Mosumgaard, Jakob R.
2017ApJ...850..110L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: VizieR Online Data Catalog: Asterosismology for solar analogues
16 Cyg A/B (Davies+, 2015)
Authors: Davies, G. R.; Chaplin, W. J.; Farr, W. M.; Garcia, R. A.;
Lund, M. N.; Mathis, S.; Metcalfe, T. S.; Appourchaux, T.; Basu, S.;
Benomar, O.; Campante, T. L.; Ceillier, T.; Elsworth, Y.; Handberg,
R.; Salabert, D.; Stello, D.
2017yCat..74462959D Altcode:
Both 16 Cyg A and B are brighter (V~6) than the saturation limit for
which Kepler observations were designed. However, it was possible to
capture the full stellar flux by using custom photometric aperture
masks. Thus, 928 d of short-cadence observations (Gilliland et
al. 2010ApJ...713L.160G) - from Quarter 7 to 16 - were generated using
simple aperture photometry (Jenkins et al. 2010ApJ...713L..87J) and
then corrected for instrumental perturbations following the methods
described by Garcia et al. (2011MNRAS.414L...6G). The final light
curves used for asteroseismic analyses were high-pass filtered using
a triangular smooth of 4 d width and have a duty cycle of 90.5 per
cent. The power density spectra were computed using a Lomb-Scargle
algorithm. <P />(2 data files).
---------------------------------------------------------
Title: NGC 6819: testing the asteroseismic mass scale, mass loss
and evidence for products of non-standard evolution
Authors: Handberg, R.; Brogaard, K.; Miglio, A.; Bossini, D.; Elsworth,
Y.; Slumstrup, D.; Davies, G. R.; Chaplin, W. J.
2017MNRAS.472..979H Altcode: 2017arXiv170708223H
We present an extensive peakbagging effort on Kepler data of ∼50
red giant stars in the open star cluster NGC 6819. By employing
sophisticated pre-processing of the time series and Markov chain Monte
Carlo techniques we extracted individual frequencies, heights and line
widths for hundreds of oscillation modes. We show that the 'average'
asteroseismic parameter δν<SUB>02</SUB>, derived from these,
can be used to distinguish the stellar evolutionary state between
the red giant branch (RGB) stars and red clump (RC) stars. Masses
and radii are estimated using asteroseismic scaling relations,
both empirically corrected to obtain self-consistency and agreement
with independent measures of distance, and using updated theoretical
corrections. Remarkable agreement is found, allowing the evolutionary
state of the giants to be determined exclusively from the empirical
correction to the scaling relations. We find a mean mass of the RGB
stars and RC stars in NGC 6819 to be 1.61 ± 0.02 and 1.64 ± 0.02
M<SUB>⊙</SUB>, respectively. The difference ΔM = -0.03 ± 0.01
M<SUB>⊙</SUB> is almost insensitive to systematics, suggesting
very little RGB mass loss, if any. Stars that are outliers relative
to the ensemble reveal overmassive members that likely evolved via
mass transfer in a blue straggler phase. We suggest that KIC 4937011,
a low-mass Li-rich giant, is a cluster member in the RC phase that
experienced very high mass loss during its evolution. Such over- and
undermassive stars need to be considered when studying field giants,
since the true age of such stars cannot be known and there is currently
no way to distinguish them from normal stars.
---------------------------------------------------------
Title: Data preparation for asteroseismology with TESS
Authors: Lund, Mikkel N.; Handberg, Rasmus; Kjeldsen, Hans; Chaplin,
William J.; Christensen-Dalsgaard, Jørgen
2017EPJWC.16001005L Altcode: 2016arXiv161002702L
The Transiting Exoplanet Survey Satellite (TESS) is a NASA Astrophysics
Explorer mission. Following its scheduled launch in 2017, TESS will
focus on detecting exoplanets around the nearest and brightest stars in
the sky, for which detailed follow-up observations are possible. TESS
will, as the NASA Kepler mission, include a asteroseismic program that
will be organized within the TESS Asteroseismic Science Consortium
(TASC), building on the success of the Kepler Asteroseismic Science
Consortium (KASC). Within TASC data for asteroseismic analysis will be
prepared by the TASC Working Group 0 (WG-0), who will facilitate data
to the community via the TESS Asteroseismic Science Operations Center
(TASOC), again building on the success of the corresponding KASOC
platform for Kepler. Here, we give an overview of the steps being
taken within WG-0 to prepare for the upcoming TESS mission.
---------------------------------------------------------
Title: The more the merrier: grid based modelling of Kepler dwarfs
with 5-dimensional stellar grids
Authors: Serenelli, Aldo; Chaplin, William J.; Huber, Daniel
2017EPJWC.16003011S Altcode: 2017arXiv170600503S
We present preliminary results of our grid based modelling (GBM) of
the dwarf/subgiant sample of stars observed with Kepler including
global asteroseismic parameters. GBM analysis in this work is
based on a large grid of stellar models that is characterized by
five independent parameters: model mass and age, initial metallicity
(Z<SUB>ini</SUB>), initial helium (Y<SUB>ini</SUB>), and mixing length
parameter (α<SUB>MLT</SUB>). Using this grid relaxes assumptions
used in all previous GBM work where the initial composition is
determined by a single parameter and that α<SUB>MLT</SUB> is fixed to
a solar-calibrated value. The new grid allows us to study, for example,
the impact of different galactic chemical enrichment models on the
determination of stellar parameters such as mass radius and age. Also,
it allows to include new results from stellar atmosphere models on
α<SUB>MLT</SUB> in the GBM analysis in a simple manner. Alternatively,
it can be tested if global asteroseismology is a useful tool to
constraint our ignorance on quantities such as Y<SUB>ini</SUB> and
α<SUB>MLT</SUB>. Initial findings show that mass determination is
robust with respect to freedom in the latter quantities, with a 4.4%
maximum deviation for extreme assumptions regarding prior information
on Y<SUB>ini</SUB> - Z<SUB>ini</SUB> relations and a<SUB>MLT</SUB>. On
the other hand, tests carried out so far seem to indicate that global
seismology does not have much power to constrain Y<SUB>ini</SUB> -
Z<SUB>ni</SUB> relations of α<SUB>MLT</SUB> values without resourcing
to additional information.
---------------------------------------------------------
Title: On the relation between activity-related frequency shifts
and the sunspot distribution over the solar cycle 23
Authors: Santos, Ângela R. G.; Cunha, Margarida S.; Avelino, Pedro
P.; Chaplin, William J.; Campante, Tiago L.
2017EPJWC.16002013S Altcode: 2016arXiv161107475S
The activity-related variations in the solar acoustic frequencies have
been known for 30 years. However, the importance of the different
contributions is still not well established. With this in mind, we
developed an empirical model to estimate the spot-induced frequency
shifts, which takes into account the sunspot properties, such as area
and latitude. The comparison between the model frequency shifts obtained
from the daily sunspot records and those observed suggests that the
contribution from a stochastic component to the total frequency
shifts is about 30%. The remaining 70% is related to a global,
long-term variation. We also propose a new observable to investigate
the short-and mid-term variations of the frequency shifts, which is
insensitive to the long-term variations contained in the data. On
the shortest time scales the variations in the frequency shifts are
strongly correlated with the variations in the total area covered by
sunspots. However, a significant loss of correlation is still found,
which cannot be fully explained by ignoring the invisible side of
the Sun when accounting for the total sunspot area. We also verify
that the times when the frequency shifts and the sunspot areas do not
vary in a similar way tend to coincide with the times of the maximum
amplitude of the quasi-biennial variations found in the seismic data.
---------------------------------------------------------
Title: The Sun in transition? Persistence of near-surface structural
changes through Cycle 24
Authors: Howe, R.; Davies, G. R.; Chaplin, W. J.; Elsworth, Y.; Basu,
S.; Hale, S. J.; Ball, W. H.; Komm, R. W.
2017MNRAS.470.1935H Altcode: 2017arXiv170509099H
We examine the frequency shifts in low-degree helioseismic modes
from the Birmingham Solar-Oscillations Network covering the period
from 1985 to 2016, and compare them with a number of global activity
proxies well as a latitudinally resolved magnetic index. As well as
looking at frequency shifts in different frequency bands, we look at a
parametrization of the shift as a cubic function of frequency. While the
shifts in the medium- and high-frequency bands are very well correlated
with all of the activity indices (with the best correlation being with
the 10.7-cm radio flux), we confirm earlier findings that there appears
to have been a change in the frequency response to activity during solar
Cycle 23, and the low-frequency shifts are less correlated with activity
in the last two cycles than they were in Cycle 22. At the same time,
the more recent cycles show a slight increase in their sensitivity to
activity levels at medium and higher frequencies, perhaps because a
greater proportion of activity is composed of weaker or more ephemeral
regions. This lends weight to the speculation that a fundamental change
in the nature of the solar dynamo may be in progress.
---------------------------------------------------------
Title: Atmospheric Extinction Coefficients in the I<SUB>c</SUB>
Band for Several Major International Observatories: Results from
the BiSON Telescopes, 1984-2016
Authors: Hale, S. J.; Chaplin, W. J.; Davies, G. R.; Elsworth, Y. P.;
Howe, R.; Lund, M. N.; Moxon, E. Z.; Thomas, A.; Pallé, P. L.;
Rhodes, E. J., Jr.
2017AJ....154...89H Altcode: 2017arXiv170706647H
Over 30 years of solar data have been acquired by the Birmingham Solar
Oscillations Network (BiSON), an international network of telescopes
used to study oscillations of the Sun. Five of the six BiSON telescopes
are located at major observatories. The observational sites are, in
order of increasing longitude: Mount Wilson (Hale) Observatory (MWO),
California, USA; Las Campanas Observatory, Chile; Observatorio del
Teide, Izaña, Tenerife, Canary Islands; the South African Astronomical
Observatory, Sutherland, South Africa; Carnarvon, Western Australia;
and the Paul Wild Observatory, Narrabri, New South Wales, Australia. The
BiSON data may be used to measure atmospheric extinction coefficients
in the {{{I}}}<SUB>{{c</SUB>}} band (approximately 700-900 nm), and
presented here are the derived atmospheric extinction coefficients
from each site over the years 1984-2016.
---------------------------------------------------------
Title: The Apache Point Observatory Galactic Evolution Experiment
(APOGEE)
Authors: Majewski, Steven R.; Schiavon, Ricardo P.; Frinchaboy, Peter
M.; Allende Prieto, Carlos; Barkhouser, Robert; Bizyaev, Dmitry;
Blank, Basil; Brunner, Sophia; Burton, Adam; Carrera, Ricardo;
Chojnowski, S. Drew; Cunha, Kátia; Epstein, Courtney; Fitzgerald,
Greg; García Pérez, Ana E.; Hearty, Fred R.; Henderson, Chuck;
Holtzman, Jon A.; Johnson, Jennifer A.; Lam, Charles R.; Lawler,
James E.; Maseman, Paul; Mészáros, Szabolcs; Nelson, Matthew;
Nguyen, Duy Coung; Nidever, David L.; Pinsonneault, Marc; Shetrone,
Matthew; Smee, Stephen; Smith, Verne V.; Stolberg, Todd; Skrutskie,
Michael F.; Walker, Eric; Wilson, John C.; Zasowski, Gail; Anders,
Friedrich; Basu, Sarbani; Beland, Stephane; Blanton, Michael R.;
Bovy, Jo; Brownstein, Joel R.; Carlberg, Joleen; Chaplin, William;
Chiappini, Cristina; Eisenstein, Daniel J.; Elsworth, Yvonne; Feuillet,
Diane; Fleming, Scott W.; Galbraith-Frew, Jessica; García, Rafael A.;
García-Hernández, D. Aníbal; Gillespie, Bruce A.; Girardi, Léo;
Gunn, James E.; Hasselquist, Sten; Hayden, Michael R.; Hekker, Saskia;
Ivans, Inese; Kinemuchi, Karen; Klaene, Mark; Mahadevan, Suvrath;
Mathur, Savita; Mosser, Benoît; Muna, Demitri; Munn, Jeffrey A.;
Nichol, Robert C.; O'Connell, Robert W.; Parejko, John K.; Robin,
A. C.; Rocha-Pinto, Helio; Schultheis, Matthias; Serenelli, Aldo M.;
Shane, Neville; Silva Aguirre, Victor; Sobeck, Jennifer S.; Thompson,
Benjamin; Troup, Nicholas W.; Weinberg, David H.; Zamora, Olga
2017AJ....154...94M Altcode: 2015arXiv150905420M
The Apache Point Observatory Galactic Evolution Experiment (APOGEE),
one of the programs in the Sloan Digital Sky Survey III (SDSS-III),
has now completed its systematic, homogeneous spectroscopic survey
sampling all major populations of the Milky Way. After a three-year
observing campaign on the Sloan 2.5 m Telescope, APOGEE has collected a
half million high-resolution (R ∼ 22,500), high signal-to-noise ratio
(>100), infrared (1.51-1.70 μm) spectra for 146,000 stars, with
time series information via repeat visits to most of these stars. This
paper describes the motivations for the survey and its overall
design—hardware, field placement, target selection, operations—and
gives an overview of these aspects as well as the data reduction,
analysis, and products. An index is also given to the complement of
technical papers that describe various critical survey components
in detail. Finally, we discuss the achieved survey performance and
illustrate the variety of potential uses of the data products by way
of a number of science demonstrations, which span from time series
analysis of stellar spectral variations and radial velocity variations
from stellar companions, to spatial maps of kinematics, metallicity,
and abundance patterns across the Galaxy and as a function of age, to
new views of the interstellar medium, the chemistry of star clusters,
and the discovery of rare stellar species. As part of SDSS-III Data
Release 12 and later releases, all of the APOGEE data products are
publicly available.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Kepler asteroseismic LEGACY
sample. I. Oscillations (Lund+, 2017)
Authors: Lund, M. N.; Silva Aguirre, V.; Davies, G. R.; Chaplin,
W. J.; Christensen-Dalsgaard, J.; Houdek, G.; White, T. R.; Bedding,
T. R.; Ball, W. H.; Huber, D.; Antia, H. M.; Lebreton, Y.; Latham,
D. W.; Handberg, R.; Verma, K.; Basu, S.; Casagrande, L.; Justesen,
A. B.; Kjeldsen, H.; Mosumgaard, J. R.
2017yCat..18350172L Altcode:
The advent of space-based missions like Kepler has revolutionized the
study of solar-type stars, particularly through the measurement and
modeling of their resonant modes of oscillation. Here we analyze
a sample of 66 Kepler main-sequence stars showing solar-like
oscillations as part of the Kepler seismic LEGACY project. We use
Kepler short-cadence data, of which each star has at least 12 months,
to create frequency-power spectra optimized for asteroseismology. For
each star, we identify its modes of oscillation and extract parameters
such as frequency, amplitude, and line width using a Bayesian Markov
chain Monte Carlo "peak-bagging" approach. We report the extracted
mode parameters for all 66 stars, as well as derived quantities such
as frequency difference ratios, the large and small separations Δν
and δν<SUB>02</SUB>; the behavior of line widths with frequency
and line widths at ν<SUB>max</SUB> with T<SUB>eff</SUB>, for which
we derive parametrizations; and behavior of mode visibilities. These
average properties can be applied in future peak-bagging exercises to
better constrain the parameters of the stellar oscillation spectra. The
frequencies and frequency ratios can tightly constrain the fundamental
parameters of these solar-type stars, and mode line widths and
amplitudes can test models of mode damping and excitation. <P />(4
data files).
---------------------------------------------------------
Title: VizieR Online Data Catalog: Kepler asteroseismic LEGACY
sample. II. (Silva Aguirre+, 2017)
Authors: Silva Aguirre, V.; Lund, M. N.; Antia, H. M.; Ball, W. H.;
Basu, S.; Christensen-Dalsgaard, J.; Lebreton, Y.; Reese, D. R.; Verma,
K.; Casagrande, L.; Justesen, A. B.; Mosumgaard, J. R.; Chaplin, W. J.;
Bedding, T. R.; Davies, G. R.; Handberg, R.; Houdek, G.; Huber, D.;
Kjeldsen, H.; Latham, D. W.; White, T. R.; Coelho, H. R.; Miglio,
A.; Rendle, B.
2017yCat..18350173S Altcode:
The 66 stars comprising the LEGACY sample were chosen from more than 500
main-sequence and subgiant targets in which Kepler detected oscillations
(Chaplin+ 2014, J/ApJS/210/1). We selected all targets that had more
than one year of short-cadence observations, and where inspection of
the power spectrum did not reveal any clear signature of bumped l=1
modes. <P />(3 data files).
---------------------------------------------------------
Title: VizieR Online Data Catalog: K2 GAP data release. I. Campaign 1
(Stello+, 2017)
Authors: Stello, D.; Zinn, J.; Elsworth, Y.; Garcia, R. A.; Kallinger,
T.; Mathur, S.; Mosser, B.; Sharma, S.; Chaplin, W. J.; Davies, G.;
Huber, D.; Jones, C. D.; Miglio, A.; Silva Aguirre, V.
2017yCat..18350083S Altcode:
All K2 Galactic Archaeology Program (GAP; Stello+ 2015ApJ...809L...3S)
targets were observed with Kepler for about 80 days from 2014 May 30
to August 21. <P />(2 data files).
---------------------------------------------------------
Title: Asteroseismology and Gaia: Testing Scaling Relations Using
2200 Kepler Stars with TGAS Parallaxes
Authors: Huber, Daniel; Zinn, Joel; Bojsen-Hansen, Mathias;
Pinsonneault, Marc; Sahlholdt, Christian; Serenelli, Aldo; Silva
Aguirre, Victor; Stassun, Keivan; Stello, Dennis; Tayar, Jamie;
Bastien, Fabienne; Bedding, Timothy R.; Buchhave, Lars A.; Chaplin,
William J.; Davies, Guy R.; García, Rafael A.; Latham, David W.;
Mathur, Savita; Mosser, Benoit; Sharma, Sanjib
2017ApJ...844..102H Altcode: 2017arXiv170504697H
We present a comparison of parallaxes and radii from asteroseismology
and Gaia DR1 (TGAS) for 2200 Kepler stars spanning from the
main sequence to the red-giant branch. We show that previously
identified offsets between TGAS parallaxes and distances derived from
asteroseismology and eclipsing binaries have likely been overestimated
for parallaxes ≲ 5{--}10 mas (≈90%-98% of the TGAS sample). The
observed differences in our sample can furthermore be partially
compensated by adopting a hotter {T}<SUB>{eff</SUB>} scale (such as the
infrared flux method) instead of spectroscopic temperatures for dwarfs
and subgiants. Residual systematic differences are at the ≈2% level
in parallax across three orders of magnitude. We use TGAS parallaxes to
empirically demonstrate that asteroseismic radii are accurate to ≈5%
or better for stars between ≈ 0.8{--}8 {R}<SUB>⊙ </SUB>. We find
no significant offset for main-sequence (≲ 1.5 {R}<SUB>⊙ </SUB>)
and low-luminosity RGB stars (≈3-8 {R}<SUB>⊙ </SUB>), but seismic
radii appear to be systematically underestimated by ≈5% for subgiants
(≈1.5-3 {R}<SUB>⊙ </SUB>). We find no systematic errors as a
function of metallicity between [{Fe}/{{H}}]≈ -0.8 to +0.4 dex,
and show tentative evidence that corrections to the scaling relation
for the large frequency separation ({{Δ }}ν ) improve the agreement
with TGAS for RGB stars. Finally, we demonstrate that beyond ≈ 3 {kpc}
asteroseismology will provide more precise distances than end-of-mission
Gaia data, highlighting the synergy and complementary nature of Gaia
and asteroseismology for studying galactic stellar populations.
---------------------------------------------------------
Title: Weighing in on the masses of retired A stars with
asteroseismology: K2 observations of the exoplanet-host star HD 212771
Authors: Campante, Tiago L.; Veras, Dimitri; North, Thomas S. H.;
Miglio, Andrea; Morel, Thierry; Johnson, John A.; Chaplin, William
J.; Davies, Guy R.; Huber, Daniel; Kuszlewicz, James S.; Lund, Mikkel
N.; Cooke, Benjamin F.; Elsworth, Yvonne P.; Rodrigues, Thaíse S.;
Vanderburg, Andrew
2017MNRAS.469.1360C Altcode: 2017arXiv170401794C
Doppler-based planet surveys point to an increasing occurrence rate
of giant planets with stellar mass. Such surveys rely on evolved
stars for a sample of intermediate-mass stars (so-called retired A
stars), which are more amenable to Doppler observations than their
main-sequence progenitors. However, it has been hypothesized that
the masses of subgiant and low-luminosity red-giant stars targeted by
these surveys - typically derived from a combination of spectroscopy
and isochrone fitting - may be systematically overestimated. Here,
we test this hypothesis for the particular case of the exoplanet-host
star HD 212771 using K2 asteroseismology. The benchmark asteroseismic
mass (1.45^{+0.10}_{-0.09} M_{⊙) is significantly higher than the
value reported in the discovery paper (1.15 ± 0.08 M<SUB>⊙</SUB>),
which has been used to inform the stellar mass-planet occurrence
relation. This result, therefore, does not lend support to the
above hypothesis. Implications for the fates of planetary systems
are sensitively dependent on stellar mass. Based on the derived
asteroseismic mass, we predict the post-main-sequence evolution of
the Jovian planet orbiting HD 212771 under the effects of tidal forces
and stellar mass-loss.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Broadband photometry of Neptune
from K2 (Rowe+, 2017)
Authors: Rowe, J. F.; Gaulme, P.; Lissauer, J. J.; Marley, M. S.;
Simon, A. A.; Hammel, H. B.; Silva Aguirre, V.; Barclay, T.; Benomar,
O.; Boumier, P.; Caldwell, D. A.; Casewell, S. L.; Chaplin, W. J.;
Colon, K. D.; Corsaro, E.; Davies, G. R.; Fortney, J. J.; Garcia,
R. A.; Gizis, J. E.; Haas, M. R.; Mosser, B.; Schmider, F. -X.
2017yCat..51530149R Altcode:
The K2 C3 field provided the first opportunity to observe the planet
Neptune for up to 80 days with short-cadence (1 minute) sampling
(the C3 campaign had an actual duration of 69.2 days, limited by
on-board data storage). We were awarded sufficient pixel allocation
from Guest Observer Programs GO3060 (PI: Rowe) and GO3057 (PI: Gaulme)
to continuously monitor Neptune for 49 days. <P />Short-cadence target
pixel files were obtained from Mikulski Archive for Space Telescopes
(MAST). The Neptune short-cadence subraster was spread across 161 FITS
files. Each file contained 1 column of time-series pixel data. Each
target pixel file contains observations starting on 2014 November 15
and finishing on 2015 January 18. <P />(1 data file).
---------------------------------------------------------
Title: Changing the ν <SUB>max</SUB> Scaling Relation: The Need
for a Mean Molecular Weight Term
Authors: Viani, Lucas S.; Basu, Sarbani; Chaplin, William J.; Davies,
Guy R.; Elsworth, Yvonne
2017ApJ...843...11V Altcode: 2017arXiv170503472V
The scaling relations that relate the average asteroseismic parameters
{{Δ }}ν and {ν }<SUB>\max </SUB> to the global properties of stars
are used quite extensively to determine stellar properties. While
the {{Δ }}ν scaling relation has been examined carefully and
the deviations from the relation have been well documented,
the {ν }<SUB>\max </SUB> scaling relation has not been examined
as extensively. In this paper, we examine the {ν }<SUB>\max </SUB>
scaling relation using a set of stellar models constructed to have a
wide range of mass, metallicity, and age. We find that as with {{Δ }}ν
, {ν }<SUB>\max </SUB> does not follow the simple scaling relation. The
most visible deviation is because of a mean molecular weight term and
a {{{Γ }}}<SUB>1</SUB> term that are commonly ignored. The remaining
deviation is more difficult to address. We find that the influence
of the scaling relation errors on asteroseismically derived values of
{log}g are well within uncertainties. The influence of the errors on
mass and radius estimates is small for main sequence and subgiants,
but can be quite large for red giants.
---------------------------------------------------------
Title: PLATO as it is : A legacy mission for Galactic archaeology
Authors: Miglio, A.; Chiappini, C.; Mosser, B.; Davies, G. R.;
Freeman, K.; Girardi, L.; Jofré, P.; Kawata, D.; Rendle, B. M.;
Valentini, M.; Casagrande, L.; Chaplin, W. J.; Gilmore, G.; Hawkins,
K.; Holl, B.; Appourchaux, T.; Belkacem, K.; Bossini, D.; Brogaard,
K.; Goupil, M. -J.; Montalbán, J.; Noels, A.; Anders, F.; Rodrigues,
T.; Piotto, G.; Pollacco, D.; Rauer, H.; Prieto, C. Allende; Avelino,
P. P.; Babusiaux, C.; Barban, C.; Barbuy, B.; Basu, S.; Baudin, F.;
Benomar, O.; Bienaymé, O.; Binney, J.; Bland-Hawthorn, J.; Bressan,
A.; Cacciari, C.; Campante, T. L.; Cassisi, S.; Christensen-Dalsgaard,
J.; Combes, F.; Creevey, O.; Cunha, M. S.; Jong, R. S.; Laverny, P.;
Degl'Innocenti, S.; Deheuvels, S.; Depagne, É.; Ridder, J.; Matteo,
P. Di; Mauro, M. P. Di; Dupret, M. -A.; Eggenberger, P.; Elsworth,
Y.; Famaey, B.; Feltzing, S.; García, R. A.; Gerhard, O.; Gibson,
B. K.; Gizon, L.; Haywood, M.; Handberg, R.; Heiter, U.; Hekker,
S.; Huber, D.; Ibata, R.; Katz, D.; Kawaler, S. D.; Kjeldsen, H.;
Kurtz, D. W.; Lagarde, N.; Lebreton, Y.; Lund, M. N.; Majewski, S. R.;
Marigo, P.; Martig, M.; Mathur, S.; Minchev, I.; Morel, T.; Ortolani,
S.; Pinsonneault, M. H.; Plez, B.; Moroni, P. G. Prada; Pricopi, D.;
Recio-Blanco, A.; Reylé, C.; Robin, A.; Roxburgh, I. W.; Salaris,
M.; Santiago, B. X.; Schiavon, R.; Serenelli, A.; Sharma, S.; Aguirre,
V. Silva; Soubiran, C.; Steinmetz, M.; Stello, D.; Strassmeier, K. G.;
Ventura, P.; Ventura, R.; Walton, N. A.; Worley, C. C.
2017AN....338..644M Altcode: 2017arXiv170603778M
Deciphering the assembly history of the Milky Way is a formidable
task, which becomes possible only if one can produce high-resolution
chrono-chemo-kinematical maps of the Galaxy. Data from large-scale
astrometric and spectroscopic surveys will soon provide us with a
well-defined view of the current chemo-kinematical structure of the
Milky Way, but will only enable a blurred view on the temporal sequence
that led to the present-day Galaxy. As demonstrated by the (ongoing)
exploitation of data from the pioneering photometric missions CoRoT,
Kepler, and K2, asteroseismology provides the way forward: solar-like
oscillating giants are excellent evolutionary clocks thanks to the
availability of seismic constraints on their mass and to the tight
age-initial-mass relation they adhere to. In this paper we identify
five key outstanding questions relating to the formation and evolution
of the Milky Way that will need precise and accurate ages for large
samples of stars to be addressed, and we identify the requirements
in terms of number of targets and the precision on the stellar
properties that are needed to tackle such questions. By quantifying
the asteroseismic yields expected from PLATO for red-giant stars, we
demonstrate that these requirements are within the capabilities of the
current instrument design, provided that observations are sufficiently
long to identify the evolutionary state and allow robust and precise
determination of acoustic-mode frequencies. This will allow us to
harvest data of sufficient quality to reach a 10% precision in age. This
is a fundamental pre-requisite to then reach the more ambitious goal
of a similar level of accuracy, which will only be possible if we
have to hand a careful appraisal of systematic uncertainties on age
deriving from our limited understanding of stellar physics, a goal
which conveniently falls within the main aims of PLATO's core science.
---------------------------------------------------------
Title: Kepler observations of the asteroseismic binary HD 176465
Authors: White, T. R.; Benomar, O.; Silva Aguirre, V.; Ball, W. H.;
Bedding, T. R.; Chaplin, W. J.; Christensen-Dalsgaard, J.; Garcia,
R. A.; Gizon, L.; Stello, D.; Aigrain, S.; Antia, H. M.; Appourchaux,
T.; Bazot, M.; Campante, T. L.; Creevey, O. L.; Davies, G. R.;
Elsworth, Y. P.; Gaulme, P.; Handberg, R.; Hekker, S.; Houdek,
G.; Howe, R.; Huber, D.; Karoff, C.; Marques, J. P.; Mathur, S.;
McQuillan, A.; Metcalfe, T. S.; Mosser, B.; Nielsen, M. B.; Régulo,
C.; Salabert, D.; Stahn, T.
2017A&A...601A..82W Altcode: 2016arXiv160909581W; 2016A&A...601A..82W
Binary star systems are important for understanding stellar structure
and evolution, and are especially useful when oscillations can be
detected and analysed with asteroseismology. However, only four
systems are known in which solar-like oscillations are detected in
both components. Here, we analyse the fifth such system, HD 176465,
which was observed by Kepler. We carefully analysed the system's
power spectrum to measure individual mode frequencies, adapting our
methods where necessary to accommodate the fact that both stars
oscillate in a similar frequency range. We also modelled the two
stars independently by fitting stellar models to the frequencies and
complementaryparameters. We are able to cleanly separate the oscillation
modes in both systems. The stellar models produce compatible ages and
initial compositions for the stars, as is expected from their common
and contemporaneous origin. Combining the individual ages, the system
is about 3.0 ± 0.5 Gyr old. The two components of HD 176465 are young
physically-similar oscillating solar analogues, the first such system
to be found, and provide important constraints for stellar evolution
and asteroseismology.
---------------------------------------------------------
Title: RAVE stars in K2. I. Improving RAVE red giants spectroscopy
using asteroseismology from K2 Campaign 1
Authors: Valentini, M.; Chiappini, C.; Davies, G. R.; Elsworth, Y. P.;
Mosser, B.; Lund, M. N.; Miglio, A.; Chaplin, W. J.; Rodrigues,
T. S.; Boeche, C.; Steinmetz, M.; Matijevič, G.; Kordopatis, G.;
Bland-Hawthorn, J.; Munari, U.; Bienaymé, O.; Freeman, K. C.; Gibson,
B. K.; Gilmore, G.; Grebel, E. K.; Helmi, A.; Kunder, A.; McMillan,
P.; Navarro, J.; Parker, Q. A.; Reid, W.; Seabroke, G.; Sharma, S.;
Siviero, A.; Watson, F.; Wyse, R. F. G.; Zwitter, T.; Mott, A.
2017A&A...600A..66V Altcode: 2016arXiv160903826V
We present a set of 87 RAVE stars with detected solar like oscillations,
observed during Campaign 1 of the K2 mission (RAVE K2-C1 sample). This
data set provides a useful benchmark for testing the gravities provided
in RAVE data release 4 (DR4), and is key for the calibration of the
RAVE data release 5 (DR5). The RAVE survey collected medium-resolution
spectra (R = 7500) centred in the Ca II triplet(8600 Å) wavelength
interval, which although being very useful for determining radial
velocity and metallicity, even at low S/N, is known be affected by a
log (g)-T<SUB>eff</SUB> degeneracy. This degeneracy is the cause of the
large spread in the RAVE DR4 gravities for giants. The understanding of
the trends and offsets that affects RAVE atmospheric parameters, and in
particular log (g), is a crucial step in obtaining not only improved
abundance measurements, but also improved distances and ages. In
the present work, we use two different pipelines, GAUFRE and Sp_Ace,
to determine atmospheric parameters and abundances by fixing log (g)
to the seismic one. Our strategy ensures highly consistent values among
all stellar parameters, leading to more accurate chemical abundances. A
comparison of the chemical abundances obtained here with and without
the use of seismic log (g) information has shown that an underestimated
(overestimated) gravity leads to an underestimated (overestimated)
elemental abundance (e.g. [Mg/H] is underestimated by 0.25 dex when
the gravity is underestimated by 0.5 dex). We then perform a comparison
between the seismic gravities and the spectroscopic gravities presented
in the RAVE DR4 catalogue, extracting a calibration for log (g) of
RAVE giants in the colour interval 0.50 < (J-K<SUB>S</SUB>) <
0.85. Finally, we show a comparison of the distances, temperatures,
extinctions (and ages) derived here for our RAVE K2-C1 sample with those
derived in RAVE DR4 and DR5. DR5 performs better than DR4 thanks to
the seismic calibration, although discrepancies can still be important
for objects for which the difference between DR4/DR5 and seismic
gravities differ by more than 0.5 dex. The method illustrated in this
work will be used for analysing RAVE targets present in the other K2
campaigns, in the framework of Galactic Archaeology investigations. <P
/>Data (atmospheric parameters, abundances, distances, ages and
reddening) are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(<A href="http://130.79.128.5">http://130.79.128.5</A>) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/600/A66">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/600/A66</A>
---------------------------------------------------------
Title: Time-series Analysis of Broadband Photometry of Neptune from K2
Authors: Rowe, Jason F.; Gaulme, Patrick; Lissauer, Jack J.; Marley,
Mark S.; Simon, Amy A.; Hammel, Heidi B.; Silva Aguirre, Víctor;
Barclay, Thomas; Benomar, Othman; Boumier, Patrick; Caldwell, Douglas
A.; Casewell, Sarah L.; Chaplin, William J.; Colón, Knicole D.;
Corsaro, Enrico; Davies, G. R.; Fortney, Jonathan J.; Garcia, Rafael
A.; Gizis, John E.; Haas, Michael R.; Mosser, Benoît; Schmider,
François-Xavier
2017AJ....153..149R Altcode: 2017arXiv170202943R
We report here on our search for excess power in photometry of
Neptune collected by the K2 mission that may be due to intrinsic
global oscillations of the planet Neptune. To conduct this search,
we developed new methods to correct for instrumental effects such
as intrapixel variability and gain variations. We then extracted and
analyzed the time-series photometry of Neptune from 49 days of nearly
continuous broadband photometry of the planet. We find no evidence
of global oscillations and place an upper limit of ∼5 ppm at 1000
μ {Hz} for the detection of a coherent signal. With an observed
cadence of 1 minute and a point-to-point scatter of less than 0.01%,
the photometric signal is dominated by reflected light from the Sun,
which is in turn modulated by atmospheric variability of Neptune at
the 2% level. A change in flux is also observed due to the increasing
distance between Neptune and the K2 spacecraft and the solar variability
with convection-driven solar p modes present.
---------------------------------------------------------
Title: VizieR Online Data Catalog: RAVE 5th data release (Kunder+,
2017)
Authors: Kunder, A.; Kordopatis, G.; Steinmetz, M.; Zwitter, T.;
McMillan, P.; Casagrande, L.; Enke, H.; Wojno, J.; Valentini,
M.; Chiappini, C.; Matijevic, G.; Siviero, A.; de Laverny, P.;
Recio-Blanco, A.; Bijaoui, A.; Wyse, R. F. G.; Binney, J.; Grebel,
E. K.; Helmi, A.; Jofre, P.; Gilmore, G.; Siebert, A.; Famaey, B.;
Bienayme, O.; Gibson, B. K.; Freeman, K. C.; Navarro, J. F.; Munari,
U.; Seabroke, G.; Anguiano Jimenez, B.; Reid, W.; Bland-Hawthorn,
J.; Watson, F.; Gerhard, O.; Davies, G. R.; Elsworth, Y. P.; Lund,
M.; Miglio, A.; Chaplin, W. J.; Mosser, B.
2017yCat.3279....0K Altcode:
Spectroscopic radial velocities for 457588 stars in the Milky-Way
southern hemisphere using the 6dF instrument at the AAO. <P />(4
data files).
---------------------------------------------------------
Title: A thorough analysis of the short- and mid-term activity-related
variations in the solar acoustic frequencies
Authors: Santos, A. R. G.; Cunha, M. S.; Avelino, P. P.; Chaplin,
W. J.; Campante, T. L.
2017MNRAS.464.4408S Altcode: 2016arXiv161006872S
The frequencies of the solar acoustic oscillations vary over
the activity cycle. The variations in other activity proxies are
found to be well correlated with the variations in the acoustic
frequencies. However, each proxy has a slightly different time
behaviour. Our goal is to characterize the differences between the time
behaviour of the frequency shifts and of two other activity proxies,
namely the area covered by sunspots and the 10.7-cm flux. We define
a new observable that is particularly sensitive to the short-term
frequency variations. We then compare the observable when computed from
model frequency shifts and from observed frequency shifts obtained
with the Global Oscillation Network Group (GONG) for cycle 23. Our
analysis shows that on the shortest time-scales, the variations
in the frequency shifts seen in the GONG observations are strongly
correlated with the variations in the area covered by sunspots. However,
a significant loss of correlation is still found. We verify that the
times when the frequency shifts and the sunspot area do not vary in
a similar way tend to coincide with the times of the maxima of the
quasi-biennial variations seen in the solar seismic data. A similar
analysis of the relation between the 10.7-cm flux and the frequency
shifts reveals that the short-time variations in the frequency shifts
follow even more closely those of the 10.7-cm flux than those of the
sunspot area. However, a loss of correlation between frequency shifts
and 10.7-cm flux variations is still found around the same times.
---------------------------------------------------------
Title: Using red clump stars to correct the Gaia DR1 parallaxes
Authors: Davies, Guy R.; Lund, Mikkel N.; Miglio, Andrea; Elsworth,
Yvonne; Kuszlewicz, James S.; North, Thomas S. H.; Rendle, Ben;
Chaplin, William J.; Rodrigues, Thaíse S.; Campante, Tiago L.;
Girardi, Léo; Hale, Steven J.; Hall, Oliver; Jones, Caitlin D.;
Kawaler, Steven D.; Roxburgh, Ian; Schofield, Mathew
2017A&A...598L...4D Altcode: 2017arXiv170102506D
Recent results have suggested that there is tension between the Gaia DR1
TGAS distances and the distances obtained using luminosities determined
by eclipsing binaries or asteroseismology on red giant stars. We use
the K<SUB>s</SUB>-band luminosities of red clump stars, identified
and characterized by asteroseismology, to make independent distance
estimates. Our results suggest that Gaia TGAS distances contain a
systematic error that decreases with increasing distance. We propose
a correction to mitigate this offset as a function of parallax that
is valid for the Kepler field and values of parallax that are less
than 1.6 mas. For parallaxes greater than this, we find agreement with
previously published values. We note that the TGAS distances to the red
clump stars of the open cluster M67 show a high level of disagreement
that is difficult to correct for.
---------------------------------------------------------
Title: A simple model to describe intrinsic stellar noise for
exoplanet detection around red giants
Authors: North, Thomas S. H.; Chaplin, William J.; Gilliland, Ronald
L.; Huber, Daniel; Campante, Tiago L.; Handberg, Rasmus; Lund, Mikkel
N.; Veras, Dimitri; Kuszlewicz, James S.; Farr, Will M.
2017MNRAS.465.1308N Altcode: 2016arXiv161008688N
In spite of the huge advances in exoplanet research provided by the
NASA Kepler Mission, there remain only a small number of transit
detections around evolved stars. Here, we present a reformulation of
the noise properties of red-giant stars, where the intrinsic stellar
granulation and the stellar oscillations described by asteroseismology
play a key role. The new noise model is a significant improvement on
the current Kepler results for evolved stars. Our noise model may be
used to help understand planet detection thresholds for the ongoing K2
and upcoming TESSmissions, and serve as a predictor of stellar noise
for these missions. As an application of our noise model, we explore
the minimum detectable planet radii for red giant stars, and find that
Neptune-sized planets should be detectable around low-luminosity red
giant branch stars.
---------------------------------------------------------
Title: Standing on the Shoulders of Dwarfs: the Kepler Asteroseismic
LEGACY Sample. I. Oscillation Mode Parameters
Authors: Lund, Mikkel N.; Silva Aguirre, Víctor; Davies, Guy R.;
Chaplin, William J.; Christensen-Dalsgaard, Jørgen; Houdek, Günter;
White, Timothy R.; Bedding, Timothy R.; Ball, Warrick H.; Huber,
Daniel; Antia, H. M.; Lebreton, Yveline; Latham, David W.; Handberg,
Rasmus; Verma, Kuldeep; Basu, Sarbani; Casagrande, Luca; Justesen,
Anders B.; Kjeldsen, Hans; Mosumgaard, Jakob R.
2017ApJ...835..172L Altcode: 2016arXiv161200436L
The advent of space-based missions like Kepler has revolutionized the
study of solar-type stars, particularly through the measurement and
modeling of their resonant modes of oscillation. Here we analyze
a sample of 66 Kepler main-sequence stars showing solar-like
oscillations as part of the Kepler seismic LEGACY project. We use
Kepler short-cadence data, of which each star has at least 12 months, to
create frequency-power spectra optimized for asteroseismology. For each
star, we identify its modes of oscillation and extract parameters
such as frequency, amplitude, and line width using a Bayesian
Markov chain Monte Carlo “peak-bagging” approach. We report
the extracted mode parameters for all 66 stars, as well as derived
quantities such as frequency difference ratios, the large and small
separations {{Δ }}ν and δ {ν }<SUB>02</SUB>; the behavior of
line widths with frequency and line widths at {ν }<SUB>\max </SUB>
with {T}<SUB>{eff</SUB>}, for which we derive parametrizations; and
behavior of mode visibilities. These average properties can be applied
in future peak-bagging exercises to better constrain the parameters of
the stellar oscillation spectra. The frequencies and frequency ratios
can tightly constrain the fundamental parameters of these solar-type
stars, and mode line widths and amplitudes can test models of mode
damping and excitation.
---------------------------------------------------------
Title: Parametrizing the time variation of the `surface term' of
stellar p-mode frequencies: application to helioseismic data
Authors: Howe, R.; Basu, S.; Davies, G. R.; Ball, W. H.; Chaplin,
W. J.; Elsworth, Y.; Komm, R.
2017MNRAS.464.4777H Altcode: 2016arXiv161004113H
The solar-cycle variation of acoustic mode frequencies has a frequency
dependence related to the inverse mode inertia. The discrepancy
between model predictions and measured oscillation frequencies for
solar and solar-type stellar acoustic modes includes a significant
frequency-dependent term known as the surface term, which is also
related to the inverse mode inertia. We parametrize both the surface
term and the frequency variations for low-degree solar data from
Birmingham Solar-Oscillations Network (BiSON) and medium-degree data
from the Global Oscillations Network Group (GONG) using the mode inertia
together with cubic and inverse frequency terms. We find that for the
central frequency of rotationally split multiplets, the cubic term
dominates both the average surface term and the temporal variation,
but for the medium-degree case, the inverse term improves the fit to
the temporal variation. We also examine the variation of the even-order
splitting coefficients for the medium-degree data and find that, as
for the central frequency, the latitude-dependent frequency variation,
which reflects the changing latitudinal distribution of magnetic
activity over the solar cycle, can be described by the combination of
a cubic and an inverse function of frequency scaled by inverse mode
inertia. The results suggest that this simple parametrization could be
used to assess the activity-related frequency variation in solar-like
asteroseismic targets.
---------------------------------------------------------
Title: The Radial Velocity Experiment (RAVE): Fifth Data Release
Authors: Kunder, Andrea; Kordopatis, Georges; Steinmetz, Matthias;
Zwitter, Tomaž; McMillan, Paul J.; Casagrande, Luca; Enke, Harry;
Wojno, Jennifer; Valentini, Marica; Chiappini, Cristina; Matijevič,
Gal; Siviero, Alessandro; de Laverny, Patrick; Recio-Blanco,
Alejandra; Bijaoui, Albert; Wyse, Rosemary F. G.; Binney, James;
Grebel, E. K.; Helmi, Amina; Jofre, Paula; Antoja, Teresa; Gilmore,
Gerard; Siebert, Arnaud; Famaey, Benoit; Bienaymé, Olivier; Gibson,
Brad K.; Freeman, Kenneth C.; Navarro, Julio F.; Munari, Ulisse;
Seabroke, George; Anguiano, Borja; Žerjal, Maruša; Minchev, Ivan;
Reid, Warren; Bland-Hawthorn, Joss; Kos, Janez; Sharma, Sanjib; Watson,
Fred; Parker, Quentin A.; Scholz, Ralf-Dieter; Burton, Donna; Cass,
Paul; Hartley, Malcolm; Fiegert, Kristin; Stupar, Milorad; Ritter,
Andreas; Hawkins, Keith; Gerhard, Ortwin; Chaplin, W. J.; Davies,
G. R.; Elsworth, Y. P.; Lund, M. N.; Miglio, A.; Mosser, B.
2017AJ....153...75K Altcode: 2016arXiv160903210K
Data Release 5 (DR5) of the Radial Velocity Experiment (RAVE) is
the fifth data release from a magnitude-limited (9< I< 12)
survey of stars randomly selected in the Southern Hemisphere. The RAVE
medium-resolution spectra (R∼ 7500) covering the Ca-triplet region
(8410-8795 Å) span the complete time frame from the start of RAVE
observations in 2003 to their completion in 2013. Radial velocities
from 520,781 spectra of 457,588 unique stars are presented, of which
255,922 stellar observations have parallaxes and proper motions from
the Tycho-Gaia astrometric solution in Gaia DR1. For our main DR5
catalog, stellar parameters (effective temperature, surface gravity, and
overall metallicity) are computed using the RAVE DR4 stellar pipeline,
but calibrated using recent K2 Campaign 1 seismic gravities and Gaia
benchmark stars, as well as results obtained from high-resolution
studies. Also included are temperatures from the Infrared Flux Method,
and we provide a catalog of red giant stars in the dereddened color
{(J-{Ks})}<SUB>0</SUB> interval (0.50, 0.85) for which the gravities
were calibrated based only on seismology. Further data products for
subsamples of the RAVE stars include individual abundances for Mg, Al,
Si, Ca, Ti, Fe, and Ni, and distances found using isochrones. Each
RAVE spectrum is complemented by an error spectrum, which has been
used to determine uncertainties on the parameters. The data can be
accessed via the RAVE Web site or the VizieR database.
---------------------------------------------------------
Title: Standing on the Shoulders of Dwarfs: the Kepler Asteroseismic
LEGACY Sample. II.Radii, Masses, and Ages
Authors: Silva Aguirre, Víctor; Lund, Mikkel N.; Antia, H. M.; Ball,
Warrick H.; Basu, Sarbani; Christensen-Dalsgaard, Jørgen; Lebreton,
Yveline; Reese, Daniel R.; Verma, Kuldeep; Casagrande, Luca; Justesen,
Anders B.; Mosumgaard, Jakob R.; Chaplin, William J.; Bedding, Timothy
R.; Davies, Guy R.; Handberg, Rasmus; Houdek, Günter; Huber, Daniel;
Kjeldsen, Hans; Latham, David W.; White, Timothy R.; Coelho, Hugo R.;
Miglio, Andrea; Rendle, Ben
2017ApJ...835..173S Altcode: 2016arXiv161108776S
We use asteroseismic data from the Kepler satellite to determine
fundamental stellar properties of the 66 main-sequence targets
observed for at least one full year by the mission. We distributed
tens of individual oscillation frequencies extracted from the time
series of each star among seven modeling teams who applied different
methods to determine radii, masses, and ages for all stars in the
sample. Comparisons among the different results reveal a good level of
agreement in all stellar properties, which is remarkable considering
the variety of codes, input physics, and analysis methods employed
by the different teams. Average uncertainties are of the order
of ∼2% in radius, ∼4% in mass, and ∼10% in age, making this
the best-characterized sample of main-sequence stars available to
date. Our predicted initial abundances and mixing-length parameters
are checked against inferences from chemical enrichment laws ΔY/ΔZ
and predictions from 3D atmospheric simulations. We test the accuracy
of the determined stellar properties by comparing them to the Sun,
angular diameter measurements, Gaia parallaxes, and binary evolution,
finding excellent agreement in all cases and further confirming the
robustness of asteroseismically determined physical parameters of stars
when individual frequencies of oscillation are available. Baptised
as the Kepler dwarfs LEGACY sample, these stars are the solar-like
oscillators with the best asteroseismic properties available for at
least another decade. All data used in this analysis and the resulting
stellar parameters are made publicly available for the community.
---------------------------------------------------------
Title: First Results from the Hertzsprung SONG Telescope:
Asteroseismology of the G5 Subgiant Star μ Herculis
Authors: Grundahl, F.; Fredslund Andersen, M.; Christensen-Dalsgaard,
J.; Antoci, V.; Kjeldsen, H.; Handberg, R.; Houdek, G.; Bedding, T. R.;
Pallé, P. L.; Jessen-Hansen, J.; Silva Aguirre, V.; White, T. R.;
Frandsen, S.; Albrecht, S.; Andersen, M. I.; Arentoft, T.; Brogaard,
K.; Chaplin, W. J.; Harpsøe, K.; Jørgensen, U. G.; Karovicova, I.;
Karoff, C.; Kjærgaard Rasmussen, P.; Lund, M. N.; Sloth Lundkvist,
M.; Skottfelt, J.; Norup Sørensen, A.; Tronsgaard, R.; Weiss, E.
2017ApJ...836..142G Altcode: 2017arXiv170103365G
We report the first asteroseismic results obtained with the Hertzsprung
Stellar Observations Network Group Telescope from an extensive
high-precision radial-velocity observing campaign of the subgiant μ
Herculis. The data set was collected during 215 nights in 2014 and
2015. We detected a total of 49 oscillation modes with l values from
zero to three, including some l = 1 mixed modes. Based on the rotational
splitting observed in l = 1 modes, we determine a rotational period of
52 days and a stellar inclination angle of 63°. The parameters obtained
through modeling of the observed oscillation frequencies agree very well
with independent observations and imply a stellar mass between 1.11 and
1.15 M <SUB>⊙</SUB> and an age of {7.8}<SUB>-0.4</SUB><SUP>+0.3</SUP>
Gyr. Furthermore, the high-quality data allowed us to determine the
acoustic depths of the He II ionization layer and the base of the
convection zone. <P />Based on observations made with the Hertzsprung
SONG telescope operated on the Spanish Observatorio del Teide on the
island of Tenerife by the Aarhus and Copenhagen Universities and by
the Instituto de Astrofísica de Canarias.
---------------------------------------------------------
Title: Asteroseismic Data Analysis: Foundations and Techniques
Authors: Basu, Sarbani; Chaplin, William J.
2017asda.book.....B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The K2 Galactic Archaeology Program Data
Release. I. Asteroseismic Results from Campaign 1
Authors: Stello, Dennis; Zinn, Joel; Elsworth, Yvonne; Garcia, Rafael
A.; Kallinger, Thomas; Mathur, Savita; Mosser, Benoit; Sharma, Sanjib;
Chaplin, William J.; Davies, Guy; Huber, Daniel; Jones, Caitlin D.;
Miglio, Andrea; Silva Aguirre, Victor
2017ApJ...835...83S Altcode: 2016arXiv161109852S
NASA's K2 mission is observing tens of thousands of stars along the
ecliptic, providing data suitable for large-scale asteroseismic analyses
to inform galactic archaeology studies. Its first campaign covered
a field near the north Galactic cap, a region never covered before
by large asteroseismic-ensemble investigations, and was therefore
of particular interest for exploring this part of our Galaxy. Here
we report the asteroseismic analysis of all stars selected by the K2
Galactic Archaeology Program during the mission's “north Galactic
cap” campaign 1. Our consolidated analysis uses six independent
methods to measure the global seismic properties, in particular the
large frequency separation and the frequency of maximum power. From
the full target sample of 8630 stars we find about 1200 oscillating
red giants, a number comparable with estimates from galactic synthesis
modeling. Thus, as a valuable by-product we find roughly 7500 stars to
be dwarfs, which provide a sample well suited for galactic exoplanet
occurrence studies because they originate from our simple and easily
reproducible selection function. In addition, to facilitate the full
potential of the data set for galactic archaeology, we assess the
detection completeness of our sample of oscillating red giants. We find
that the sample is at least nearly complete for stars with 40 ≲ {ν
}<SUB>\max </SUB>/μHz ≲ 270 and {ν }<SUB>\max ,{detect</SUB>}<
2.6× {10}<SUP>6</SUP>\cdot {2}<SUP>-{\text{Kp</SUP>}} μHz. There is a
detection bias against helium core burning stars with {ν }<SUB>\max
</SUB> ∼ 30 μHz, affecting the number of measurements of {{Δ
}}ν and possibly also {ν }<SUB>\max </SUB>. Although we can detect
oscillations down to {\text{Kp}} = 15, our campaign 1 sample lacks
enough faint giants to assess the detection completeness for stars
fainter than {\text{Kp}} ∼ 14.5.
---------------------------------------------------------
Title: Asteroseismology of the Hyades with K2: first detection of
main-sequence solar-like oscillations in an open cluster
Authors: Lund, Mikkel N.; Basu, Sarbani; Silva Aguirre, Víctor;
Chaplin, William J.; Serenelli, Aldo M.; García, Rafael A.; Latham,
David W.; Casagrande, Luca; Bieryla, Allyson; Davies, Guy R.; Viani,
Lucas S.; Buchhave, Lars A.; Miglio, Andrea; Soderblom, David R.;
Valenti, Jeff A.; Stefanik, Robert P.; Handberg, Rasmus
2016MNRAS.463.2600L Altcode: 2016arXiv160807290L; 2016MNRAS.tmp.1271L
The Hyades open cluster was targeted during Campaign 4 (C4) of the NASA
K2 mission, and short-cadence data were collected on a number of cool
main-sequence stars. Here, we report results on two F-type stars that
show detectable oscillations of a quality that allows asteroseismic
analyses to be performed. These are the first ever detections of
solar-like oscillations in main-sequence stars in an open cluster.
---------------------------------------------------------
Title: A Distant Mirror: Solar Oscillations Observed on Neptune by
the Kepler K2 Mission
Authors: Gaulme, P.; Rowe, J. F.; Bedding, T. R.; Benomar, O.;
Corsaro, E.; Davies, G. R.; Hale, S. J.; Howe, R.; Garcia, R. A.;
Huber, D.; Jiménez, A.; Mathur, S.; Mosser, B.; Appourchaux, T.;
Boumier, P.; Jackiewicz, J.; Leibacher, J.; Schmider, F. -X.; Hammel,
H. B.; Lissauer, J. J.; Marley, M. S.; Simon, A. A.; Chaplin, W. J.;
Elsworth, Y.; Guzik, J. A.; Murphy, N.; Silva Aguirre, V.
2016ApJ...833L..13G Altcode: 2016arXiv161204287G
Starting in 2014 December, Kepler K 2 observed Neptune continuously
for 49 days at a 1 minute cadence. The goals consisted of studying its
atmospheric dynamics, detecting its global acoustic oscillations, and
those of the Sun, which we report on here. We present the first indirect
detection of solar oscillations in intensity measurements. Beyond
the remarkable technical performance, it indicates how Kepler would
see a star like the Sun. The result from the global asteroseismic
approach, which consists of measuring the oscillation frequency
at maximum amplitude ν <SUB>max</SUB> and the mean frequency
separation between mode overtones Δν, is surprising as the ν
<SUB>max</SUB> measured from Neptune photometry is larger than the
accepted value. Compared to the usual reference ν <SUB>max,⊙</SUB>
= 3100 μHz, the asteroseismic scaling relations therefore make the
solar mass and radius appear larger by 13.8 ± 5.8% and 4.3 ± 1.9%,
respectively. The higher ν <SUB>max</SUB> is caused by a combination
of the value of ν <SUB>max,⊙</SUB>, being larger at the time
of observations than the usual reference from SOHO/VIRGO/SPM data
(3160 ± 10 μHz), and the noise level of the K 2 time series, being
10 times larger than VIRGO’s. The peak-bagging method provides
more consistent results: despite a low signal-to-noise ratio (S/N),
we model 10 overtones for degrees ℓ = 0, 1, 2. We compare the K 2
data with simultaneous SOHO/VIRGO/SPM photometry and BiSON velocity
measurements. The individual frequencies, widths, and amplitudes mostly
match those from VIRGO and BiSON within 1σ, except for the few peaks
with the lowest S/N.
---------------------------------------------------------
Title: Asteroseismic Properties of Solar-type Stars Observed with
the NASA K2 Mission: Results from Campaigns 1-3 and Prospects for
Future Observations
Authors: Lund, Mikkel N.; Chaplin, William J.; Casagrande,
Luca; Silva Aguirre, Víctor; Basu, Sarbani; Bieryla, Allyson;
Christensen-Dalsgaard, Jørgen; Latham, David W.; White, Timothy R.;
Davies, Guy R.; Huber, Daniel; Buchhave, Lars A.; Handberg, Rasmus
2016PASP..128l4204L Altcode: 2016arXiv160807292L
We present an asteroseismic analysis of 33 solar-type stars observed in
short cadence (SC) during Campaigns (C) 1-3 of the NASA K2 mission. We
were able to extract both average seismic parameters and individual mode
frequencies for stars with dominant frequencies up to ∼3300 μHz,
and we find that data for some targets are good enough to allow for
a measurement of the rotational splitting. Modeling of the extracted
parameters is performed by using grid-based methods using average
parameters and individual frequencies together with spectroscopic
parameters. For the target selection in C3, stars were chosen as in C1
and C2 to cover a wide range in parameter space to better understand
the performance and noise characteristics. For C3 we still detected
oscillations in 73% of the observed stars that we proposed. Future K2
campaigns hold great promise for the study of nearby clusters and the
chemical evolution and age-metallicity relation of nearby field stars in
the solar neighborhood. We expect oscillations to be detected in ∼388
SC targets if the K2 mission continues until C18, which will greatly
complement the ∼500 detections of solar-like oscillations made for
SC targets during the nominal Kepler mission. For ∼30-40 of these,
including several members of the Hyades open cluster, we furthermore
expect that inference from interferometry should be possible.
---------------------------------------------------------
Title: Detection of Solar-like Oscillations, Observational
Constraints, and Stellar Models for θ Cyg, the Brightest Star
Observed By the Kepler Mission
Authors: Guzik, J. A.; Houdek, G.; Chaplin, W. J.; Smalley, B.; Kurtz,
D. W.; Gilliland, R. L.; Mullally, F.; Rowe, J. F.; Bryson, S. T.;
Still, M. D.; Antoci, V.; Appourchaux, T.; Basu, S.; Bedding, T. R.;
Benomar, O.; Garcia, R. A.; Huber, D.; Kjeldsen, H.; Latham, D. W.;
Metcalfe, T. S.; Pápics, P. I.; White, T. R.; Aerts, C.; Ballot, J.;
Boyajian, T. S.; Briquet, M.; Bruntt, H.; Buchhave, L. A.; Campante,
T. L.; Catanzaro, G.; Christensen-Dalsgaard, J.; Davies, G. R.;
Doğan, G.; Dragomir, D.; Doyle, A. P.; Elsworth, Y.; Frasca, A.;
Gaulme, P.; Gruberbauer, M.; Handberg, R.; Hekker, S.; Karoff, C.;
Lehmann, H.; Mathias, P.; Mathur, S.; Miglio, A.; Molenda-Żakowicz,
J.; Mosser, B.; Murphy, S. J.; Régulo, C.; Ripepi, V.; Salabert,
D.; Sousa, S. G.; Stello, D.; Uytterhoeven, K.
2016ApJ...831...17G Altcode: 2016arXiv160701035G
θ Cygni is an F3 spectral type magnitude V = 4.48 main-sequence star
that was the brightest star observed by the original Kepler spacecraft
mission. Short-cadence (58.8 s) photometric data using a custom
aperture were first obtained during Quarter 6 (2010 June-September) and
subsequently in Quarters 8 and 12-17. We present analyses of solar-like
oscillations based on Q6 and Q8 data, identifying angular degree l = 0,
1, and 2 modes with frequencies of 1000-2700 μHz, a large frequency
separation of 83.9 ± 0.4 μHz, and maximum oscillation amplitude
at frequency ν <SUB>max</SUB> = 1829 ± 54 μHz. We also present
analyses of new ground-based spectroscopic observations, which,
combined with interferometric angular diameter measurements, give T
<SUB>eff</SUB> = 6697 ± 78 K, radius 1.49 ± 0.03 R <SUB>⊙</SUB>,
[Fe/H] = -0.02 ± 0.06 dex, and log g = 4.23 ± 0.03. We calculate
stellar models matching these constraints using the Yale Rotating
Evolution Code and the Asteroseismic Modeling Portal. The best-fit
models have masses of 1.35-1.39 M <SUB>⊙</SUB> and ages of 1.0-1.6
Gyr. θ Cyg’s T <SUB>eff</SUB> and log g place it cooler than the red
edge of the γ Doradus instability region established from pre-Kepler
ground-based observations, but just at the red edge derived from
pulsation modeling. The pulsation models show γ Dor gravity modes
driven by the convective blocking mechanism, with frequencies of 1-3
cycles per day (11 to 33 μHz). However, gravity modes were not seen
in Kepler data; one signal at 1.776 cycles per day (20.56 μHz) may
be attributable to a faint, possibly background, binary.
---------------------------------------------------------
Title: Oscillation mode linewidths and heights of 23 main-sequence
stars observed by Kepler (Corrigendum)
Authors: Appourchaux, T.; Antia, H. M.; Benomar, O.; Campante, T. L.;
Davies, G. R.; Handberg, R.; Howe, R.; Régulo, C.; Belkacem, K.;
Houdek, G.; García, R. A.; Chaplin, W. J.
2016A&A...595C...2A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Asteroseismic Potential of TESS: Exoplanet-host Stars
Authors: Campante, T. L.; Schofield, M.; Kuszlewicz, J. S.; Bouma,
L.; Chaplin, W. J.; Huber, D.; Christensen-Dalsgaard, J.; Kjeldsen,
H.; Bossini, D.; North, T. S. H.; Appourchaux, T.; Latham, D. W.;
Pepper, J.; Ricker, G. R.; Stassun, K. G.; Vanderspek, R.; Winn, J. N.
2016ApJ...830..138C Altcode: 2016arXiv160801138C
New insights on stellar evolution and stellar interior physics are
being made possible by asteroseismology. Throughout the course of the
Kepler mission, asteroseismology has also played an important role
in the characterization of exoplanet-host stars and their planetary
systems. The upcoming NASA Transiting Exoplanet Survey Satellite
(TESS) will be performing a near all-sky survey for planets that
transit bright nearby stars. In addition, its excellent photometric
precision, combined with its fine time sampling and long intervals of
uninterrupted observations, will enable asteroseismology of solar-type
and red-giant stars. Here we develop a simple test to estimate the
detectability of solar-like oscillations in TESS photometry of any given
star. Based on an all-sky stellar and planetary synthetic population,
we go on to predict the asteroseismic yield of the TESS mission,
placing emphasis on the yield of exoplanet-host stars for which we
expect to detect solar-like oscillations. This is done for both the
target stars (observed at a 2-minute cadence) and the full-frame-image
stars (observed at a 30-minute cadence). A similar exercise is also
conducted based on a compilation of known host stars. We predict that
TESS will detect solar-like oscillations in a few dozen target hosts
(mainly subgiant stars but also in a smaller number of F dwarfs), in up
to 200 low-luminosity red-giant hosts, and in over 100 solar-type and
red-giant known hosts, thereby leading to a threefold improvement in the
asteroseismic yield of exoplanet-host stars when compared to Kepler's.
---------------------------------------------------------
Title: On the contribution of sunspots to the observed frequency
shifts of solar acoustic modes
Authors: Santos, A. R. G.; Cunha, M. S.; Avelino, P. P.; Chaplin,
W. J.; Campante, T. L.
2016MNRAS.461..224S Altcode: 2016arXiv160602133S; 2016MNRAS.tmp.1003S
Activity-related variations in the solar oscillation properties
have been known for 30 years. However, the relative importance of
the different contributions to the observed variations is not yet
fully understood. Our goal is to estimate the relative contribution
from sunspots to the observed activity-related variations in the
frequencies of the acoustic modes. We use a variational principle to
relate the phase differences induced by sunspots on the acoustic waves
to the corresponding changes in the frequencies of the global acoustic
oscillations. From the sunspot properties (area and latitude as a
function of time), we are able to estimate the spot-induced frequency
shifts. These are then combined with a smooth frequency shift component,
associated with long-term solar-cycle variations, and the results
compared with the frequency shifts derived from the Global Oscillation
Network Group data. The result of this comparison is consistent with
a sunspot contribution to the observed frequency shifts of roughly
30 per cent, with the remaining 70 per cent resulting mostly from
a global, non-stochastic variation, possibly related to the changes
in the overall magnetic field. Moreover, analysis of the residuals
obtained after the subtraction of the model frequency shifts from the
observations indicates the presence of a 1.5-yr periodicity in the data
in phase with the quasi-biennial variations reported in the literature.
---------------------------------------------------------
Title: Detection of solar-like oscillations in relics of the Milky
Way: asteroseismology of K giants in M4 using data from the NASA
K2 mission
Authors: Miglio, A.; Chaplin, W. J.; Brogaard, K.; Lund, M. N.;
Mosser, B.; Davies, G. R.; Handberg, R.; Milone, A. P.; Marino, A. F.;
Bossini, D.; Elsworth, Y. P.; Grundahl, F.; Arentoft, T.; Bedin,
L. R.; Campante, T. L.; Jessen-Hansen, J.; Jones, C. D.; Kuszlewicz,
J. S.; Malavolta, L.; Nascimbeni, V.; Sandquist, E. L.
2016MNRAS.461..760M Altcode: 2016arXiv160602115M
Asteroseismic constraints on K giants make it possible to infer
radii, masses and ages of tens of thousands of field stars. Tests
against independent estimates of these properties are however scarce,
especially in the metal-poor regime. Here, we report the detection of
solar-like oscillations in eight stars belonging to the red-giant branch
(RGB) and red-horizontal branch (RHB) of the globular cluster M4. The
detections were made in photometric observations from the K2 Mission
during its Campaign 2. Making use of independent constraints on the
distance, we estimate masses of the eight stars by utilizing different
combinations of seismic and non-seismic inputs. When introducing a
correction to the Δν scaling relation as suggested by stellar models,
for RGB stars we find excellent agreement with the expected masses from
isochrone fitting, and with a distance modulus derived using independent
methods. The offset with respect to independent masses is lower, or
comparable with, the uncertainties on the average RGB mass (4-10 per
cent, depending on the combination of constraints used). Our results
lend confidence to asteroseismic masses in the metal-poor regime. We
note that a larger sample will be needed to allow more stringent tests
to be made of systematic uncertainties in all the observables (both
seismic and non-seismic), and to explore the properties of RHB stars,
and of different populations in the cluster.
---------------------------------------------------------
Title: SpaceInn hare-and-hounds exercise: Estimation of stellar
properties using space-based asteroseismic data
Authors: Reese, D. R.; Chaplin, W. J.; Davies, G. R.;
Miglio, A.; Antia, H. M.; Ball, W. H.; Basu, S.; Buldgen, G.;
Christensen-Dalsgaard, J.; Coelho, H. R.; Hekker, S.; Houdek, G.;
Lebreton, Y.; Mazumdar, A.; Metcalfe, T. S.; Silva Aguirre, V.;
Stello, D.; Verma, K.
2016A&A...592A..14R Altcode: 2016arXiv160408404R
Context. Detailed oscillation spectra comprising individual frequencies
for numerous solar-type stars and red giants are either currently
available, e.g. courtesy of the CoRoT, Kepler, and K2 missions, or
will become available with the upcoming NASA TESS and ESA PLATO 2.0
missions. The data can lead to a precise characterisation of these
stars thereby improving our understanding of stellar evolution,
exoplanetary systems, and the history of our galaxy. <BR /> Aims:
Our goal is to test and compare different methods for obtaining
stellar properties from oscillation frequencies and spectroscopic
constraints. Specifically, we would like to evaluate the accuracy of
the results and reliability of the associated error bars, and to see
where there is room for improvement. <BR /> Methods: In the context
of the SpaceInn network, we carried out a hare-and-hounds exercise
in which one group, the hares, simulated observations of oscillation
spectra for a set of ten artificial solar-type stars, and a number of
hounds applied various methods for characterising these stars based on
the data produced by the hares. Most of the hounds fell into two main
groups. The first group used forward modelling (I.e. applied various
search/optimisation algorithms in a stellar parameter space) whereas
the second group relied on acoustic glitch signatures. <BR /> Results:
Results based on the forward modelling approach were accurate to 1.5%
(radius), 3.9% (mass), 23% (age), 1.5% (surface gravity), and 1.8% (mean
density), as based on the root mean square difference. Individual hounds
reached different degrees of accuracy, some of which were substantially
better than the above average values. For the two 1M<SUB>⊙</SUB>
stellar targets, the accuracy on the age is better than 10% thereby
satisfying the requirements for the PLATO 2.0 mission. High stellar
masses and atomic diffusion (which in our models does not include
the effects of radiative accelerations) proved to be sources of
difficulty. The average accuracies for the acoustic radii of the base
of the convection zone, the He II ionisation, and the Γ<SUB>1</SUB>
peak located between the two He ionisation zones were 17%, 2.4%, and
1.9%, respectively. The results from the forward modelling were on
average more accurate than those from the glitch fitting analysis as
the latter seemed to be affected by aliasing problems for some of the
targets. <BR /> Conclusions: Our study indicates that forward modelling
is the most accurate way of interpreting the pulsation spectra of
solar-type stars. However, given its model-dependent nature, this
method needs to be complemented by model-independent results from,
e.g. glitch analysis. Furthermore, our results indicate that global
rather than local optimisation algorithms should be used in order to
obtain robust error bars.
---------------------------------------------------------
Title: That's How We Roll: The NASA K2 Mission Science Products and
Their Performance Metrics
Authors: Van Cleve, Jeffrey E.; Howell, Steve B.; Smith, Jeffrey
C.; Clarke, Bruce D.; Thompson, Susan E.; Bryson, Stephen T.; Lund,
Mikkel N.; Handberg, Rasmus; Chaplin, William J.
2016PASP..128g5002V Altcode: 2015arXiv151206162V
NASA's exoplanet Discovery mission Kepler was reconstituted as the
K2 mission a year after the failure of the second of Kepler's four
reaction wheels in 2013 May. Fine control of the spacecraft pointing is
now accomplished through the use of the two remaining well-functioning
reaction wheels and balancing the pressure of sunlight on the solar
panels, which constrains K2 observations to fields in the ecliptic for
up to approximately 80 days each. This pseudo-stable mechanism gives
typical roll motion in the focal plane of 1.0 pixels peak-to-peak over
6 hr at the edges of the field, two orders of magnitude greater than
typical 6 hr pointing errors in the Kepler primary mission. Despite
these roll errors, the joint performance of the flight system and
its modified science data processing pipeline restores much of the
photometric precision of the primary mission while viewing a wide
variety of targets, thus turning adversity into diversity. We define K2
performance metrics for data compression and pixel budget available in
each campaign; the photometric noise on exoplanet transit and stellar
activity timescales; residual correlations in corrected long-cadence
light curves; and the protection of test sinusoidal signals from
overfitting in the systematic error removal process. We find that data
compression and noise both increase linearly with radial distance from
the center of the field of view, with the data compression proportional
to star count as well. At the center, where roll motion is nearly
negligible, the limiting 6 hr photometric precision for a quiet 12th
magnitude star can be as low as 30 ppm, only 25% higher than that of
Kepler. This noise performance is achieved without sacrificing signal
fidelity; test sinusoids injected into the data are attenuated by less
than 10% for signals with periods upto 15 days, so that a wide range
of stellar rotation and variability signatures are preserved by the
K2 pipeline. At timescales relevant to asteroseismology, light curves
derived from K2 archive calibrated pixels have high-frequency noise
amplitude within 40% of that achieved by Kepler. The improvements
in K2 operations and science data analysis resulting from 1.5 years
of experience with this new mission concept, and quantified by the
metrics in this paper, will support continuation of K2's already high
level of scientific productivity in an extended K2 mission.
---------------------------------------------------------
Title: That's How We Roll - The NASA K2 Mission Science Planning,
Products, and Performance Metrics
Authors: Van Cleve, Jeffrey E.; Howell, Steve B.; Smith, Jeffrey C.;
Clarke, Bruce; Thompson, Susan E.; Bryson, Steve; Lund, Mikkel N.;
Handberg, Rasmus; Chaplin, William J.; Kepler Science Office, Kepler
Science Operations Center, Ball Aerospace, U. Colorado LASP
2016AAS...22810209V Altcode:
NASA’s exoplanet Discovery mission Kepler was reconstituted as the
K2 mission a year after the failure of the 2nd of Kepler’s 4 reaction
wheels in May 2013. The new spacecraft pointing method now gives typical
roll motion of 1.0 pixels peak-to-peak over 6 hours at the edges of
the field, two orders of magnitude greater than for Kepler. Despite
these roll errors, the flight system and its modified data processing
pipeline restores much of the photometric precision of the primary
mission while viewing a wide variety of targets, thus turning adversity
into diversity. We define metrics for data compression and pixel budget
available in each campaign; the photometric noise on exoplanet transit
and stellar activity time scales; residual correlations in corrected
long cadence light curves; and the protection of test sinusoidal signals
from overfitting in the systematic error removal process. We find that
data compression and noise both increase linearly with radial distance
from the center of the field of view, while the data compression also
increases as the square root of star count. For sufficiently dense
star fields, such as the Galactic Center, the data entropy so high
that Huffman compression is ineffective and only requantization is
used. At the FOV center, where roll motion is nearly negligible, the
limiting 6 hour photometric precision for a quiet 12th magnitude star
can be as low as 30 ppm, only 25% higher than that of Kepler. This
noise performance is achieved without sacrificing signal fidelity;
test sinusoids injected into the data are attenuated by less than
10% for signals with periods up 15 days. At time scales relevant to
asteroseismology, light curves derived from K2 archive calibrated
pixels have high-frequency noise amplitude within 40% of that achieved
by Kepler. These improvements follow from the data analysis efforts of
Kepler Science Operation Center and Kepler Science Office, and from
the operational improvements developed by Ball Aerospace and LASP,
during the first 1.5 yr of K2. Our results through December 2015 are
shown in detail in http://arxiv.org/abs/1512.06162; in this talk,
we will emphasize what we have learned in the last 6 month.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Surface gravity for 220 Kepler
stars (Campante+, 2014)
Authors: Campante, T. L.; Chaplin, W. J.; Lund, M. N.; Huber, D.;
Hekker, S.; Garcia, R. A.; Corsaro, E.; Handberg, R.; Miglio, A.;
Arentoft, T.; Basu, S.; Bedding, T. R.; Christensen-Dalsgaard, J.;
Davies, G. R.; Elsworth, Y. P.; Gilliland, R. L.; Karoff, C.; Kawaler,
S. D.; Kjeldsen, H.; Lundkvist, M.; Metcalfe, T. S.; Silva Aguirre,
V.; Stello, D.
2016yCat..17830123C Altcode:
We propose lower-limit surface gravity estimates for Kepler solar-type
planet-candidate host stars with no detected oscillations, as given
in Table4. <P />(1 data file).
---------------------------------------------------------
Title: Hot super-Earths stripped by their host stars
Authors: Lundkvist, M. S.; Kjeldsen, H.; Albrecht, S.; Davies, G. R.;
Basu, S.; Huber, D.; Justesen, A. B.; Karoff, C.; Silva Aguirre, V.;
van Eylen, V.; Vang, C.; Arentoft, T.; Barclay, T.; Bedding, T. R.;
Campante, T. L.; Chaplin, W. J.; Christensen-Dalsgaard, J.; Elsworth,
Y. P.; Gilliland, R. L.; Handberg, R.; Hekker, S.; Kawaler, S. D.;
Lund, M. N.; Metcalfe, T. S.; Miglio, A.; Rowe, J. F.; Stello, D.;
Tingley, B.; White, T. R.
2016NatCo...711201L Altcode: 2016arXiv160405220L
Simulations predict that hot super-Earth sized exoplanets can have their
envelopes stripped by photoevaporation, which would present itself as
a lack of these exoplanets. However, this absence in the exoplanet
population has escaped a firm detection. Here we demonstrate, using
asteroseismology on a sample of exoplanets and exoplanet candidates
observed during the Kepler mission that, while there is an abundance of
super-Earth sized exoplanets with low incident fluxes, none are found
with high incident fluxes. We do not find any exoplanets with radii
between 2.2 and 3.8 Earth radii with incident flux above 650 times
the incident flux on Earth. This gap in the population of exoplanets
is explained by evaporation of volatile elements and thus supports
the predictions. The confirmation of a hot-super-Earth desert caused
by evaporation will add an important constraint on simulations of
planetary systems, since they must be able to reproduce the dearth of
close-in super-Earths.
---------------------------------------------------------
Title: Spin-Orbit Alignment of Exoplanet Systems: Ensemble Analysis
Using Asteroseismology
Authors: Campante, T. L.; Lund, M. N.; Kuszlewicz, J. S.; Davies,
G. R.; Chaplin, W. J.; Albrecht, S.; Winn, J. N.; Bedding, T. R.;
Benomar, O.; Bossini, D.; Handberg, R.; Santos, A. R. G.; Van Eylen,
V.; Basu, S.; Christensen-Dalsgaard, J.; Elsworth, Y. P.; Hekker, S.;
Hirano, T.; Huber, D.; Karoff, C.; Kjeldsen, H.; Lundkvist, M. S.;
North, T. S. H.; Silva Aguirre, V.; Stello, D.; White, T. R.
2016ApJ...819...85C Altcode: 2016arXiv160106052C
The angle ψ between a planet’s orbital axis and the spin axis
of its parent star is an important diagnostic of planet formation,
migration, and tidal evolution. We seek empirical constraints on ψ by
measuring the stellar inclination I<SUB>s</SUB> via asteroseismology
for an ensemble of 25 solar-type hosts observed with NASA’s Kepler
satellite. Our results for I<SUB>s</SUB> are consistent with alignment
at the 2σ level for all stars in the sample, meaning that the
system surrounding the red-giant star Kepler-56 remains as the only
unambiguous misaligned multiple-planet system detected to date. The
availability of a measurement of the projected spin-orbit angle λ
for two of the systems allows us to estimate ψ. We find that the
orbit of the hot Jupiter HAT-P-7b is likely to be retrograde (\psi
=116\buildrel{\circ}\over{.} {4}<SUB>-14.7</SUB><SUP>+30.2</SUP>),
whereas that of Kepler-25c seems to be well aligned with
the stellar spin axis (\psi =12\buildrel{\circ}\over{.}
{6}<SUB>-11.0</SUB><SUP>+6.7</SUP>). While the latter result is
in apparent contradiction with a statement made previously in the
literature that the multi-transiting system Kepler-25 is misaligned,
we show that the results are consistent, given the large associated
uncertainties. Finally, we perform a hierarchical Bayesian analysis
based on the asteroseismic sample in order to recover the underlying
distribution of ψ. The ensemble analysis suggests that the directions
of the stellar spin and planetary orbital axes are correlated, as
conveyed by a tendency of the host stars to display large values
of inclination.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Fundamental parameters of Kepler
stars (Silva Aguirre+, 2015)
Authors: Silva Aguirre, V.; Davies, G. R.; Basu, S.;
Christensen-Dalsgaard, J.; Creevey, O.; Metcalfe, T. S.; Bedding,
T. R.; Casagrande, L.; Handberg, R.; Lund, M. N.; Nissen, P. E.;
Chaplin, W. J.; Huber, D.; Serenelli, A. M.; Stello, D.; van Eylen,
V.; Campante, T. L.; Elsworth, Y.; Gilliland, R. L.; Hekker, S.;
Karoff, C.; Kawaler, S. D.; Kjeldsen, H.; Lundkvist, M. S.
2016yCat..74522127S Altcode:
Our sample has been extracted from the 77 exoplanet host stars presented
in Huber et al. (2013, Cat. J/ApJ/767/127). <P />We have made use of the
full time-base of observations from the Kepler satellite to uniformly
determine precise fundamental stellar parameters, including ages,
for a sample of exoplanet host stars where high-quality asteroseismic
data were available. We devised a Bayesian procedure flexible in its
input and applied it to different grids of models to study systematics
from input physics and extract statistically robust properties for
all stars. <P />(4 data files).
---------------------------------------------------------
Title: Oscillation frequencies for 35 Kepler solar-type planet-hosting
stars using Bayesian techniques and machine learning
Authors: Davies, G. R.; Silva Aguirre, V.; Bedding, T. R.; Handberg,
R.; Lund, M. N.; Chaplin, W. J.; Huber, D.; White, T. R.; Benomar,
O.; Hekker, S.; Basu, S.; Campante, T. L.; Christensen-Dalsgaard, J.;
Elsworth, Y.; Karoff, C.; Kjeldsen, H.; Lundkvist, M. S.; Metcalfe,
T. S.; Stello, D.
2016MNRAS.456.2183D Altcode: 2015arXiv151102105D
Kepler has revolutionized our understanding of both exoplanets and their
host stars. Asteroseismology is a valuable tool in the characterization
of stars and Kepler is an excellent observing facility to perform
asteroseismology. Here we select a sample of 35 Kepler solar-type stars
which host transiting exoplanets (or planet candidates) with detected
solar-like oscillations. Using available Kepler short cadence data up
to Quarter 16 we create power spectra optimized for asteroseismology
of solar-type stars. We identify modes of oscillation and estimate
mode frequencies by `peak bagging' using a Bayesian Markov Chain Monte
Carlo framework. In addition, we expand the methodology of quality
assurance using a Bayesian unsupervised machine learning approach. We
report the measured frequencies of the modes of oscillation for all
35 stars and frequency ratios commonly used in detailed asteroseismic
modelling. Due to the high correlations associated with frequency
ratios we report the covariance matrix of all frequencies measured
and frequency ratios calculated. These frequencies, frequency ratios,
and covariance matrices can be used to obtain tight constraint on the
fundamental parameters of these planet-hosting stars.
---------------------------------------------------------
Title: Performance of the Birmingham Solar-Oscillations Network
(BiSON)
Authors: Hale, S. J.; Howe, R.; Chaplin, W. J.; Davies, G. R.;
Elsworth, Y. P.
2016SoPh..291....1H Altcode: 2015arXiv151007085H; 2015SoPh..tmp..172H
The Birmingham Solar-Oscillations Network (BiSON) has been operating
with a full complement of six stations since 1992. Over 20 years later,
we look back on the network history. The meta-data from the sites
have been analysed to assess performance in terms of site insolation,
with a brief look at the challenges that have been encountered over
the years. We explain how the international community can gain easy
access to the ever-growing dataset produced by the network, and finally
look to the future of the network and the potential impact of nearly
25 years of technology miniaturisation.
---------------------------------------------------------
Title: The Kepler-454 System: A Small, Not-rocky Inner Planet,
a Jovian World, and a Distant Companion
Authors: Gettel, Sara; Charbonneau, David; Dressing, Courtney D.;
Buchhave, Lars A.; Dumusque, Xavier; Vanderburg, Andrew; Bonomo, Aldo
S.; Malavolta, Luca; Pepe, Francesco; Collier Cameron, Andrew; Latham,
David W.; Udry, Stéphane; Marcy, Geoffrey W.; Isaacson, Howard;
Howard, Andrew W.; Davies, Guy R.; Silva Aguirre, Victor; Kjeldsen,
Hans; Bedding, Timothy R.; Lopez, Eric; Affer, Laura; Cosentino,
Rosario; Figueira, Pedro; Fiorenzano, Aldo F. M.; Harutyunyan, Avet;
Johnson, John Asher; Lopez-Morales, Mercedes; Lovis, Christophe;
Mayor, Michel; Micela, Giusi; Molinari, Emilio; Motalebi, Fatemeh;
Phillips, David F.; Piotto, Giampaolo; Queloz, Didier; Rice, Ken;
Sasselov, Dimitar; Ségransan, Damien; Sozzetti, Alessandro; Watson,
Chris; Basu, Sarbani; Campante, Tiago L.; Christensen-Dalsgaard,
Jørgen; Kawaler, Steven D.; Metcalfe, Travis S.; Handberg, Rasmus;
Lund, Mikkel N.; Lundkvist, Mia S.; Huber, Daniel; Chaplin, William J.
2016ApJ...816...95G Altcode: 2015arXiv151109097G
Kepler-454 (KOI-273) is a relatively bright (V = 11.69 mag), Sun-like
star that hosts a transiting planet candidate in a 10.6 day orbit. From
spectroscopy, we estimate the stellar temperature to be 5687 ± 50
K, its metallicity to be [m/H] = 0.32 ± 0.08, and the projected
rotational velocity to be v sin I < 2.4 km s<SUP>-1</SUP>. We
combine these values with a study of the asteroseismic frequencies
from short cadence Kepler data to estimate the stellar mass to
be {1.028}<SUB>-0.03</SUB><SUP>+0.04</SUP>{M}<SUB>⊙ </SUB>,
the radius to be 1.066 ± 0.012 R<SUB>⊙</SUB>, and the age to be
{5.25}<SUB>-1.39</SUB><SUP>+1.41</SUP> Gyr. We estimate the radius
of the 10.6 day planet as 2.37 ± 0.13 R<SUB>⊕</SUB>. Using 63
radial velocity observations obtained with the HARPS-N spectrograph
on the Telescopio Nazionale Galileo and 36 observations made with
the HIRES spectrograph at the Keck Observatory, we measure the mass
of this planet to be 6.8 ± 1.4 M<SUB>⊕</SUB>. We also detect two
additional non-transiting companions, a planet with a minimum mass
of 4.46 ± 0.12 M<SUB>J</SUB> in a nearly circular 524 day orbit
and a massive companion with a period >10 years and mass >12.1
M<SUB>J</SUB>. The 12 exoplanets with radii <2.7 R<SUB>⊕</SUB>
and precise mass measurements appear to fall into two populations, with
those <1.6 R<SUB>⊕</SUB> following an Earth-like composition curve
and larger planets requiring a significant fraction of volatiles. With
a density of 2.76 ± 0.73 g cm<SUP>-3</SUP>, Kepler-454b lies near
the mass transition between these two populations and requires the
presence of volatiles and/or H/He gas.
---------------------------------------------------------
Title: Asteroseismology of Red-Giant Stars as a Novel Approach in
the Search for Gravitational Waves
Authors: Campante, Tiago L.; Lopes, Ilídio; Bossini, D.; Miglio,
A.; Chaplin, W. J.
2016IAUFM..29B.363C Altcode:
Stars are massive resonators that may be used as gravitational-wave (GW)
detectors with isotropic sensitivity. New insights on stellar physics
are being made possible by asteroseismology, the study of stars by the
observation of their natural oscillations. The continuous monitoring
of oscillation modes in stars of different masses and sizes (e.g., as
carried out by NASA's Kepler mission) opens the possibility of surveying
the local Universe for GW radiation. Red-giant stars are of particular
interest in this regard. Since the mean separation between red giants
in open clusters is small (a few light years), this can in principle
be used to look for the same GW imprint on the oscillation modes of
different stars as a GW propagates across the cluster. Furthermore,
the frequency range probed by oscillations in red giants complements
the capabilities of the planned eLISA space interferometer. We propose
asteroseismology of red giants as a novel approach in the search for
gravitational waves.
---------------------------------------------------------
Title: Asteroseismology of Exoplanet-Host Stars in the TESS Era
Authors: Campante, Tiago L.; Schofield, Mathew; Chaplin, William J.;
Huber, Daniel; Christensen-Dalsgaard, Jørgen; Kjeldsen, Hans; Latham,
David W.; Ricker, George R.; Winn, Joshua
2015ESS.....350303C Altcode:
New insights on stellar evolution and stellar interiors physics are
being made possible by asteroseismology, the study of stars by the
observation of their natural, resonant oscillations. Throughout the
duration of the Kepler mission, asteroseismology has also played
an important role in the characterization of host stars and their
planetary systems. Examples include the precise estimation of the
fundamental properties of stellar hosts, the obliquity determination
of planetary systems, or the orbital eccentricity determination via
asterodensity profiling. The Transiting Exoplanet Survey Satellite
(TESS) will perform a wide-field survey for planets that transit bright
host stars. Its excellent photometric precision and long intervals of
uninterrupted observations will enable asteroseismology of solar-type
stars and their evolved counterparts. Based on existing all-sky
simulations of the stellar and planetary populations, we investigate
the asteroseismic yield of the mission, placing particular emphasis
on the yield of exoplanet-host stars for which we expect to detect
solar-like oscillations. This is done both for the cohort of target
stars (observed at a 2-min cadence), which will mainly involve low-mass
main-sequence hosts, as well as for the cohort of “full-frame image”
stars (observed at a 30-min cadence). The latter cohort offers the
exciting prospect of conducting asteroseismology on a significant
number of evolved hosts. Also, the brightest solar-type hosts with
asteroseismology will become some of the best characterized planetary
systems known to date. Finally, we discuss the impact of the detected
oscillations on the accuracy/precision of the derived properties of
the host stars and their planetary systems.
---------------------------------------------------------
Title: Validation of solar-cycle changes in low-degree helioseismic
parameters from the Birmingham Solar-Oscillations Network
Authors: Howe, R.; Davies, G. R.; Chaplin, W. J.; Elsworth, Y. P.;
Hale, S. J.
2015MNRAS.454.4120H Altcode: 2015arXiv150906894H
We present a new and up-to-date analysis of the solar low-degree p-mode
parameter shifts from the Birmingham Solar-Oscillations Network over
the past 22 years, up to the end of 2014. We aim to demonstrate that
they are not dominated by changes in the asymmetry of the resonant peak
profiles of the modes and that the previously published results on the
solar-cycle variations of mode parameters are reliable. We compare the
results obtained using a conventional maximum-likelihood estimation
algorithm and a new one based on the Markov Chain Monte Carlo (MCMC)
technique, both taking into account mode asymmetry. We assess the
reliability of the solar-cycle trends seen in the data by applying
the same analysis to artificially generated spectra. We find that the
two methods are in good agreement. Both methods accurately reproduce
the input frequency shifts in the artificial data and underestimate
the amplitude and width changes by a small amount, around 10 per
cent. We confirm earlier findings that the frequency and line width
are positively correlated, and the mode amplitude anticorrelated,
with the level of solar activity, with the energy supplied to the modes
remaining essentially unchanged. For the mode asymmetry the correlation
with activity is marginal, but the MCMC algorithm gives more robust
results than the MLE (Maximum-Likelihood Estimate). The magnitude
of the parameter shifts is consistent with earlier work. There is no
evidence that the frequency changes we see arise from changes in the
asymmetry, which would need to be much larger than those observed in
order to give the observed frequency shift.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Stellar noise for 4529 Kepler
solar-type dwarfs (Gilliland+, 2015)
Authors: Gilliland, R. L.; Chaplin, W. J.; Jenkins, J. M.; Ramsey,
L. W.; Smith, J. C.
2015yCat..51500133G Altcode:
The NASA Kepler Mission has left an indelible imprint on the research
of exoplanet and stellar properties for a large number of stars
(~150000), over four years. <P />Our earlier study (Gilliland et al.,
2011ApJS..197....6G; Paper I) provided a discussion about the Kepler
Mission noise properties. The earlier study over the first six quarters
of Kepler data is extended to the full four years ultimately comprising
the mission. <P />A total of 4529 stars (see Table3) brighter than
K<SUB>p</SUB>=12.5 met the selection criteria for solar-type dwarfs
as detailed in Paper I (Gilliland et al., 2011ApJS..197....6G). <P
/>(1 data file).
---------------------------------------------------------
Title: A seismic and gravitationally bound double star observed by
Kepler. Implication for the presence of a convective core
Authors: Appourchaux, T.; Antia, H. M.; Ball, W.; Creevey, O.;
Lebreton, Y.; Verma, K.; Vorontsov, S.; Campante, T. L.; Davies,
G. R.; Gaulme, P.; Régulo, C.; Horch, E.; Howell, S.; Everett, M.;
Ciardi, D.; Fossati, L.; Miglio, A.; Montalbán, J.; Chaplin, W. J.;
García, R. A.; Gizon, L.
2015A&A...582A..25A Altcode:
Context. Solar-like oscillations have been observed by Kepler and CoRoT
in many solar-type stars, thereby providing a way to probe stars using
asteroseismology. <BR /> Aims: The derivation of stellar parameters
has usually been done with single stars. The aim of the paper is to
derive the stellar parameters of a double-star system (HIP 93511),
for which an interferometric orbit has been observed along with
asteroseismic measurements. <BR /> Methods: We used a time series
of nearly two years of data for the double star to detect the two
oscillation-mode envelopes that appear in the power spectrum. Using
a new scaling relation based on luminosity, we derived the radius and
mass of each star. We derived the age of each star using two proxies:
one based upon the large frequency separation and a new one based
upon the small frequency separation. Using stellar modelling, the mode
frequencies allowed us to derive the radius, the mass, and the age of
each component. In addition, speckle interferometry performed since 2006
has enabled us to recover the orbit of the system and the total mass
of the system. <BR /> Results: From the determination of the orbit,
the total mass of the system is 2.34<SUB>-0.33</SUB><SUP>+0.45</SUP>
M<SUB>⊙</SUB>. The total seismic mass using scaling relations
is 2.47 ± 0.07 M<SUB>⊙</SUB>. The seismic age derived using the
new proxy based upon the small frequency separation is 3.5 ± 0.3
Gyr. Based on stellar modelling, the mean common age of the system is
2.7-3.9 Gyr. The mean total seismic mass of the system is 2.34-2.53
M<SUB>⊙</SUB> consistent with what we determined independently
with the orbit. The stellar models provide the mean radius, mass,
and age of the stars as R<SUB>A</SUB> = 1.82-1.87R<SUB>⊙</SUB>,
M<SUB>A</SUB> = 1.25-1.39 M<SUB>⊙</SUB>, Age<SUB>A</SUB> = 2.6-3.5
Gyr; R<SUB>B</SUB> = 1.22-1.25 R<SUB>⊙</SUB>, M<SUB>B</SUB> =
1.08-1.14 M<SUB>⊙</SUB>, Age<SUB>B</SUB> = 3.35-4.21 Gyr. The
models provide two sets of values for Star A: [1.25-1.27]
M<SUB>⊙</SUB> and [1.34-1.39] M<SUB>⊙</SUB>. We detect a
convective core in Star A, while Star B does not have any. For the
metallicity of the binary system of Z ≈ 0.02, we set the limit
between stars having a convective core in the range [1.14-1.25]
M<SUB>⊙</SUB>. <P />Appendices are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201526610/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Asteroseismology of Solar-Type Stars with K2: Detection of
Oscillations in C1 Data
Authors: Chaplin, W. J.; Lund, M. N.; Handberg, R.; Basu, S.;
Buchhave, L. A.; Campante, T. L.; Davies, G. R.; Huber, D.; Latham,
D. W.; Latham, C. A.; Serenelli, A.; Antia, H. M.; Appourchaux, T.;
Ball, W. H.; Benomar, O.; Casagrande, L.; Christensen-Dalsgaard, J.;
Coelho, H. R.; Creevey, O. L.; Elsworth, Y.; García, R. A.; Gaulme,
P.; Hekker, S.; Kallinger, T.; Karoff, C.; Kawaler, S. D.; Kjeldsen,
H.; Lundkvist, M. S.; Marcadon, F.; Mathur, S.; Miglio, A.; Mosser,
B.; Régulo, C.; Roxburgh, I. W.; Silva Aguirre, V.; Stello, D.;
Verma, K.; White, T. R.; Bedding, T. R.; Barclay, T.; Buzasi, D. L.;
Dehuevels, S.; Gizon, L.; Houdek, G.; Howell, S. B.; Salabert, D.;
Soderblom, D. R.
2015PASP..127.1038C Altcode: 2015arXiv150701827C
We present the first detections by the NASA K2 Mission of oscillations
in solar-type stars, using short-cadence data collected during
K2 Campaign\,1 (C1). We understand the asteroseismic detection
thresholds for C1-like levels of photometric performance, and we
can detect oscillations in subgiants having dominant oscillation
frequencies around $1000\,\rm \mu Hz$. Changes to the operation of the
fine-guidance sensors are expected to give significant improvements
in the high-frequency performance from C3 onwards. A reduction in the
excess high-frequency noise by a factor of two-and-a-half in amplitude
would bring main-sequence stars with dominant oscillation frequencies as
high as ${\simeq 2500}\,\rm \mu Hz$ into play as potential asteroseismic
targets for K2.
---------------------------------------------------------
Title: Kepler Mission Stellar and Instrument Noise Properties
Revisited
Authors: Gilliland, Ronald L.; Chaplin, William J.; Jenkins, Jon M.;
Ramsey, Lawrence W.; Smith, Jeffrey C.
2015AJ....150..133G Altcode: 2015arXiv150805054G
An earlier study of the Kepler Mission noise properties on timescales
of primary relevance to detection of exoplanet transits found that
higher than expected noise followed, to a large extent, from the stars
rather than instrument or data analysis performance. The earlier study
over the first six quarters of Kepler data is extended to the full
four years ultimately comprising the mission. Efforts to improve the
pipeline data analysis have been successful in reducing noise levels
modestly as evidenced by smaller values derived from the current data
products. The new analyses of noise properties on transit timescales
show significant changes in the component attributed to instrument
and data analysis, with essentially no change in the inferred stellar
noise. We also extend the analyses to timescales of several days,
instead of several hours to better sample stellar noise that follows
from magnetic activity. On the longer timescale there is a shift in
stellar noise for solar-type stars to smaller values in comparison to
solar values.
---------------------------------------------------------
Title: Using BiSON to detect solar internal g-modes
Authors: Kuszlewicz, J.; Davies, G. R.; Chaplin, W. J.
2015EPJWC.10106041K Altcode:
The unambiguous detection of individual solar internal g modes continues
to elude us. With the aid of new additions to calibration procedures,
as well as updated methods to combine multi-site time series more
effectively, the noise and signal detection threshold levels in the
low-frequency domain (where the g modes are expected to be found)
have been greatly improved. In the BiSON 23-year dataset these levels
now rival those of GOLF, and with much greater frequency resolution
available, due to the long time series, there is an opportunity
to place more constraints on the upper limits of individual g mode
amplitudes. Here we detail recent work dedicated to the challenges of
observing low-frequency oscillations using a ground-based network,
including the role of the window function as well as the effect of
calibration on the low frequency domain.
---------------------------------------------------------
Title: Testing the ν<SUB>max</SUB> scaling relation
Authors: Coelho, H. R.; Chaplin, W. J.; Basu, S.; Serenelli, A.;
Miglio, A.; Reese, D.
2015EPJWC.10106017C Altcode:
Two key global seismic quantities are relevant to estimate the
fundamental properties of a star: the frequency of maximum power
(ν<SUB>max</SUB>) and the large frequency separation (Δν). The
focus of this work is to test the ν<SUB>max</SUB> scaling relation in
order to ascertain it's level of accuracy. Here we report our results
using artificial data and real Kepler data, based on a grid-modelling
approach.
---------------------------------------------------------
Title: KOI-3158: The oldest known system of terrestrial-size planets
Authors: Campante, T. L.; Barclay, T.; Swift, J. J.; Huber, D.;
Adibekyan, V. Zh.; Cochran, W.; Burke, C. J.; Isaacson, H.; Quintana,
E. V.; Davies, G. R.; Silva Aguirre, V.; Ragozzine, D.; Riddle, R.;
Baranec, C.; Basu, S.; Chaplin, W. J.; Christensen-Dalsgaard, J.;
Metcalfe, T. S.; Bedding, T. R.; Handberg, R.; Stello, D.; Brewer,
J. M.; Hekker, S.; Karoff, C.; Kolbl, R.; Law, N. M.; Lundkvist, M.;
Miglio, A.; Rowe, J. F.; Santos, N. C.; Van Laerhoven, C.; Arentoft,
T.; Elsworth, Y. P.; Fischer, D. A.; Kawaler, S. D.; Kjeldsen, H.;
Lund, M. N.; Marcy, G. W.; Sousa, S. G.; Sozzetti, A.; White, T. R.
2015EPJWC.10102004C Altcode: 2015arXiv150107869C
The first discoveries of exoplanets around Sun-like stars have fueled
efforts to find ever smaller worlds evocative of Earth and other
terrestrial planets in the Solar System. While gas-giant planets
appear to form preferentially around metal-rich stars, small planets
(with radii less than four Earth radii) can form under a wide range of
metallicities. This implies that small, including Earth-size, planets
may have readily formed at earlier epochs in the Universe's history when
metals were far less abundant. We report Kepler spacecraft observations
of KOI-3158, a metal-poor Sun-like star from the old population of the
Galactic thick disk, which hosts five planets with sizes between Mercury
and Venus. We used asteroseismology to directly measure a precise age
of 11.2 ± 1.0 Gyr for the host star, indicating that KOI-3158 formed
when the Universe was less than 20 % of its current age and making
it the oldest known system of terrestrial-size planets. We thus show
that Earth-size planets have formed throughout most of the Universe's
13.8-billion-year history, providing scope for the existence of ancient
life in the Galaxy.
---------------------------------------------------------
Title: What asteroseismology can do for exoplanets
Authors: Van Eylen, Vincent; Lund, Mikkel N.; Silva Aguirre, Victor;
Arentoft, Torben; Kjeldsen, Hans; Albrecht, Simon; Chaplin, William
J.; Isaacson, Howard; Pedersen, May G.; Jessen-Hansen, Jens; Tingley,
Brandon; Christensen-Dalsgaard, Jørgen; Aerts, Conny; Campante,
Tiago L.; Bryson, Steve T.
2015EPJWC.10102005V Altcode: 2014arXiv1412.4848V
We describe three useful applications of asteroseismology in the
context of exoplanet science: (1) the detailed characterisation of
exoplanet host stars; (2) the measurement of stellar inclinations; and
(3) the determination of orbital eccentricity from transit duration
making use of asteroseismic stellar densities. We do so using the
example system Kepler-410 [1]. This is one of the brightest (V = 9.4)
Kepler exoplanet host stars, containing a small (2.8 R<SUB>⊕</SUB>)
transiting planet in a long orbit (17.8 days), and one or more
additional non-transiting planets as indicated by transit timing
variations. The validation of Kepler-410 (KOI-42) was complicated due
to the presence of a companion star, and the planetary nature of the
system was confirmed after analyzing a Spitzer transit observation as
well as ground-based follow-up observations.
---------------------------------------------------------
Title: Asteroseismic estimate of helium abundance of 16 Cyg A, B
Authors: Verma, Kuldeep; Faria, João P.; Antia, H. M.; Basu, Sarbani;
Mazumdar, Anwesh; Monteiro, Mário J. P. F. G.; Appourchaux, Thierry;
Chaplin, William J.; García, Rafael A.; Metcalfe, Travis S.
2015EPJWC.10106066V Altcode:
The helium ionization zone in a star leaves a characteristic signature
on its oscillation frequencies, which can be used to estimate the
helium content in the envelope of the star. We use the oscillation
frequencies of 16 Cyg A and B, obtained using 2.5 years of Kepler data,
to estimate the envelope helium abundance of these stars. We find the
envelope helium abundance to lie in the range 0.231-0.251 for 16 Cyg
A and 0.218-0.266 for 16 Cyg B.
---------------------------------------------------------
Title: Ages and fundamental properties of Kepler exoplanet host
stars from asteroseismology
Authors: Silva Aguirre, V.; Davies, G. R.; Basu, S.;
Christensen-Dalsgaard, J.; Creevey, O.; Metcalfe, T. S.; Bedding,
T. R.; Casagrande, L.; Handberg, R.; Lund, M. N.; Nissen, P. E.;
Chaplin, W. J.; Huber, D.; Serenelli, A. M.; Stello, D.; Van Eylen,
V.; Campante, T. L.; Elsworth, Y.; Gilliland, R. L.; Hekker, S.;
Karoff, C.; Kawaler, S. D.; Kjeldsen, H.; Lundkvist, M. S.
2015MNRAS.452.2127S Altcode: 2015arXiv150407992S
We present a study of 33 Kepler planet-candidate host stars for which
asteroseismic observations have sufficiently high signal-to-noise
ratio to allow extraction of individual pulsation frequencies. We
implement a new Bayesian scheme that is flexible in its input to process
individual oscillation frequencies, combinations of them, and average
asteroseismic parameters, and derive robust fundamental properties for
these targets. Applying this scheme to grids of evolutionary models
yields stellar properties with median statistical uncertainties
of 1.2 per cent (radius), 1.7 per cent (density), 3.3 per cent
(mass), 4.4 per cent (distance), and 14 per cent (age), making this
the exoplanet host-star sample with the most precise and uniformly
determined fundamental parameters to date. We assess the systematics
from changes in the solar abundances and mixing-length parameter,
showing that they are smaller than the statistical errors. We also
determine the stellar properties with three other fitting algorithms
and explore the systematics arising from using different evolution
and pulsation codes, resulting in 1 per cent in density and radius,
and 2 per cent and 7 per cent in mass and age, respectively. We
confirm previous findings of the initial helium abundance being a
source of systematics comparable to our statistical uncertainties,
and discuss future prospects for constraining this parameter by
combining asteroseismology and data from space missions. Finally, we
compare our derived properties with those obtained using the global
average asteroseismic observables along with effective temperature and
metallicity, finding excellent level of agreement. Owing to selection
effects, our results show that the majority of the high signal-to-noise
ratio asteroseismic Kepler host stars are older than the Sun.
---------------------------------------------------------
Title: Oscillating Red Giants Observed during Campaign 1 of the
Kepler K2 Mission: New Prospects for Galactic Archaeology
Authors: Stello, Dennis; Huber, Daniel; Sharma, Sanjib; Johnson,
Jennifer; Lund, Mikkel N.; Handberg, Rasmus; Buzasi, Derek L.; Silva
Aguirre, Victor; Chaplin, William J.; Miglio, Andrea; Pinsonneault,
Marc; Basu, Sarbani; Bedding, Tim R.; Bland-Hawthorn, Joss; Casagrande,
Luca; Davies, Guy; Elsworth, Yvonne; Garcia, Rafael A.; Mathur,
Savita; Di Mauro, Maria Pia; Mosser, Benoit; Schneider, Donald P.;
Serenelli, Aldo; Valentini, Marica
2015ApJ...809L...3S Altcode: 2015arXiv150608931S
NASA’s re-purposed Kepler mission—dubbed K2—has brought new
scientific opportunities that were not anticipated for the original
Kepler mission. One science goal that makes optimal use of K2's
capabilities, in particular its 360° ecliptic field of view, is
galactic archaeology—the study of the evolution of the Galaxy from
the fossil stellar record. The thrust of this research is to exploit
high-precision, time-resolved photometry from K2 in order to detect
oscillations in red giant stars. This asteroseismic information can
provide estimates of stellar radius (hence distance), mass, and age of
vast numbers of stars across the Galaxy. Here we present the initial
analysis of a subset of red giants, observed toward the north galactic
gap, during the mission’s first full science campaign. We investigate
the feasibility of using K2 data for detecting oscillations in red
giants that span a range in apparent magnitude and evolutionary state
(hence intrinsic luminosity). We demonstrate that oscillations are
detectable for essentially all cool giants within the {log}g range
∼1.9-3.2. Our detection is complete down to {\text{Kp}} ∼ 14.5,
which results in a seismic sample with little or no detection bias. This
sample is ideally suited to stellar population studies that seek to
investigate potential shortcomings of contemporary Galaxy models.
---------------------------------------------------------
Title: Asteroseismology of red-giant stars as a novel approach in
the search for gravitational waves
Authors: Campante, Tiago L.; Lopes, Ilídio; Bossini, Diego; Miglio,
Andrea; Chaplin, William J.
2015IAUGA..2252323C Altcode: 2016arXiv160203667C
Stars are massive resonators that may in principle be used as
gravitational-wave (GW) detectors with an isotropic sensitivity. New
insights on stellar physics have been made possible by asteroseismology,
the study of stars by the observation of their natural, resonant
oscillations. The continuous monitoring of oscillation modes in stars
of different masses and sizes (e.g., as carried out by NASA’s Kepler
space telescope) thus opens the possibility of surveying the local
Universe for GW radiation. Red-giant stars are of particular interest
in this regard. Since the mean separation between red giants in open
clusters is small (of a few light years), this can in principle be
used to look for the same GW imprint on the oscillation modes of
different stars as a GW propagates across the cluster. Furthermore,
the frequency range probed by oscillations in red giants overlaps
with, and complements, the capabilities of the planned eLISA space
interferometer. We propose asteroseismology of red-giant stars as a
novel approach in the search for gravitational waves and assess to
what extent oscillations in these stars can be excited by a passing,
monochromatic GW.
---------------------------------------------------------
Title: The legacy of CoRoT and Kepler on the physics of stellar
evolution
Authors: Chaplin, William
2015IAUGA..2235114C Altcode:
It is a golden era for stellar astrophysics studies, driven by new
satellite observations of unprecedented quality and scope. In this
talk I will review advances in our understanding that have followed
from asteroseismic studies with CoRoT and Kepler data, not only for
stellar evolution theory but also in respect of the legacy for exoplanet
and Galactic stellar population studies. I will also highlight the
huge amount of work that remains to be performed to fully exploit
the CoRoT and Kepler databases, and look to ongoing studies with K2,
and the future promise of the NASA TESS and ESA PLATO Missions.
---------------------------------------------------------
Title: A test of the asteroseismic ν<SUB>max</SUB> scaling relation
for solar-like oscillations in main-sequence and subgiant stars
Authors: Coelho, H. R.; Chaplin, W. J.; Basu, S.; Serenelli, A.;
Miglio, A.; Reese, D. R.
2015MNRAS.451.3011C Altcode: 2015arXiv150506087C
Large-scale analyses of stellar samples comprised of cool, solar-like
oscillators now commonly utilize the so-called asteroseismic scaling
relations to estimate fundamental stellar properties. In this paper,
we present a test of the scaling relation for the global asteroseismic
parameter ν<SUB>max</SUB>, the frequency at which a solar-like
oscillator presents its strongest observed pulsation amplitude. The
classic relation assumes that this characteristic frequency scales with
a particular combination of surface gravity and effective temperature
that also describes the dependence of the cut-off frequency for acoustic
waves in an isothermal atmosphere, i.e. ν _max ∝ gT_eff^{-1/2}. We
test how well the oscillations of cool main-sequence and subgiant
stars adhere to this relation, using a sample of asteroseismic targets
observed by the NASA Kepler Mission. Our results, which come from a
grid-based analysis, rule out departures from the classic gT_eff^{-1/2}
scaling dependence at the level of ≃1.5 per cent over the full
≃ 1560 K range in T<SUB>eff</SUB> that we tested. There is some
uncertainty over the absolute calibration of the scaling. However,
any variation with T<SUB>eff</SUB> is evidently small, with limits
similar to those above.
---------------------------------------------------------
Title: Young α-enriched giant stars in the solar neighbourhood
Authors: Martig, Marie; Rix, Hans-Walter; Silva Aguirre, Victor;
Hekker, Saskia; Mosser, Benoit; Elsworth, Yvonne; Bovy, Jo; Stello,
Dennis; Anders, Friedrich; García, Rafael A.; Tayar, Jamie;
Rodrigues, Thaíse S.; Basu, Sarbani; Carrera, Ricardo; Ceillier,
Tugdual; Chaplin, William J.; Chiappini, Cristina; Frinchaboy,
Peter M.; García-Hernández, D. A.; Hearty, Fred R.; Holtzman, Jon;
Johnson, Jennifer A.; Majewski, Steven R.; Mathur, Savita; Mészáros,
Szabolcs; Miglio, Andrea; Nidever, David; Pan, Kaike; Pinsonneault,
Marc; Schiavon, Ricardo P.; Schneider, Donald P.; Serenelli, Aldo;
Shetrone, Matthew; Zamora, Olga
2015MNRAS.451.2230M Altcode: 2014arXiv1412.3453M
We derive age constraints for 1639 red giants in the APOKASC sample
for which seismic parameters from Kepler, as well as effective
temperatures, metallicities and [α/Fe] values from APOGEE DR12 (Apache
Point Observatory Galactic Evolution Experiment Data Release 12)
are available. We investigate the relation between age and chemical
abundances for these stars, using a simple and robust approach to
obtain ages. We first derive stellar masses using standard seismic
scaling relations, then determine the maximum possible age for each
star as function of its mass and metallicity, independently of its
evolutionary stage. While the overall trend between maximum age
and chemical abundances is a declining fraction of young stars with
increasing [α/Fe], at least 14 out of 241 stars with [α/Fe] >0.13
are younger than 6 Gyr. Five stars with [α/Fe] ≥0.2 have ages below
4 Gyr. We examine the effect of modifications in the standard seismic
scaling relations, as well as the effect of very low helium fractions,
but these changes are not enough to make these stars as old as usually
expected for α-rich stars (i.e. ages greater than 8-9 Gyr). Such
unusual α-rich young stars have also been detected by other surveys,
but defy simple explanations in a galaxy evolution context.
---------------------------------------------------------
Title: Global helioseismology and asteroseismology of solar-type stars
Authors: Howe, R.; Chaplin, W. J.
2015exse.book...63H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Rapid Rotation of Low-mass Red Giants Using APOKASC: A Measure
of Interaction Rates on the Post-main-sequence
Authors: Tayar, Jamie; Ceillier, Tugdual; García-Hernández, D. A.;
Troup, Nicholas W.; Mathur, Savita; García, Rafael A.; Zamora, O.;
Johnson, Jennifer A.; Pinsonneault, Marc H.; Mészáros, Szabolcs;
Allende Prieto, Carlos; Chaplin, William J.; Elsworth, Yvonne; Hekker,
Saskia; Nidever, David L.; Salabert, David; Schneider, Donald P.;
Serenelli, Aldo; Shetrone, Matthew; Stello, Dennis
2015ApJ...807...82T Altcode: 2015arXiv150503536T
We investigate the occurrence rate of rapidly rotating (v{sin}i >10
km s<SUP>-1</SUP>), low-mass giant stars in the Apache Point Observatory
Galaxy Evolution Experiment-Kepler (APOKASC) fields with asteroseismic
mass and surface gravity measurements. Such stars are likely merger
products and their frequency places interesting constraints on stellar
population models. We also identify anomalous rotators, i.e., stars
with 5 km s<SUP>-1</SUP> < v{sin}i < 10 km s<SUP>-1</SUP> that
are rotating significantly faster than both angular momentum evolution
predictions and the measured rates of similar stars. Our data set
contains fewer rapid rotators than one would expect given measurements
of the Galactic field star population, which likely indicates that
asteroseismic detections are less common in rapidly rotating red
giants. The number of low-mass moderate (5-10 km s<SUP>-1</SUP>)
rotators in our sample gives a lower limit of 7% for the rate at which
low-mass stars interact on the upper red giant branch because single
stars in this mass range are expected to rotate slowly. Finally,
we classify the likely origin of the rapid or anomalous rotation
where possible. KIC 10293335 is identified as a merger product and
KIC 6501237 is a possible binary system of two oscillating red giants.
---------------------------------------------------------
Title: The Eleventh and Twelfth Data Releases of the Sloan Digital
Sky Survey: Final Data from SDSS-III
Authors: Alam, Shadab; Albareti, Franco D.; Allende Prieto, Carlos;
Anders, F.; Anderson, Scott F.; Anderton, Timothy; Andrews, Brett
H.; Armengaud, Eric; Aubourg, Éric; Bailey, Stephen; Basu, Sarbani;
Bautista, Julian E.; Beaton, Rachael L.; Beers, Timothy C.; Bender,
Chad F.; Berlind, Andreas A.; Beutler, Florian; Bhardwaj, Vaishali;
Bird, Jonathan C.; Bizyaev, Dmitry; Blake, Cullen H.; Blanton, Michael
R.; Blomqvist, Michael; Bochanski, John J.; Bolton, Adam S.; Bovy,
Jo; Shelden Bradley, A.; Brandt, W. N.; Brauer, D. E.; Brinkmann,
J.; Brown, Peter J.; Brownstein, Joel R.; Burden, Angela; Burtin,
Etienne; Busca, Nicolás G.; Cai, Zheng; Capozzi, Diego; Carnero
Rosell, Aurelio; Carr, Michael A.; Carrera, Ricardo; Chambers,
K. C.; Chaplin, William James; Chen, Yen-Chi; Chiappini, Cristina;
Chojnowski, S. Drew; Chuang, Chia-Hsun; Clerc, Nicolas; Comparat,
Johan; Covey, Kevin; Croft, Rupert A. C.; Cuesta, Antonio J.; Cunha,
Katia; da Costa, Luiz N.; Da Rio, Nicola; Davenport, James R. A.;
Dawson, Kyle S.; De Lee, Nathan; Delubac, Timothée; Deshpande,
Rohit; Dhital, Saurav; Dutra-Ferreira, Letícia; Dwelly, Tom; Ealet,
Anne; Ebelke, Garrett L.; Edmondson, Edward M.; Eisenstein, Daniel J.;
Ellsworth, Tristan; Elsworth, Yvonne; Epstein, Courtney R.; Eracleous,
Michael; Escoffier, Stephanie; Esposito, Massimiliano; Evans, Michael
L.; Fan, Xiaohui; Fernández-Alvar, Emma; Feuillet, Diane; Filiz Ak,
Nurten; Finley, Hayley; Finoguenov, Alexis; Flaherty, Kevin; Fleming,
Scott W.; Font-Ribera, Andreu; Foster, Jonathan; Frinchaboy, Peter M.;
Galbraith-Frew, J. G.; García, Rafael A.; García-Hernández, D. A.;
García Pérez, Ana E.; Gaulme, Patrick; Ge, Jian; Génova-Santos,
R.; Georgakakis, A.; Ghezzi, Luan; Gillespie, Bruce A.; Girardi, Léo;
Goddard, Daniel; Gontcho, Satya Gontcho A.; González Hernández, Jonay
I.; Grebel, Eva K.; Green, Paul J.; Grieb, Jan Niklas; Grieves, Nolan;
Gunn, James E.; Guo, Hong; Harding, Paul; Hasselquist, Sten; Hawley,
Suzanne L.; Hayden, Michael; Hearty, Fred R.; Hekker, Saskia; Ho,
Shirley; Hogg, David W.; Holley-Bockelmann, Kelly; Holtzman, Jon A.;
Honscheid, Klaus; Huber, Daniel; Huehnerhoff, Joseph; Ivans, Inese
I.; Jiang, Linhua; Johnson, Jennifer A.; Kinemuchi, Karen; Kirkby,
David; Kitaura, Francisco; Klaene, Mark A.; Knapp, Gillian R.; Kneib,
Jean-Paul; Koenig, Xavier P.; Lam, Charles R.; Lan, Ting-Wen; Lang,
Dustin; Laurent, Pierre; Le Goff, Jean-Marc; Leauthaud, Alexie; Lee,
Khee-Gan; Lee, Young Sun; Licquia, Timothy C.; Liu, Jian; Long,
Daniel C.; López-Corredoira, Martín; Lorenzo-Oliveira, Diego;
Lucatello, Sara; Lundgren, Britt; Lupton, Robert H.; Mack, Claude E.,
III; Mahadevan, Suvrath; Maia, Marcio A. G.; Majewski, Steven R.;
Malanushenko, Elena; Malanushenko, Viktor; Manchado, A.; Manera, Marc;
Mao, Qingqing; Maraston, Claudia; Marchwinski, Robert C.; Margala,
Daniel; Martell, Sarah L.; Martig, Marie; Masters, Karen L.; Mathur,
Savita; McBride, Cameron K.; McGehee, Peregrine M.; McGreer, Ian D.;
McMahon, Richard G.; Ménard, Brice; Menzel, Marie-Luise; Merloni,
Andrea; Mészáros, Szabolcs; Miller, Adam A.; Miralda-Escudé, Jordi;
Miyatake, Hironao; Montero-Dorta, Antonio D.; More, Surhud; Morganson,
Eric; Morice-Atkinson, Xan; Morrison, Heather L.; Mosser, Benôit;
Muna, Demitri; Myers, Adam D.; Nandra, Kirpal; Newman, Jeffrey A.;
Neyrinck, Mark; Nguyen, Duy Cuong; Nichol, Robert C.; Nidever,
David L.; Noterdaeme, Pasquier; Nuza, Sebastián E.; O'Connell,
Julia E.; O'Connell, Robert W.; O'Connell, Ross; Ogando, Ricardo
L. C.; Olmstead, Matthew D.; Oravetz, Audrey E.; Oravetz, Daniel J.;
Osumi, Keisuke; Owen, Russell; Padgett, Deborah L.; Padmanabhan,
Nikhil; Paegert, Martin; Palanque-Delabrouille, Nathalie; Pan, Kaike;
Parejko, John K.; Pâris, Isabelle; Park, Changbom; Pattarakijwanich,
Petchara; Pellejero-Ibanez, M.; Pepper, Joshua; Percival, Will J.;
Pérez-Fournon, Ismael; Pérez-Ràfols, Ignasi; Petitjean, Patrick;
Pieri, Matthew M.; Pinsonneault, Marc H.; Porto de Mello, Gustavo
F.; Prada, Francisco; Prakash, Abhishek; Price-Whelan, Adrian M.;
Protopapas, Pavlos; Raddick, M. Jordan; Rahman, Mubdi; Reid, Beth A.;
Rich, James; Rix, Hans-Walter; Robin, Annie C.; Rockosi, Constance M.;
Rodrigues, Thaíse S.; Rodríguez-Torres, Sergio; Roe, Natalie A.;
Ross, Ashley J.; Ross, Nicholas P.; Rossi, Graziano; Ruan, John J.;
Rubiño-Martín, J. A.; Rykoff, Eli S.; Salazar-Albornoz, Salvador;
Salvato, Mara; Samushia, Lado; Sánchez, Ariel G.; Santiago, Basílio;
Sayres, Conor; Schiavon, Ricardo P.; Schlegel, David J.; Schmidt,
Sarah J.; Schneider, Donald P.; Schultheis, Mathias; Schwope, Axel
D.; Scóccola, C. G.; Scott, Caroline; Sellgren, Kris; Seo, Hee-Jong;
Serenelli, Aldo; Shane, Neville; Shen, Yue; Shetrone, Matthew; Shu,
Yiping; Silva Aguirre, V.; Sivarani, Thirupathi; Skrutskie, M. F.;
Slosar, Anže; Smith, Verne V.; Sobreira, Flávia; Souto, Diogo;
Stassun, Keivan G.; Steinmetz, Matthias; Stello, Dennis; Strauss,
Michael A.; Streblyanska, Alina; Suzuki, Nao; Swanson, Molly E. C.;
Tan, Jonathan C.; Tayar, Jamie; Terrien, Ryan C.; Thakar, Aniruddha
R.; Thomas, Daniel; Thomas, Neil; Thompson, Benjamin A.; Tinker,
Jeremy L.; Tojeiro, Rita; Troup, Nicholas W.; Vargas-Magaña, Mariana;
Vazquez, Jose A.; Verde, Licia; Viel, Matteo; Vogt, Nicole P.; Wake,
David A.; Wang, Ji; Weaver, Benjamin A.; Weinberg, David H.; Weiner,
Benjamin J.; White, Martin; Wilson, John C.; Wisniewski, John P.;
Wood-Vasey, W. M.; Ye`che, Christophe; York, Donald G.; Zakamska,
Nadia L.; Zamora, O.; Zasowski, Gail; Zehavi, Idit; Zhao, Gong-Bo;
Zheng, Zheng; Zhou, Xu; Zhou, Zhimin; Zou, Hu; Zhu, Guangtun
2015ApJS..219...12A Altcode: 2015arXiv150100963A
The third generation of the Sloan Digital Sky Survey (SDSS-III) took
data from 2008 to 2014 using the original SDSS wide-field imager, the
original and an upgraded multi-object fiber-fed optical spectrograph,
a new near-infrared high-resolution spectrograph, and a novel optical
interferometer. All of the data from SDSS-III are now made public. In
particular, this paper describes Data Release 11 (DR11) including all
data acquired through 2013 July, and Data Release 12 (DR12) adding data
acquired through 2014 July (including all data included in previous
data releases), marking the end of SDSS-III observing. Relative to our
previous public release (DR10), DR12 adds one million new spectra of
galaxies and quasars from the Baryon Oscillation Spectroscopic Survey
(BOSS) over an additional 3000 deg<SUP>2</SUP> of sky, more than
triples the number of H-band spectra of stars as part of the Apache
Point Observatory (APO) Galactic Evolution Experiment (APOGEE), and
includes repeated accurate radial velocity measurements of 5500 stars
from the Multi-object APO Radial Velocity Exoplanet Large-area Survey
(MARVELS). The APOGEE outputs now include the measured abundances of
15 different elements for each star. In total, SDSS-III added 5200
deg<SUP>2</SUP> of ugriz imaging; 155,520 spectra of 138,099 stars as
part of the Sloan Exploration of Galactic Understanding and Evolution
2 (SEGUE-2) survey; 2,497,484 BOSS spectra of 1,372,737 galaxies,
294,512 quasars, and 247,216 stars over 9376 deg<SUP>2</SUP>; 618,080
APOGEE spectra of 156,593 stars; and 197,040 MARVELS spectra of 5513
stars. Since its first light in 1998, SDSS has imaged over 1/3 of
the Celestial sphere in five bands and obtained over five million
astronomical spectra.
---------------------------------------------------------
Title: Hubble Space Telescope search for the transit of the Earth-mass
exoplanet α Centauri B b
Authors: Demory, Brice-Olivier; Ehrenreich, David; Queloz, Didier;
Seager, Sara; Gilliland, Ronald; Chaplin, William J.; Proffitt,
Charles; Gillon, Michael; Günther, Maximilian N.; Benneke, Björn;
Dumusque, Xavier; Lovis, Christophe; Pepe, Francesco; Ségransan,
Damien; Triaud, Amaury; Udry, Stéphane
2015MNRAS.450.2043D Altcode: 2015arXiv150307528D
Results from exoplanet surveys indicate that small planets (super-Earth
size and below) are abundant in our Galaxy. However, little is known
about their interiors and atmospheres. There is therefore a need to find
small planets transiting bright stars, which would enable a detailed
characterization of this population of objects. We present the results
of a search for the transit of the Earth-mass exoplanet α Centauri B b
with the Hubble Space Telescope (HST). We observed α Centauri B twice
in 2013 and 2014 for a total of 40 h. We achieve a precision of 115 ppm
per 6-s exposure time in a highly saturated regime, which is found to
be consistent across HST orbits. We rule out the transiting nature of
α Centauri B b with the orbital parameters published in the literature
at 96.6 per cent confidence. We find in our data a single transit-like
event that could be associated with another Earth-sized planet in
the system, on a longer period orbit. Our programme demonstrates the
ability of HST to obtain consistent, high-precision photometry of
saturated stars over 26 h of continuous observations.
---------------------------------------------------------
Title: K2P<SUP>2</SUP>— A Photometry Pipeline for the K2 Mission
Authors: Lund, Mikkel N.; Handberg, Rasmus; Davies, Guy R.; Chaplin,
William J.; Jones, Caitlin D.
2015ApJ...806...30L Altcode: 2015arXiv150405199L
With the loss of a second reaction wheel, resulting in the inability
to point continuously and stably at the same field of view, the NASA
Kepler satellite recently entered a new mode of observation known
as the K2 mission. The data from this redesigned mission present a
specific challenge; the targets systematically drift in position on an
∼6 hr timescale, inducing a significant instrumental signal in the
photometric time series—this greatly impacts the ability to detect
planetary signals and perform asteroseismic analysis. Here we detail
our version of a reduction pipeline for K2 target pixel data, which
automatically defines masks for all targets in a given frame; extracts
the target’s flux and position time series; corrects the time series
based on the apparent movement on the CCD (either in 1D or 2D), combined
with the correction of instrumental and/or planetary signals via the
Kepler Asteroseismic Science Operations Center (KASOC) filter, thus
rendering the time series ready for asteroseismic analysis; computes
power spectra for all targets and identifies potential contaminations
between targets. From a test of our pipeline on a sample of targets from
the K2 campaign 0, the recovery of data for multiple targets increases
the amount of potential light curves by a factor of ≥slant 10. Our
pipeline could be applied to the upcoming TESS and PLATO 2.0 missions.
---------------------------------------------------------
Title: VizieR Online Data Catalog: KIC giants Bayesian distances
and extinctions (Rodrigues+ 2014)
Authors: Rodrigues, T. S.; Girardi, L.; Miglio, A.; Bossini, D.;
Bovy, J.; Epstein, C.; Pinsonneault, M. H.; Stello, D.; Zasowski,
G.; Allende Prieto, C.; Chaplin, W. J.; Hekker, S.; Johnson, J. A.;
Meszaros, S.; Mosser, B.; Anders, F.; Basu, S.; Beers, T. C.;
Chiappini, C.; da Costa, L. A. N.; Elsworth, Y.; Garcia, R. A.;
Garcia Perez, A. E.; Hearty, F. R.; Maia, M. A. G.; Majewski, S. R.;
Mathur, S.; Montalban, J.; Nidever, D. L.; Santiago, B.; Schultheis,
M.; Serenelli, A.; Shetrone, M.
2015yCat..74452758R Altcode:
APOGEE uses a high-resolution infrared spectrograph, mounted at the
Apache Point Observatory 2.5m telescope, with a mean resolution of
~22500 in the H band (spectral coverage: 1.51-1.70um). APOGEE has
already observed more than 100000 stars selected from 2MASS photometry,
at typical signal-to-noise ratios of ~140 per resolution element. The
targeted stars are mostly red giant branch (RGB), red clump (RC), and
asymptotic giant branch stars (Zasowski et al., 2013AJ....146...81Z),
and are spread over all regions of the MW, including the bulge, disc,
and halo. <P />The Kepler space telescope has observed ~196400 stars
(Huber et al., 2014ApJS..211....2H, Cat. J/ApJS/211/2) in a field
of 105deg<SUP>2</SUP> towards the constellations of Cygnus and Lyra
(Borucki et al., 2010Sci...327..977B...327..997B). Apart from the
discovery of exoplanets and multiple stellar systems, the high temporal
and photometric quality of the data provides the possibility to study
red giants by detection of solar-like oscillations (e.g. Huber et al.,
2010ApJ...723.1607H; Chaplin et al., 2011Sci...332..213C). <P />In
addition to the spectroscopic and asteroseismic parameters, stars
in the APOKASC catalogue have measured apparent magnitudes in SDSS
griz and DDO51, as measured by the KIC team (Brown et al., 2011,
Cat. J/AJ/142/112), and corrected by Pinsonneault et al. (2012,
Cat. J/ApJS/199/30); <P />JHKs from 2MASS (Cutri et al., 2003,
Cat. II/246; Skrutskie et al., 2006, Cat. VII/233); <P />the Kepler
magnitude, Kp, as derived from a combination of the griz magnitudes
(Brown et al., 2011, Cat. J/AJ/142/112); <P />WISE photometry (at 3.35,
4.6, 11.6 and 22.1um, or W1 to W4) from the Preliminary Release Source
Catalog (Wright et al., 2010AJ....140.1868W). <P />(1 data file).
---------------------------------------------------------
Title: VizieR Online Data Catalog: Kepler planetary
candidates. VI. 4yr Q1-Q16 (Mullally+, 2015)
Authors: Mullally, F.; Coughlin, J. L.; Thompson, S. E.; Rowe, J.;
Burke, C.; Latham, D. W.; Batalha, N. M.; Bryson, S. T.; Christiansen,
J.; Henze, C. E.; Ofir, A.; Quarles, B.; Shporer, A.; van Eylen, V.;
van Laerhoven, C.; Shah, Y.; Wolfgang, A.; Chaplin, W. J.; Xie, J. -W.;
Akeson, R.; Argabright, V.; Bachtell, E.; Barclay, T.; Borucki, W. J.;
Caldwell, D. A.; Campbell, J. R.; Catanzarite, J. H.; Cochran, W. D.;
Duren, R. M.; Fleming, S. W.; Fraquelli, D.; Girouard, F. R.; Haas,
M. R.; Helminiak, K. G.; Howell, S. B.; Huber, D.; Larson, K.; Gautier,
T. N., III; Jenkins, J. M.; Li, J.; Lissauer, J. J.; McArthur, S.;
Miller, C.; Morris, R. L.; Patil-Sabale, A.; Plavchan, P.; Putnam,
D.; Quintana, E. V.; Ramirez, S.; Aguirre, V. S.; Seader, S.; Smith,
J. C.; Steffen, J. H.; Stewart, C.; Stober, J.; Still, M.; Tenenbaum,
P.; Troeltzsch, J.; Twicken, J. D.; Zamudio, K. A.
2015yCat..22170031M Altcode:
The Q1-Q16 catalog is based on the analysis of 16 quarters of data
obtained by the Kepler spacecraft from 2009 May 13 to 2013 April 8. <P
/>(2 data files).
---------------------------------------------------------
Title: Planetary Candidates Observed by Kepler. VI. Planet Sample
from Q1--Q16 (47 Months)
Authors: Mullally, F.; Coughlin, Jeffrey L.; Thompson, Susan E.; Rowe,
Jason; Burke, Christopher; Latham, David W.; Batalha, Natalie M.;
Bryson, Stephen T.; Christiansen, Jessie; Henze, Christopher E.; Ofir,
Aviv; Quarles, Billy; Shporer, Avi; Van Eylen, Vincent; Van Laerhoven,
Christa; Shah, Yash; Wolfgang, Angie; Chaplin, W. J.; Xie, Ji-Wei;
Akeson, Rachel; Argabright, Vic; Bachtell, Eric; Barclay, Thomas;
Borucki, William J.; Caldwell, Douglas A.; Campbell, Jennifer R.;
Catanzarite, Joseph H.; Cochran, William D.; Duren, Riley M.; Fleming,
Scott W.; Fraquelli, Dorothy; Girouard, Forrest R.; Haas, Michael R.;
Hełminiak, Krzysztof G.; Howell, Steve B.; Huber, Daniel; Larson,
Kipp; Gautier, Thomas N., III; Jenkins, Jon M.; Li, Jie; Lissauer, Jack
J.; McArthur, Scot; Miller, Chris; Morris, Robert L.; Patil-Sabale,
Anima; Plavchan, Peter; Putnam, Dustin; Quintana, Elisa V.; Ramirez,
Solange; Silva Aguirre, V.; Seader, Shawn; Smith, Jeffrey C.; Steffen,
Jason H.; Stewart, Chris; Stober, Jeremy; Still, Martin; Tenenbaum,
Peter; Troeltzsch, John; Twicken, Joseph D.; Zamudio, Khadeejah A.
2015ApJS..217...31M Altcode: 2015arXiv150202038M
We present the sixth catalog of Kepler candidate planets based on
nearly four years of high precision photometry. This catalog builds
on the legacy of previous catalogs released by the Kepler project and
includes 1493 new Kepler Objects of Interest (KOIs) of which 554 are
planet candidates, and 131 of these candidates have best-fit radii \lt
1.5 {{R}<SUB>\oplus </SUB>}. This brings the total number of KOIs and
planet candidates to 7348 and 4175 respectively. We suspect that many
of these new candidates at the low signal-to-noise ratio limit may be
false alarms created by instrumental noise, and discuss our efforts to
identify such objects. We re-evaluate all previously published KOIs with
orbital periods of \gt 50 days to provide a consistently vetted sample
that can be used to improve planet occurrence rate calculations. We
discuss the performance of our planet detection algorithms, and the
consistency of our vetting products. The full catalog is publicly
available at the NASA Exoplanet Archive.
---------------------------------------------------------
Title: Kepler-432: A Red Giant Interacting with One of its Two
Long-period Giant Planets
Authors: Quinn, Samuel N.; White, Timothy. R.; Latham, David W.;
Chaplin, William J.; Handberg, Rasmus; Huber, Daniel; Kipping, David
M.; Payne, Matthew J.; Jiang, Chen; Silva Aguirre, Victor; Stello,
Dennis; Sliski, David H.; Ciardi, David R.; Buchhave, Lars A.; Bedding,
Timothy R.; Davies, Guy R.; Hekker, Saskia; Kjeldsen, Hans; Kuszlewicz,
James S.; Everett, Mark E.; Howell, Steve B.; Basu, Sarbani; Campante,
Tiago L.; Christensen-Dalsgaard, Jørgen; Elsworth, Yvonne P.; Karoff,
Christoffer; Kawaler, Steven D.; Lund, Mikkel N.; Lundkvist, Mia;
Esquerdo, Gilbert A.; Calkins, Michael L.; Berlind, Perry
2015ApJ...803...49Q Altcode: 2014arXiv1411.4666Q
We report the discovery of Kepler-432b, a giant planet
({{M}<SUB>b</SUB>}=5.41<SUB>-0.18</SUB><SUP>+0.32</SUP>
{{M}<SUB>Jup</SUB>},
{{R}<SUB>b</SUB>}=1.145<SUB>-0.039</SUB><SUP>+0.036</SUP>
{{R}<SUB>Jup</SUB>}) transiting an evolved star ({{M}<SUB>\star
</SUB>}=1.32<SUB>-0.07</SUB><SUP>+0.10</SUP> {{M}<SUB>⊙
</SUB>},{{R}<SUB>\star </SUB>}=4.06<SUB>-0.08</SUB><SUP>+0.12</SUP>
{{R}<SUB>⊙ </SUB>}) with an orbital period of
{{P}<SUB>b</SUB>}=52.501129<SUB>-0.000053</SUB><SUP>+0.000067</SUP>
days. Radial velocities (RVs) reveal that Kepler-432b
orbits its parent star with an eccentricity of
e=0.5134<SUB>-0.0089</SUB><SUP>+0.0098</SUP>, which we
also measure independently with asterodensity profiling (AP;
e=0.507<SUB>-0.114</SUB><SUP>+0.039</SUP>), thereby confirming the
validity of AP on this particular evolved star. The well-determined
planetary properties and unusually large mass also make this planet
an important benchmark for theoretical models of super-Jupiter
formation. Long-term RV monitoring detected the presence of a
non-transiting outer planet (Kepler-432c; {{M}<SUB>c</SUB>}sin
{{i}<SUB>c</SUB>}=2.43<SUB>-0.24</SUB><SUP>+0.22</SUP>
{{M}<SUB>Jup</SUB>},
{{P}<SUB>c</SUB>}=406.2<SUB>-2.5</SUB><SUP>+3.9</SUP>
days), and adaptive optics imaging revealed a nearby
(0\buildrel{\prime\prime}\over{.} 87), faint companion (Kepler-432B)
that is a physically bound M dwarf. The host star exhibits high
signal-to-noise ratio asteroseismic oscillations, which enable precise
measurements of the stellar mass, radius, and age. Analysis of the
rotational splitting of the oscillation modes additionally reveals
the stellar spin axis to be nearly edge-on, which suggests that the
stellar spin is likely well aligned with the orbit of the transiting
planet. Despite its long period, the obliquity of the 52.5 day orbit may
have been shaped by star-planet interaction in a manner similar to hot
Jupiter systems, and we present observational and theoretical evidence
to support this scenario. Finally, as a short-period outlier among giant
planets orbiting giant stars, study of Kepler-432b may help explain the
distribution of massive planets orbiting giant stars interior to 1 AU.
---------------------------------------------------------
Title: An Ancient Extrasolar System with Five Sub-Earth-size Planets
Authors: Campante, T. L.; Barclay, T.; Swift, J. J.; Huber, D.;
Adibekyan, V. Zh.; Cochran, W.; Burke, C. J.; Isaacson, H.; Quintana,
E. V.; Davies, G. R.; Silva Aguirre, V.; Ragozzine, D.; Riddle, R.;
Baranec, C.; Basu, S.; Chaplin, W. J.; Christensen-Dalsgaard, J.;
Metcalfe, T. S.; Bedding, T. R.; Handberg, R.; Stello, D.; Brewer,
J. M.; Hekker, S.; Karoff, C.; Kolbl, R.; Law, N. M.; Lundkvist, M.;
Miglio, A.; Rowe, J. F.; Santos, N. C.; Van Laerhoven, C.; Arentoft,
T.; Elsworth, Y. P.; Fischer, D. A.; Kawaler, S. D.; Kjeldsen, H.;
Lund, M. N.; Marcy, G. W.; Sousa, S. G.; Sozzetti, A.; White, T. R.
2015ApJ...799..170C Altcode: 2015arXiv150106227C
The chemical composition of stars hosting small exoplanets (with radii
less than four Earth radii) appears to be more diverse than that of
gas-giant hosts, which tend to be metal-rich. This implies that small,
including Earth-size, planets may have readily formed at earlier
epochs in the universe's history when metals were more scarce. We
report Kepler spacecraft observations of Kepler-444, a metal-poor
Sun-like star from the old population of the Galactic thick disk and
the host to a compact system of five transiting planets with sizes
between those of Mercury and Venus. We validate this system as a true
five-planet system orbiting the target star and provide a detailed
characterization of its planetary and orbital parameters based on
an analysis of the transit photometry. Kepler-444 is the densest
star with detected solar-like oscillations. We use asteroseismology
to directly measure a precise age of 11.2 ± 1.0 Gyr for the host
star, indicating that Kepler-444 formed when the universe was less
than 20% of its current age and making it the oldest known system of
terrestrial-size planets. We thus show that Earth-size planets have
formed throughout most of the universe's 13.8 billion year history,
leaving open the possibility for the existence of ancient life in the
Galaxy. The age of Kepler-444 not only suggests that thick-disk stars
were among the hosts to the first Galactic planets, but may also help
to pinpoint the beginning of the era of planet formation.
---------------------------------------------------------
Title: VizieR Online Data Catalog: APOKASC catalog of Kepler red
giants (Pinsonneault+, 2014)
Authors: Pinsonneault, M. H.; Elsworth, Y.; Epstein, C.; Hekker,
S.; Meszaros, Sz.; Chaplin, W. J.; Johnson, J. A.; Garcia, R. A.;
Holtzman, J.; Mathur, S.; Garcia Perez, A.; Silva Aguirre, V.; Girardi,
L.; Basu, S.; Shetrone, M.; Stello, D.; Allende Prieto, C.; An, D.;
Beck, P.; Beers, T. C.; Bizyaev, D.; Bloemen, S.; Bovy, J.; Cunha, K.;
De Ridder, J.; Frinchaboy, P. M.; Garcia-Hernandez, D. A.; Gilliland,
R.; Harding, P.; Hearty, F. R.; Huber, D.; Ivans, I.; Kallinger, T.;
Majewski, S. R.; Metcalfe, T. S.; Miglio, A.; Mosser, B.; Muna, D.;
Nidever, D. L.; Schneider, D. P.; Serenelli, A.; Smith, V. V.; Tayar,
J.; Zamora, O.; Zasowski, G.
2015yCat..22150019P Altcode:
In this paper we present the first release of the joint APOKASC
asteroseismic and spectroscopic survey for targets with both
high-resolution Apache Point Observatory Galactic Evolution Experiment
(APOGEE) spectra analyzed by members of the third Sloan Digital
Sky Survey (SDSS-III) and asteroseismic data obtained by the Kepler
mission and analyzed by members of the Kepler Asteroseismology Science
Consortium (KASC). <P />(4 data files).
---------------------------------------------------------
Title: A Pair of Massive Planets Orbiting an Oscillating Kepler Red
Giant in a Binary System
Authors: Quinn, Samuel Noah; Huber, Daniel; Latham, David W.; Payne,
Matthew J.; Kipping, David M.; Sliski, David; Ciardi, David R.;
Chaplin, William J.; Handberg, Rasmus; Stello, Dennis; White, Timothy
R.; Buchhave, Lars A.; Kepler Science Team; Kepler Asteroseismic
Science Consortium
2015AAS...22525704Q Altcode: 2015AAS...22525704N
We present the radial-velocity confirmation of a massive planet
transiting an evolved Kepler star, as well as the discovery of an outer
non-transiting planet and a faint visual stellar companion that may
be physically bound. The host star exhibits high S/N asteroseismic
oscillations, which enable a measurement of the stellar mass,
radius, age, and spin axis inclination. In conjunction with the
radial velocities, an N-body simulation and stability analysis
help constrain the parameters of the outer planetary orbit. With
precisely derived stellar and planetary properties, the system
provides a rare opportunity to study giant planet evolution around
evolved stars and at long periods. The planets reside inside the ice
line (P<SUB>b</SUB>≈52.5 days, P<SUB>c</SUB>≈407 days), which
indicates that migration has occurred, and their high eccentricities
(e<SUB>b</SUB>≈0.51, e<SUB>c</SUB>≈0.48) hint that they may have
been scattered inward. However, the inclination of the stellar spin
axis is nearly edge-on, implying a likely alignment between the stellar
spin and the orbit of the inner (transiting) planet. We suggest that
despite the long period, the star and planet may have experienced
tidal interaction leading to realignment of the stellar spin axis.
---------------------------------------------------------
Title: Erratum: Sounding stellar cycles with Kepler - II. Ground-based
observations
Authors: Karoff, C.; Metcalfe, T. S.; Chaplin, W. J.; Frandsen, S.;
Grundahl, F.; Kjeldsen, H.; Christensen-Dalsgaard, J.; Nielsen, M. B.;
Frimann, S.; Thygesen, A. O.; Arentoft, T.; Amby, T. M.; Sousa, S. G.;
Buzasi, D. L.
2015MNRAS.446.1139K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Inferences on Stellar Activity and Stellar Cycles from
Asteroseismology
Authors: Chaplin, William J.; Basu, Sarbani
2015sac..book..437C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Transiting Exoplanet Survey Satellite (TESS)
Authors: Ricker, George R.; Winn, Joshua N.; Vanderspek, Roland;
Latham, David W.; Bakos, Gáspár Á.; Bean, Jacob L.; Berta-Thompson,
Zachory K.; Brown, Timothy M.; Buchhave, Lars; Butler, Nathaniel
R.; Butler, R. Paul; Chaplin, William J.; Charbonneau, David;
Christensen-Dalsgaard, Jørgen; Clampin, Mark; Deming, Drake; Doty,
John; De Lee, Nathan; Dressing, Courtney; Dunham, Edward W.; Endl,
Michael; Fressin, Francois; Ge, Jian; Henning, Thomas; Holman, Matthew
J.; Howard, Andrew W.; Ida, Shigeru; Jenkins, Jon M.; Jernigan,
Garrett; Johnson, John Asher; Kaltenegger, Lisa; Kawai, Nobuyuki;
Kjeldsen, Hans; Laughlin, Gregory; Levine, Alan M.; Lin, Douglas;
Lissauer, Jack J.; MacQueen, Phillip; Marcy, Geoffrey; McCullough,
Peter R.; Morton, Timothy D.; Narita, Norio; Paegert, Martin; Palle,
Enric; Pepe, Francesco; Pepper, Joshua; Quirrenbach, Andreas; Rinehart,
Stephen A.; Sasselov, Dimitar; Sato, Bun'ei; Seager, Sara; Sozzetti,
Alessandro; Stassun, Keivan G.; Sullivan, Peter; Szentgyorgyi, Andrew;
Torres, Guillermo; Udry, Stephane; Villasenor, Joel
2015JATIS...1a4003R Altcode:
The Transiting Exoplanet Survey Satellite (TESS) will search for
planets transiting bright and nearby stars. TESS has been selected
by NASA for launch in 2017 as an Astrophysics Explorer mission. The
spacecraft will be placed into a highly elliptical 13.7-day orbit
around the Earth. During its 2-year mission, TESS will employ four
wide-field optical charge-coupled device cameras to monitor at least
200,000 main-sequence dwarf stars with I<SUB>C</SUB>≈4-13 for
temporary drops in brightness caused by planetary transits. Each
star will be observed for an interval ranging from 1 month to 1
year, depending mainly on the star's ecliptic latitude. The longest
observing intervals will be for stars near the ecliptic poles, which
are the optimal locations for follow-up observations with the James
Webb Space Telescope. Brightness measurements of preselected target
stars will be recorded every 2 min, and full frame images will be
recorded every 30 min. TESS stars will be 10 to 100 times brighter
than those surveyed by the pioneering Kepler mission. This will make
TESS planets easier to characterize with follow-up observations. TESS
is expected to find more than a thousand planets smaller than Neptune,
including dozens that are comparable in size to the Earth. Public data
releases will occur every 4 months, inviting immediate community-wide
efforts to study the new planets. The TESS legacy will be a catalog
of the nearest and brightest stars hosting transiting planets, which
will endure as highly favorable targets for detailed investigations.
---------------------------------------------------------
Title: Stellar Populations with APOGEE and Kepler
Authors: Johnson, Jennifer; Pinsonneault, Marc H.; Elsworth, Yvonne P.;
Epstein, Courtney R.; Hekker, Saskia; Meszaros, Szabolcs; Chaplin,
William J.; Garcia, Rafael; Holtzman, Jon A.; Mathur, Savita;
García Pérez, Ana; Basu, Sarbani; Girardi, Leo; Silva Aguirre,
Víctor; Shetrone, Matthew D.; Stello, Dennis; Rodrigues, Thaise;
Allende-Prieto, Carlos; An, Deokkeun; Beck, Paul; Bizyaev, Dmitry;
Bovy, Jo; Cunha, Katia M. L.; De Ridder, Joris; Garcia-Hernandez, D.
2015AAS...22530202J Altcode:
The history of the Milky Way is recorded in its stars, but dissecting
stellar populations is not a straighforward process. Key information
is gained by analyzing the absorption lines from high-resolution
spectroscopy of stellar atmospheres by the APOGEE survey and analyzing
the frequencies in power spectra of photometric lightcurves by Kepler
Asteroseismic Science Consortium, in particular the large frequency
separation and the frequency of maximum power. From spectroscopy,
we measure effective temperature, rotation, metallicity and abundance
ratios, while seismology provides gravities, rotation,and evolutionary
state. Combined, these two techniques yield other fundamental parameters
such as mass and radius. I will discuss revolutionary insights into
Galactic evolution gained by this extensive dataset.
---------------------------------------------------------
Title: &ldquo;Rapid-Fire&rdquo; Spectroscopy of Kepler
Solar-Like Oscillators
Authors: Thygesen, Anders O.; Bruntt, Hans; Chaplin, William J.;
Basu, Sarbani
2015ASSP...39..105T Altcode: 2014arXiv1402.3794T
The NASA Kepler mission has been continuously monitoring the
same field of the sky since the successful launch in March 2009,
providing high-quality stellar lightcurves that are excellent data for
asteroseismology, far superior to any other observations available at
the present. In order to make a meaningful analysis and interpretation
of the asteroseismic data, accurate fundamental parameters for the
observed stars are needed. The currently available parameters are quite
uncertain as illustrated by e.g. Thygesen et al. (A&A 543:A160,
2012), who found deviations as extreme as 2 dex in [Fe/H] and logg,
compared to catalogue values. Thus, additional follow-up observations
for these targets are needed in order to put firm limits on the
parameter space investigated by the asteroseismic modellers. Here, we
propose a method for deriving accurate metallicities of main sequence
and subgiant solar-like oscillators from medium resolution spectra with
a moderate S/N. The method takes advantage of the additional constraints
on the fundamental parameters, available from asteroseismology and
multi-color photometry. The approach enables us to reduce the analysis
overhead significantly when doing spectral synthesis, which in turn
will increases the efficiency of follow-up observations.
---------------------------------------------------------
Title: Asteroseismic inference on rotation, gyrochronology and
planetary system dynamics of 16 Cygni
Authors: Davies, G. R.; Chaplin, W. J.; Farr, W. M.; García, R. A.;
Lund, M. N.; Mathis, S.; Metcalfe, T. S.; Appourchaux, T.; Basu, S.;
Benomar, O.; Campante, T. L.; Ceillier, T.; Elsworth, Y.; Handberg,
R.; Salabert, D.; Stello, D.
2015MNRAS.446.2959D Altcode: 2014arXiv1411.1359D
The solar analogues 16 Cyg A and B are excellent asteroseismic targets
in the Kepler field of view and together with a red dwarf and a Jovian
planet form an interesting system. For these more evolved Sun-like
stars we cannot detect surface rotation with the current Kepler
data but instead use the technique of asteroseimology to determine
rotational properties of both 16 Cyg A and B. We find the rotation
periods to be 23.8^{+1.5}_{-1.8} and 23.2^{+11.5}_{-3.2} d, and
the angles of inclination to be 56^{+6}_{-5}° and 36^{+17}_{-7}°,
for A and B, respectively. Together with these results we use the
published mass and age to suggest that, under the assumption of a
solar-like rotation profile, 16 Cyg A could be used when calibrating
gyrochronology relations. In addition, we discuss the known 16 Cyg B
star-planet eccentricity and measured low obliquity which is consistent
with Kozai cycling and tidal theory.
---------------------------------------------------------
Title: Solar-Like Oscillating Stars as Standard Clocks and Rulers
for Galactic Studies
Authors: Miglio, Andrea; Girardi, Léo; Rodrigues, Thaíse S.; Stello,
Dennis; Chaplin, William J.
2015ASSP...39...11M Altcode: 2014arXiv1409.2267M
The CoRoT and Kepler space missions have detected oscillations in
hundreds of Sun-like stars and thousands of field red-giant stars. This
has opened the door to a new era of stellar population studies in the
Milky Way. We report on the current status and future prospects of
harvesting space-based photometric data for ensemble asteroseismology,
and highlight some of the challenges that need to be faced to use
these stars as accurate clocks and rulers for Galactic studies.
---------------------------------------------------------
Title: Mixed modes in red giants: a window on stellar evolution
Authors: Mosser, B.; Benomar, O.; Belkacem, K.; Goupil, M. J.;
Lagarde, N.; Michel, E.; Lebreton, Y.; Stello, D.; Vrard, M.; Barban,
C.; Bedding, T. R.; Deheuvels, S.; Chaplin, W. J.; De Ridder, J.;
Elsworth, Y.; Montalban, J.; Noels, A.; Ouazzani, R. M.; Samadi, R.;
White, T. R.; Kjeldsen, H.
2014A&A...572L...5M Altcode: 2014arXiv1411.1082M
Context. The detection of oscillations with a mixed character in
subgiants and red giants allows us to probe the physical conditions
in their cores. <BR /> Aims: With these mixed modes, we aim at
determining seismic markers of stellar evolution. <BR /> Methods:
Kepler asteroseismic data were selected to map various evolutionary
stages and stellar masses. Seismic evolutionary tracks were then drawn
with the combination of the frequency and period spacings. <BR />
Results: We measured the asymptotic period spacing for 1178 stars
at various evolutionary stages. This allows us to monitor stellar
evolution from the main sequence to the asymptotic giant branch and draw
seismic evolutionary tracks. We present clear quantified asteroseismic
definitions that characterize the change in the evolutionary stages, in
particular the transition from the subgiant stage to the early red giant
branch, and the end of the horizontal branch. <BR /> Conclusions: The
seismic information is so precise that clear conclusions can be drawn
independently of evolution models. The quantitative seismic information
can now be used for stellar modeling, especially for studying
the energy transport in the helium-burning core or for specifying
the inner properties of stars entering the red or asymptotic giant
branches. Modeling will also allow us to study stars that are identified
to be in the helium-subflash stage, high-mass stars either arriving or
quitting the secondary clump, or stars that could be in the blue-loop
stage. <P />Table 1 is only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/572/L5">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/572/L5</A>
---------------------------------------------------------
Title: Inferences on Stellar Activity and Stellar Cycles from
Asteroseismology
Authors: Chaplin, William J.; Basu, Sarbani
2014SSRv..186..437C Altcode: 2014SSRv..tmp...49C
The solar activity cycle can be studied using many different types of
observations, such as counting sunspots, measuring emission in the Ca
II H&K lines, magnetograms, radio emissions, etc. One of the more
recent ways of studying solar activity is to use the changing properties
of solar oscillations. Stellar activity cycles are generally studied
using the Ca II lines, or sometimes using photometry. Asteroseismology
is potentially an exciting means of studying these cycles. In this
article we examine whether or not asteroseismic data can be used
for this purpose, and what the asteroseismic signatures of stellar
activity are. We also examine how asteroseismology may help in more
indirect ways.
---------------------------------------------------------
Title: Rotation and magnetism of Kepler pulsating solar-like
stars. Towards asteroseismically calibrated age-rotation relations
Authors: García, R. A.; Ceillier, T.; Salabert, D.; Mathur, S.; van
Saders, J. L.; Pinsonneault, M.; Ballot, J.; Beck, P. G.; Bloemen, S.;
Campante, T. L.; Davies, G. R.; do Nascimento, J. -D., Jr.; Mathis,
S.; Metcalfe, T. S.; Nielsen, M. B.; Suárez, J. C.; Chaplin, W. J.;
Jiménez, A.; Karoff, C.
2014A&A...572A..34G Altcode: 2014arXiv1403.7155G
Kepler ultra-high precision photometry of long and continuous
observations provides a unique dataset in which surface rotation and
variability can be studied for thousands of stars. Because many of these
old field stars also have independently measured asteroseismic ages,
measurements of rotation and activity are particularly interesting
in the context of age-rotation-activity relations. In particular,
age-rotation relations generally lack good calibrators at old ages, a
problem that this Kepler sample of old-field stars is uniquely suited
to address. We study the surface rotation and photometric magnetic
activity of a subset of 540 solar-like stars on the main-sequence and
the subgiant branch for which stellar pulsations have been measured. The
rotation period was determined by comparing the results from two
different analysis methods: i) the projection onto the frequency domain
of the time-period analysis, and ii) the autocorrelation function of
the light curves. Reliable surface rotation rates were then extracted
by comparing the results from two different sets of calibrated data
and from the two complementary analyses. General photometric levels of
magnetic activity in this sample of stars were also extracted by using
a photometric activity index, which takes into account the rotation
period of the stars. We report rotation periods for 310 out of 540
targets (excluding known binaries and candidate planet-host stars); our
measurements span a range of 1 to 100 days. The photometric magnetic
activity levels of these stars were computed, and for 61.5% of the
dwarfs, this level is similar to the range, from minimum to maximum,
of the solar magnetic activity. We demonstrate that hot dwarfs, cool
dwarfs, and subgiants have very different rotation-age relationships,
highlighting the importance of separating out distinct populations
when interpreting stellar rotation periods. Our sample of cool
dwarf stars with age and metallicity data of the highest quality is
consistent with gyrochronology relations reported in the literature. <P
/>Full Table 3 is only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/572/A34">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/572/A34</A>
---------------------------------------------------------
Title: Bayesian distances and extinctions for giants observed by
Kepler and APOGEE
Authors: Rodrigues, Thaíse S.; Girardi, Léo; Miglio, Andrea; Bossini,
Diego; Bovy, Jo; Epstein, Courtney; Pinsonneault, Marc H.; Stello,
Dennis; Zasowski, Gail; Allende Prieto, Carlos; Chaplin, William
J.; Hekker, Saskia; Johnson, Jennifer A.; Mészáros, Szabolcs;
Mosser, Benoît; Anders, Friedrich; Basu, Sarbani; Beers, Timothy C.;
Chiappini, Cristina; da Costa, Luiz A. N.; Elsworth, Yvonne; García,
Rafael A.; García Pérez, Ana E.; Hearty, Fred R.; Maia, Marcio A. G.;
Majewski, Steven R.; Mathur, Savita; Montalbán, Josefina; Nidever,
David L.; Santiago, Basilio; Schultheis, Mathias; Serenelli, Aldo;
Shetrone, Matthew
2014MNRAS.445.2758R Altcode: 2014arXiv1410.1350R
We present a first determination of distances and extinctions for
individual stars in the first release of the APOKASC catalogue,
built from the joint efforts of the Apache Point Observatory Galactic
Evolution Experiment (APOGEE) and the Kepler Asteroseismic Science
Consortium (KASC). Our method takes into account the spectroscopic
constraints derived from the APOGEE Stellar Parameters and Chemical
Abundances Pipeline, together with the asteroseismic parameters
from KASC. These parameters are then employed to estimate intrinsic
stellar properties, including absolute magnitudes, using the Bayesian
tool PARAM. We then find the distance and extinction that best fit
the observed photometry in Sloan Digital Sky Survey (SDSS), 2MASS,
and WISE passbands. The first 1989 giants targetted by APOKASC are
found at typical distances between 0.5 and 5 kpc, with individual
uncertainties of just ∼1.8 per cent. Our extinction estimates are
systematically smaller than provided in the Kepler Input Catalogue
and by the Schlegel et al. maps. Distances to individual stars in the
NGC 6791 and NGC 6819 star clusters agree to within their credible
intervals. Comparison with the APOGEE red clump and SAGA catalogues
provide another useful check, exhibiting agreement with our measurements
to within a few per cent. Overall, present methods seem to provide
excellent distance and extinction determinations for the bulk of the
APOKASC sample. Approximately one third of the stars present broad
or multiple-peaked probability density functions and hence increased
uncertainties. Uncertainties are expected to be reduced in future
releases of the catalogue, when a larger fraction of the stars will
have seismically determined evolutionary status classifications.
---------------------------------------------------------
Title: The APOKASC Catalog: An Asteroseismic and Spectroscopic Joint
Survey of Targets in the Kepler Fields
Authors: Pinsonneault, Marc H.; Elsworth, Yvonne; Epstein, Courtney;
Hekker, Saskia; Mészáros, Sz.; Chaplin, William J.; Johnson,
Jennifer A.; García, Rafael A.; Holtzman, Jon; Mathur, Savita;
García Pérez, Ana; Silva Aguirre, Victor; Girardi, Léo; Basu,
Sarbani; Shetrone, Matthew; Stello, Dennis; Allende Prieto, Carlos;
An, Deokkeun; Beck, Paul; Beers, Timothy C.; Bizyaev, Dmitry; Bloemen,
Steven; Bovy, Jo; Cunha, Katia; De Ridder, Joris; Frinchaboy, Peter M.;
García-Hernández, D. A.; Gilliland, Ronald; Harding, Paul; Hearty,
Fred R.; Huber, Daniel; Ivans, Inese; Kallinger, Thomas; Majewski,
Steven R.; Metcalfe, Travis S.; Miglio, Andrea; Mosser, Benoit; Muna,
Demitri; Nidever, David L.; Schneider, Donald P.; Serenelli, Aldo;
Smith, Verne V.; Tayar, Jamie; Zamora, Olga; Zasowski, Gail
2014ApJS..215...19P Altcode: 2014arXiv1410.2503P
We present the first APOKASC catalog of spectroscopic and
asteroseismic properties of 1916 red giants observed in the Kepler
fields. The spectroscopic parameters provided from the Apache Point
Observatory Galactic Evolution Experiment project are complemented
with asteroseismic surface gravities, masses, radii, and mean
densities determined by members of the Kepler Asteroseismology
Science Consortium. We assess both random and systematic sources of
error and include a discussion of sample selection for giants in the
Kepler fields. Total uncertainties in the main catalog properties are
of the order of 80 K in T <SUB>eff</SUB>, 0.06 dex in [M/H], 0.014
dex in log g, and 12% and 5% in mass and radius, respectively; these
reflect a combination of systematic and random errors. Asteroseismic
surface gravities are substantially more precise and accurate than
spectroscopic ones, and we find good agreement between their mean
values and the calibrated spectroscopic surface gravities. There are,
however, systematic underlying trends with T <SUB>eff</SUB> and log
g. Our effective temperature scale is between 0 and 200 K cooler
than that expected from the infrared flux method, depending on the
adopted extinction map, which provides evidence for a lower value on
average than that inferred for the Kepler Input Catalog (KIC). We
find a reasonable correspondence between the photometric KIC and
spectroscopic APOKASC metallicity scales, with increased dispersion
in KIC metallicities as the absolute metal abundance decreases, and
offsets in T <SUB>eff</SUB> and log g consistent with those derived
in the literature. We present mean fitting relations between APOKASC
and KIC observables and discuss future prospects, strengths, and
limitations of the catalog data.
---------------------------------------------------------
Title: Why should we correct reported pulsation frequencies for
stellar line-of-sight Doppler velocity shifts?
Authors: Davies, G. R.; Handberg, R.; Miglio, A.; Campante, T. L.;
Chaplin, W. J.; Elsworth, Y.
2014MNRAS.445L..94D Altcode: 2014arXiv1408.7042D
In the age of Kepler and CoRoT, extended observations have provided
estimates of stellar pulsation frequencies that have achieved new
levels of precision, regularly exceeding fractional levels of a
few parts in 10<SUP>4</SUP>. These high levels of precision now in
principle exceed the point where one can ignore the Doppler shift
of pulsation frequencies caused by the motion of a star relative
to the observer. We present a correction for these Doppler shifts
and use previously published pulsation frequencies to demonstrate
the significance of the effect. We suggest that reported pulsation
frequencies should be routinely corrected for stellar line-of-sight
velocity Doppler shifts, or if a line-of-sight velocity estimate is
not available, the frame of reference in which the frequencies are
reported should be clearly stated.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Evolution state of red giants
from seismology (Mosser+, 2014)
Authors: Mosser, B.; Benomar, O.; Belkacem, K.; Goupil, M. J.;
Lagarde, N.; Michel, E.; Lebreton, Y.; Stello, D.; Vrard, M.; Barban,
C.; Bedding, T. R.; Deheuvels, S.; Chaplin, W. J.; De Ridder, J.;
Elsworth, Y.; Montalban, J.; Noels, A.; Ouazzani, R. M.; Samadi, R.;
White, T. R.; Kjeldsen, H.
2014yCat..35729005M Altcode:
Seismic global parameters of the stars listed in the paper. Each star
is identified with its KIC number (Kepler Input Catalog). <P />The
asymptotic frequency and period spacing are derived from the fit of
the radial and dipole oscillation modes. The stellar mass is derived
from the seismic scaling relations. The evolutionary status is derived
according to the location of the star in the DPi1 - Dnu diagram (Fig. 1)
<P />(1 data file).
---------------------------------------------------------
Title: Super-Nyquist asteroseismology of solar-like oscillators with
Kepler and K2 - expanding the asteroseismic cohort at the base of
the red giant branch
Authors: Chaplin, W. J.; Elsworth, Y.; Davies, G. R.; Campante, T. L.;
Handberg, R.; Miglio, A.; Basu, S.
2014MNRAS.445..946C Altcode: 2014arXiv1409.0696C
We consider the prospects for detecting solar-like oscillations in
the `super-Nyquist' regime of long-cadence (LC) Kepler photometry,
i.e. above the associated Nyquist frequency of ≃ 283 μHz. Targets
of interest are cool, evolved subgiants and stars lying at the base
of the red giant branch. These stars would ordinarily be studied using
the short-cadence (SC) data, since the associated SC Nyquist frequency
lies well above the frequencies of the detectable oscillations. However,
the number of available SC target slots is quite limited. This imposes
a severe restriction on the size of the ensemble available for SC
asteroseismic study. We find that archival Kepler LC data from the
nominal mission may be utilized for asteroseismic studies of targets
whose dominant oscillation frequencies lie as high as ≃ 500 μHz,
i.e. about 1.75-times the LC Nyquist frequency. The frequency detection
threshold for the shorter duration science campaigns of the re-purposed
Kepler mission, K2, is lower. The maximum threshold will probably
lie somewhere between ≃400 and 450 μHz. The potential to exploit
the archival Kepler and K2 LC data in this manner opens the door to
increasing significantly the number of subgiant and low-luminosity red
giant targets amenable to asteroseismic analysis, overcoming target
limitations imposed by the small number of SC slots. We estimate that
around 400 such targets are now available for study in the Kepler LC
archive. That number could potentially be a lot higher for K2, since
there will be a new target list for each of its campaigns.
---------------------------------------------------------
Title: Determining stellar macroturbulence using asteroseismic
rotational velocities from Kepler
Authors: Doyle, Amanda P.; Davies, Guy R.; Smalley, Barry; Chaplin,
William J.; Elsworth, Yvonne
2014MNRAS.444.3592D Altcode: 2014arXiv1408.3988D
The Rossiter-McLaughlin effect observed for transiting exoplanets often
requires prior knowledge of the stellar projected equatorial rotational
velocity (v sin i). This is usually provided by measuring the broadening
of spectral lines, however this method has uncertainties as lines are
also broadened by velocity fields in the stellar photosphere known as
macroturbulence (v<SUB>mac</SUB>). We have estimated accurate v sin i
values from asteroseismic analyses of main-sequence stars observed by
Kepler. The rotational frequency splittings of the detected solar-like
oscillations of these stars are determined largely by the near-surface
rotation. These estimates have been used to infer the v<SUB>mac</SUB>
values for 28 Kepler stars. Out of this sample, 26 stars were used
along with the Sun to obtain a new calibration between v<SUB>mac</SUB>,
effective temperature and surface gravity. The new calibration is valid
for the temperature range 5200 to 6400 K and the gravity range 4.0 to
4.6 dex. A comparison is also provided with previous v<SUB>mac</SUB>
calibrations. As a result of this work, v<SUB>mac</SUB>, and thus v
sin i, can now be determined with confidence for stars that do not
have asteroseismic data available. We present new spectroscopic v
sin i values for the WASP planet host stars, using high-resolution
HARPS spectra.
---------------------------------------------------------
Title: The PLATO 2.0 mission
Authors: Rauer, H.; Catala, C.; Aerts, C.; Appourchaux, T.; Benz,
W.; Brandeker, A.; Christensen-Dalsgaard, J.; Deleuil, M.; Gizon,
L.; Goupil, M. -J.; Güdel, M.; Janot-Pacheco, E.; Mas-Hesse,
M.; Pagano, I.; Piotto, G.; Pollacco, D.; Santos, Ċ.; Smith, A.;
Suárez, J. -C.; Szabó, R.; Udry, S.; Adibekyan, V.; Alibert, Y.;
Almenara, J. -M.; Amaro-Seoane, P.; Eiff, M. Ammler-von; Asplund, M.;
Antonello, E.; Barnes, S.; Baudin, F.; Belkacem, K.; Bergemann, M.;
Bihain, G.; Birch, A. C.; Bonfils, X.; Boisse, I.; Bonomo, A. S.;
Borsa, F.; Brandão, I. M.; Brocato, E.; Brun, S.; Burleigh, M.;
Burston, R.; Cabrera, J.; Cassisi, S.; Chaplin, W.; Charpinet, S.;
Chiappini, C.; Church, R. P.; Csizmadia, Sz.; Cunha, M.; Damasso, M.;
Davies, M. B.; Deeg, H. J.; Díaz, R. F.; Dreizler, S.; Dreyer, C.;
Eggenberger, P.; Ehrenreich, D.; Eigmüller, P.; Erikson, A.; Farmer,
R.; Feltzing, S.; de Oliveira Fialho, F.; Figueira, P.; Forveille,
T.; Fridlund, M.; García, R. A.; Giommi, P.; Giuffrida, G.; Godolt,
M.; Gomes da Silva, J.; Granzer, T.; Grenfell, J. L.; Grotsch-Noels,
A.; Günther, E.; Haswell, C. A.; Hatzes, A. P.; Hébrard, G.; Hekker,
S.; Helled, R.; Heng, K.; Jenkins, J. M.; Johansen, A.; Khodachenko,
M. L.; Kislyakova, K. G.; Kley, W.; Kolb, U.; Krivova, N.; Kupka, F.;
Lammer, H.; Lanza, A. F.; Lebreton, Y.; Magrin, D.; Marcos-Arenal,
P.; Marrese, P. M.; Marques, J. P.; Martins, J.; Mathis, S.; Mathur,
S.; Messina, S.; Miglio, A.; Montalban, J.; Montalto, M.; Monteiro,
M. J. P. F. G.; Moradi, H.; Moravveji, E.; Mordasini, C.; Morel, T.;
Mortier, A.; Nascimbeni, V.; Nelson, R. P.; Nielsen, M. B.; Noack,
L.; Norton, A. J.; Ofir, A.; Oshagh, M.; Ouazzani, R. -M.; Pápics,
P.; Parro, V. C.; Petit, P.; Plez, B.; Poretti, E.; Quirrenbach, A.;
Ragazzoni, R.; Raimondo, G.; Rainer, M.; Reese, D. R.; Redmer, R.;
Reffert, S.; Rojas-Ayala, B.; Roxburgh, I. W.; Salmon, S.; Santerne,
A.; Schneider, J.; Schou, J.; Schuh, S.; Schunker, H.; Silva-Valio,
A.; Silvotti, R.; Skillen, I.; Snellen, I.; Sohl, F.; Sousa, S. G.;
Sozzetti, A.; Stello, D.; Strassmeier, K. G.; Švanda, M.; Szabó,
Gy. M.; Tkachenko, A.; Valencia, D.; Van Grootel, V.; Vauclair,
S. D.; Ventura, P.; Wagner, F. W.; Walton, N. A.; Weingrill, J.;
Werner, S. C.; Wheatley, P. J.; Zwintz, K.
2014ExA....38..249R Altcode: 2014ExA...tmp...41R; 2013arXiv1310.0696R
PLATO 2.0 has recently been selected for ESA's M3 launch opportunity
(2022/24). Providing accurate key planet parameters (radius, mass,
density and age) in statistical numbers, it addresses fundamental
questions such as: How do planetary systems form and evolve? Are there
other systems with planets like ours, including potentially habitable
planets? The PLATO 2.0 instrument consists of 34 small aperture
telescopes (32 with 25 s readout cadence and 2 with 2.5 s candence)
providing a wide field-of-view (2232 deg <SUP>2</SUP>) and a large
photometric magnitude range (4-16 mag). It focusses on bright (4-11
mag) stars in wide fields to detect and characterize planets down to
Earth-size by photometric transits, whose masses can then be determined
by ground-based radial-velocity follow-up measurements. Asteroseismology
will be performed for these bright stars to obtain highly accurate
stellar parameters, including masses and ages. The combination of
bright targets and asteroseismology results in high accuracy for
the bulk planet parameters: 2 %, 4-10 % and 10 % for planet radii,
masses and ages, respectively. The planned baseline observing strategy
includes two long pointings (2-3 years) to detect and bulk characterize
planets reaching into the habitable zone (HZ) of solar-like stars
and an additional step-and-stare phase to cover in total about 50 %
of the sky. PLATO 2.0 will observe up to 1,000,000 stars and detect
and characterize hundreds of small planets, and thousands of planets
in the Neptune to gas giant regime out to the HZ. It will therefore
provide the first large-scale catalogue of bulk characterized planets
with accurate radii, masses, mean densities and ages. This catalogue
will include terrestrial planets at intermediate orbital distances,
where surface temperatures are moderate. Coverage of this parameter
range with statistical numbers of bulk characterized planets is unique
to PLATO 2.0. The PLATO 2.0 catalogue allows us to e.g.: - complete
our knowledge of planet diversity for low-mass objects, - correlate the
planet mean density-orbital distance distribution with predictions from
planet formation theories,- constrain the influence of planet migration
and scattering on the architecture of multiple systems, and - specify
how planet and system parameters change with host star characteristics,
such as type, metallicity and age. The catalogue will allow us to study
planets and planetary systems at different evolutionary phases. It
will further provide a census for small, low-mass planets. This will
serve to identify objects which retained their primordial hydrogen
atmosphere and in general the typical characteristics of planets
in such low-mass, low-density range. Planets detected by PLATO 2.0
will orbit bright stars and many of them will be targets for future
atmosphere spectroscopy exploring their atmosphere. Furthermore,
the mission has the potential to detect exomoons, planetary rings,
binary and Trojan planets. The planetary science possible with PLATO
2.0 is complemented by its impact on stellar and galactic science via
asteroseismology as well as light curves of all kinds of variable stars,
together with observations of stellar clusters of different ages. This
will allow us to improve stellar models and study stellar activity. A
large number of well-known ages from red giant stars will probe the
structure and evolution of our Galaxy. Asteroseismic ages of bright
stars for different phases of stellar evolution allow calibrating
stellar age-rotation relationships. Together with the results of ESA's
Gaia mission, the results of PLATO 2.0 will provide a huge legacy to
planetary, stellar and galactic science.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Pulsating solar-like stars in
Kepler (Garcia+, 2014)
Authors: Garcia, R. A.; Ceillier, T.; Salabert, D.; Mathur, S.; van
Saders, J. L.; Pinsonneault, M.; Ballot, J.; Beck, P. G.; Bloemen, S.;
Campante, T. L.; Davies, G. R.; Do Nascimento, J. -D., Jr.; Mathis,
S.; Metcalfe, T. S.; Nielsen, M. B.; Suarez, J. C.; Chaplin, W. J.;
Jimenez, A.; Karoff, C.
2014yCat..35720034G Altcode: 2014yCat..35729034G
We used data collected by the NASA planet-hunter mission Kepler. <P
/>(2 data files).
---------------------------------------------------------
Title: Properties of 42 Solar-type Kepler Targets from the
Asteroseismic Modeling Portal
Authors: Metcalfe, T. S.; Creevey, O. L.; Doğan, G.; Mathur, S.;
Xu, H.; Bedding, T. R.; Chaplin, W. J.; Christensen-Dalsgaard, J.;
Karoff, C.; Trampedach, R.; Benomar, O.; Brown, B. P.; Buzasi, D. L.;
Campante, T. L.; Çelik, Z.; Cunha, M. S.; Davies, G. R.; Deheuvels,
S.; Derekas, A.; Di Mauro, M. P.; García, R. A.; Guzik, J. A.;
Howe, R.; MacGregor, K. B.; Mazumdar, A.; Montalbán, J.; Monteiro,
M. J. P. F. G.; Salabert, D.; Serenelli, A.; Stello, D.; Ste&şacute;
licki, M.; Suran, M. D.; Yıldız, M.; Aksoy, C.; Elsworth, Y.;
Gruberbauer, M.; Guenther, D. B.; Lebreton, Y.; Molaverdikhani, K.;
Pricopi, D.; Simoniello, R.; White, T. R.
2014ApJS..214...27M Altcode: 2014arXiv1402.3614M
Recently the number of main-sequence and subgiant stars exhibiting
solar-like oscillations that are resolved into individual mode
frequencies has increased dramatically. While only a few such data
sets were available for detailed modeling just a decade ago, the
Kepler mission has produced suitable observations for hundreds of
new targets. This rapid expansion in observational capacity has been
accompanied by a shift in analysis and modeling strategies to yield
uniform sets of derived stellar properties more quickly and easily. We
use previously published asteroseismic and spectroscopic data sets
to provide a uniform analysis of 42 solar-type Kepler targets from
the Asteroseismic Modeling Portal. We find that fitting the individual
frequencies typically doubles the precision of the asteroseismic radius,
mass, and age compared to grid-based modeling of the global oscillation
properties, and improves the precision of the radius and mass by about
a factor of three over empirical scaling relations. We demonstrate
the utility of the derived properties with several applications.
---------------------------------------------------------
Title: Asteroseismic inference on the spin-orbit misalignment and
stellar parameters of HAT-P-7
Authors: Lund, Mikkel N.; Lundkvist, Mia; Silva Aguirre, Victor;
Houdek, Günter; Casagrande, Luca; Van Eylen, Vincent; Campante,
Tiago L.; Karoff, Christoffer; Kjeldsen, Hans; Albrecht, Simon;
Chaplin, William J.; Nielsen, Martin Bo; Degroote, Pieter; Davies,
Guy R.; Handberg, Rasmus
2014A&A...570A..54L Altcode: 2014arXiv1407.7516L
Context. The measurement of obliquities - the angle between the orbital
and stellar rotation - in star-planet systems is of great importance
for understanding planet system formation and evolution. The bright and
well-studied HAT-P-7 (Kepler-2) system is intriguing because several
Rossiter-McLaughlin (RM) measurements found a high projected obliquity
in this system, but it was not possible so far to determine whether
the orbit is polar and/or retrograde. <BR /> Aims: The goal of this
study is to measure the stellar inclination and hereby the full 3D
obliquity of the HAT-P-7 system instead of only the 2D projection
as measured by the RM effect. In addition, we provide an updated
set of stellar parameters for the star. <BR /> Methods: We used the
full set of available observations from Kepler spanning Q0-Q17 to
produce the power spectrum of HAT-P-7. We extracted oscillation-mode
frequencies via an Markov chain Monte Carlo peak-bagging routine
and used the results from this to estimate the stellar inclination
angle. Combining this with the projected obliquity from RM and the
inclination of the orbital plane allowed us to determine the stellar
obliquity. Furthermore, we used asteroseismology to model the star
from the extracted frequencies using two different approaches to
the modelling, for which either the stellar evolution codes MESA
or GARSTEC were adopted. <BR /> Results: Our updated asteroseismic
modelling shows, i.a., the following stellar parameters for HAT-P-7:
M<SUB>⋆</SUB> = 1.51<SUP>+ 0.04</SUP><SUB>-0.05</SUB> M<SUB>⊙</SUB>,
R<SUB>⋆</SUB> = 2.00<SUP>+ 0.01</SUP><SUB>-0.02</SUB> R<SUB>⊙</SUB>,
and age = 2.07<SUP>+ 0.28</SUP><SUB>-0.23</SUB> Gyr. The modelling
offers a high precision on the stellar parameters, the uncertainty
on age, for instance, is of the order ∼ 11%. For the stellar
inclination we estimate i<SUB>⋆</SUB>< 36.5<SUP>°</SUP>,
which translates into an obliquity of 83<SUP>°</SUP><ψ<
111<SUP>°</SUP>. The planet HAT-P-7b is likely retrograde in its
orbit, and the orbit is close to being polar. The new parameters
for the star give an updated planetary density of ρ<SUB>p</SUB>
= 0.65 ± 0.03 g cm<SUP>-3</SUP>, which is lower than previous
estimates. <P />Appendices are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201424326/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Observational Constraints, Stellar Models, and Kepler Data
for θ Cyg, the Brightest Star Observable by Kepler
Authors: Guzik, J. A.; Houdek, G.; Chaplin, W. J.; Kurtz, D.;
Gilliland, R. L.; Mullally, F.; Rowe, J. F.; Haas, M. R.; Bryson,
S. T.; Still, M. D.; Boyajian, T.
2014ASPC..487..105G Altcode:
The V = 4.48 F4 main-sequence star θ Cyg is the brightest star
observable in the Kepler spacecraft field of view. Short-cadence (58.8
s) photometric data were obtained by Kepler during June-September
2010. Preliminary analysis shows solar-like oscillations in the
frequency range 1200- 2500 μHz. To interpret these data and to
motivate further observations, we use observational constraints from
the literature to construct stellar evolution and pulsation models
for this star. We compare the observed large frequency separation of
the solar-like oscillations with the model predictions and discuss the
prospects for γ Doradus-like g-mode pulsations, given the observational
constraints. We discuss the value of angular diameter measurements
from optical interferometry for constraining stellar properties and
the implications for asteroseismology.
---------------------------------------------------------
Title: The APOGEE Red-clump Catalog: Precise Distances, Velocities,
and High-resolution Elemental Abundances over a Large Area of the
Milky Way's Disk
Authors: Bovy, Jo; Nidever, David L.; Rix, Hans-Walter; Girardi,
Léo; Zasowski, Gail; Chojnowski, S. Drew; Holtzman, Jon; Epstein,
Courtney; Frinchaboy, Peter M.; Hayden, Michael R.; Rodrigues, Thaíse
S.; Majewski, Steven R.; Johnson, Jennifer A.; Pinsonneault, Marc H.;
Stello, Dennis; Allende Prieto, Carlos; Andrews, Brett; Basu, Sarbani;
Beers, Timothy C.; Bizyaev, Dmitry; Burton, Adam; Chaplin, William J.;
Cunha, Katia; Elsworth, Yvonne; García, Rafael A.; García-Herńandez,
Domingo A.; García Pérez, Ana E.; Hearty, Fred R.; Hekker, Saskia;
Kallinger, Thomas; Kinemuchi, Karen; Koesterke, Lars; Mészáros,
Szabolcs; Mosser, Benoît; O'Connell, Robert W.; Oravetz, Daniel; Pan,
Kaike; Robin, Annie C.; Schiavon, Ricardo P.; Schneider, Donald P.;
Schultheis, Mathias; Serenelli, Aldo; Shetrone, Matthew; Silva Aguirre,
Victor; Simmons, Audrey; Skrutskie, Michael; Smith, Verne V.; Stassun,
Keivan; Weinberg, David H.; Wilson, John C.; Zamora, Olga
2014ApJ...790..127B Altcode: 2014arXiv1405.1032B
The Sloan Digital Sky Survey III's Apache Point Observatory Galactic
Evolution Experiment (APOGEE) is a high-resolution near-infrared
spectroscopic survey covering all of the major components of the Galaxy,
including the dust-obscured regions of the inner Milky Way disk and
bulge. Here we present a sample of 10,341 likely red-clump stars (RC)
from the first two years of APOGEE operations, selected based on their
position in color-metallicity-surface-gravity-effective-temperature
space using a new method calibrated using stellar evolution models and
high-quality asteroseismology data. The narrowness of the RC locus in
color-metallicity-luminosity space allows us to assign distances to
the stars with an accuracy of 5%-10%. The sample extends to typical
distances of about 3 kpc from the Sun, with some stars out to 8 kpc,
and spans a volume of approximately 100 kpc<SUP>3</SUP> over 5 kpc
<~ R <~ 14 kpc, |Z| <~ 2 kpc, and -15° <~ Galactocentric
azimuth <~ 30°. The APOGEE red-clump (APOGEE-RC) catalog contains
photometry from the Two Micron All Sky Survey, reddening estimates,
distances, line-of-sight velocities, stellar parameters and elemental
abundances determined from the high-resolution APOGEE spectra, and
matches to major proper motion catalogs. We determine the survey
selection function for this data set and discuss how the RC selection
samples the underlying stellar populations. We use this sample to
limit any azimuthal variations in the median metallicity within the
≈45° azimuthal region covered by the current sample to be <=0.02
dex, which is more than an order of magnitude smaller than the radial
metallicity gradient. This result constrains coherent non-axisymmetric
flows within a few kiloparsecs from the Sun.
---------------------------------------------------------
Title: Transiting Exoplanet Survey Satellite (TESS)
Authors: Ricker, George R.; Winn, Joshua N.; Vanderspek, Roland;
Latham, David W.; Bakos, Gáspár. Á.; Bean, Jacob L.; Berta-Thompson,
Zachory K.; Brown, Timothy M.; Buchhave, Lars; Butler, Nathaniel
R.; Butler, R. Paul; Chaplin, William J.; Charbonneau, David;
Christensen-Dalsgaard, Jørgen; Clampin, Mark; Deming, Drake; Doty,
John; De Lee, Nathan; Dressing, Courtney; Dunham, E. W.; Endl, Michael;
Fressin, Francois; Ge, Jian; Henning, Thomas; Holman, Matthew J.;
Howard, Andrew W.; Ida, Shigeru; Jenkins, Jon; Jernigan, Garrett;
Johnson, John A.; Kaltenegger, Lisa; Kawai, Nobuyuki; Kjeldsen, Hans;
Laughlin, Gregory; Levine, Alan M.; Lin, Douglas; Lissauer, Jack J.;
MacQueen, Phillip; Marcy, Geoffrey; McCullough, P. R.; Morton, Timothy
D.; Narita, Norio; Paegert, Martin; Palle, Enric; Pepe, Francesco;
Pepper, Joshua; Quirrenbach, Andreas; Rinehart, S. A.; Sasselov,
Dimitar; Sato, Bun'ei; Seager, Sara; Sozzetti, Alessandro; Stassun,
Keivan G.; Sullivan, Peter; Szentgyorgyi, Andrew; Torres, Guillermo;
Udry, Stephane; Villasenor, Joel
2014SPIE.9143E..20R Altcode: 2014arXiv1406.0151R
The Transiting Exoplanet Survey Satellite (TESS ) will search for
planets transiting bright and nearby stars. TESS has been selected
by NASA for launch in 2017 as an Astrophysics Explorer mission. The
spacecraft will be placed into a highly elliptical 13.7-day orbit
around the Earth. During its two-year mission, TESS will employ
four wide-field optical CCD cameras to monitor at least 200,000
main-sequence dwarf stars with I<SUB>C</SUB> (approximately less than)
13 for temporary drops in brightness caused by planetary transits. Each
star will be observed for an interval ranging from one month to one
year, depending mainly on the star's ecliptic latitude. The longest
observing intervals will be for stars near the ecliptic poles, which
are the optimal locations for follow-up observations with the James
Webb Space Telescope. Brightness measurements of preselected target
stars will be recorded every 2 min, and full frame images will be
recorded every 30 min. TESS stars will be 10-100 times brighter than
those surveyed by the pioneering Kepler mission. This will make TESS
planets easier to characterize with follow-up observations. TESS is
expected to find more than a thousand planets smaller than Neptune,
including dozens that are comparable in size to the Earth. Public data
releases will occur every four months, inviting immediate community-wide
efforts to study the new planets. The TESS legacy will be a catalog
of the nearest and brightest stars hosting transiting planets, which
will endure as highly favorable targets for detailed investigations.
---------------------------------------------------------
Title: Asteroseismic Estimate of Helium Abundance of a Solar Analog
Binary System
Authors: Verma, Kuldeep; Faria, João P.; Antia, H. M.; Basu, Sarbani;
Mazumdar, Anwesh; Monteiro, Mário J. P. F. G.; Appourchaux, Thierry;
Chaplin, William J.; García, Rafael A.; Metcalfe, Travis S.
2014ApJ...790..138V Altcode: 2014arXiv1405.7512V
16 Cyg A and B are among the brightest stars observed by Kepler. What
makes these stars more interesting is that they are solar analogs. 16
Cyg A and B exhibit solar-like oscillations. In this work we use
oscillation frequencies obtained using 2.5 yr of Kepler data to
determine the current helium abundance of these stars. For this we
use the fact that the helium ionization zone leaves a signature on
the oscillation frequencies and that this signature can be calibrated
to determine the helium abundance of that layer. By calibrating the
signature of the helium ionization zone against models of known helium
abundance, the helium abundance in the envelope of 16 Cyg A is found
to lie in the range of 0.231 to 0.251 and that of 16 Cyg B lies in
the range of 0.218 to 0.266.
---------------------------------------------------------
Title: BiSON data preparation: a correction for differential
extinction and the weighted averaging of contemporaneous data
Authors: Davies, G. R.; Chaplin, W. J.; Elsworth, Y.; Hale, S. J.
2014MNRAS.441.3009D Altcode: 2014arXiv1405.0160D
The Birmingham Solar Oscillations Network (BiSON) has provided
high-quality high-cadence observations from as far back in time as
1978. These data must be calibrated from the raw observations into
radial velocity and the quality of the calibration has a large impact
on the signal-to-noise ratio of the final time series. The aim of
this work is to maximize the potential science that can be performed
with the BiSON data set by optimizing the calibration procedure. To
achieve better levels of signal-to-noise ratio, we perform two
key steps in the calibration process: we attempt a correction for
terrestrial atmospheric differential extinction; and the resulting
improvement in the calibration allows us to perform weighted averaging
of contemporaneous data from different BiSON stations. The improvements
listed produce significant improvement in the signal-to-noise ratio of
the BiSON frequency-power spectrum across all frequency ranges. The
reduction of noise in the power spectrum will allow future work to
provide greater constraint on changes in the oscillation spectrum
with solar activity. In addition, the analysis of the low-frequency
region suggests that we have achieved a noise level that may allow us
to improve estimates of the upper limit of g-mode amplitudes.
---------------------------------------------------------
Title: Kepler-93b: A Terrestrial World Measured to within 120 km,
and a Test Case for a New Spitzer Observing Mode
Authors: Ballard, Sarah; Chaplin, William J.; Charbonneau,
David; Désert, Jean-Michel; Fressin, Francois; Zeng, Li; Werner,
Michael W.; Davies, Guy R.; Silva Aguirre, Victor; Basu, Sarbani;
Christensen-Dalsgaard, Jørgen; Metcalfe, Travis S.; Stello, Dennis;
Bedding, Timothy R.; Campante, Tiago L.; Handberg, Rasmus; Karoff,
Christoffer; Elsworth, Yvonne; Gilliland, Ronald L.; Hekker, Saskia;
Huber, Daniel; Kawaler, Steven D.; Kjeldsen, Hans; Lund, Mikkel N.;
Lundkvist, Mia
2014ApJ...790...12B Altcode: 2014arXiv1405.3659B
We present the characterization of the Kepler-93 exoplanetary
system, based on three years of photometry gathered by the Kepler
spacecraft. The duration and cadence of the Kepler observations,
in tandem with the brightness of the star, enable unusually precise
constraints on both the planet and its host. We conduct an asteroseismic
analysis of the Kepler photometry and conclude that the star has an
average density of 1.652 ± 0.006 g cm<SUP>-3</SUP>. Its mass of 0.911
± 0.033 M <SUB>⊙</SUB> renders it one of the lowest-mass subjects
of asteroseismic study. An analysis of the transit signature produced
by the planet Kepler-93b, which appears with a period of 4.72673978
± 9.7 × 10<SUP>-7</SUP> days, returns a consistent but less precise
measurement of the stellar density, 1.72<SUP>+0.02</SUP><SUB>-0.28</SUB>
g cm<SUP>-3</SUP>. The agreement of these two values lends credence to
the planetary interpretation of the transit signal. The achromatic
transit depth, as compared between Kepler and the Spitzer Space
Telescope, supports the same conclusion. We observed seven transits
of Kepler-93b with Spitzer, three of which we conducted in a new
observing mode. The pointing strategy we employed to gather this subset
of observations halved our uncertainty on the transit radius ratio
R<SUB>P</SUB> /R <SUB>sstarf</SUB>. We find, after folding together the
stellar radius measurement of 0.919 ± 0.011 R <SUB>⊙</SUB> with the
transit depth, a best-fit value for the planetary radius of 1.481 ±
0.019 R <SUB>⊕</SUB>. The uncertainty of 120 km on our measurement
of the planet's size currently renders it one of the most precisely
measured planetary radii outside of the solar system. Together with the
radius, the planetary mass of 3.8 ± 1.5 M <SUB>⊕</SUB> corresponds
to a rocky density of 6.3 ± 2.6 g cm<SUP>-3</SUP>. After applying
a prior on the plausible maximum densities of similarly sized worlds
between 1 and 1.5 R <SUB>⊕</SUB>, we find that Kepler-93b possesses
an average density within this group.
---------------------------------------------------------
Title: Oscillation mode linewidths and heights of 23 main-sequence
stars observed by Kepler
Authors: Appourchaux, T.; Antia, H. M.; Benomar, O.; Campante, T. L.;
Davies, G. R.; Handberg, R.; Howe, R.; Régulo, C.; Belkacem, K.;
Houdek, G.; García, R. A.; Chaplin, W. J.
2014A&A...566A..20A Altcode: 2014arXiv1403.7046A
Context. Solar-like oscillations have been observed by Kepler and
CoRoT in many solar-type stars, thereby providing a way to probe
the stars using asteroseismology. <BR /> Aims: We provide the mode
linewidths and mode heights of the oscillations of various stars as
a function of frequency and of effective temperature. <BR /> Methods:
We used a time series of nearly two years of data for each star. The
23 stars observed belong to the simple or F-like category. The power
spectra of the 23 main-sequence stars were analysed using both maximum
likelihood estimators and Bayesian estimators, providing individual mode
characteristics such as frequencies, linewidths, and mode heights. We
study the source of systematic errors in the mode linewidths and mode
heights, and we present a way to correct these errors with respect to
a common reference fit. <BR /> Results: Using the correction, we can
explain all sources of systematic errors, which could be reduced to
less than ±15% for mode linewidths and heights, and less than ±5%
for amplitude, when compared to the reference fit. The effect of
a different estimated stellar background and a different estimated
splitting will provide frequency-dependent systematic errors that
might affect the comparison with theoretical mode linewidth and mode
height, therefore affecting the understanding of the physical nature of
these parameters. All other sources of relative systematic errors are
less dependent upon frequency. We also provide the dependence of the
so-called linewidth dip in the middle of the observed frequency range as
a function of effective temperature. We show that the depth of the dip
decreases with increasing effective temperature. The dependence of the
dip on effective temperature may imply that the mixing length parameter
α or the convective flux may increase with effective temperature. <P
/>Tables 4-27 and Appendices are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201323317/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Prospects for asteroseismic inference on the envelope helium
abundance in red giant stars
Authors: Broomhall, A. -M.; Miglio, A.; Montalbán, J.; Eggenberger,
P.; Chaplin, W. J.; Elsworth, Y.; Scuflaire, R.; Ventura, P.; Verner,
G. A.
2014MNRAS.440.1828B Altcode: 2014MNRAS.tmp..576B; 2014arXiv1403.7045B
Regions of rapid variation in the internal structure of a star are often
referred to as acoustic glitches since they create a characteristic
periodic signature in the frequencies of p modes. Here we examine the
localized disturbance arising from the helium second ionization zone
in red giant branch and clump stars. More specifically, we determine
how accurately and precisely the parameters of the ionization zone
can be obtained from the oscillation frequencies of stellar models. We
use models produced by three different generation codes that not only
cover a wide range of stages of evolution along the red giant phase
but also incorporate different initial helium abundances. To study the
acoustic glitch caused by the second ionization zone of helium we have
determined the second differences in frequencies of modes with the same
angular degree, l, and then we fit the periodic function described by
Houdek & Gough to the second differences. We discuss the conditions
under which such fits robustly and accurately determine the acoustic
radius of the second ionization zone of helium. When the frequency of
maximum amplitude of the p-mode oscillations was greater than 40 μHz
a robust value for the radius of the ionization zone was recovered for
the majority of models. The determined radii of the ionization zones as
inferred from the mode frequencies were found to be coincident with the
local maximum in the first adiabatic exponent described by the models,
which is associated with the outer edge of the second ionization zone
of helium. Finally, we consider whether this method can be used to
distinguish stars with different helium abundances. Although a definite
trend in the amplitude of the signal is observed any distinction
would be difficult unless the stars come from populations with
vastly different helium abundances or the uncertainties associated
with the fitted parameters can be reduced. However, application of
our methodology could be useful for distinguishing between different
populations of red giant stars in globular clusters, where distinct
populations with very different helium abundances have been observed.
---------------------------------------------------------
Title: Amplitude variability in satellite photometry of the
non-radially pulsating O9.5 V star ζ Oph
Authors: Howarth, Ian D.; Goss, K. J. F.; Stevens, I. R.; Chaplin,
W. J.; Elsworth, Y.
2014MNRAS.440.1674H Altcode: 2014MNRAS.tmp..577H; 2014arXiv1402.6551H
We report a time series analysis of satellite photometry of the
non-radially pulsating Oe star ζ Oph, principally using data from the
Solar Mass Ejection Imager obtained during 2003-2008, but augmented
with Microvariability and Oscillations of STars and Wide-field InfraRed
Explorer results. Amplitudes of the strongest photometric signals,
at 5.18, 2.96 and 2.67 d<SUP>-1</SUP>, each vary independently over
the 51/2-year monitoring period (from ∼50 to ≲2 mmag at 5.18
d<SUP>-1</SUP>), on time-scales of hundreds of days. Signals at 7.19
and 5.18 d<SUP>-1</SUP> have persisted (or recurred) for at least two
decades. Supplementary spectroscopic observations show an Hα emission
episode in 2006; this coincided with small increases in amplitudes of
the three strongest photometric signals.
---------------------------------------------------------
Title: Testing the Asteroseismic Mass Scale Using Metal-poor Stars
Characterized with APOGEE and Kepler
Authors: Epstein, Courtney R.; Elsworth, Yvonne P.; Johnson, Jennifer
A.; Shetrone, Matthew; Mosser, Benoît; Hekker, Saskia; Tayar,
Jamie; Harding, Paul; Pinsonneault, Marc; Silva Aguirre, Víctor;
Basu, Sarbani; Beers, Timothy C.; Bizyaev, Dmitry; Bedding, Timothy
R.; Chaplin, William J.; Frinchaboy, Peter M.; García, Rafael A.;
García Pérez, Ana E.; Hearty, Fred R.; Huber, Daniel; Ivans, Inese
I.; Majewski, Steven R.; Mathur, Savita; Nidever, David; Serenelli,
Aldo; Schiavon, Ricardo P.; Schneider, Donald P.; Schönrich, Ralph;
Sobeck, Jennifer S.; Stassun, Keivan G.; Stello, Dennis; Zasowski, Gail
2014ApJ...785L..28E Altcode: 2014arXiv1403.1872E
Fundamental stellar properties, such as mass, radius, and age,
can be inferred using asteroseismology. Cool stars with convective
envelopes have turbulent motions that can stochastically drive and damp
pulsations. The properties of the oscillation frequency power spectrum
can be tied to mass and radius through solar-scaled asteroseismic
relations. Stellar properties derived using these scaling relations
need verification over a range of metallicities. Because the age and
mass of halo stars are well-constrained by astrophysical priors, they
provide an independent, empirical check on asteroseismic mass estimates
in the low-metallicity regime. We identify nine metal-poor red giants
(including six stars that are kinematically associated with the halo)
from a sample observed by both the Kepler space telescope and the
Sloan Digital Sky Survey-III APOGEE spectroscopic survey. We compare
masses inferred using asteroseismology to those expected for halo
and thick-disk stars. Although our sample is small, standard scaling
relations, combined with asteroseismic parameters from the APOKASC
Catalog, produce masses that are systematically higher (<ΔM >
=0.17 ± 0.05 M <SUB>⊙</SUB>) than astrophysical expectations. The
magnitude of the mass discrepancy is reduced by known theoretical
corrections to the measured large frequency separation scaling
relationship. Using alternative methods for measuring asteroseismic
parameters induces systematic shifts at the 0.04 M <SUB>⊙</SUB>
level. We also compare published asteroseismic analyses with scaling
relationship masses to examine the impact of using the frequency
of maximum power as a constraint. Upcoming APOKASC observations will
provide a larger sample of ~100 metal-poor stars, important for detailed
asteroseismic characterization of Galactic stellar populations.
---------------------------------------------------------
Title: The K2 Mission: Characterization and Early Results
Authors: Howell, Steve B.; Sobeck, Charlie; Haas, Michael; Still,
Martin; Barclay, Thomas; Mullally, Fergal; Troeltzsch, John; Aigrain,
Suzanne; Bryson, Stephen T.; Caldwell, Doug; Chaplin, William J.;
Cochran, William D.; Huber, Daniel; Marcy, Geoffrey W.; Miglio, Andrea;
Najita, Joan R.; Smith, Marcie; Twicken, J. D.; Fortney, Jonathan J.
2014PASP..126..398H Altcode: 2014arXiv1402.5163H
The K2 mission will make use of the Kepler spacecraft and its assets
to expand upon Kepler's groundbreaking discoveries in the fields of
exoplanets and astrophysics through new and exciting observations. K2
will use an innovative way of operating the spacecraft to observe
target fields along the ecliptic for the next 2-3 years. Early science
commissioning observations have shown an estimated photometric precision
near 400 ppm in a single 30 minute observation, and a 6-hour photometric
precision of 80 ppm (both at V=12). The K2 mission offers long-term,
simultaneous optical observation of thousands of objects at a precision
far better than is achievable from ground-based telescopes. Ecliptic
fields will be observed for approximately 75-days enabling a unique
exoplanet survey which fills the gaps in duration and sensitivity
between the Kepler and TESS missions, and offers pre-launch exoplanet
target identification for JWST transit spectroscopy. Astrophysics
observations with K2 will include studies of young open clusters,
bright stars, galaxies, supernovae, and asteroseismology.
---------------------------------------------------------
Title: Seismic analysis of HD 43587Aa, a solar-like oscillator in
a multiple system
Authors: Boumier, P.; Benomar, O.; Baudin, F.; Verner, G.; Appourchaux,
T.; Lebreton, Y.; Gaulme, P.; Chaplin, W.; García, R. A.; Hekker,
S.; Regulo, C.; Salabert, D.; Stahn, T.; Elsworth, Y.; Gizon, L.;
Hall, M.; Mathur, S.; Michel, E.; Morel, T.; Mosser, B.; Poretti,
E.; Rainer, M.; Roxburgh, I.; do Nascimento, J. -D., Jr.; Samadi,
R.; Auvergne, M.; Chaintreuil, S.; Baglin, A.; Catala, C.
2014A&A...564A..34B Altcode: 2014arXiv1402.5053B
Context. The object HD 43587Aa is a G0V star observed during the
145-day LRa03 run of the COnvection, ROtation and planetary Transits
space mission (CoRoT), for which complementary High Accuracy Radial
velocity Planet Searcher (HARPS) spectra with S/N > 300 were also
obtained. Its visual magnitude is 5.71, and its effective temperature is
close to 5950 K. It has a known companion in a highly eccentric orbit
and is also coupled with two more distant companions. <BR /> Aims:
We undertake a preliminary investigation of the internal structure
of HD 43587Aa. <BR /> Methods: We carried out a seismic analysis of
the star, using maximum likelihood estimators and Markov chain Monte
Carlo methods. <BR /> Results: We established the first table of the
eigenmode frequencies, widths, and heights for HD 43587Aa. The star
appears to have a mass and a radius slightly larger than the Sun, and is
slightly older (5.6 Gyr). Two scenarios are suggested for the geometry
of the star: either its inclination angle is very low, or the rotation
velocity of the star is very low. <BR /> Conclusions: A more detailed
study of the rotation and of the magnetic and chromospheric activity for
this star is needed, and will be the subject of a further study. New
high resolution spectrometric observations should be performed for at
least several months in duration.
---------------------------------------------------------
Title: Low-frequency, low-degree solar p-mode properties from 22
years of Birmingham Solar Oscillations Network data
Authors: Davies, G. R.; Broomhall, A. M.; Chaplin, W. J.; Elsworth,
Y.; Hale, S. J.
2014MNRAS.439.2025D Altcode: 2014MNRAS.tmp..243D
The solar low-degree low-frequency modes of oscillation are of
particular interest as their frequencies can be measured with very high
precision and hence provide good constraints on seismic models. Here we
detect and characterize these valuable measures of the solar interior
from a 22 yr Birmingham Solar Oscillations Network data set. We report
mode frequencies, line widths, heights, amplitudes, and rotational
splitting, all with robust uncertainties. The new values of frequency,
rotational splitting, amplitude, and line width we provide will
help place new constraints on hydrostatic and rotational structure,
plus diagnostics of near-surface convection. Further to this, by
assuming simple power laws, we extrapolate mode properties to lower
frequencies. We demonstrate that the low-l low-frequency p modes have
a low signal-to-noise ratio and that this cannot be overcome simply
by continued observation. It will be necessary to observe the Sun in
novel ways to `beat' the intrinsic granulation noise.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Revised stellar properties of
Q1-16 Kepler targets (Huber+, 2014)
Authors: Huber, D.; Silva Aguirre, V.; Matthews, J. M.; Pinsonneault,
M. H.; Gaidos, E.; Garcia, R. A.; Hekker, S.; Mathur, S.; Mosser,
B.; Torres, G.; Bastien, F. A.; Basu, S.; Bedding, T. R.; Chaplin,
W. J.; Demory, B. -O.; Fleming, S. W.; Guo, Z.; Mann, A. W.; Rowe,
J. F.; Serenelli, A. M.; Smith, M. A.; Stello, D.
2014yCat..22110002H Altcode:
We present revised properties for 196468 stars observed by the NASA
Kepler mission and used in the analysis of Quarter 1-16 (Q1-16; May 2009
to Dec 2012) data to detect and characterize transiting planets. The
catalog is based on a compilation of literature values for atmospheric
properties (temperature, surface gravity, and metallicity) derived
from different observational techniques (photometry, spectroscopy,
asteroseismology, and exoplanet transits), which were then homogeneously
fitted to a grid of Dartmouth stellar isochrones. We use broadband
photometry and asteroseismology to characterize 11532 Kepler targets
which were previously unclassified in the Kepler Input Catalog
(KIC). We report the detection of oscillations in 2762 of these
targets, classifying them as giant stars and increasing the number
of known oscillating giant stars observed by Kepler by ~20% to a
total of ~15500 stars. Typical uncertainties in derived radii and
masses are ~40% and ~20%, respectively, for stars with photometric
constraints only, and 5%-15% and ~10% for stars based on spectroscopy
and/or asteroseismology, although these uncertainties vary strongly
with spectral type and luminosity class. A comparison with the Q1-Q12
catalog shows a systematic decrease in radii of M dwarfs, while radii
for K dwarfs decrease or increase depending on the Q1-Q12 provenance
(KIC or Yonsei-Yale isochrones). Radii of F-G dwarfs are on average
unchanged, with the exception of newly identified giants. The
Q1-Q16 star properties catalog is a first step toward an improved
characterization of all Kepler targets to support planet-occurrence
studies. <P />(3 data files).
---------------------------------------------------------
Title: Flicker as a Tool for Characterizing Planets Through
Asterodensity Profiling
Authors: Kipping, D. M.; Bastien, F. A.; Stassun, K. G.; Chaplin,
W. J.; Huber, D.; Buchhave, L. A.
2014ApJ...785L..32K Altcode: 2014arXiv1403.5264K
Variability in the time series brightness of a star on a timescale of
8 hr, known as "flicker," has been previously demonstrated to serve as
a proxy for the surface gravity of a star by Bastien et al. Although
surface gravity is crucial for stellar classification, it is the mean
stellar density that is most useful when studying transiting exoplanets,
due to its direct impact on the transit light curve shape. Indeed,
an accurate and independent measure of the stellar density can be
leveraged to infer subtle properties of a transiting system, such as the
companion's orbital eccentricity via asterodensity profiling (AP). We
here calibrate flicker to the mean stellar density of 439 Kepler targets
with asteroseismology, allowing us to derive a new empirical relation
given by log<SUB>10</SUB>(ρ<SUB>sstarf</SUB> (kg m<SUP>-3</SUP>)) =
5.413 - 1.850log<SUB>10</SUB>(F <SUB>8</SUB> (ppm)). The calibration
is valid for stars with 4500 < T <SUB>eff</SUB> < 6500 K,
K<SUB>P</SUB> < 14, and flicker estimates corresponding to stars
with 3.25 < log g <SUB>sstarf</SUB> < 4.43. Our relation has
a model error in the stellar density of 31.7% and so has ~8 times
lower precision than that from asteroseismology but is applicable to
a sample ~40 times greater. Flicker therefore provides an empirical
method to enable AP on hundreds of planetary candidates from present
and future missions.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Kepler planetary candidates. IV. 22
months (Burke+, 2014)
Authors: Burke, C. J.; Bryson, S. T.; Mullally, F.; Rowe, J. F.;
Christiansen, J. L.; Thompson, S. E.; Coughlin, J. L.; Haas, M. R.;
Batalha, N. M.; Caldwell, D. A.; Jenkins, J. M.; Still, M.; Barclay,
T.; Borucki, W. J.; Chaplin, W. J.; Ciardi, D. R.; Clarke, B. D.;
Cochran, W. D.; Demory, B. -O.; Esquerdo, G. A.; Gautier, T. N., III;
Gilliland, R. L.; Girouard, F. R.; Havel, M.; Henze, C. E.; Howell,
S. B.; Huber, D.; Latham, D. W.; Li, J.; Morehead, R. C.; Morton,
T. D.; Pepper, J.; Quintana, E.; Ragozzine, D.; Seader, S. E.; Shah,
Y.; Shporer, A.; Tenenbaum, P.; Twicken, J. D.; Wolfgang, A.
2014yCat..22100019B Altcode:
In 2011 November, the Q1-Q8 (22 months of data) Kepler pipeline run
generated one or more TCEs (threshold crossing events) for ~13400
Kepler targets out of ~191000 targets searched. <P />(1 data file).
---------------------------------------------------------
Title: VizieR Online Data Catalog: Small Kepler planets radial
velocities (Marcy+, 2014)
Authors: Marcy, G. W.; Isaacson, H.; Howard, A. W.; Rowe, J. F.;
Jenkins, J. M.; Bryson, S. T.; Latham, D. W.; Howell, S. B.;
Gautier, T. N., III; Batalha, N. M.; Rogers, L.; Ciardi, D.; Fischer,
D. A.; Gilliland, R. L.; Kjeldsen, H.; Christensen-Dalsgaard, J.;
Huber, D.; Chaplin, W. J.; Basu, S.; Buchhave, L. A.; Quinn, S. N.;
Borucki, W. J.; Koch, D. G.; Hunter, R.; Caldwell, D. A.; van Cleve,
J.; Kolbl, R.; Weiss, L. M.; Petigura, E.; Seager, S.; Morton, T.;
Johnson, J. A.; Ballard, S.; Burke, C.; Cochran, W. D.; Endl, M.;
MacQueen, P.; Everett, M. E.; Lissauer, J. J.; Ford, E. B.; Torres,
G.; Fressin, F.; Brown, T. M.; Steffen, J. H.; Charbonneau, D.; Basri,
G. S.; Sasselov, D. D.; Winn, J.; Sanchis-Ojeda, R.; Christiansen,
J.; Adams, E.; Henze, C.; Dupree, A.; Fabrycky, D. C.; Fortney, J. J.;
Tarter, J.; Holman, M. J.; Tenenbaum, P.; Shporer, A.; Lucas, P. W.;
Welsh, W. F.; Orosz, J. A.; Bedding, T. R.; Campante, T. L.; Davies,
G. R.; Elsworth, Y.; Handberg, R.; Hekker, S.; Karoff, C.; Kawaler,
S. D.; Lund, M. N.; Lundkvist, M.; Metcalfe, T. S.; Miglio, A.; Silva
Aguirre, V.; Stello, D.; White, T. R.; Boss, A.; Devore, E.; Gould,
A.; Prsa, A.; Agol, E.; Barclay, T.; Coughlin, J.; Brugamyer, E.;
Mullally, F.; Quintana, E. V.; Still, M.; Thompson, S. E.; Morrison,
D.; Twicken, J. D.; Desert, J. -M.; Carter, J.; Crepp, J. R.; Hebrard,
G.; Santerne, A.; Moutou, C.; Sobeck, C.; Hudgins, D.; Haas, M. R.;
Robertson, P.; Lillo-Box, J.; Barrado, D.
2014yCat..22100020M Altcode:
Here we report measured masses, radii, and densities (or upper limits
on those values) for 42 transiting planet candidates contained within
22 bright Kepler Objects of Interest (KOIs) from Batalha et al. (2013,
Cat. J/ApJS/204/24). We carried out multiple Doppler-shift measurements
of the host stars using the Keck 1 telescope. From the spectroscopy
and Doppler measurements, we compute self-consistent measurements of
stellar and planet radii, employing either stellar structure models
or asteroseismology measurements from the Kepler photometry. We also
search for (and report) 7 additional non-transiting planets revealed
by the precise radial velocities (RVs), for a total of 49 planets. <P
/>We carried out "reconnaissance" high-resolution spectroscopy on ~1000
KOIs with spectral resolution, R~50000, and S/N=20-100 per pixel. The
dual goals were searching for false positives and refining the stellar
parameters. We obtained one or two such reconnaissance spectra using
one of four facilities: the McDonald Observatory 2.7m, the Tillinghast
1.5m on Mt. Hopkins, the Lick Observatory 3m, and the 2.6m Nordic
Optical Telescope. <P />Speckle imaging of each of the selected 22
KOIs was obtained using the two-color DSSI speckle camera at the WIYN
3.5m telescope on Kitt Peak. <P />All 22 KOIs were observed with the
Keck NIRC2-AO system. <P />(3 data files).
---------------------------------------------------------
Title: Seismic constraints on the radial dependence of the internal
rotation profiles of six Kepler subgiants and young red giants
Authors: Deheuvels, S.; Doğan, G.; Goupil, M. J.; Appourchaux, T.;
Benomar, O.; Bruntt, H.; Campante, T. L.; Casagrande, L.; Ceillier,
T.; Davies, G. R.; De Cat, P.; Fu, J. N.; García, R. A.; Lobel,
A.; Mosser, B.; Reese, D. R.; Regulo, C.; Schou, J.; Stahn, T.;
Thygesen, A. O.; Yang, X. H.; Chaplin, W. J.; Christensen-Dalsgaard,
J.; Eggenberger, P.; Gizon, L.; Mathis, S.; Molenda-Żakowicz, J.;
Pinsonneault, M.
2014A&A...564A..27D Altcode: 2014arXiv1401.3096D
Context. We still do not understand which physical mechanisms are
responsible for the transport of angular momentum inside stars. The
recent detection of mixed modes that contain the clear signature of
rotation in the spectra of Kepler subgiants and red giants gives us
the opportunity to make progress on this question. <BR /> Aims: Our
aim is to probe the radial dependence of the rotation profiles for a
sample of Kepler targets. For this purpose, subgiants and early red
giants are particularly interesting targets because their rotational
splittings are more sensitive to the rotation outside the deeper core
than is the case for their more evolved counterparts. <BR /> Methods:
We first extracted the rotational splittings and frequencies of the
modes for six young Kepler red giants. We then performed a seismic
modeling of these stars using the evolutionary codes Cesam2k and
astec. By using the observed splittings and the rotational kernels
of the optimal models, we inverted the internal rotation profiles
of the six stars. <BR /> Results: We obtain estimates of the core
rotation rates for these stars, and upper limits to the rotation in
their convective envelope. We show that the rotation contrast between
the core and the envelope increases during the subgiant branch. Our
results also suggest that the core of subgiants spins up with time,
while their envelope spins down. For two of the stars, we show that a
discontinuous rotation profile with a deep discontinuity reproduces
the observed splittings significantly better than a smooth rotation
profile. Interestingly, the depths that are found to be most probable
for the discontinuities roughly coincide with the location of the
H-burning shell, which separates the layers that contract from those
that expand. <BR /> Conclusions: We characterized the differential
rotation pattern of six young giants with a range of metallicities, and
with both radiative and convective cores on the main sequence. This will
bring observational constraints to the scenarios of angular momentum
transport in stars. Moreover, if the existence of sharp gradients in
the rotation profiles of young red giants is confirmed, it is expected
to help in distinguishing between the physical processes that could
transport angular momentum in the subgiant and red giant branches. <P
/>Appendices and Tables 3-9 are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201322779/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Revised Stellar Properties of Kepler Targets for the Quarter
1-16 Transit Detection Run
Authors: Huber, Daniel; Silva Aguirre, Victor; Matthews, Jaymie M.;
Pinsonneault, Marc H.; Gaidos, Eric; García, Rafael A.; Hekker,
Saskia; Mathur, Savita; Mosser, Benoit; Torres, Guillermo; Bastien,
Fabienne A.; Basu, Sarbani; Bedding, Timothy R.; Chaplin, William J.;
Demory, Brice-Olivier; Fleming, Scott W.; Guo, Zhao; Mann, Andrew W.;
Rowe, Jason F.; Serenelli, Aldo M.; Smith, Myron A.; Stello, Dennis
2014ApJS..211....2H Altcode: 2013arXiv1312.0662H
We present revised properties for 196,468 stars observed by the NASA
Kepler mission and used in the analysis of Quarter 1-16 (Q1-Q16)
data to detect and characterize transiting planets. The catalog is
based on a compilation of literature values for atmospheric properties
(temperature, surface gravity, and metallicity) derived from different
observational techniques (photometry, spectroscopy, asteroseismology,
and exoplanet transits), which were then homogeneously fitted to a
grid of Dartmouth stellar isochrones. We use broadband photometry
and asteroseismology to characterize 11,532 Kepler targets which
were previously unclassified in the Kepler Input Catalog (KIC). We
report the detection of oscillations in 2762 of these targets,
classifying them as giant stars and increasing the number of known
oscillating giant stars observed by Kepler by ~20% to a total of
~15,500 stars. Typical uncertainties in derived radii and masses are
~40% and ~20%, respectively, for stars with photometric constraints
only, and 5%-15% and ~10% for stars based on spectroscopy and/or
asteroseismology, although these uncertainties vary strongly with
spectral type and luminosity class. A comparison with the Q1-Q12 catalog
shows a systematic decrease in radii of M dwarfs, while radii for K
dwarfs decrease or increase depending on the Q1-Q12 provenance (KIC or
Yonsei-Yale isochrones). Radii of F-G dwarfs are on average unchanged,
with the exception of newly identified giants. The Q1-Q16 star
properties catalog is a first step toward an improved characterization
of all Kepler targets to support planet-occurrence studies.
---------------------------------------------------------
Title: Prospects for Detecting Asteroseismic Binaries in Kepler Data
Authors: Miglio, A.; Chaplin, W. J.; Farmer, R.; Kolb, U.; Girardi,
L.; Elsworth, Y.; Appourchaux, T.; Handberg, R.
2014ApJ...784L...3M Altcode: 2014arXiv1402.2480M
Asteroseismology may in principle be used to detect unresolved stellar
binary systems comprised of solar-type stars and/or red giants. This
novel method relies on the detection of the presence of two solar-like
oscillation spectra in the frequency spectrum of a single light
curve. Here, we make predictions of the numbers of systems that may be
detectable in data already collected by the NASA Kepler Mission. Our
predictions, which are based upon TRILEGAL and BiSEPS simulations
of the Kepler field of view, indicate that as many as 200 or more
"asteroseismic binaries" may be detectable in this manner. Most
of these binaries should be comprised of two He-core-burning red
giants. Owing largely to the limited numbers of targets with the
requisite short-cadence Kepler data, we expect only a small number of
detected binaries containing solar-type stars. The predicted yield of
detections is sensitive to the assumed initial mass ratio distribution
(IMRD) of the binary components and therefore represents a sensitive
calibration of the much debated IMRD near mass ratio unity.
---------------------------------------------------------
Title: Limits on Surface Gravities of Kepler Planet-candidate Host
Stars from Non-detection of Solar-like Oscillations
Authors: Campante, T. L.; Chaplin, W. J.; Lund, M. N.; Huber, D.;
Hekker, S.; García, R. A.; Corsaro, E.; Handberg, R.; Miglio, A.;
Arentoft, T.; Basu, S.; Bedding, T. R.; Christensen-Dalsgaard, J.;
Davies, G. R.; Elsworth, Y. P.; Gilliland, R. L.; Karoff, C.; Kawaler,
S. D.; Kjeldsen, H.; Lundkvist, M.; Metcalfe, T. S.; Silva Aguirre,
V.; Stello, D.
2014ApJ...783..123C Altcode: 2014arXiv1401.6324C
We present a novel method for estimating lower-limit surface gravities
(log g) of Kepler targets whose data do not allow the detection of
solar-like oscillations. The method is tested using an ensemble of
solar-type stars observed in the context of the Kepler Asteroseismic
Science Consortium. We then proceed to estimate lower-limit log g for a
cohort of Kepler solar-type planet-candidate host stars with no detected
oscillations. Limits on fundamental stellar properties, as provided
by this work, are likely to be useful in the characterization of the
corresponding candidate planetary systems. Furthermore, an important
byproduct of the current work is the confirmation that amplitudes of
solar-like oscillations are suppressed in stars with increased levels
of surface magnetic activity.
---------------------------------------------------------
Title: Study of KIC 8561221 observed by Kepler: an early red giant
showing depressed dipolar modes
Authors: García, R. A.; Pérez Hernández, F.; Benomar, O.; Silva
Aguirre, V.; Ballot, J.; Davies, G. R.; Doğan, G.; Stello, D.;
Christensen-Dalsgaard, J.; Houdek, G.; Lignières, F.; Mathur, S.;
Takata, M.; Ceillier, T.; Chaplin, W. J.; Mathis, S.; Mosser, B.;
Ouazzani, R. M.; Pinsonneault, M. H.; Reese, D. R.; Régulo, C.;
Salabert, D.; Thompson, M. J.; van Saders, J. L.; Neiner, C.; De
Ridder, J.
2014A&A...563A..84G Altcode: 2013arXiv1311.6990G
Context. The continuous high-precision photometric observations
provided by the CoRoT and Kepler space missions have allowed us to
understand the structure and dynamics of red giants better using
asteroseismic techniques. A small fraction of these stars show
dipole modes with unexpectedly low amplitudes. The reduction in
amplitude is more pronounced for stars with a higher frequency of
maximum power, ν<SUB>max</SUB>. <BR /> Aims: In this work we want to
characterise KIC 8561221 in order to confirm that it is currently the
least evolved star among this peculiar subset and to discuss several
hypotheses that could help explain the reduction of the dipole mode
amplitudes. <BR /> Methods: We used Kepler short- and long-cadence
data combined with spectroscopic observations to infer the stellar
structure and dynamics of KIC 8561221. We then discussed different
scenarios that could contribute to reducing the dipole amplitudes,
such as a fast-rotating interior or the effect of a magnetic field
on the properties of the modes. We also performed a detailed study
of the inertia and damping of the modes. <BR /> Results: We have
been able to characterise 36 oscillations modes, in particular, a
few dipole modes above ν<SUB>max</SUB> that exhibit nearly normal
amplitudes. The frequencies of all the measured modes were used
to determine the overall properties and the internal structure of
the star. We have inferred a surface rotation period of ~91 days
and uncovered a variation in the surface magnetic activity during
the last 4 years. The analysis of the convective background did not
reveal any difference compared to "normal" red giants. As expected,
the internal regions of the star probed by the ℓ = 2 and 3 modes
spin 4 to 8 times faster than the surface. <BR /> Conclusions: With
our grid of standard models we are able to properly fit the observed
frequencies. Our model calculation of mode inertia and damping give
no explanation for the depressed dipole modes. A fast-rotating core
is also ruled out as a possible explanation. Finally, we do not have
any observational evidence of a strong deep magnetic field inside the
star. <P />Table 3 and Appendix A are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201322823/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Planetary Candidates Observed by Kepler IV: Planet Sample
from Q1-Q8 (22 Months)
Authors: Burke, Christopher J.; Bryson, Stephen T.; Mullally, F.;
Rowe, Jason F.; Christiansen, Jessie L.; Thompson, Susan E.; Coughlin,
Jeffrey L.; Haas, Michael R.; Batalha, Natalie M.; Caldwell, Douglas
A.; Jenkins, Jon M.; Still, Martin; Barclay, Thomas; Borucki, William
J.; Chaplin, William J.; Ciardi, David R.; Clarke, Bruce D.; Cochran,
William D.; Demory, Brice-Olivier; Esquerdo, Gilbert A.; Gautier,
Thomas N., III; Gilliland, Ronald L.; Girouard, Forrest R.; Havel,
Mathieu; Henze, Christopher E.; Howell, Steve B.; Huber, Daniel;
Latham, David W.; Li, Jie; Morehead, Robert C.; Morton, Timothy D.;
Pepper, Joshua; Quintana, Elisa; Ragozzine, Darin; Seader, Shawn
E.; Shah, Yash; Shporer, Avi; Tenenbaum, Peter; Twicken, Joseph D.;
Wolfgang, Angie
2014ApJS..210...19B Altcode: 2013arXiv1312.5358B
We provide updates to the Kepler planet candidate sample based upon
nearly two years of high-precision photometry (i.e., Q1-Q8). From an
initial list of nearly 13,400 threshold crossing events, 480 new host
stars are identified from their flux time series as consistent with
hosting transiting planets. Potential transit signals are subjected to
further analysis using the pixel-level data, which allows background
eclipsing binaries to be identified through small image position shifts
during transit. We also re-evaluate Kepler Objects of Interest (KOIs)
1-1609, which were identified early in the mission, using substantially
more data to test for background false positives and to find additional
multiple systems. Combining the new and previous KOI samples, we provide
updated parameters for 2738 Kepler planet candidates distributed
across 2017 host stars. From the combined Kepler planet candidates,
472 are new from the Q1-Q8 data examined in this study. The new Kepler
planet candidates represent ~40% of the sample with R <SUB>P</SUB> ~ 1
R <SUB>⊕</SUB> and represent ~40% of the low equilibrium temperature
(T <SUB>eq</SUB> < 300 K) sample. We review the known biases in the
current sample of Kepler planet candidates relevant to evaluating planet
population statistics with the current Kepler planet candidate sample.
---------------------------------------------------------
Title: Sounding the solar cycle with helioseismology: Implications
for asteroseismology
Authors: Chaplin, William J.
2014aste.book....1C Altcode: 2011arXiv1109.4842C
My brief for the IAC Winter School was to cover observational results
on helioseismology, flagging where possible implications of those
results for the asteroseismic study of solar-type stars. My desire
to make such links meant that I concentrated largely upon results
for low angular-degree (low-l) solar p modes, in particular results
derived from "Sun-as-a-star" observations (which are of course most
instructive for the transfer of experience from helioseismology to
asteroseismology). The lectures covered many aspects of helioseismology
- modern helioseismology is a diverse field. In these notes, rather
than discuss each aspect to a moderate level of detail, I have
instead made the decision to concentrate upon one theme, that of
"sounding" the solar activity cycle with helioseismology. I cover
the topics from the lectures and I also include some new material,
relating both to the lecture topics and other aspects I did not have
time to cover. Implications for asteroseismology are developed and
discussed throughout.
---------------------------------------------------------
Title: Precision Asteroseismology
Authors: Guzik, Joyce A.; Chaplin, William J.; Handler, Gerald;
Pigulski, Andrzej
2014IAUS..301.....G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Measurement of Acoustic Glitches in Solar-type Stars from
Oscillation Frequencies Observed by Kepler
Authors: Mazumdar, A.; Monteiro, M. J. P. F. G.; Ballot, J.; Antia,
H. M.; Basu, S.; Houdek, G.; Mathur, S.; Cunha, M. S.; Silva Aguirre,
V.; García, R. A.; Salabert, D.; Verner, G. A.; Christensen-Dalsgaard,
J.; Metcalfe, T. S.; Sanderfer, D. T.; Seader, S. E.; Smith, J. C.;
Chaplin, W. J.
2014ApJ...782...18M Altcode: 2013arXiv1312.4907M
For the very best and brightest asteroseismic solar-type targets
observed by Kepler, the frequency precision is sufficient to determine
the acoustic depths of the surface convective layer and the helium
ionization zone. Such sharp features inside the acoustic cavity of
the star, which we call acoustic glitches, create small oscillatory
deviations from the uniform spacing of frequencies in a sequence of
oscillation modes with the same spherical harmonic degree. We use these
oscillatory signals to determine the acoustic locations of such features
in 19 solar-type stars observed by the Kepler mission. Four independent
groups of researchers utilized the oscillation frequencies themselves,
the second differences of the frequencies and the ratio of the small
and large separation to locate the base of the convection zone and the
second helium ionization zone. Despite the significantly different
methods of analysis, good agreement was found between the results
of these four groups, barring a few cases. These results also agree
reasonably well with the locations of these layers in representative
models of the stars. These results firmly establish the presence of
the oscillatory signals in the asteroseismic data and the viability
of several techniques to determine the location of acoustic glitches
inside stars.
---------------------------------------------------------
Title: What Asteroseismology can do for Exoplanets: Kepler-410A
b is a Small Neptune around a Bright Star, in an Eccentric Orbit
Consistent with Low Obliquity
Authors: Van Eylen, V.; Lund, M. N.; Silva Aguirre, V.; Arentoft, T.;
Kjeldsen, H.; Albrecht, S.; Chaplin, W. J.; Isaacson, H.; Pedersen,
M. G.; Jessen-Hansen, J.; Tingley, B.; Christensen-Dalsgaard, J.;
Aerts, C.; Campante, T. L.; Bryson, S. T.
2014ApJ...782...14V Altcode: 2013arXiv1312.4938V
We confirm the Kepler planet candidate Kepler-410A b (KOI-42b) as a
Neptune-sized exoplanet on a 17.8 day, eccentric orbit around the
bright (K <SUB>p</SUB> = 9.4) star Kepler-410A (KOI-42A). This is
the third brightest confirmed planet host star in the Kepler field
and one of the brightest hosts of all currently known transiting
exoplanets. Kepler-410 consists of a blend between the fast rotating
planet host star (Kepler-410A) and a fainter star (Kepler-410B), which
has complicated the confirmation of the planetary candidate. Employing
asteroseismology, using constraints from the transit light curve,
adaptive optics and speckle images, and Spitzer transit observations,
we demonstrate that the candidate can only be an exoplanet orbiting
Kepler-410A. We determine via asteroseismology the following stellar
and planetary parameters with high precision; M <SUB>sstarf</SUB> =
1.214 ± 0.033 M <SUB>⊙</SUB>, R <SUB>sstarf</SUB> = 1.352 ± 0.010 R
<SUB>⊙</SUB>, age =2.76 ± 0.54 Gyr, planetary radius (2.838 ± 0.054
R <SUB>⊕</SUB>), and orbital eccentricity (0.17^{+0.07}_{-0.06}). In
addition, rotational splitting of the pulsation modes allows for
a measurement of Kepler-410A's inclination and rotation rate. Our
measurement of an inclination of 82.5^{+7.5}_{-2.5} [°] indicates
a low obliquity in this system. Transit timing variations indicate
the presence of at least one additional (non-transiting) planet
(Kepler-410A c) in the system.
---------------------------------------------------------
Title: Masses, Radii, and Orbits of Small Kepler Planets: The
Transition from Gaseous to Rocky Planets
Authors: Marcy, Geoffrey W.; Isaacson, Howard; Howard, Andrew W.;
Rowe, Jason F.; Jenkins, Jon M.; Bryson, Stephen T.; Latham, David
W.; Howell, Steve B.; Gautier, Thomas N., III; Batalha, Natalie M.;
Rogers, Leslie; Ciardi, David; Fischer, Debra A.; Gilliland, Ronald
L.; Kjeldsen, Hans; Christensen-Dalsgaard, Jørgen; Huber, Daniel;
Chaplin, William J.; Basu, Sarbani; Buchhave, Lars A.; Quinn, Samuel
N.; Borucki, William J.; Koch, David G.; Hunter, Roger; Caldwell,
Douglas A.; Van Cleve, Jeffrey; Kolbl, Rea; Weiss, Lauren M.;
Petigura, Erik; Seager, Sara; Morton, Timothy; Johnson, John Asher;
Ballard, Sarah; Burke, Chris; Cochran, William D.; Endl, Michael;
MacQueen, Phillip; Everett, Mark E.; Lissauer, Jack J.; Ford, Eric
B.; Torres, Guillermo; Fressin, Francois; Brown, Timothy M.; Steffen,
Jason H.; Charbonneau, David; Basri, Gibor S.; Sasselov, Dimitar D.;
Winn, Joshua; Sanchis-Ojeda, Roberto; Christiansen, Jessie; Adams,
Elisabeth; Henze, Christopher; Dupree, Andrea; Fabrycky, Daniel C.;
Fortney, Jonathan J.; Tarter, Jill; Holman, Matthew J.; Tenenbaum,
Peter; Shporer, Avi; Lucas, Philip W.; Welsh, William F.; Orosz,
Jerome A.; Bedding, T. R.; Campante, T. L.; Davies, G. R.; Elsworth,
Y.; Handberg, R.; Hekker, S.; Karoff, C.; Kawaler, S. D.; Lund,
M. N.; Lundkvist, M.; Metcalfe, T. S.; Miglio, A.; Silva Aguirre, V.;
Stello, D.; White, T. R.; Boss, Alan; Devore, Edna; Gould, Alan; Prsa,
Andrej; Agol, Eric; Barclay, Thomas; Coughlin, Jeff; Brugamyer, Erik;
Mullally, Fergal; Quintana, Elisa V.; Still, Martin; Thompson, Susan
E.; Morrison, David; Twicken, Joseph D.; Désert, Jean-Michel; Carter,
Josh; Crepp, Justin R.; Hébrard, Guillaume; Santerne, Alexandre;
Moutou, Claire; Sobeck, Charlie; Hudgins, Douglas; Haas, Michael R.;
Robertson, Paul; Lillo-Box, Jorge; Barrado, David
2014ApJS..210...20M Altcode: 2014arXiv1401.4195M
We report on the masses, sizes, and orbits of the planets orbiting
22 Kepler stars. There are 49 planet candidates around these stars,
including 42 detected through transits and 7 revealed by precise
Doppler measurements of the host stars. Based on an analysis of the
Kepler brightness measurements, along with high-resolution imaging and
spectroscopy, Doppler spectroscopy, and (for 11 stars) asteroseismology,
we establish low false-positive probabilities (FPPs) for all of the
transiting planets (41 of 42 have an FPP under 1%), and we constrain
their sizes and masses. Most of the transiting planets are smaller
than three times the size of Earth. For 16 planets, the Doppler
signal was securely detected, providing a direct measurement of the
planet's mass. For the other 26 planets we provide either marginal mass
measurements or upper limits to their masses and densities; in many
cases we can rule out a rocky composition. We identify six planets
with densities above 5 g cm<SUP>-3</SUP>, suggesting a mostly rocky
interior for them. Indeed, the only planets that are compatible with a
purely rocky composition are smaller than ~2 R <SUB>⊕</SUB>. Larger
planets evidently contain a larger fraction of low-density material (H,
He, and H<SUB>2</SUB>O). <P />Based in part on observations obtained
at the W. M. Keck Observatory, which is operated by the University of
California and the California Institute of Technology.
---------------------------------------------------------
Title: Exploring Stellar Populations and Asteroseismology with APOGEE
and Kepler
Authors: Epstein, Courtney R.; Elsworth, Y. P.; Shetrone, M. D.;
Mosser, B.; Tayar, J.; Harding, P.; Pinsonneault, M. H.; Silva Aguirre,
V.; Basu, S.; Bizyaev, D.; Bedding, T.; Chaplin, W. J.; Garcia, R.;
Garcia Perez, A.; Hearty, F.; Hekker, S.; Huber, D.; Ivans, I. I.;
Majewski, S.; Mathur, S.; Serenelli, A.; Schiavon, R. P.; Schoenrich,
R.; Sobeck, J.; Zasowski, G.
2014AAS...22340304E Altcode:
Accurate measurements of fundamental stellar properties are vital
for improving our understanding of stellar populations and galactic
evolution. Asteroseismology makes possible precise measurements of
stellar mass, radius, and surface gravity. Combining these asteroseismic
measurements with spectroscopic temperatures and abundances enables
the derivation of precise ages for field stars. To achieve that goal,
two complementary surveys, the Apache Point Observatory Galactic
Evolution Experiment (APOGEE) and the Kepler Asteroseismic Science
Consortium (KASC), are working together to characterize the fundamental
properties thousands of red giants in the Kepler field. As a first step
toward deriving ages, asteroseismic masses need to be calibrated with
independent mass constraints. I will describe how we use a sample of
halo stars to test asteroseismic results in the metal-poor regime. The
age of halo stars is well constrained by many lines of evidence,
including isochrones fits to globular clusters, white dwarf cooling
sequence, and the radioactive decay of uranium and thorium. These age
constraints translate to a strict prior on halo star masses. I show that
the seismic masses are sensitive to the method used to derive seismic
parameters and to published, theoretically motivated corrections. The
implications of this work for stellar populations are discussed.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Asteroseismic study of solar-type
stars (Chaplin+, 2014)
Authors: Chaplin, W. J.; Basu, S.; Huber, D.; Serenelli, A.;
Casagrande, L.; Silva Aguirre, V.; Ball, W. H.; Creevey, O. L.;
Gizon, L.; Handberg, R.; Karoff, C.; Lutz, R.; Marques, J. P.;
Miglio, A.; Stello, D.; Suran, M. D.; Pricopi, D.; Metcalfe, T. S.;
Monteiro, M. J. P. F. G.; Molenda-Zakowicz, J.; Appourchaux, T.;
Christensen-Dalsgaard, J.; Elsworth, Y.; Garcia, R. A.; Houdek, G.;
Kjeldsen, H.; Bonanno, A.; Campante, T. L.; Corsaro, E.; Gaulme, P.;
Hekker, S.; Mathur, S.; Mosser, B.; Regulo, C.; Salabert, D.
2014yCat..22100001C Altcode:
During the first 10 months of science operations more than 2000
solar-type stars were selected by the Kepler Asteroseismic Science
Consortium (KASC) to be observed as part of an asteroseismic survey
of the Sun-like population in the Kepler field of view. Solar-like
oscillations were detected by Kepler in more than 500 stars (Chaplin
et al. 2011Sci...332..213C), and from these data robust global or
average asteroseismic parameters were determined for all targets in the
sample. These asteroseismic parameters allow us to estimate fundamental
properties of the stars. In this paper we present stellar properties
- namely masses, radii, surface gravities, mean densities and ages -
of this asteroseismic sample of main-sequence and subgiant stars. <P
/>(5 data files).
---------------------------------------------------------
Title: Asteroseismic Fundamental Properties of Solar-type Stars
Observed by the NASA Kepler Mission
Authors: Chaplin, W. J.; Basu, S.; Huber, D.; Serenelli, A.;
Casagrande, L.; Silva Aguirre, V.; Ball, W. H.; Creevey, O. L.;
Gizon, L.; Handberg, R.; Karoff, C.; Lutz, R.; Marques, J. P.;
Miglio, A.; Stello, D.; Suran, M. D.; Pricopi, D.; Metcalfe, T. S.;
Monteiro, M. J. P. F. G.; Molenda-Żakowicz, J.; Appourchaux, T.;
Christensen-Dalsgaard, J.; Elsworth, Y.; García, R. A.; Houdek, G.;
Kjeldsen, H.; Bonanno, A.; Campante, T. L.; Corsaro, E.; Gaulme, P.;
Hekker, S.; Mathur, S.; Mosser, B.; Régulo, C.; Salabert, D.
2014ApJS..210....1C Altcode: 2013arXiv1310.4001C
We use asteroseismic data obtained by the NASA Kepler mission to
estimate the fundamental properties of more than 500 main-sequence and
sub-giant stars. Data obtained during the first 10 months of Kepler
science operations were used for this work, when these solar-type
targets were observed for one month each in survey mode. Stellar
properties have been estimated using two global asteroseismic parameters
and complementary photometric and spectroscopic data. Homogeneous sets
of effective temperatures, T <SUB>eff</SUB>, were available for the
entire ensemble from complementary photometry; spectroscopic estimates
of T <SUB>eff</SUB> and [Fe/H] were available from a homogeneous
analysis of ground-based data on a subset of 87 stars. We adopt
a grid-based analysis, coupling six pipeline codes to 11 stellar
evolutionary grids. Through use of these different grid-pipeline
combinations we allow implicitly for the impact on the results of
stellar model dependencies from commonly used grids, and differences
in adopted pipeline methodologies. By using just two global parameters
as the seismic inputs we are able to perform a homogenous analysis
of all solar-type stars in the asteroseismic cohort, including many
targets for which it would not be possible to provide robust estimates
of individual oscillation frequencies (due to a combination of low
signal-to-noise ratio and short dataset lengths). The median final
quoted uncertainties from consolidation of the grid-based analyses
are for the full ensemble (spectroscopic subset) approximately 10.8%
(5.4%) in mass, 4.4% (2.2%) in radius, 0.017 dex (0.010 dex) in log g,
and 4.3% (2.8%) in mean density. Around 36% (57%) of the stars have
final age uncertainties smaller than 1 Gyr. These ages will be useful
for ensemble studies, but should be treated carefully on a star-by-star
basis. Future analyses using individual oscillation frequencies will
offer significant improvements on up to 150 stars, in particular for
estimates of the ages, where having the individual frequency data is
most important.
---------------------------------------------------------
Title: Asteroseismic Analysis of the CoRoT Target HD 169392
Authors: Mathur, S.; Bruntt, H.; Catala, C.; Benomar, O.; Davies,
G. R.; García, R. A.; Salabert, D.; Ballot, J.; Mosser, B.; Régulo,
C.; Chaplin, W. J.; Elsworth, Y.; Handberg, R.; Hekker, S.; Mantegazza,
L.; Michel, E.; Poretti, E.; Rainer, M.; Roxburgh, I. W.; Samadi,
R.; Steslicki, M.; Uytterhoeven, K.; Verner, G. A.; Auvergne, M.;
Baglin, A.; Barceló Forteza, S.; Baudin, F.; Roca Cortés, T.
2013ASPC..479..155M Altcode: 2013arXiv1308.0647M
The satellite CoRoT (Convection, Rotation, and planetary Transits)
has provided high-quality data for almost six years. We show here
the asteroseismic analysis and modeling of HD 169392A, which belongs
to a weakly-bound binary system as the distance between the two
components is ∼4250 au. The main component, HD 169392A, is a G0 IV
star with a magnitude of 7.50 while the second component is a G0 V -
G2 IV star with a magnitude of 8.98. This analysis focuses on the
main component, as the secondary is too faint for the measurement of
seismic parameters. A complete modeling has been possible thanks to
complementary spectroscopic observations from HARPS (High Accuracy
Radial Velocity Planet Searcher), providing T<SUB>eff</SUB> = 5985 ±
60 K, log g = 3.96 ± 0.07, and [Fe/H] = -0.04 ± 0.10.
---------------------------------------------------------
Title: Challenges and Opportunities for Ground-based Helioseismic
Observations
Authors: Chaplin, W. J.
2013ASPC..478..101C Altcode:
I summarize the current status of ground-based helioseismic
observations, in particular the two operational networks GONG and
BiSON. I then discuss requirements for continued and future ground-based
observations based on key science drivers, finishing with a discussion
of SPRING, a proposed future high-spatial-resolution network that would
provide helioseismic data and a broad range of synoptic data products.
---------------------------------------------------------
Title: Comparing the Internal Structure of the Sun During the Cycle
23 and Cycle 24 Minima
Authors: Basu, S.; Broomhall, A. -M.; Chaplin, W. J.; Elsworth, Y.;
Davies, G. R.; Schou, J.; Larson, T. P.
2013ASPC..478..161B Altcode:
The Birmingham Solar-Oscillations Network (BiSON) has been collecting
helioseismic data for the last three solar cycles. We use these data to
determine whether the internal properties of the Sun during the minimum
preceding cycle 24 was different compared to that preceding cycle 23.
---------------------------------------------------------
Title: Mode Line Widths in Red-Giant Stars
Authors: Baudin, F.; Elsworth, Y.; Hekker, S.; Kallinger, T.; Stello,
D.; Mosser, B.; Appourchaux, T.; Belkacem, K.; Benomar, O.; Barban,
C.; Chaplin, W. J.
2013ASPC..479..179B Altcode:
Mode line widths and amplitudes provide valuable information on stellar
oscillation excitation and damping, and thus on physical processes such
as convection, radiative losses and convection/pulsation coupling. We
present preliminary results for mode line widths obtained by fitting
mode spectra from Kepler observations. The difficulties of such fitting
are discussed as well as these preliminary estimates in the context
of models.
---------------------------------------------------------
Title: Calibrations of Atmospheric Parameters Obtained from the
First Year of SDSS-III APOGEE Observations
Authors: Mészáros, Sz.; Holtzman, J.; García Pérez, A. E.; Allende
Prieto, C.; Schiavon, R. P.; Basu, S.; Bizyaev, D.; Chaplin, W. J.;
Chojnowski, S. D.; Cunha, K.; Elsworth, Y.; Epstein, C.; Frinchaboy,
P. M.; García, R. A.; Hearty, F. R.; Hekker, S.; Johnson, J. A.;
Kallinger, T.; Koesterke, L.; Majewski, S. R.; Martell, S. L.; Nidever,
D.; Pinsonneault, M. H.; O'Connell, J.; Shetrone, M.; Smith, V. V.;
Wilson, J. C.; Zasowski, G.
2013AJ....146..133M Altcode: 2013arXiv1308.6617M
The Sloan Digital Sky Survey III (SDSS-III) Apache Point Observatory
Galactic Evolution Experiment (APOGEE) is a three-year survey that is
collecting 10<SUP>5</SUP> high-resolution spectra in the near-IR across
multiple Galactic populations. To derive stellar parameters and chemical
compositions from this massive data set, the APOGEE Stellar Parameters
and Chemical Abundances Pipeline (ASPCAP) has been developed. Here,
we describe empirical calibrations of stellar parameters presented
in the first SDSS-III APOGEE data release (DR10). These calibrations
were enabled by observations of 559 stars in 20 globular and open
clusters. The cluster observations were supplemented by observations of
stars in NASA's Kepler field that have well determined surface gravities
from asteroseismic analysis. We discuss the accuracy and precision
of the derived stellar parameters, considering especially effective
temperature, surface gravity, and metallicity; we also briefly discuss
the derived results for the abundances of the α-elements, carbon, and
nitrogen. Overall, we find that ASPCAP achieves reasonably accurate
results for temperature and metallicity, but suffers from systematic
errors in surface gravity. We derive calibration relations that bring
the raw ASPCAP results into better agreement with independently
determined stellar parameters. The internal scatter of ASPCAP
parameters within clusters suggests that metallicities are measured
with a precision better than 0.1 dex, effective temperatures better
than 150 K, and surface gravities better than 0.2 dex. The understanding
provided by the clusters and Kepler giants on the current accuracy and
precision will be invaluable for future improvements of the pipeline.
---------------------------------------------------------
Title: Stellar Spin-Orbit Misalignment in a Multiplanet System
Authors: Huber, Daniel; Carter, Joshua A.; Barbieri, Mauro; Miglio,
Andrea; Deck, Katherine M.; Fabrycky, Daniel C.; Montet, Benjamin T.;
Buchhave, Lars A.; Chaplin, William J.; Hekker, Saskia; Montalbán,
Josefina; Sanchis-Ojeda, Roberto; Basu, Sarbani; Bedding, Timothy R.;
Campante, Tiago L.; Christensen-Dalsgaard, Jørgen; Elsworth, Yvonne
P.; Stello, Dennis; Arentoft, Torben; Ford, Eric B.; Gilliland, Ronald
L.; Handberg, Rasmus; Howard, Andrew W.; Isaacson, Howard; Johnson,
John Asher; Karoff, Christoffer; Kawaler, Steven D.; Kjeldsen, Hans;
Latham, David W.; Lund, Mikkel N.; Lundkvist, Mia; Marcy, Geoffrey W.;
Metcalfe, Travis S.; Silva Aguirre, Victor; Winn, Joshua N.
2013Sci...342..331H Altcode: 2013arXiv1310.4503H
Stars hosting hot Jupiters are often observed to have high obliquities,
whereas stars with multiple coplanar planets have been seen to have low
obliquities. This has been interpreted as evidence that hot-Jupiter
formation is linked to dynamical disruption, as opposed to planet
migration through a protoplanetary disk. We used asteroseismology to
measure a large obliquity for Kepler-56, a red giant star hosting two
transiting coplanar planets. These observations show that spin-orbit
misalignments are not confined to hot-Jupiter systems. Misalignments
in a broader class of systems had been predicted as a consequence of
torques from wide-orbiting companions, and indeed radial velocity
measurements revealed a third companion in a wide orbit in the
Kepler-56 system.
---------------------------------------------------------
Title: Kepler-63b: A Giant Planet in a Polar Orbit around a Young
Sun-like Star
Authors: Sanchis-Ojeda, Roberto; Winn, Joshua N.; Marcy, Geoffrey W.;
Howard, Andrew W.; Isaacson, Howard; Johnson, John Asher; Torres,
Guillermo; Albrecht, Simon; Campante, Tiago L.; Chaplin, William J.;
Davies, Guy R.; Lund, Mikkel N.; Carter, Joshua A.; Dawson, Rebekah
I.; Buchhave, Lars A.; Everett, Mark E.; Fischer, Debra A.; Geary,
John C.; Gilliland, Ronald L.; Horch, Elliott P.; Howell, Steve B.;
Latham, David W.
2013ApJ...775...54S Altcode: 2013arXiv1307.8128S
We present the discovery and characterization of a giant planet
orbiting the young Sun-like star Kepler-63 (KOI-63, m <SUB>Kp</SUB>
= 11.6, T <SUB>eff</SUB> = 5576 K, M <SUB>sstarf</SUB> = 0.98
M <SUB>⊙</SUB>). The planet transits every 9.43 days, with
apparent depth variations and brightening anomalies caused by large
starspots. The planet's radius is 6.1 ± 0.2 R <SUB>⊕</SUB>, based
on the transit light curve and the estimated stellar parameters. The
planet's mass could not be measured with the existing radial-velocity
data, due to the high level of stellar activity, but if we assume
a circular orbit, then we can place a rough upper bound of 120
M <SUB>⊕</SUB> (3σ). The host star has a high obliquity (ψ =
104°), based on the Rossiter-McLaughlin effect and an analysis of
starspot-crossing events. This result is valuable because almost all
previous obliquity measurements are for stars with more massive planets
and shorter-period orbits. In addition, the polar orbit of the planet
combined with an analysis of spot-crossing events reveals a large and
persistent polar starspot. Such spots have previously been inferred
using Doppler tomography, and predicted in simulations of magnetic
activity of young Sun-like stars.
---------------------------------------------------------
Title: Tests of the asymptotic large frequency separation of acoustic
oscillations in solar-type and red-giant stars
Authors: Hekker, S.; Elsworth, Y.; Basu, S.; Mazumdar, A.; Silva
Aguirre, V.; Chaplin, W. J.
2013MNRAS.434.1668H Altcode: 2013arXiv1306.4323H; 2013MNRAS.tmp.1776H
Asteroseismology, i.e. the study of the internal structures of
stars via their global oscillations, is a valuable tool to obtain
stellar parameters such as mass, radius, surface gravity and mean
density. These parameters can be obtained using certain scaling
relations which are based on an asymptotic approximation. Usually the
observed oscillation parameters are assumed to follow these scaling
relations. Recently, it has been questioned whether this is a valid
approach, i.e. whether the order of the observed oscillation modes is
high enough to be approximated with an asymptotic theory. In this work,
we use stellar models to investigate whether the differences between
observable oscillation parameters and their asymptotic estimates are
indeed significant. We compute the asymptotic values directly from the
stellar models and derive the observable values from adiabatic pulsation
calculations of the same models. We find that the extent to which the
atmosphere is included in the models is a key parameter. Considering
a larger extension of the atmosphere beyond the photosphere reduces
the difference between the asymptotic and observable values of the
large frequency separation. Therefore, we conclude that the currently
suggested discrepancies in the scaling relations might have been
overestimated. Hence, based on the results presented here we believe
that the suggestions of Mosser et al. should not be followed without
careful consideration.
---------------------------------------------------------
Title: Kepler White Paper: Asteroseismology of Solar-Like Oscillators
in a 2-Wheel Mission
Authors: Chaplin, W. J; Kjeldsen, H.; Christensen-Dalsgaard, J.;
Gilliland, R. L.; Kawaler, S. D.; Basu, S.; De Ridder, J.; Huber, D.;
Arentoft, T.; Schou, J.; Garcia, R. A.; Metcalfe, T. S.; Brogaard, K.;
Campante, T. L.; Elsworth, Y.; Miglio, A.; Appourchaux, T.; Bedding,
T. R.; Hekker, S.; Houdek, G.; Karoff, C.; Molenda-Zakowicz, J.;
Monteiro, M. J. P. F. G.; Silva Aguirre, V.; Stello, D.; Ball, W.;
Beck, P. G.; Birch, A. C.; Buzasi, D. L.; Casagrande, L.; Cellier,
T.; Corsaro, E.; Creevey, O. L.; Davies, G. R.; Deheuvels, S.; Dogan,
G.; Gizon, L.; Grundahl, F.; Guzik, J.; Handberg, R.; Jimenez, A.;
Kallinger, T.; Lund, M. N.; Lundkvist, M.; Mathis, S.; Mathur, S.;
Mazumdar, A.; Mosser, B.; Neiner, C.; Nielsen, M. B.; Palle, P. L.;
Pinsonneault, M. H.; Salabert, D.; Serenelli, A. M.; Shunker, H.;
White, T. R.
2013arXiv1309.0702C Altcode:
We comment on the potential for continuing asteroseismology of
solar-type and red-giant stars in a 2-wheel Kepler Mission. Our main
conclusion is that by targeting stars in the ecliptic it should be
possible to perform high-quality asteroseismology, as long as favorable
scenarios for 2-wheel pointing performance are met. Targeting the
ecliptic would potentially facilitate unique science that was not
possible in the nominal Mission, notably from the study of clusters
that are significantly brighter than those in the Kepler field. Our
conclusions are based on predictions of 2-wheel observations made by
a space photometry simulator, with information provided by the Kepler
Project used as input to describe the degraded pointing scenarios. We
find that elevated levels of frequency-dependent noise, consistent with
the above scenarios, would have a significant negative impact on our
ability to continue asteroseismic studies of solar-like oscillators in
the Kepler field. However, the situation may be much more optimistic
for observations in the ecliptic, provided that pointing resets of the
spacecraft during regular desaturations of the two functioning reaction
wheels are accurate at the < 1 arcsec level. This would make it
possible to apply a post-hoc analysis that would recover most of the
lost photometric precision. Without this post-hoc correction---and the
accurate re-pointing it requires---the performance would probably be
as poor as in the Kepler-field case. Critical to our conclusions for
both fields is the assumed level of pointing noise (in the short-term
jitter and the longer-term drift). We suggest that further tests will
be needed to clarify our results once more detail and data on the
expected pointing performance becomes available, and we offer our
assistance in this work.
---------------------------------------------------------
Title: Erratum: "A Revised Effective Temperature Scale for the
Kepler Input Catalog" <A href="/abs/2012ApJS..199...30P">(2012,
ApJS, 199, 30)</A>
Authors: Pinsonneault, Marc H.; An, Deokkeun; Molenda-Żakowicz,
Joanna; Chaplin, William J.; Metcalfe, Travis S.; Bruntt, Hans
2013ApJS..208...12P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Asteroseismic surface gravity for evolved stars
Authors: Hekker, S.; Elsworth, Y.; Mosser, B.; Kallinger, T.; Basu,
S.; Chaplin, W. J.; Stello, D.
2013A&A...556A..59H Altcode: 2013arXiv1305.6586H
Context. Asteroseismic surface gravity values can be important for
determining spectroscopic stellar parameters. The independent log
(g) value from asteroseismology can be used as a fixed value in
the spectroscopic analysis to reduce uncertainties because log
(g) and effective temperature cannot be determined independently
from spectra. Since 2012, a combined analysis of seismically and
spectroscopically derived stellar properties has been ongoing for
a large survey with SDSS/APOGEE and Kepler. Therefore, knowledge
of any potential biases and uncertainties in asteroseismic log (g)
values is now becoming important. <BR /> Aims: The seismic parameter
needed to derive log (g) is the frequency of maximum oscillation power
(ν<SUB>max</SUB>). Here, we investigate the influence on the derived
log (g) values of ν<SUB>max</SUB> derived with different methods. The
large frequency separation between modes of the same degree and
consecutive radial orders (Δν) is often used as an additional
constraint for determining log (g). Additionally, we checked the
influence of small corrections applied to Δν on the derived values
of log (g). <BR /> Methods: We use methods extensively described in the
literature to determine ν<SUB>max</SUB> and Δν together with seismic
scaling relations and grid-based modelling to derive log (g). <BR
/> Results: We find that different approaches to derive oscillation
parameters give results for log (g) with small, but different, biases
for red-clump and red-giant-branch stars. These biases are well within
the quoted uncertainties of ~0.01 dex (cgs). Corrections suggested
in the literature to the Δν scaling relation have no significant
effect on log (g); however, somewhat unexpectedly, method specific
solar reference values induce biases close to the uncertainties,
which is not the case when canonical solar reference values are used.
---------------------------------------------------------
Title: Seismic constraints on rotation of Sun-like star and mass
of exoplanet
Authors: Gizon, L.; Ballot, J.; Michel, E.; Stahn, T.; Vauclair, G.;
Bruntt, H.; Quirion, P. -O.; Benomar, O.; Vauclair, S.; Appourchaux,
T.; Auvergne, M.; Baglin, A.; Barban, C.; Baudin, F.; Bazot, M.;
Campante, T.; Catala, C.; Chaplin, W.; Creevey, O.; Deheuvels, S.;
Dolez, N.; Elsworth, Y.; Garcia, R.; Gaulme, P.; Mathis, S.; Mathur,
S.; Mosser, B.; Regulo, C.; Roxburgh, I.; Salabert, D.; Samadi, R.;
Sato, K.; Verner, G.; Hanasoge, S.; Sreenivasan, K. R.
2013PNAS..11013267G Altcode: 2013arXiv1308.4352G
Rotation is thought to drive cyclic magnetic activity in the Sun
and Sun-like stars. Stellar dynamos, however, are poorly understood
owing to the scarcity of observations of rotation and magnetic fields
in stars. Here, inferences are drawn on the internal rotation of a
distant Sun-like star by studying its global modes of oscillation. We
report asteroseismic constraints imposed on the rotation rate and the
inclination of the spin axis of the Sun-like star HD 52265, a principal
target observed by the CoRoT satellite that is known to host a planetary
companion. These seismic inferences are remarkably consistent with an
independent spectroscopic observation (rotational line broadening)
and with the observed rotation period of star spots. Furthermore,
asteroseismology constrains the mass of exoplanet HD 52265b. Under
the standard assumption that the stellar spin axis and the axis of the
planetary orbit coincide, the minimum spectroscopic mass of the planet
can be converted into a true mass of 1.85 (+0.52,-0.42) M_Jupiter,
which implies that it is a planet, not a brown dwarf.
---------------------------------------------------------
Title: Asteroseismology of Solar-Type and Red-Giant Stars
Authors: Chaplin, William J.; Miglio, Andrea
2013ARA&A..51..353C Altcode: 2013arXiv1303.1957C
We are entering a golden era for stellar physics driven by satellite
and telescope observations of unprecedented quality and scope. New
insights on stellar evolution and stellar interiors physics are
being made possible by asteroseismology, the study of stars by the
observation of natural, resonant oscillations. Asteroseismology is
proving to be particularly significant for the study of solar-type
and red-giant stars. These stars show rich spectra of solar-like
oscillations, which are excited and intrinsically damped by turbulence
in the outermost layers of the convective envelopes. In this review we
discuss the current state of the field, with a particular emphasis on
recent advances provided by the Kepler and COROT (Convection, Rotation
& Planetary Transits) space missions and the wider significance
to astronomy of the results from asteroseismology, such as stellar
populations studies and exoplanet studies.
---------------------------------------------------------
Title: Sounding stellar cycles with Kepler - II. Ground-based
observations
Authors: Karoff, C.; Metcalfe, T. S.; Chaplin, W. J.; Frandsen, S.;
Grundahl, F.; Kjeldsen, H.; Christensen-Dalsgaard, J.; Nielsen, M. B.;
Frimann, S.; Thygesen, A. O.; Arentoft, T.; Amby, T. M.; Sousa, S. G.;
Buzasi, D. L.
2013MNRAS.433.3227K Altcode: 2013arXiv1306.3306K; 2013MNRAS.tmp.1612K
We have monitored 20 Sun-like stars in the Kepler field-of-view for
excess flux with the Fibre-fed Echelle Spectrograph on the Nordic
Optical Telescope since the launch of Kepler spacecraft in 2009. These
20 stars were selected based on their asteroseismic properties to
sample the parameter space (effective temperature, surface gravity,
activity level, etc.) around the Sun. Though the ultimate goal is
to improve stellar dynamo models, we focus the present paper on the
combination of space-based and ground-based observations that can
be used to test the age-rotation-activity relations. In this paper
we describe the considerations behind the selection of these 20
Sun-like stars and present an initial asteroseismic analysis, which
includes stellar age estimates. We also describe the observations
from the Nordic Optical Telescope and present mean values of measured
excess fluxes. These measurements are combined with estimates of the
rotation periods obtained from a simple analysis of the modulation
in photometric observations from Kepler caused by starspots, and
asteroseismic determinations of stellar ages, to test relations between
age, rotation and activity.
---------------------------------------------------------
Title: "Rapid Fire" Spectroscopy of Kepler Solar-Like Oscillators
Authors: Thygesen, A. O.; Bruntt, H.; Chaplin, W. J.; Basu, S.
2013aspm.confE..25T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Low-degree multi-spectral p-mode fitting
Authors: Howe, R.; Broomhall, A. -M.; Chaplin, W. J.; Elsworth, Y.;
Jain, K.
2013JPhCS.440a2011H Altcode:
We combine unresolved-Sun velocity and intensity observations at
multiple wavelengths from the Helioseismic and Magnetic Imager and
Atmospheric Imaging Array onboard the Solar Dynamics Observatory to
investigate the possibility of multi-spectral mode-frequency estimation
at low spherical harmonic degree. We test a simple multi-spectral
algorithm using a common line width and frequency for each mode and a
separate amplitude, background and asymmetry parameter, and compare the
results with those from fits to the individual spectra. The preliminary
results suggest that this approach may provide a more stable fit than
using the observables separately.
---------------------------------------------------------
Title: Stellar Ages and Convective Cores in Field Main-sequence Stars:
First Asteroseismic Application to Two Kepler Targets
Authors: Silva Aguirre, V.; Basu, S.; Brandão, I. M.;
Christensen-Dalsgaard, J.; Deheuvels, S.; Doğan, G.; Metcalfe, T. S.;
Serenelli, A. M.; Ballot, J.; Chaplin, W. J.; Cunha, M. S.; Weiss,
A.; Appourchaux, T.; Casagrande, L.; Cassisi, S.; Creevey, O. L.;
García, R. A.; Lebreton, Y.; Noels, A.; Sousa, S. G.; Stello, D.;
White, T. R.; Kawaler, S. D.; Kjeldsen, H.
2013ApJ...769..141S Altcode: 2013arXiv1304.2772S
Using asteroseismic data and stellar evolution models we obtain the
first detection of a convective core in a Kepler field main-sequence
star, putting a stringent constraint on the total size of the mixed
zone and showing that extra mixing beyond the formal convective
boundary exists. In a slightly less massive target the presence of
a convective core cannot be conclusively discarded, and thus its
remaining main-sequence lifetime is uncertain. Our results reveal
that best-fit models found solely by matching individual frequencies
of oscillations corrected for surface effects do not always properly
reproduce frequency combinations. Moreover, slightly different criteria
to define what the best-fit model is can lead to solutions with similar
global properties but very different interior structures. We argue that
the use of frequency ratios is a more reliable way to obtain accurate
stellar parameters, and show that our analysis in field main-sequence
stars can yield an overall precision of 1.5%, 4%, and 10% in radius,
mass, and age, respectively. We compare our results with those obtained
from global oscillation properties, and discuss the possible sources of
uncertainties in asteroseismic stellar modeling where further studies
are still needed.
---------------------------------------------------------
Title: The Sun-as-a-star observations: GOLF & VIRGO on SoHO,
and BiSON network
Authors: García, R. A.; Davies, G. R.; Jiménez, A.; Ballot, J.;
Mathur, S.; Salabert, D.; Chaplin, W. J.; Elsworth, Y.; Régulo, C.;
Turck-Chièze, S.
2013JPhCS.440a2040G Altcode: 2013arXiv1301.6934G
Sun-as-a-star observations are very important for the study of the
conditions within the Sun and in particular for the deep interior where
higher degree modes do not penetrate. They are also of significance
in this era of dramatic advances in stellar asteroseismology as they
are comparable to those measured in other stars by asteroseismic
missions such as CoRoT, Kepler, and MOST. More than 17 years of
continuous measurements of SoHO and more than 30 years of BiSON
observations provide very long data sets of uninterrupted helioseismic
observations. In this work, we discuss the present status of all these
facilities that continue to provide state-of-the-art measurements and
invaluable data to improve our knowledge of the deepest layers of the
Sun and its structural changes during the activity cycle.
---------------------------------------------------------
Title: A large sample of calibration stars for Gaia: log g from
Kepler and CoRoT fields
Authors: Creevey, O. L.; Thévenin, F.; Basu, S.; Chaplin, W. J.;
Bigot, L.; Elsworth, Y.; Huber, D.; Monteiro, M. J. P. F. G.;
Serenelli, A.
2013MNRAS.431.2419C Altcode: 2013arXiv1302.7158C
Asteroseismic data can be used to determine stellar surface gravities
with precisions of <0.05 dex by using the global seismic quantities
<Δν> and ν<SUB>max</SUB> along with standard atmospheric data
such as T<SUB>eff</SUB> and metallicity. Surface gravity is also one
of the four stellar properties to be derived by automatic analyses for
one billion stars from Gaia data (workpackage GSP_PHOT). In this paper,
we explore seismic data from main-sequence F, G, K stars (solar-like
stars) observed by the Kepler spacecraft as a potential calibration
source for the methods that Gaia will use for object characterization
(log g). We calculate log g for some bright nearby stars for which
radii and masses are known (e.g. from interferometry or binaries),
and using their global seismic quantities in a grid-based method,
we determine an asteroseismic log g to within 0.01 dex of the direct
calculation, thus validating the accuracy of our method. We also find
that errors in adopted atmospheric parameters (mainly [Fe/H]) can,
however, cause systematic errors of the order of 0.02 dex. We then
apply our method to a list of 40 stars to deliver precise values of
surface gravity, i.e. uncertainties of the order of 0.02 dex, and we
find agreement with recent literature values. Finally, we explore the
typical precision that we expect in a sample of more than 400 Kepler
stars which have their global seismic quantities measured. We find a
mean uncertainty (precision) of the order of better than 0.02 dex in
log g over the full explored range 3.8 < log g < 4.6, with the
mean value varying only with stellar magnitude (0.01-0.02 dex). We
study sources of systematic errors in log g and find possible biases
of the order of 0.04 dex, independent of log g and magnitude, which
accounts for errors in the T<SUB>eff</SUB> and [Fe/H] measurements,
as well as from using a different grid-based method. We conclude that
Kepler stars provide a wealth of reliable information that can help
to calibrate methods that Gaia will use, in particular, for source
characterization with GSP_PHOT, where excellent precision (small
uncertainties) and accuracy in log g is obtained from seismic data.
---------------------------------------------------------
Title: Erratum: A sub-Mercury-sized exoplanet
Authors: Barclay, Thomas; Rowe, Jason F.; Lissauer, Jack J.; Huber,
Daniel; Fressin, François; Howell, Steve B.; Bryson, Stephen
T.; Chaplin, William J.; Désert, Jean-Michel; Lopez, Eric D.;
Marcy, Geoffrey W.; Mullally, Fergal; Ragozzine, Darin; Torres,
Guillermo; Adams, Elisabeth R.; Agol, Eric; Barrado, David; Basu,
Sarbani; Bedding, Timothy R.; Buchhave, Lars A.; Charbonneau, David;
Christiansen, Jessie L.; Christensen-Dalsgaard, Jørgen; Ciardi, David;
Cochran, William D.; Dupree, Andrea K.; Elsworth, Yvonne; Everett,
Mark; Fischer, Debra A.; Ford, Eric B.; Fortney, Jonathan J.; Geary,
John C.; Haas, Michael R.; Handberg, Rasmus; Hekker, Saskia; Henze,
Christopher E.; Horch, Elliott; Howard, Andrew W.; Hunter, Roger C.;
Isaacson, Howard; Jenkins, Jon M.; Karoff, Christoffer; Kawaler,
Steven D.; Kjeldsen, Hans; Klaus, Todd C.; Latham, David W.; Li,
Jie; Lillo-Box, Jorge; Lund, Mikkel N.; Lundkvist, Mia; Metcalfe,
Travis S.; Miglio, Andrea; Morris, Robert L.; Quintana, Elisa V.;
Stello, Dennis; Smith, Jeffrey C.; Still, Martin; Thompson, Susan E.
2013Natur.496..252B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Fundamental Properties of Kepler Planet-candidate Host Stars
using Asteroseismology
Authors: Huber, Daniel; Chaplin, William J.; Christensen-Dalsgaard,
Jørgen; Gilliland, Ronald L.; Kjeldsen, Hans; Buchhave, Lars A.;
Fischer, Debra A.; Lissauer, Jack J.; Rowe, Jason F.; Sanchis-Ojeda,
Roberto; Basu, Sarbani; Handberg, Rasmus; Hekker, Saskia; Howard,
Andrew W.; Isaacson, Howard; Karoff, Christoffer; Latham, David W.;
Lund, Mikkel N.; Lundkvist, Mia; Marcy, Geoffrey W.; Miglio, Andrea;
Silva Aguirre, Victor; Stello, Dennis; Arentoft, Torben; Barclay,
Thomas; Bedding, Timothy R.; Burke, Christopher J.; Christiansen,
Jessie L.; Elsworth, Yvonne P.; Haas, Michael R.; Kawaler, Steven D.;
Metcalfe, Travis S.; Mullally, Fergal; Thompson, Susan E.
2013ApJ...767..127H Altcode: 2013arXiv1302.2624H
We have used asteroseismology to determine fundamental properties for
66 Kepler planet-candidate host stars, with typical uncertainties of
3% and 7% in radius and mass, respectively. The results include new
asteroseismic solutions for four host stars with confirmed planets
(Kepler-4, Kepler-14, Kepler-23 and Kepler-25) and increase the
total number of Kepler host stars with asteroseismic solutions to
77. A comparison with stellar properties in the planet-candidate
catalog by Batalha et al. shows that radii for subgiants and giants
obtained from spectroscopic follow-up are systematically too low by
up to a factor of 1.5, while the properties for unevolved stars are
in good agreement. We furthermore apply asteroseismology to confirm
that a large majority of cool main-sequence hosts are indeed dwarfs
and not misclassified giants. Using the revised stellar properties,
we recalculate the radii for 107 planet candidates in our sample, and
comment on candidates for which the radii change from a previously
giant-planet/brown-dwarf/stellar regime to a sub-Jupiter size or
vice versa. A comparison of stellar densities from asteroseismology
with densities derived from transit models in Batalha et al. assuming
circular orbits shows significant disagreement for more than half of
the sample due to systematics in the modeled impact parameters or
due to planet candidates that may be in eccentric orbits. Finally,
we investigate tentative correlations between host-star masses and
planet-candidate radii, orbital periods, and multiplicity, but caution
that these results may be influenced by the small sample size and
detection biases.
---------------------------------------------------------
Title: The SOAPS project - Spin-orbit alignment of planetary
systems. Exoplanets' evolution histories in systems with different
architectures
Authors: Faedi, F.; Gómez Maqueo Chew, Y.; Fossati, L.; Pollacco,
D.; McQuillan, A.; Hebb, L.; Chaplin, W. J.; Aigrain, S.
2013EPJWC..4702001F Altcode:
The wealth of information rendered by Kepler planets and planet
candidates is indispensable for statistically significant studies
of distinct planet populations, in both single and multiple
systems. Empirical evidences suggest that Kepler's planet population
shows different physical properties as compared to the bulk of
known exoplanets. The SOAPS project, aims to shed light on Kepler's
planets formation, their migration and architecture. By measuring v
sini accurately for Kepler hosts with rotation periods measured from
their high-precision light curves, we will assess the alignment of the
planetary orbit with respect to the stellar spin axis. This degree of
alignment traces the formation history and evolution of the planetary
systems, and thus, allows to distinguish between different proposed
migration theories. SOAPS will increase by a factor of 2 the number
of spin-orbit alignment measurements pushing the parameters space down
to the SuperEarth domain. Here we present our preliminary results.
---------------------------------------------------------
Title: Asteroseismic Determination of Obliquities of the Exoplanet
Systems Kepler-50 and Kepler-65
Authors: Chaplin, W. J.; Sanchis-Ojeda, R.; Campante, T. L.; Handberg,
R.; Stello, D.; Winn, J. N.; Basu, S.; Christensen-Dalsgaard, J.;
Davies, G. R.; Metcalfe, T. S.; Buchhave, L. A.; Fischer, D. A.;
Bedding, T. R.; Cochran, W. D.; Elsworth, Y.; Gilliland, R. L.; Hekker,
S.; Huber, D.; Isaacson, H.; Karoff, C.; Kawaler, S. D.; Kjeldsen,
H.; Latham, D. W.; Lund, M. N.; Lundkvist, M.; Marcy, G. W.; Miglio,
A.; Barclay, T.; Lissauer, J. J.
2013ApJ...766..101C Altcode: 2013arXiv1302.3728C
Results on the obliquity of exoplanet host stars—the angle between
the stellar spin axis and the planetary orbital axis—provide important
diagnostic information for theories describing planetary formation. Here
we present the first application of asteroseismology to the problem
of stellar obliquity determination in systems with transiting planets
and Sun-like host stars. We consider two systems observed by the NASA
Kepler mission which have multiple transiting small (super-Earth sized)
planets: the previously reported Kepler-50 and a new system, Kepler-65,
whose planets we validate in this paper. Both stars show rich spectra
of solar-like oscillations. From the asteroseismic analysis we find
that each host has its rotation axis nearly perpendicular to the line
of sight with the sines of the angles constrained at the 1σ level to
lie above 0.97 and 0.91, respectively. We use statistical arguments to
show that coplanar orbits are favored in both systems, and that the
orientations of the planetary orbits and the stellar rotation axis
are correlated.
---------------------------------------------------------
Title: Kepler-68: Three Planets, One with a Density between that of
Earth and Ice Giants
Authors: Gilliland, Ronald L.; Marcy, Geoffrey W.; Rowe, Jason F.;
Rogers, Leslie; Torres, Guillermo; Fressin, Francois; Lopez, Eric
D.; Buchhave, Lars A.; Christensen-Dalsgaard, Jørgen; Désert,
Jean-Michel; Henze, Christopher E.; Isaacson, Howard; Jenkins,
Jon M.; Lissauer, Jack J.; Chaplin, William J.; Basu, Sarbani;
Metcalfe, Travis S.; Elsworth, Yvonne; Handberg, Rasmus; Hekker,
Saskia; Huber, Daniel; Karoff, Christoffer; Kjeldsen, Hans; Lund,
Mikkel N.; Lundkvist, Mia; Miglio, Andrea; Charbonneau, David; Ford,
Eric B.; Fortney, Jonathan J.; Haas, Michael R.; Howard, Andrew W.;
Howell, Steve B.; Ragozzine, Darin; Thompson, Susan E.
2013ApJ...766...40G Altcode: 2013arXiv1302.2596G
NASA's Kepler Mission has revealed two transiting planets orbiting
Kepler-68. Follow-up Doppler measurements have established the mass of
the innermost planet and revealed a third Jovian-mass planet orbiting
beyond the two transiting planets. Kepler-68b, in a 5.4 day orbit,
has M_P=8.3^{+2.2}_{-2.4} M <SUB>⊕</SUB>, R_P=2.31^{+0.06}_{-0.09}
R <SUB>⊕</SUB>, and \rho _P=3.32^{+0.86}_{-0.98} g cm<SUP>-3</SUP>,
giving Kepler-68b a density intermediate between that of the
ice giants and Earth. Kepler-68c is Earth-sized, with a radius
R_P=0.953^{+0.037}_{-0.042} R <SUB>⊕</SUB> and transits on a 9.6 day
orbit; validation of Kepler-68c posed unique challenges. Kepler-68d
has an orbital period of 580 ± 15 days and a minimum mass of M
<SUB>P</SUB>sin i = 0.947 ± 0.035M<SUB>J</SUB> . Power spectra of
the Kepler photometry at one minute cadence exhibit a rich and strong
set of asteroseismic pulsation modes enabling detailed analysis of the
stellar interior. Spectroscopy of the star coupled with asteroseismic
modeling of the multiple pulsation modes yield precise measurements
of stellar properties, notably T <SUB>eff</SUB> = 5793 ± 74 K, M
<SUB>sstarf</SUB> = 1.079 ± 0.051 M <SUB>⊙</SUB>, R <SUB>sstarf</SUB>
= 1.243 ± 0.019 R <SUB>⊙</SUB>, and ρ<SUB>sstarf</SUB> = 0.7903 ±
0.0054 g cm<SUP>-3</SUP>, all measured with fractional uncertainties
of only a few percent. Models of Kepler-68b suggest that it is likely
composed of rock and water, or has a H and He envelope to yield its
density ~3 g cm<SUP>-3</SUP>.
---------------------------------------------------------
Title: Differential population studies using asteroseismology:
Solar-like oscillating giants in CoRoT fields LRc01 and LRa01
Authors: Miglio, A.; Chiappini, C.; Morel, T.; Barbieri, M.; Chaplin,
W. J.; Girardi, L.; Montalbán, J.; Noels, A.; Valentini, M.; Mosser,
B.; Baudin, F.; Casagrande, L.; Fossati, L.; Silva Aguirre, V.;
Baglin, A.
2013EPJWC..4303004M Altcode: 2013arXiv1301.1515M
Solar-like oscillating giants observed by the space-borne satellites
CoRoT and Kepler can be used as key tracers of stellar populations in
the Milky Way. When combined with additional photometric/spectroscopic
constraints, the pulsation spectra of solar-like oscillating giant
stars not only reveal their radii, and hence distances, but also
provide well-constrained estimates of their masses, which can be used
as proxies for the ages of these evolved stars. In this contribution
we provide supplementary material to the comparison we presented in
Miglio et al. (2013) between populations of giants observed by CoRoT
in the fields designated LRc01 and LRa01.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Abundances of 93 solar-type Kepler
targets (Bruntt+, 2012)
Authors: Bruntt, H.; Basu, S.; Smalley, B.; Chaplin, W. J.; Verner,
G. A.; Bedding, T. R.; Catala, C.; Gazzano, J. -C.; Molenda-Zakowicz,
J.; Thygesen, A. O.; Uytterhoeven, K.; Hekker, S.; Huber, D.; Karoff,
C.; Mathur, S.; Mosser, B.; Appourchaux, T.; Campante, T. L.; Elsworth,
Y.; Garcia, R. A.; Handberg, R.; Metcalfe, T. S.; Quirion, P. -O.;
Regulo, C.; Roxburgh, I. W.; Stello, D.; Christensen-Dalsgaard,
J.; Kawaler, S. D.; Kjeldsen, H.; Morris, R. L.; Quintana, E. V.;
Sanderfer, D. T.
2013yCat..74230122B Altcode:
The spectra were obtained with the ESPaDOnS spectrograph at the 3.6-m
Canada-France-Hawaii Telescope (CFHT) in USA and with the NARVAL
spectrograph mounted on the 2-m Bernard Lyot Telescope at the Pic du
Midi Observatory in France. In both the facilities, the observations
were carried out as service observations from May to September in
2010. <P />(3 data files).
---------------------------------------------------------
Title: A sub-Mercury-sized exoplanet
Authors: Barclay, Thomas; Rowe, Jason F.; Lissauer, Jack J.; Huber,
Daniel; Fressin, François; Howell, Steve B.; Bryson, Stephen
T.; Chaplin, William J.; Désert, Jean-Michel; Lopez, Eric D.;
Marcy, Geoffrey W.; Mullally, Fergal; Ragozzine, Darin; Torres,
Guillermo; Adams, Elisabeth R.; Agol, Eric; Barrado, David; Basu,
Sarbani; Bedding, Timothy R.; Buchhave, Lars A.; Charbonneau, David;
Christiansen, Jessie L.; Christensen-Dalsgaard, Jørgen; Ciardi, David;
Cochran, William D.; Dupree, Andrea K.; Elsworth, Yvonne; Everett,
Mark; Fischer, Debra A.; Ford, Eric B.; Fortney, Jonathan J.; Geary,
John C.; Haas, Michael R.; Handberg, Rasmus; Hekker, Saskia; Henze,
Christopher E.; Horch, Elliott; Howard, Andrew W.; Hunter, Roger C.;
Isaacson, Howard; Jenkins, Jon M.; Karoff, Christoffer; Kawaler,
Steven D.; Kjeldsen, Hans; Klaus, Todd C.; Latham, David W.; Li,
Jie; Lillo-Box, Jorge; Lund, Mikkel N.; Lundkvist, Mia; Metcalfe,
Travis S.; Miglio, Andrea; Morris, Robert L.; Quintana, Elisa V.;
Stello, Dennis; Smith, Jeffrey C.; Still, Martin; Thompson, Susan E.
2013Natur.494..452B Altcode: 2013arXiv1305.5587B
Since the discovery of the first exoplanets, it has been known that
other planetary systems can look quite unlike our own. Until fairly
recently, we have been able to probe only the upper range of the planet
size distribution, and, since last year, to detect planets that are
the size of Earth or somewhat smaller. Hitherto, no planets have been
found that are smaller than those we see in the Solar System. Here we
report a planet significantly smaller than Mercury. This tiny planet
is the innermost of three that orbit the Sun-like host star, which we
have designated Kepler-37. Owing to its extremely small size, similar to
that of the Moon, and highly irradiated surface, the planet, Kepler-37b,
is probably rocky with no atmosphere or water, similar to Mercury.
---------------------------------------------------------
Title: Correlating Photometric Variability and Chromospheric Activity
in Kepler Stars
Authors: Bastien, Fabienne A.; Stassun, Keivan G.; Pepper, Joshua;
Chaplin, William; Huber, Daniel
2013noao.prop..218B Altcode:
The panoply of photometric variability due to the magnetic activity
of Sun-like stars, as revealed by missions like it Kepler, has
significantly impacted our understanding of stars, calling for a
thorough characterization of this behavior, an important noise source in
planet detection. Our work, based on previous WIYN/Hydra observations
of it Kepler stars, reveals that many stars that appear “inactive”
by traditional measures may be highly variable in radial-velocity
and/or exhibit complex photometric variations. Our preliminary
results, along with recent modeling efforts, suggest promising and
testable observational predictors of this behavior. We propose to
measure the magnetic activity of 280 stars in the it Kepler field,
including asteroseismic targets with precisely determined parameters,
via their Ca II H&K emission, over a relatively long time-baseline,
in order to link activity and its degree of variation to photometric
variability. We will also use these data to test and refine models that
seek to predict photometric and radial-velocity variations of potential
planet-hosting stars. This analysis will inform theories of the causes
of stellar activity and improve the efficiency of planet detection.
---------------------------------------------------------
Title: The solar-stellar connection: Insights from helioseismology
Authors: Chaplin, W. J.
2013AN....334..133C Altcode: 2013csss...17..133C
In this review we discuss helioseismology as a probe of the solar
activity cycle, highlighting in particular results on studies of
the recent, unusual solar minimum. We then discuss the solar-stellar
connection, in the context of the potential for performing asteroseismic
studies of stellar activity cycles of solar-type stars using data from
Kepler, CoRoT and ground-based observations.
---------------------------------------------------------
Title: Galactic archaeology: mapping and dating stellar populations
with asteroseismology of red-giant stars
Authors: Miglio, A.; Chiappini, C.; Morel, T.; Barbieri, M.; Chaplin,
W. J.; Girardi, L.; Montalbán, J.; Valentini, M.; Mosser, B.; Baudin,
F.; Casagrande, L.; Fossati, L.; Silva Aguirre, V.; Baglin, A.
2013MNRAS.429..423M Altcode: 2012arXiv1211.0146M
Our understanding of how the Galaxy was formed and evolves is severely
hampered by the lack of precise constraints on basic stellar properties
such as distances, masses and ages. Here, we show that solar-like
pulsating red giants represent a well-populated class of accurate
distance indicators, spanning a large age range, which can be used to
map and date the Galactic disc in the regions probed by observations
made by the CoRoT and Kepler space telescopes. When combined with
photometric constraints, the pulsation spectra of such evolved stars
not only reveal their radii, and hence distances, but also provide
well-constrained estimates of their masses, which are reliable proxies
for the ages of the stars. As a first application, we consider red
giants observed by CoRoT in two different parts of the Milky Way, and
determine precise distances for ∼2000 stars spread across nearly 15
000 pc of the Galactic disc, exploring regions which are a long way from
the solar neighbourhood. We find significant differences in the mass
distributions of these two samples which, by comparison with predictions
of synthetic models of the Milky Way, we interpret as mainly due to the
vertical gradient in the distribution of stellar masses (hence ages) in
the disc. In the future, the availability of spectroscopic constraints
for this sample of stars will not only improve the age determination,
but also provide crucial constraints on age-velocity and age-metallicity
relations at different Galactocentric radii and heights from the plane.
---------------------------------------------------------
Title: Determining distances using asteroseismic methods
Authors: Silva Aguirre, V.; Casagrande, L.; Basu, S.; Campante, T. L.;
Chaplin, W. J.; Huber, D.; Miglio, A.; Serenelli, A. M.
2013AN....334...22S Altcode: 2012arXiv1210.7343S; 2013csss...17...22S
Asteroseismology has been extremely successful in determining the
properties of stars in different evolutionary stages with a remarkable
level of precision. However, to fully exploit its potential, robust
methods for estimating stellar parameters are required and independent
verification of the results is needed. In this talk, I present a
new technique developed to obtain stellar properties by coupling
asteroseismic analysis with the infrared flux method. Using two global
seismic observables and multi-band photometry, the technique determines
masses, radii, effective temperatures, bolometric fluxes, and thus
distances for field stars in a self-consistent manner. Applying our
method to a sample of solar-like oscillators in the Kepler field that
have accurate Hipparcos parallaxes, we find agreement in our distance
determinations to better than 5 %. Comparison with measurements of
spectroscopic effective temperatures and interferometric radii also
validate our results, and show that our technique can be applied to
stars evolved beyond the main-sequence phase.
---------------------------------------------------------
Title: Frequency Dependence of Δν of Solar-Like Oscillators
Investigated: Influence of HeII Ionization Zone
Authors: Hekker, S.; Basu, Sarbani; Elsworth, Y.; Chaplin, W. J.
2013ASSP...31...73H Altcode: 2012arXiv1203.4588H
Oscillations in solar-like oscillators tend to follow an approximately
regular pattern in which oscillation modes of a certain degree
and consecutive order appear at regular intervals in frequency,
i.e. the so-called large frequency separation. This is true to first
order approximation for acoustic modes. However, to a second order
approximation it is evident that the large frequency separation changes
as a function of frequency. This frequency dependence has been seen in
the Sun and in other main-sequence stars. However, from observations of
giant stars, this effect seemed to be less pronounced. We investigate
the difference in frequency dependence of the large frequency separation
between main-sequence and giant stars using YREC evolutionary models.
---------------------------------------------------------
Title: Study of HD 169392A observed by CoRoT and HARPS
Authors: Mathur, S.; Bruntt, H.; Catala, C.; Benomar, O.; Davies,
G. R.; García, R. A.; Salabert, D.; Ballot, J.; Mosser, B.; Régulo,
C.; Chaplin, W. J.; Elsworth, Y.; Handberg, R.; Hekker, S.; Mantegazza,
L.; Michel, E.; Poretti, E.; Rainer, M.; Roxburgh, I. W.; Samadi,
R.; Stȩślicki, M.; Uytterhoeven, K.; Verner, G. A.; Auvergne, M.;
Baglin, A.; Barceló Forteza, S.; Baudin, F.; Roca Cortés, T.
2013A&A...549A..12M Altcode: 2012arXiv1209.5696M
Context. The results obtained by asteroseismology with data from
space missions such as CoRoT and Kepler are providing new insights
into stellar evolution. After five years of observations, CoRoT
is continuing to provide high-quality data and we here present an
analysis of the CoRoT observations of the double star HD 169392,
complemented by ground-based spectroscopic observations. <BR /> Aims:
This work aims at characterising the fundamental parameters of the two
stars, their chemical composition, the acoustic-mode global parameters
including their individual frequencies, and their dynamics. <BR />
Methods: We analysed HARPS observations of the two stars to derive
their chemical compositions. Several methods were used and compared
to determine the global properties of stars' acoustic modes and their
individual frequencies from the photometric data of CoRoT. <BR />
Results: The new spectroscopic observations and archival astrometric
values suggest that HD 169392 is a weakly bound wide binary system. We
obtained spectroscopic parameters for both components which suggest
that they originate from the same interstellar cloud. However, only
the signature of oscillation modes of HD 169392 A was measured;
the signal-to-noise ratio of the modes in HD 169392B is too low
to allow any confident detection. For HD 169392 A we were able to
extract parameters of modes for ℓ = 0, 1, 2, and 3. The analysis
of splittings and inclination angle gives two possible solutions: one
with with splittings and inclination angles of 0.4-1.0 μHz and 20 -
40°, the other with 0.2-0.5 μHz and 55-86°. Modelling this star
using the Asteroseismic Modeling Portal (AMP) gives a mass of 1.15
± 0.01 M<SUB>⊙</SUB>, a radius of 1.88 ± 0.02 R<SUB>⊙</SUB>,
and an age of 4.33 ± 0.12 Gyr. The uncertainties come from estimated
errors on the observables but do not include uncertainties on the
surface layer correction or the physics of stellar models. <P />The
CoRoT space mission, launched on December 27 2006, has been developed
and is operated by CNES, with the contribution of Austria, Belgium,
Brazil, ESA (RSSD and Science Programme), Germany and Spain.This
work is based on ground-based observations made with the ESO 3.6
m-telescope at La Silla Observatory under the ESO Large Programme
LP185-D.0056.Tables 5 and 7 are available in electronic form at <A
href="http://www.aanda.org">http://www.aanda.org</A>
---------------------------------------------------------
Title: Characterizing Two Solar-type Kepler Subgiants with
Asteroseismology: KIC 10920273 and KIC 11395018
Authors: Doǧan, G.; Metcalfe, T. S.; Deheuvels, S.; Di Mauro,
M. P.; Eggenberger, P.; Creevey, O. L.; Monteiro, M. J. P. F. G.;
Pinsonneault, M.; Frasca, A.; Karoff, C.; Mathur, S.; Sousa, S. G.;
Brandão, I. M.; Campante, T. L.; Handberg, R.; Thygesen, A. O.;
Biazzo, K.; Bruntt, H.; Niemczura, E.; Bedding, T. R.; Chaplin, W. J.;
Christensen-Dalsgaard, J.; García, R. A.; Molenda-Żakowicz, J.;
Stello, D.; Van Saders, J. L.; Kjeldsen, H.; Still, M.; Thompson,
S. E.; Van Cleve, J.
2013ApJ...763...49D Altcode: 2012arXiv1211.6650D
Determining fundamental properties of stars through stellar
modeling has improved substantially due to recent advances in
asteroseismology. Thanks to the unprecedented data quality obtained by
space missions, particularly CoRoT and Kepler, invaluable information
is extracted from the high-precision stellar oscillation frequencies,
which provide very strong constraints on possible stellar models for a
given set of classical observations. In this work, we have characterized
two relatively faint stars, KIC 10920273 and KIC 11395018, using
oscillation data from Kepler photometry and atmospheric constraints from
ground-based spectroscopy. Both stars have very similar atmospheric
properties; however, using the individual frequencies extracted from
the Kepler data, we have determined quite distinct global properties,
with increased precision compared to that of earlier results. We found
that both stars have left the main sequence and characterized them
as follows: KIC 10920273 is a one-solar-mass star (M = 1.00 ± 0.04 M
<SUB>⊙</SUB>), but much older than our Sun (t = 7.12 ± 0.47 Gyr),
while KIC 11395018 is significantly more massive than the Sun (M =
1.27 ± 0.04 M <SUB>⊙</SUB>) with an age close to that of the Sun
(t = 4.57 ± 0.23 Gyr). We confirm that the high lithium abundance
reported for these stars should not be considered to represent young
ages, as we precisely determined them to be evolved subgiants. We
discuss the use of surface lithium abundance, rotation, and activity
relations as potential age diagnostics.
---------------------------------------------------------
Title: Asteroseismology with NASA's Kepler Mission
Authors: Huber, Daniel; Chaplin, W. J.; Christensen-Dalsgaard, J.;
Gilliland, R. L.; Kawaler, S. D.; Kjeldsen, H.; Working Groups of
Kepler Asteroseismic Science Consortium (KASC)
2013AAS...22130101H Altcode:
The measurement of stellar oscillations - also called asteroseismology -
is among the most powerful observational tools to study the structure
and evolution of stars. The high precision photometry collected by the
Kepler space telescope has revolutionized asteroseismology over the past
few years by boosting the number of stars with detected oscillations by
nearly two orders of magnitude over ground-based efforts, and delivering
data with unprecedented signal-to-noise. In this talk I will highlight
some of the recent breakthrough discoveries by the Kepler Mission,
focusing in particular on the internal composition and rotation of red
giants and the study of fundamental properties in large ensembles of
stars throughout the Hertzsprung-Russell diagram. I will furthermore
present results for an ensemble of ~80 Kepler Objects of Interest for
which accurate host star and planet candidate properties have been
determined using asteroseismology.
---------------------------------------------------------
Title: Erratum: A new method to detect solar-like oscillations at
very low S/N using statistical significance testing
Authors: Lund, Mikkel N.; Chaplin, William J.; Kjeldsen, Hans
2012MNRAS.427.3489L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Acoustic glitches in solar-type stars from Kepler
Authors: Mazumdar, A.; Monteiro, M. J. P. F. G.; Ballot, J.; Antia,
H. M.; Basu, S.; Houdek, G.; Mathur, S.; Cunha, M. S.; Silva Aguirre,
V.; García, R. A.; Salabert, D.; Verner, G. A.; Christensen-Dalsgaard,
J.; Metcalfe, T. S.; Chaplin, W. J.
2012AN....333.1040M Altcode:
We report the measurement of the acoustic locations of layers of
sharp variation in sound speed in the interiors of 19 solar-type
stars observed by the Kepler mission. The oscillatory signal in the
frequencies arising due to the acoustic glitches at the base of the
convection zone and the second helium ionisation zone was utilised
to determine their location by four independent methods. Despite the
significantly different methods of analysis, remarkable agreement
was found between the results of these four methods. Further, the
extracted locations of these layers were found to be consistent with
representative models of the stars.
---------------------------------------------------------
Title: A new method to detect solar-like oscillations at very low
S/N using statistical significance testing
Authors: Lund, Mikkel N.; Chaplin, William J.; Kjeldsen, Hans
2012MNRAS.427.1784L Altcode: 2012arXiv1209.3792L
We introduce a new method to detect solar-like oscillations in frequency
power spectra of stellar observations, under conditions of very low
signal-to-noise ratio. The Moving-Windowed-Power-Search (MWPS) searches
the power spectrum for signatures of excess power, over and above slowly
varying (in frequency) background contributions from stellar granulation
and shot or instrumental noise. We adopt a false-alarm approach to
ascertain whether flagged excess power, which is consistent with the
excess expected from solar-like oscillations, is hard to explain by
chance alone (and hence a candidate detection). <P />We apply the method
to solar photometry data, whose quality was systematically degraded
to test the performance of the MWPS at low signal-to-noise ratios. We
also compare the performance of the MWPS against the frequently applied
power-spectrum-of-power-spectrum (PS⊗PS) detection method. The MWPS
is found to outperform the PS⊗PS method.
---------------------------------------------------------
Title: Fundamental Properties of Stars Using Asteroseismology from
Kepler and CoRoT and Interferometry from the CHARA Array
Authors: Huber, D.; Ireland, M. J.; Bedding, T. R.; Brandão, I. M.;
Piau, L.; Maestro, V.; White, T. R.; Bruntt, H.; Casagrande, L.;
Molenda-Żakowicz, J.; Silva Aguirre, V.; Sousa, S. G.; Barclay,
T.; Burke, C. J.; Chaplin, W. J.; Christensen-Dalsgaard, J.; Cunha,
M. S.; De Ridder, J.; Farrington, C. D.; Frasca, A.; García, R. A.;
Gilliland, R. L.; Goldfinger, P. J.; Hekker, S.; Kawaler, S. D.;
Kjeldsen, H.; McAlister, H. A.; Metcalfe, T. S.; Miglio, A.; Monteiro,
M. J. P. F. G.; Pinsonneault, M. H.; Schaefer, G. H.; Stello, D.;
Stumpe, M. C.; Sturmann, J.; Sturmann, L.; ten Brummelaar, T. A.;
Thompson, M. J.; Turner, N.; Uytterhoeven, K.
2012ApJ...760...32H Altcode: 2012arXiv1210.0012H
We present results of a long-baseline interferometry campaign using
the PAVO beam combiner at the CHARA Array to measure the angular
sizes of five main-sequence stars, one subgiant and four red
giant stars for which solar-like oscillations have been detected
by either Kepler or CoRoT. By combining interferometric angular
diameters, Hipparcos parallaxes, asteroseismic densities, bolometric
fluxes, and high-resolution spectroscopy, we derive a full set of
near-model-independent fundamental properties for the sample. We
first use these properties to test asteroseismic scaling relations
for the frequency of maximum power (ν<SUB>max</SUB>) and the large
frequency separation (Δν). We find excellent agreement within the
observational uncertainties, and empirically show that simple estimates
of asteroseismic radii for main-sequence stars are accurate to <~
4%. We furthermore find good agreement of our measured effective
temperatures with spectroscopic and photometric estimates with mean
deviations for stars between T <SUB>eff</SUB> = 4600-6200 K of -22 ±
32 K (with a scatter of 97 K) and -58 ± 31 K (with a scatter of 93 K),
respectively. Finally, we present a first comparison with evolutionary
models, and find differences between observed and theoretical properties
for the metal-rich main-sequence star HD 173701. We conclude that
the constraints presented in this study will have strong potential
for testing stellar model physics, in particular when combined with
detailed modeling of individual oscillation frequencies.
---------------------------------------------------------
Title: Thinning of the Sun's Magnetic Layer: The Peculiar Solar
Minimum Could Have Been Predicted
Authors: Basu, Sarbani; Broomhall, Anne-Marie; Chaplin, William J.;
Elsworth, Yvonne
2012ApJ...758...43B Altcode: 2012arXiv1208.5493B
The solar magnetic activity cycle causes changes in the Sun on
timescales that are equivalent to human lifetimes. The minimum solar
activity that preceded the current solar cycle (cycle 24) was deeper and
quieter than any other recent minimum. Using data from the Birmingham
Solar Oscillations Network (BiSON), we show that the structure of the
solar sub-surface layers during the descending phase of the preceding
cycle (cycle 23) was very different from that during cycle 22. This
leads us to believe that a detailed examination of the data would
have led to the prediction that the cycle 24 minimum would be out
of the ordinary. The behavior of the oscillation frequencies allows
us to infer that changes in the Sun that affected the oscillation
frequencies in cycle 23 were localized mainly to layers above about
0.996 R <SUB>⊙</SUB>, depths shallower than about 3000 km. In cycle
22, on the other hand, the changes must have also occurred in the
deeper-lying layers.
---------------------------------------------------------
Title: Asteroseismology of the Open Clusters NGC 6791, NGC 6811,
and NGC 6819 from 19 Months of Kepler Photometry
Authors: Corsaro, Enrico; Stello, Dennis; Huber, Daniel; Bedding,
Timothy R.; Bonanno, Alfio; Brogaard, Karsten; Kallinger, Thomas;
Benomar, Othman; White, Timothy R.; Mosser, Benoit; Basu, Sarbani;
Chaplin, William J.; Christensen-Dalsgaard, Jørgen; Elsworth, Yvonne
P.; García, Rafael A.; Hekker, Saskia; Kjeldsen, Hans; Mathur,
Savita; Meibom, Søren; Hall, Jennifer R.; Ibrahim, Khadeejah A.;
Klaus, Todd C.
2012ApJ...757..190C Altcode: 2012arXiv1205.4023C
We studied solar-like oscillations in 115 red giants in the three open
clusters, NGC 6791, NGC 6811, and NGC 6819, based on photometric data
covering more than 19 months with NASA's Kepler space telescope. We
present the asteroseismic diagrams of the asymptotic parameters
δν<SUB>02</SUB>, δν<SUB>01</SUB>, and epsilon, which show clear
correlation with fundamental stellar parameters such as mass and
radius. When the stellar populations from the clusters are compared,
we see evidence for a difference in mass of the red giant branch
stars and possibly a difference in structure of the red clump stars,
from our measurements of the small separations δν<SUB>02</SUB> and
δν<SUB>01</SUB>. Ensemble échelle diagrams and upper limits to the
linewidths of l = 0 modes as a function of Δν of the clusters NGC
6791 and NGC 6819 are also shown, together with the correlation between
the l = 0 ridge width and the T <SUB>eff</SUB> of the stars. Lastly,
we distinguish between red giant branch and red clump stars through
the measurement of the period spacing of mixed dipole modes in 53 stars
among all the three clusters to verify the stellar classification from
the color-magnitude diagram. These seismic results also allow us to
identify a number of special cases, including evolved blue stragglers
and binaries, as well as stars in late He-core burning phases, which can
be potentially interesting targets for detailed theoretical modeling.
---------------------------------------------------------
Title: Future Prospects for Inference on Solar-type Stars
Authors: Chaplin, W. J.
2012ASPC..462..525C Altcode: 2011arXiv1109.6175C
We discuss prospects for asteroseismic inference on solar-type stars,
in particular opportunities that are being made possible by the large
ensemble of exquisite-quality Kepler data.
---------------------------------------------------------
Title: How Different Was the Last Solar Minimum?
Authors: Basu, S.; Chaplin, W. J.; Elsworth, Y.; Broomhall, A.;
Jarvis, E.
2012ASPC..462..261B Altcode:
The activity minimum between solar Cycles 23 and 24 has been exceptional
in its quietness. It had the lowest sustained 10.7 cm flux since since
observation of this proxy began in 1947. The internal dynamics of
the Sun have been found to be very different for the minimum of Cycle
24 compared with that of Cycle 23. There have only been preliminary
attempts to determine whether there were differences in the structure
of the Sun during the Cycle 24 minimum compared with the Cycle 23
minimum. Early studies have shown differences between solar oscillation
frequencies at the two minima. We expand the earlier study and use a
hybrid forward-modelling and fitting method to determine whether the
frequency differences imply differences in the structure of the Sun
between the two minima.
---------------------------------------------------------
Title: Verifying Asteroseismically Determined Parameters of Kepler
Stars Using Hipparcos Parallaxes: Self-consistent Stellar Properties
and Distances
Authors: Silva Aguirre, V.; Casagrande, L.; Basu, S.; Campante, T. L.;
Chaplin, W. J.; Huber, D.; Miglio, A.; Serenelli, A. M.; Ballot, J.;
Bedding, T. R.; Christensen-Dalsgaard, J.; Creevey, O. L.; Elsworth,
Y.; García, R. A.; Gilliland, R. L.; Hekker, S.; Kjeldsen, H.;
Mathur, S.; Metcalfe, T. S.; Monteiro, M. J. P. F. G.; Mosser, B.;
Pinsonneault, M. H.; Stello, D.; Weiss, A.; Tenenbaum, P.; Twicken,
J. D.; Uddin, K.
2012ApJ...757...99S Altcode: 2012arXiv1208.6294S
Accurately determining the properties of stars is of prime importance
for characterizing stellar populations in our Galaxy. The field of
asteroseismology has been thought to be particularly successful in
such an endeavor for stars in different evolutionary stages. However,
to fully exploit its potential, robust methods for estimating stellar
parameters are required and independent verification of the results
is mandatory. With this purpose, we present a new technique to obtain
stellar properties by coupling asteroseismic analysis with the InfraRed
Flux Method. By using two global seismic observables and multi-band
photometry, the technique allows us to obtain masses, radii, effective
temperatures, bolometric fluxes, and hence distances for field stars
in a self-consistent manner. We apply our method to 22 solar-like
oscillators in the Kepler short-cadence sample, that have accurate
Hipparcos parallaxes. Our distance determinations agree to better than
5%, while measurements of spectroscopic effective temperatures and
interferometric radii also validate our results. We briefly discuss
the potential of our technique for stellar population analysis and
models of Galactic Chemical Evolution.
---------------------------------------------------------
Title: Ensemble Asteroseismology of Red-giant Stars
Authors: Hekker, S.; Gilliland, R. L.; Basu, S.; De Ridder, J.;
Chaplin, W. J.; Elsworth, Y.
2012ASPC..462..139H Altcode: 2011arXiv1109.0144H
The successful launches of the CoRoT and Kepler space missions have
led to the detections of solar-like oscillations in large samples
of red-giant stars. The large numbers of red giants with observed
oscillations make it possible to investigate the properties of the
sample as a whole: ensemble asteroseismology. In this article we
summarise ensemble asteroseismology results obtained from data released
by the Kepler Science Team (∼150 000 field stars) as presented by
Hekker et al. (2011b) and for the clusters NGC 6791, NGC 6811 and NGC
6819 (Hekker et al. 2011a); we discuss the importance of such studies.
---------------------------------------------------------
Title: Fast Rotating Solar-like Stars Using Asteroseismic Datasets
Authors: García, R. A.; Ceillier, T.; Campante, T. L.; Davies, G. R.;
Mathur, S.; Suárez, J. C.; Ballot, J.; Benomar, O.; Bonanno, A.;
Brun, A. S.; Chaplin, W. J.; Christensen-Dalsgaard, J.; Deheuvels,
S.; Elsworth, Y.; Handberg, R.; Hekker, S.; Jiménez, A.; Karoff, C.;
Kjeldsen, H.; Mathis, S.; Mosser, B.; Pallé, P. L.; Pinsonneault, M.;
Régulo, C.; Salabert, D.; Silva Aguirre, V.; Stello, D.; Thompson,
M. J.; Verner, G.; PE11 Team of Kepler WG#1
2012ASPC..462..133G Altcode: 2011arXiv1109.6488G
The NASA Kepler mission is providing an unprecedented set of
asteroseismic data. In particular, short-cadence light-curves (∼ 60
s samplings), allow us to study solar-like stars covering a wide range
of masses, spectral types and evolutionary stages. Oscillations have
been observed in around 600 out of 2000 stars observed for one month
during the survey phase of the Kepler mission. The measured light
curves can present features related to the surface magnetic activity
(starspots) and, thus we are able to obtain a good estimate of the
surface (differential) rotation. In this work we establish the basis
of such research and we show a potential method to find stars with
fast surface rotation.
---------------------------------------------------------
Title: Seismic Analysis of Four Solar-like Stars Observed during
More Than Eight Months by Kepler
Authors: Mathur, S.; Campante, T. L.; Handberg, R.; García, R. A.;
Appourchaux, T.; Bedding, T. R.; Mosser, B.; Chaplin, W. J.; Ballot,
J.; Benomar, O.; Bonanno, A.; Corsaro, E.; Gaulme, P.; Hekker,
S.; Régulo, C.; Salabert, D.; Verner, G.; White, T. R.; Brandão,
I. M.; Creevey, O. L.; Dogan, G.; Bazot, M.; Cunha, M. S.; Elsworth,
Y.; Huber, D.; Hale, S. J.; Houdek, G.; Karoff, C.; Lundkvist, M.;
Metcalfe, T. S.; Molenda-Zakowicz, J.; Monteiro, M. J. P. F. G.;
Thompson, M. J.; Stello, D.; Christensen-Dalsgaard, J.; Gilliland,
R. L.; Kawaler, S. D.; Kjeldsen, H.; Clarke, B. D.; Girouard, F. R.;
Hall, J. R.; Quintana, E. V.; Sanderfer, D. T.; Seader, S. E.
2012ASPC..462..180M Altcode: 2011arXiv1110.0135M
Having started science operations in May 2009, the Kepler photometer
has been able to provide exquisite data for solar-like stars. Five
out of the 42 stars observed continuously during the survey phase
show evidence of oscillations, even though they are rather faint
(magnitudes from 10.5 to 12). In this paper, we present an overview
of the results of the seismic analysis of 4 of these stars observed
during more than eight months.
---------------------------------------------------------
Title: Investigating the Properties of Granulation in the Red Giants
Observed by Kepler
Authors: Mathur, S.; Hekker, S.; Trampedach, R.; Ballot, J.; Kallinger,
T.; Buzasi, D.; García, R. A.; Huber, D.; Jiménez, A.; Mosser, B.;
Bedding, T. R.; Elsworth, Y.; Régulo, C.; Stello, D.; Chaplin, W. J.;
De Ridder, J.; Hale, S. J.; Kinemuchi, K.; Kjeldsen, H.; Mullally,
F.; Thompson, S. E.
2012ASPC..462..375M Altcode: 2011arXiv1110.0117M
More than 1000 red giants have been observed by NASA/Kepler mission
during a nearly continuous period of ∼ 13 months. The resulting
high-frequency resolution (< 0.03 μHz) allows us to study the
granulation parameters of these stars. The granulation pattern results
from the convection motions leading to upward flows of hot plasma
and downward flows of cooler plasma. We fitted Harvey-like functions
to the power spectra, to retrieve the timescale and amplitude of
granulation. We show that there is an anti-correlation between both of
these parameters and the position of maximum power of acoustic modes,
while we also find a correlation with the radius, which agrees with the
theory. We finally compare our results with 3D models of the convection.
---------------------------------------------------------
Title: Seismic Evidence for a Rapidly Rotating Core in a
Lower-giant-branch Star Observed with Kepler
Authors: Deheuvels, S.; García, R. A.; Chaplin, W. J.; Basu, S.;
Antia, H. M.; Appourchaux, T.; Benomar, O.; Davies, G. R.; Elsworth,
Y.; Gizon, L.; Goupil, M. J.; Reese, D. R.; Regulo, C.; Schou, J.;
Stahn, T.; Casagrande, L.; Christensen-Dalsgaard, J.; Fischer, D.;
Hekker, S.; Kjeldsen, H.; Mathur, S.; Mosser, B.; Pinsonneault, M.;
Valenti, J.; Christiansen, J. L.; Kinemuchi, K.; Mullally, F.
2012ApJ...756...19D Altcode: 2012arXiv1206.3312D
Rotation is expected to have an important influence on the structure
and the evolution of stars. However, the mechanisms of angular momentum
transport in stars remain theoretically uncertain and very complex to
take into account in stellar models. To achieve a better understanding
of these processes, we desperately need observational constraints on the
internal rotation of stars, which until very recently was restricted to
the Sun. In this paper, we report the detection of mixed modes—i.e.,
modes that behave both as g modes in the core and as p modes in
the envelope—in the spectrum of the early red giant KIC 7341231,
which was observed during one year with the Kepler spacecraft. By
performing an analysis of the oscillation spectrum of the star, we
show that its non-radial modes are clearly split by stellar rotation
and we are able to determine precisely the rotational splittings of
18 modes. We then find a stellar model that reproduces very well the
observed atmospheric and seismic properties of the star. We use this
model to perform inversions of the internal rotation profile of the
star, which enables us to show that the core of the star is rotating at
least five times faster than the envelope. This will shed new light on
the processes of transport of angular momentum in stars. In particular,
this result can be used to place constraints on the angular momentum
coupling between the core and the envelope of early red giants, which
could help us discriminate between the theories that have been proposed
over the last few decades.
---------------------------------------------------------
Title: Estimating the p-mode frequencies of the solar twin 18 Scorpii
Authors: Bazot, M.; Campante, T. L.; Chaplin, W. J.; Carfantan, H.;
Bedding, T. R.; Dumusque, X.; Broomhall, A. -M.; Petit, P.; Théado,
S.; Van Grootel, V.; Arentoft, T.; Castro, M.; Christensen-Dalsgaard,
J.; do Nascimento, J. -D., Jr.; Dintrans, B.; Kjeldsen, H.; Monteiro,
M. J. P. F. G.; Santos, N. C.; Sousa, S.; Vauclair, S.
2012A&A...544A.106B Altcode: 2012arXiv1209.0218B
Solar twins have been a focus of attention for more than a
decade, because their structure is extremely close to that of
the Sun. Today, thanks to high-precision spectrometers, it is
possible to use asteroseismology to probe their interiors. Our
goal is to use time series obtained from the HARPS spectrometer
to extract the oscillation frequencies of 18 Sco, the brightest
solar twin. We used the tools of spectral analysis to estimate these
quantities. We estimate 52 frequencies using an MCMC algorithm. After
examination of their probability densities and comparison with
results from direct MAP optimization, we obtain a minimal set of
21 reliable modes. The identification of each pulsation mode is
straightforwardly accomplished by comparing to the well-established
solar pulsation modes. We also derived some basic seismic indicators
using these values. These results offer a good basis to start
a detailed seismic analysis of 18 Sco using stellar models. <P
/>Based on observations collected at the European Organisation for
Astronomical Research in the Southern Hemisphere, Chile (run ID:
183.D-0729(A)).Results of the MCMC analysis are only available at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/544/A106">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/544/A106</A>
---------------------------------------------------------
Title: Calibrating Convective Properties of Solar-like Stars in the
Kepler Field of View
Authors: Bonaca, Ana; Tanner, Joel D.; Basu, Sarbani; Chaplin,
William J.; Metcalfe, Travis S.; Monteiro, Mário J. P. F. G.; Ballot,
Jérôme; Bedding, Timothy R.; Bonanno, Alfio; Broomhall, Anne-Marie;
Bruntt, Hans; Campante, Tiago L.; Christensen-Dalsgaard, Jørgen;
Corsaro, Enrico; Elsworth, Yvonne; García, Rafael A.; Hekker, Saskia;
Karoff, Christoffer; Kjeldsen, Hans; Mathur, Savita; Régulo, Clara;
Roxburgh, Ian; Stello, Dennis; Trampedach, Regner; Barclay, Thomas;
Burke, Christopher J.; Caldwell, Douglas A.
2012ApJ...755L..12B Altcode: 2012arXiv1207.2765B
Stellar models generally use simple parameterizations to treat
convection. The most widely used parameterization is the so-called
mixing-length theory where the convective eddy sizes are described
using a single number, α, the mixing-length parameter. This is a free
parameter, and the general practice is to calibrate α using the known
properties of the Sun and apply that to all stars. Using data from
NASA's Kepler mission we show that using the solar-calibrated α is not
always appropriate, and that in many cases it would lead to estimates
of initial helium abundances that are lower than the primordial
helium abundance. Kepler data allow us to calibrate α for many other
stars and we show that for the sample of stars we have studied, the
mixing-length parameter is generally lower than the solar value. We
studied the correlation between α and stellar properties, and we find
that α increases with metallicity. We therefore conclude that results
obtained by fitting stellar models or by using population-synthesis
models constructed with solar values of α are likely to have large
systematic errors. Our results also confirm theoretical expectations
that the mixing-length parameter should vary with stellar properties.
---------------------------------------------------------
Title: Solar-like oscillations in red giants observed with Kepler:
influence of increased timespan on global oscillation parameters
Authors: Hekker, S.; Elsworth, Y.; Mosser, B.; Kallinger, T.; Chaplin,
W. J.; De Ridder, J.; García, R. A.; Stello, D.; Clarke, B. D.;
Hall, J. R.; Ibrahim, K. A.
2012A&A...544A..90H Altcode: 2012arXiv1207.0615H
Context. The length of the asteroseismic timeseries obtained from the
Kepler satellite analysed here span 19 months. Kepler provides the
longest continuous timeseries currently available, which calls for a
study of the influence of the increased timespan on the accuracy and
precision of the obtained results. <BR /> Aims: We aim to investigate
how the increased timespan influences the detectability of the
oscillation modes, and the absolute values and uncertainties of the
global oscillation parameters, i.e., frequency of maximum oscillation
power, ν<SUB>max</SUB>, and large frequency separation between modes of
the same degree and consecutive orders, ⟨ Δν ⟩ . <BR /> Methods:
We use published methods to derive ν<SUB>max</SUB> and ⟨ Δν ⟩
for timeseries ranging from 50 to 600 days and compare these results
as a function of method, timespan and ⟨ Δν ⟩ . <BR /> Results: We
find that in general a minimum of the order of 400 day long timeseries
are necessary to obtain reliable results for the global oscillation
parameters in more than 95% of the stars, but this does depend on
⟨ Δν ⟩ . In a statistical sense the quoted uncertainties seem to
provide a reasonable indication of the precision of the obtained results
in short (50-day) runs, they do however seem to be overestimated for
results of longer runs. Furthermore, the different definitions of the
global parameters used in the different methods have non-negligible
effects on the obtained values. Additionally, we show that there is
a correlation between ν<SUB>max</SUB> and the flux variance. <BR />
Conclusions: We conclude that longer timeseries improve the likelihood
to detect oscillations with automated codes (from ~60% in 50 day runs
to >95% in 400 day runs with a slight method dependence) and the
precision of the obtained global oscillation parameters. The trends
suggest that the improvement will continue for even longer timeseries
than the 600 days considered here, with a reduction in the median
absolute deviation of more than a factor of 10 for an increase in
timespan from 50 to 2000 days (the currently foreseen length of the
mission). This work shows that global parameters determined with high
precision - thus from long datasets - using different definitions can
be used to identify the evolutionary state of the stars. <P />Values
of the global oscillation parameters can be obtained from the authors
upon request.
---------------------------------------------------------
Title: Kepler-36: A Pair of Planets with Neighboring Orbits and
Dissimilar Densities
Authors: Carter, Joshua A.; Agol, Eric; Chaplin, William J.; Basu,
Sarbani; Bedding, Timothy R.; Buchhave, Lars A.; Christensen-Dalsgaard,
Jørgen; Deck, Katherine M.; Elsworth, Yvonne; Fabrycky, Daniel C.;
Ford, Eric B.; Fortney, Jonathan J.; Hale, Steven J.; Handberg,
Rasmus; Hekker, Saskia; Holman, Matthew J.; Huber, Daniel; Karoff,
Christopher; Kawaler, Steven D.; Kjeldsen, Hans; Lissauer, Jack J.;
Lopez, Eric D.; Lund, Mikkel N.; Lundkvist, Mia; Metcalfe, Travis S.;
Miglio, Andrea; Rogers, Leslie A.; Stello, Dennis; Borucki, William J.;
Bryson, Steve; Christiansen, Jessie L.; Cochran, William D.; Geary,
John C.; Gilliland, Ronald L.; Haas, Michael R.; Hall, Jennifer;
Howard, Andrew W.; Jenkins, Jon M.; Klaus, Todd; Koch, David G.;
Latham, David W.; MacQueen, Phillip J.; Sasselov, Dimitar; Steffen,
Jason H.; Twicken, Joseph D.; Winn, Joshua N.
2012Sci...337..556C Altcode: 2012arXiv1206.4718C
In the solar system, the planets’ compositions vary with orbital
distance, with rocky planets in close orbits and lower-density gas
giants in wider orbits. The detection of close-in giant planets around
other stars was the first clue that this pattern is not universal
and that planets’ orbits can change substantially after their
formation. Here, we report another violation of the orbit-composition
pattern: two planets orbiting the same star with orbital distances
differing by only 10% and densities differing by a factor of 8. One
planet is likely a rocky “super-Earth,” whereas the other is more
akin to Neptune. These planets are 20 times more closely spaced and
have a larger density contrast than any adjacent pair of planets in
the solar system.
---------------------------------------------------------
Title: Helioseismology - a clear view of the interior
Authors: Elsworth, Yvonne; Broomhall, Anne-Marie; Chaplin, William
2012IAUS..286...77E Altcode:
Helioseismology is a very powerful tool that allows us to explore
the interior of the Sun. Here we give particular emphasis to the
justification for the likely location of the zone that is most sensitive
to cycle-related changes. For the low degree modes we find that more
than one timescale for changes in the oscillations is discovered. We
also note the successive cycles have differing sensitivities to the
activity. We end with a warning of the risk of being misled with short
datasets such as are seen with stellar data.
---------------------------------------------------------
Title: VizieR Online Data Catalog: p-mode frequencies of the solar
twin 18 Sco (Bazot+, 2012)
Authors: Bazot, M.; Campante, T. L.; Chaplin, W. J.; Carfantan, H.;
Bedding, T. R.; Dumusque, X.; Broomhall, A. -M.; Petit, P.; Theado,
S.; Van Grootel, V.; Arentoft, T.; Castro, M.; Christensen-Dalsgaard,
J.; Do Nascimento, J. -D., Jr.; Dintrans, B.; Kjeldsen, H.; Monteiro,
M. J. P. F. G.; Santos, N. C.; Sousa, S.; Vauclair, S.
2012yCat..35440106B Altcode: 2012yCat..35449106B
Results from the estimation of the parameter of the spectrum model using
the Markov Chain Monte-Carlo (MCMC) algorithm described in Sect.4. A
burn-in sequence has been removed. The data is stored in the form of
an array [1975001x54] The first 52 columns give the frequencies of
the modes order by degree (13 l=0 modes, 13 l=1 modes, 13 l=2 modes,
13 l=3 modes). For each mode, they are sorted in ascending order. The
last two columns of each line give the parameters Gamma<SUB>1</SUB>
and Gamma<SUB>2</SUB>. <P />(1 data file).
---------------------------------------------------------
Title: Oscillation mode frequencies of 61 main-sequence and subgiant
stars observed by Kepler
Authors: Appourchaux, T.; Chaplin, W. J.; García, R. A.; Gruberbauer,
M.; Verner, G. A.; Antia, H. M.; Benomar, O.; Campante, T. L.; Davies,
G. R.; Deheuvels, S.; Handberg, R.; Hekker, S.; Howe, R.; Régulo,
C.; Salabert, D.; Bedding, T. R.; White, T. R.; Ballot, J.; Mathur,
S.; Silva Aguirre, V.; Elsworth, Y. P.; Basu, S.; Gilliland, R. L.;
Christensen-Dalsgaard, J.; Kjeldsen, H.; Uddin, K.; Stumpe, M. C.;
Barclay, T.
2012A&A...543A..54A Altcode: 2012arXiv1204.3147A
Context. Solar-like oscillations have been observed by Kepler and CoRoT
in several solar-type stars, thereby providing a way to probe the stars
using asteroseismology <BR /> Aims: We provide the mode frequencies of
the oscillations of various stars required to perform a comparison with
those obtained from stellar modelling. <BR /> Methods: We used a time
series of nine months of data for each star. The 61 stars observed were
categorised in three groups: simple, F-like, and mixed-mode. The simple
group includes stars for which the identification of the mode degree is
obvious. The F-like group includes stars for which the identification
of the degree is ambiguous. The mixed-mode group includes evolved stars
for which the modes do not follow the asymptotic relation of low-degree
frequencies. Following this categorisation, the power spectra of the
61 main-sequence and subgiant stars were analysed using both maximum
likelihood estimators and Bayesian estimators, providing individual mode
characteristics such as frequencies, linewidths, and mode heights. We
developed and describe a methodology for extracting a single set of
mode frequencies from multiple sets derived by different methods and
individual scientists. We report on how one can assess the quality of
the fitted parameters using the likelihood ratio test and the posterior
probabilities. <BR /> Results: We provide the mode frequencies of
61 stars (with their 1-σ error bars), as well as their associated
échelle diagrams. <P />Appendices are available in electronic form
at <A href="http://www.aanda.org">http://www.aanda.org</A>
---------------------------------------------------------
Title: Accurate fundamental parameters and detailed abundance patterns
from spectroscopy of 93 solar-type Kepler targets
Authors: Bruntt, H.; Basu, S.; Smalley, B.; Chaplin, W. J.; Verner,
G. A.; Bedding, T. R.; Catala, C.; Gazzano, J. -C.; Molenda-Żakowicz,
J.; Thygesen, A. O.; Uytterhoeven, K.; Hekker, S.; Huber, D.; Karoff,
C.; Mathur, S.; Mosser, B.; Appourchaux, T.; Campante, T. L.; Elsworth,
Y.; García, R. A.; Handberg, R.; Metcalfe, T. S.; Quirion, P. -O.;
Régulo, C.; Roxburgh, I. W.; Stello, D.; Christensen-Dalsgaard,
J.; Kawaler, S. D.; Kjeldsen, H.; Morris, R. L.; Quintana, E. V.;
Sanderfer, D. T.
2012MNRAS.423..122B Altcode: 2012arXiv1203.0611B; 2012MNRAS.tmp.3037B
We present a detailed spectroscopic study of 93 solar-type stars
that are targets of the NASA/Kepler mission and provide detailed
chemical composition of each target. We find that the overall
metallicity is well represented by Fe lines. Relative abundances
of light elements (CNO) and α elements are generally higher for
low-metallicity stars. Our spectroscopic analysis benefits from the
accurately measured surface gravity from the asteroseismic analysis
of the Kepler light curves. The accuracy on the log g parameter is
better than 0.03 dex and is held fixed in the analysis. We compare
our T<SUB>eff</SUB> determination with a recent colour calibration of
V<SUB>T</SUB>-K<SUB>S</SUB> [TYCHO V magnitude minus Two Micron All Sky
Survey (2MASS) K<SUB>S</SUB> magnitude] and find very good agreement
and a scatter of only 80 K, showing that for other nearby Kepler
targets, this index can be used. The asteroseismic log g values agree
very well with the classical determination using Fe I-Fe II balance,
although we find a small systematic offset of 0.08 dex (asteroseismic
log g values are lower). The abundance patterns of metals, α elements
and the light elements (CNO) show that a simple scaling by [Fe/H]
is adequate to represent the metallicity of the stars, except for
the stars with metallicity below -0.3, where α-enhancement becomes
important. However, this is only important for a very small fraction of
the Kepler sample. We therefore recommend that a simple scaling with
[Fe/H] be employed in the asteroseismic analyses of large ensembles
of solar-type stars.
---------------------------------------------------------
Title: Misleading variations in estimated rotational frequency
splittings of solar p modes: consequences for helioseismology and
asteroseismology
Authors: Broomhall, Anne-Marie; Salabert, David; Chaplin, William J.;
García, Rafael A.; Elsworth, Yvonne; Howe, Rachel; Mathur, Savita
2012MNRAS.422.3564B Altcode: 2012arXiv1204.1168B; 2012MNRAS.tmp.2800B
The aim of this paper is to investigate whether there are any 11-yr
or quasi-biennial solar-cycle-related variations in solar rotational
splitting frequencies of low-degree solar p modes. Although no 11-yr
signals were observed, variations on a shorter time-scale (∼2 yr) were
apparent. We show that the variations arose from complications/artefacts
associated with the realization noise in the data and the process by
which the data were analysed. More specifically, the realization noise
was observed to have a larger effect on the rotational splittings than
accounted for by the formal uncertainties. When used to infer the
rotation profile of the Sun these variations are not important. The
outer regions of the solar interior can be constrained using higher
degree modes. While the variations in the low-l splittings do make large
differences to the inferred rotation rate of the core, the core rotation
rate is so poorly constrained, even by low-l modes, that the different
inferred rotation profiles still agree within their respective 1σ
uncertainties. By contrast, in asteroseismology, only low-l modes are
visible and so higher l modes cannot be used to constrain the rotation
profile of stars. Furthermore, we usually only have one data set from
which to measure the observed low-l splitting. In such circumstances
the inferred internal rotation rate of a main-sequence star could
differ significantly from estimates of the surface rotation rate,
hence leading to spurious conclusions. Therefore, extreme care must be
taken when using only the splittings of low-l modes to draw conclusions
about the average internal rotation rate of a star.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Effective temperature scale for
KIC stars (Pinsonneault+, 2012)
Authors: Pinsonneault, M. H.; An, D.; Molenda-Zakowicz, J.; Chaplin,
W. J.; Metcalfe, T. S.; Bruntt, H.
2012yCat..21990030P Altcode:
We took griz photometry from long-cadence targets in the Kepler Input
Catalog (KIC) (Brown et al. 2011AJ....142..112B, see Cat. V/133);
photometric uncertainties were taken as 0.01mag in gri and 0.03mag in
z. Errors were taken from the quadrature sum of uncertainties in the
individual filters. JHKs photometry was taken from the All Sky Data
Release of the 2MASS Point Source Catalog (Skrutskie et al. 2006,
Cat. VII/233) and checked against complementary information in the
KIC itself. <P />(2 data files).
---------------------------------------------------------
Title: Solving the Mode Identification Problem in Asteroseismology
of F Stars Observed with Kepler
Authors: White, Timothy R.; Bedding, Timothy R.; Gruberbauer, Michael;
Benomar, Othman; Stello, Dennis; Appourchaux, Thierry; Chaplin,
William J.; Christensen-Dalsgaard, Jørgen; Elsworth, Yvonne P.;
García, Rafael A.; Hekker, Saskia; Huber, Daniel; Kjeldsen, Hans;
Mosser, Benoît; Kinemuchi, Karen; Mullally, Fergal; Still, Martin
2012ApJ...751L..36W Altcode: 2012arXiv1205.0544W
Asteroseismology of F-type stars has been hindered by an ambiguity in
identification of their oscillation modes. The regular mode pattern
that makes this task trivial in cooler stars is masked by increased
line widths. The absolute mode frequencies, encapsulated in the
asteroseismic variable epsilon, can help solve this impasse because
the values of epsilon implied by the two possible mode identifications
are distinct. We find that the correct epsilon can be deduced from the
effective temperature and the line widths and we apply these methods
to a sample of solar-like oscillators observed with Kepler.
---------------------------------------------------------
Title: Evolutionary influences on the structure of red-giant acoustic
oscillation spectra from 600d of Kepler observations
Authors: Kallinger, T.; Hekker, S.; Mosser, B.; De Ridder, J.;
Bedding, T. R.; Elsworth, Y. P.; Gruberbauer, M.; Guenther, D. B.;
Stello, D.; Basu, S.; García, R. A.; Chaplin, W. J.; Mullally, F.;
Still, M.; Thompson, S. E.
2012A&A...541A..51K Altcode: 2012arXiv1203.3134K
Context. It was recently discovered that the period spacings of mixed
pressure/gravity dipole modes in red giants permit a distinction between
the otherwise unknown evolutionary stage of these stars. The Kepler
space mission is reaching continuous observing times long enough to
also start studying the fine structure of the observed pressure-mode
spectra. <BR /> Aims: In this paper, we aim to study the signature of
stellar evolution on the radial and pressure-dominated l = 2 modes in
an ensemble of red giants that show solar-type oscillations. <BR />
Methods: We use established methods to automatically identify the mode
degree of l = 0 and 2 modes and measure the large (Δν<SUB>c</SUB>)
and small (δν<SUB>02</SUB>) frequency separation around the central
radial mode. We then determine the phase shift ɛ<SUB>c</SUB> of the
central radial mode, i.e. the linear offset in the asymptotic fit to the
acoustic modes. Furthermore we measure the individual frequencies of
radial modes and investigate their average curvature. <BR /> Results:
We find that ɛ<SUB>c</SUB> is significantly different for red giants
at a given Δν<SUB>c</SUB> but which burn only H in a shell (RGB)
than those that have already ignited core He burning. Even though not
directly probing the stellar core the pair of local seismic observables
(Δν<SUB>c</SUB>, ɛ<SUB>c</SUB>) can be used as an evolutionary
stage discriminator that turned out to be as reliable as the period
spacing of the mixed dipole modes. We find a tight correlation between
ɛ<SUB>c</SUB> and Δν<SUB>c</SUB> for RGB stars and unlike less
evolved stars we find no indication that ɛ<SUB>c</SUB> depends
on other properties of the star. It appears that the difference
in ɛ<SUB>c</SUB> between the two populations becomes smaller and
eventually indistinguishable if we use an average of several radial
orders, instead of a local, i.e. only around the central radial mode,
large separation to determine the phase shift. This indicates that
the information on the evolutionary stage is encoded locally, more
precisely in the shape of the radial mode sequence. This shape turns
out to be approximately symmetric around the central radial mode for
RGB stars but asymmetric for core He burning stars. We computed radial
mode frequencies for a sequence of red-giant models and find them to
qualitatively confirm our findings. We also find that, at least in our
models, the local Δν is an at least as good and mostly better proxy
for both the asymptotic spacing and the large separation scaled from
the model density than the average Δν. Finally, we investigate the
signature of the evolutionary stage on δν<SUB>02</SUB> and quantify
the mass dependency of this seismic parameter.
---------------------------------------------------------
Title: Kepler Observations and Asteroseismology of θ Cyg, the
Brightest StarObservable in the Kepler Field of View
Authors: Guzik, Joyce A.; Houdek, G.; Chaplin, W. J.; Kurtz, D.;
Gilliland, R. L.; Mullally, F.; Rowe, J. F.; Haas, M. R.; Bryson,
S. T.; Still, M. D.
2012AAS...22041905G Altcode:
θ Cyg (13 Cyg) is an F4 main sequence star that, at visual
magnitude V=4.48, is the brightest star observable by the Kepler
spacecraft. Short-cadence photometric data using a custom aperture
requiring 1800 pixels were obtained for this star during Quarter 6
(June-Sept 2010) and Quarter 8 (Jan-March 2011). <P />We present
analyses of the solar-like oscillations first discovered in the Q6
data [1, 2]. We use observational constraints from the literature
and recent ground-based observations including angular diameters
from optical interferometry in conjunction with the frequency data
to derive stellar properties (e.g., mass, age, metallicity, extent of
convection zones). We also discuss the prospects for detecting longer
period gravity-mode pulsations as seen in gamma Doradus variable stars
of spectral type A-F, given these constraints. <P />With an effective
temperature near 6500 K and near ‘solar’ element abundances,
θ Cyg is near the red edge of the gamma Doradus instability strip,
where high-order gravity-mode pulsations with periods of 1 day may be
present. If the envelope convection zone of the star is not too deep,
these gravity-mode pulsations may be driven by the convective blocking
mechanism. The calculated envelope convection zone depth depends
on the element abundance mixtures adopted for the stellar models
[2]. Asteroseismic studies of θ Cyg therefore have potential to
shed light on the solar abundance problem [3, 4], as well as to put
constraints on the presence and detectability of g-mode pulsations
for main-sequence solar-like stars. <P />References: <P />[1] Haas,
M.R. et al. 2011, BAAS, 43, No. 2, 140.07. <P />[2] Guzik, J.A. et
al. 2011, in Resolving the Future of Astronomy with Long Baseline
Interferometry, Soccoro, NM, <P />March 2011, ASP, in press. <P />[3]
Guzik, J.A. and Mussack, K. 2010, ApJ 713, 1108. <P />[4] Basu, S. and
Antia, H.M. 2008, Phys. Rep. 457, 217.
---------------------------------------------------------
Title: A Uniform Asteroseismic Analysis of 22 Solar-type Stars
Observed by Kepler
Authors: Mathur, S.; Metcalfe, T. S.; Woitaszek, M.; Bruntt, H.;
Verner, G. A.; Christensen-Dalsgaard, J.; Creevey, O. L.; Doǧan, G.;
Basu, S.; Karoff, C.; Stello, D.; Appourchaux, T.; Campante, T. L.;
Chaplin, W. J.; García, R. A.; Bedding, T. R.; Benomar, O.; Bonanno,
A.; Deheuvels, S.; Elsworth, Y.; Gaulme, P.; Guzik, J. A.; Handberg,
R.; Hekker, S.; Herzberg, W.; Monteiro, M. J. P. F. G.; Piau, L.;
Quirion, P. -O.; Régulo, C.; Roth, M.; Salabert, D.; Serenelli, A.;
Thompson, M. J.; Trampedach, R.; White, T. R.; Ballot, J.; Brandão,
I. M.; Molenda-Żakowicz, J.; Kjeldsen, H.; Twicken, J. D.; Uddin,
K.; Wohler, B.
2012ApJ...749..152M Altcode: 2012arXiv1202.2844M
Asteroseismology with the Kepler space telescope is providing not
only an improved characterization of exoplanets and their host stars,
but also a new window on stellar structure and evolution for the
large sample of solar-type stars in the field. We perform a uniform
analysis of 22 of the brightest asteroseismic targets with the highest
signal-to-noise ratio observed for 1 month each during the first year
of the mission, and we quantify the precision and relative accuracy
of asteroseismic determinations of the stellar radius, mass, and age
that are possible using various methods. We present the properties
of each star in the sample derived from an automated analysis of the
individual oscillation frequencies and other observational constraints
using the Asteroseismic Modeling Portal (AMP), and we compare them to
the results of model-grid-based methods that fit the global oscillation
properties. We find that fitting the individual frequencies typically
yields asteroseismic radii and masses to ~1% precision, and ages to
~2.5% precision (respectively, 2, 5, and 8 times better than fitting
the global oscillation properties). The absolute level of agreement
between the results from different approaches is also encouraging,
with model-grid-based methods yielding slightly smaller estimates of
the radius and mass and slightly older values for the stellar age
relative to AMP, which computes a large number of dedicated models
for each star. The sample of targets for which this type of analysis
is possible will grow as longer data sets are obtained during the
remainder of the mission.
---------------------------------------------------------
Title: A Revised Effective Temperature Scale for the Kepler Input
Catalog
Authors: Pinsonneault, Marc H.; An, Deokkeun; Molenda-Żakowicz,
Joanna; Chaplin, William J.; Metcalfe, Travis S.; Bruntt, Hans
2012ApJS..199...30P Altcode: 2011arXiv1110.4456P
We present a catalog of revised effective temperatures for stars
observed in long-cadence mode in the Kepler Input Catalog (KIC). We use
Sloan Digital Sky Survey (SDSS) griz filters tied to the fundamental
temperature scale. Polynomials for griz color-temperature relations are
presented, along with correction terms for surface gravity effects,
metallicity, and statistical corrections for binary companions or
blending. We compare our temperature scale to the published infrared
flux method (IRFM) scale for V<SUB>T</SUB>JK<SUB>s</SUB> in both open
clusters and the Kepler fields. We find good agreement overall, with
some deviations between (J - K<SUB>s</SUB> )-based temperatures from the
IRFM and both SDSS filter and other diagnostic IRFM color-temperature
relationships above 6000 K. For field dwarfs, we find a mean shift
toward hotter temperatures relative to the KIC, of order 215 K,
in the regime where the IRFM scale is well defined (4000 K to 6500
K). This change is of comparable magnitude in both color systems and in
spectroscopy for stars with T <SUB>eff</SUB> below 6000 K. Systematic
differences between temperature estimators appear for hotter stars,
and we define corrections to put the SDSS temperatures on the IRFM scale
for them. When the theoretical dependence on gravity is accounted for,
we find a similar temperature scale offset between the fundamental and
KIC scales for giants. We demonstrate that statistical corrections
to color-based temperatures from binaries are significant. Typical
errors, mostly from uncertainties in extinction, are of order 100
K. Implications for other applications of the KIC are discussed.
---------------------------------------------------------
Title: Asteroseismology of the Solar Analogs 16 Cyg A and B from
Kepler Observations
Authors: Metcalfe, T. S.; Chaplin, W. J.; Appourchaux, T.; García,
R. A.; Basu, S.; Brandão, I.; Creevey, O. L.; Deheuvels, S.; Doǧan,
G.; Eggenberger, P.; Karoff, C.; Miglio, A.; Stello, D.; Yıldız,
M.; Çelik, Z.; Antia, H. M.; Benomar, O.; Howe, R.; Régulo, C.;
Salabert, D.; Stahn, T.; Bedding, T. R.; Davies, G. R.; Elsworth, Y.;
Gizon, L.; Hekker, S.; Mathur, S.; Mosser, B.; Bryson, S. T.; Still,
M. D.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Kawaler, S. D.;
Kjeldsen, H.; Ibrahim, K. A.; Klaus, T. C.; Li, J.
2012ApJ...748L..10M Altcode: 2012arXiv1201.5966M
The evolved solar-type stars 16 Cyg A and B have long been studied
as solar analogs, yielding a glimpse into the future of our own
Sun. The orbital period of the binary system is too long to provide
meaningful dynamical constraints on the stellar properties, but
asteroseismology can help because the stars are among the brightest
in the Kepler field. We present an analysis of three months of nearly
uninterrupted photometry of 16 Cyg A and B from the Kepler space
telescope. We extract a total of 46 and 41 oscillation frequencies
for the two components, respectively, including a clear detection
of octupole (l = 3) modes in both stars. We derive the properties
of each star independently using the Asteroseismic Modeling Portal,
fitting the individual oscillation frequencies and other observational
constraints simultaneously. We evaluate the systematic uncertainties
from an ensemble of results generated by a variety of stellar evolution
codes and fitting methods. The optimal models derived by fitting each
component individually yield a common age (t = 6.8 ± 0.4 Gyr) and
initial composition (Z <SUB>i</SUB> = 0.024 ± 0.002, Y <SUB>i</SUB> =
0.25 ± 0.01) within the uncertainties, as expected for the components
of a binary system, bolstering our confidence in the reliability of
asteroseismic techniques. The longer data sets that will ultimately
become available will allow future studies of differential rotation,
convection zone depths, and long-term changes due to stellar activity
cycles.
---------------------------------------------------------
Title: Acoustic spectrum fitting for a large set of solar-like
pulsators
Authors: Benomar, O.; Baudin, F.; Chaplin, W. J.; Elsworth, Y.;
Appourchaux, T.
2012MNRAS.420.2178B Altcode: 2011MNRAS.tmp.2149B
Asteroseismology provides the means both to constrain the global
properties and to probe the internal structures of stars. Asteroseismic
data are now available on large numbers of solar-type stars, thanks
in particular to the CoRoT and Kepler space missions, and automated
data-analysis pipelines are needed to provide efficient and timely
results. Here, we present an automated algorithm that is able to extract
mode parameters under low signal-to-noise ratio conditions. We use a
Bayesian framework to ensure the robustness of the algorithm. We discuss
the efficiency of the method and test it using Variability of Solar
Irradiance and Gravity Oscillations (VIRGO) Sun-as-a-star photometry
data and the artificial Astero Fitting at Low Angular degree Group
(asteroFLAG) Kepler ensemble. Analysis of the VIRGO data shows that
it is possible to track variations of the individual mode parameters
(frequency, height, width) through the solar cycle, using short time
series (30 days). The present analysis also revealed a modulation
of the degree l = 2 relative height through the solar cycle. Applied
on asteroFLAG data, we show that the pipeline extracts accurately the
central frequency and the large separation. It is also able to identify
the degree of the modes in 78 per cent of stars.
---------------------------------------------------------
Title: Kepler-22b: A 2.4 Earth-radius Planet in the Habitable Zone
of a Sun-like Star
Authors: Borucki, William J.; Koch, David G.; Batalha, Natalie;
Bryson, Stephen T.; Rowe, Jason; Fressin, Francois; Torres,
Guillermo; Caldwell, Douglas A.; Christensen-Dalsgaard, Jørgen;
Cochran, William D.; DeVore, Edna; Gautier, Thomas N.; Geary, John
C.; Gilliland, Ronald; Gould, Alan; Howell, Steve B.; Jenkins,
Jon M.; Latham, David W.; Lissauer, Jack J.; Marcy, Geoffrey W.;
Sasselov, Dimitar; Boss, Alan; Charbonneau, David; Ciardi, David;
Kaltenegger, Lisa; Doyle, Laurance; Dupree, Andrea K.; Ford, Eric B.;
Fortney, Jonathan; Holman, Matthew J.; Steffen, Jason H.; Mullally,
Fergal; Still, Martin; Tarter, Jill; Ballard, Sarah; Buchhave, Lars
A.; Carter, Josh; Christiansen, Jessie L.; Demory, Brice-Olivier;
Désert, Jean-Michel; Dressing, Courtney; Endl, Michael; Fabrycky,
Daniel; Fischer, Debra; Haas, Michael R.; Henze, Christopher; Horch,
Elliott; Howard, Andrew W.; Isaacson, Howard; Kjeldsen, Hans; Johnson,
John Asher; Klaus, Todd; Kolodziejczak, Jeffery; Barclay, Thomas;
Li, Jie; Meibom, Søren; Prsa, Andrej; Quinn, Samuel N.; Quintana,
Elisa V.; Robertson, Paul; Sherry, William; Shporer, Avi; Tenenbaum,
Peter; Thompson, Susan E.; Twicken, Joseph D.; Van Cleve, Jeffrey;
Welsh, William F.; Basu, Sarbani; Chaplin, William; Miglio, Andrea;
Kawaler, Steven D.; Arentoft, Torben; Stello, Dennis; Metcalfe,
Travis S.; Verner, Graham A.; Karoff, Christoffer; Lundkvist, Mia;
Lund, Mikkel N.; Handberg, Rasmus; Elsworth, Yvonne; Hekker, Saskia;
Huber, Daniel; Bedding, Timothy R.; Rapin, William
2012ApJ...745..120B Altcode: 2011arXiv1112.1640B
A search of the time-series photometry from NASA's Kepler spacecraft
reveals a transiting planet candidate orbiting the 11th magnitude G5
dwarf KIC 10593626 with a period of 290 days. The characteristics of the
host star are well constrained by high-resolution spectroscopy combined
with an asteroseismic analysis of the Kepler photometry, leading to
an estimated mass and radius of 0.970 ± 0.060 M <SUB>⊙</SUB> and
0.979 ± 0.020 R <SUB>⊙</SUB>. The depth of 492 ± 10 ppm for the
three observed transits yields a radius of 2.38 ± 0.13 Re for the
planet. The system passes a battery of tests for false positives,
including reconnaissance spectroscopy, high-resolution imaging, and
centroid motion. A full BLENDER analysis provides further validation
of the planet interpretation by showing that contamination of the
target by an eclipsing system would rarely mimic the observed shape
of the transits. The final validation of the planet is provided by
16 radial velocities (RVs) obtained with the High Resolution Echelle
Spectrometer on Keck I over a one-year span. Although the velocities
do not lead to a reliable orbit and mass determination, they are able
to constrain the mass to a 3σ upper limit of 124 M <SUB>⊕</SUB>,
safely in the regime of planetary masses, thus earning the designation
Kepler-22b. The radiative equilibrium temperature is 262 K for a planet
in Kepler-22b's orbit. Although there is no evidence that Kepler-22b
is a rocky planet, it is the first confirmed planet with a measured
radius to orbit in the habitable zone of any star other than the Sun.
---------------------------------------------------------
Title: Kepler-21b: A 1.6 R <SUB>Earth</SUB> Planet Transiting the
Bright Oscillating F Subgiant Star HD 179070
Authors: Howell, Steve B.; Rowe, Jason F.; Bryson, Stephen T.; Quinn,
Samuel N.; Marcy, Geoffrey W.; Isaacson, Howard; Ciardi, David R.;
Chaplin, William J.; Metcalfe, Travis S.; Monteiro, Mario J. P. F. G.;
Appourchaux, Thierry; Basu, Sarbani; Creevey, Orlagh L.; Gilliland,
Ronald L.; Quirion, Pierre-Olivier; Stello, Denis; Kjeldsen, Hans;
Christensen-Dalsgaard, Jörgen; Elsworth, Yvonne; García, Rafael
A.; Houdek, Günter; Karoff, Christoffer; Molenda-Żakowicz, Joanna;
Thompson, Michael J.; Verner, Graham A.; Torres, Guillermo; Fressin,
Francois; Crepp, Justin R.; Adams, Elisabeth; Dupree, Andrea; Sasselov,
Dimitar D.; Dressing, Courtney D.; Borucki, William J.; Koch, David
G.; Lissauer, Jack J.; Latham, David W.; Buchhave, Lars A.; Gautier,
Thomas N., III; Everett, Mark; Horch, Elliott; Batalha, Natalie M.;
Dunham, Edward W.; Szkody, Paula; Silva, David R.; Mighell, Ken;
Holberg, Jay; Ballot, Jerôme; Bedding, Timothy R.; Bruntt, Hans;
Campante, Tiago L.; Handberg, Rasmus; Hekker, Saskia; Huber, Daniel;
Mathur, Savita; Mosser, Benoit; Régulo, Clara; White, Timothy R.;
Christiansen, Jessie L.; Middour, Christopher K.; Haas, Michael R.;
Hall, Jennifer R.; Jenkins, Jon M.; McCaulif, Sean; Fanelli, Michael
N.; Kulesa, Craig; McCarthy, Don; Henze, Christopher E.
2012ApJ...746..123H Altcode: 2011arXiv1112.2165H
We present Kepler observations of the bright (V = 8.3), oscillating
star HD 179070. The observations show transit-like events which
reveal that the star is orbited every 2.8 days by a small, 1.6 R
<SUB>Earth</SUB> object. Seismic studies of HD 179070 using short
cadence Kepler observations show that HD 179070 has a frequency-power
spectrum consistent with solar-like oscillations that are acoustic
p-modes. Asteroseismic analysis provides robust values for the mass
and radius of HD 179070, 1.34 ± 0.06 M <SUB>⊙</SUB> and 1.86 ±
0.04 R <SUB>⊙</SUB>, respectively, as well as yielding an age of
2.84 ± 0.34 Gyr for this F5 subgiant. Together with ground-based
follow-up observations, analysis of the Kepler light curves and
image data, and blend scenario models, we conservatively show at the
>99.7% confidence level (3σ) that the transit event is caused by
a 1.64 ± 0.04 R <SUB>Earth</SUB> exoplanet in a 2.785755 ± 0.000032
day orbit. The exoplanet is only 0.04 AU away from the star and our
spectroscopic observations provide an upper limit to its mass of ~10 M
<SUB>Earth</SUB> (2σ). HD 179070 is the brightest exoplanet host star
yet discovered by Kepler. <P />Based in part on observations obtained
at the W. M. Keck Observatory, which is operated by the University
of California and the California Institute of Technology, the Mayall
telescope at Kitt Peak National Observatory, and the WIYN Observatory
which is a joint facility of NOAO, University of Wisconsin-Madison,
Indiana University, and Yale University.
---------------------------------------------------------
Title: Effect of Uncertainties in Stellar Model Parameters on
Estimated Masses and Radii of Single Stars
Authors: Basu, Sarbani; Verner, Graham A.; Chaplin, William J.;
Elsworth, Yvonne
2012ApJ...746...76B Altcode: 2011arXiv1111.6976B
Accurate and precise values of radii and masses of stars are needed
to correctly estimate properties of extrasolar planets. We examine
the effect of uncertainties in stellar model parameters on estimates
of the masses, radii, and average densities of solar-type stars. We
find that in the absence of seismic data on solar-like oscillations,
stellar masses can be determined to a greater accuracy than either
stellar radii or densities; but to get reasonably accurate results
the effective temperature, log g, and metallicity must be measured to
high precision. When seismic data are available, stellar density is
the most well-determined property, followed by radius, with mass the
least well-determined property. Uncertainties in stellar convection,
quantified in terms of uncertainties in the value of the mixing
length parameter, cause the most significant errors in the estimates
of stellar properties.
---------------------------------------------------------
Title: Quasi-biennial variations in helioseismic frequencies: can
the source of the variation be localized?
Authors: Broomhall, A. -M.; Chaplin, W. J.; Elsworth, Y.; Simoniello,
R.
2012MNRAS.420.1405B Altcode: 2011MNRAS.tmp.2018B; 2011arXiv1111.2492B
We investigate the spherical harmonic degree (l) dependence of the
'seismic' quasi-biennial oscillation (QBO) observed in low-degree solar
p-mode frequencies, using Sun-as-a-star Birmingham Solar Oscillations
Network data. The amplitude of the seismic QBO is modulated by the 11-yr
solar cycle, with the amplitude of the signal being largest at solar
maximum. The amplitude of the signal is noticeably larger for the l=
2 and 3 modes than for the l= 0 and 1 modes. The seismic QBO shows
some frequency dependence but this dependence is not as strong as
observed in the 11-yr solar cycle. These results are consistent with
the seismic QBO having its origins in shallow layers of the interior
(one possibility being the bottom of the shear layer extending 5 per
cent below the solar surface). Under this scenario the magnetic flux
responsible for the seismic QBO is brought to the surface (where its
influence on the p modes is stronger) by buoyant flux from the 11-yr
cycle, the strong component of which is observed at predominantly low
latitudes. As the l= 2 and 3 modes are much more sensitive to equatorial
latitudes than the l= 0 and 1 modes the influence of the 11-yr cycle
on the seismic QBO is more visible in l= 2 and 3 mode frequencies. Our
results imply that close to solar maximum the main influence of the
seismic QBO occurs at low latitudes (<45°), which is where the
strong component of the 11-yr solar cycle resides. To isolate the
latitudinal dependence of the seismic QBO from the 11-yr solar cycle
we must consider epochs when the 11-yr solar cycle is weak. However,
away from solar maximum, the amplitude of the seismic QBO is weak
making the latitudinal dependence hard to constrain.
---------------------------------------------------------
Title: Asteroseismology of old open clusters with Kepler: direct
estimate of the integrated red giant branch mass-loss in NGC 6791
and 6819
Authors: Miglio, A.; Brogaard, K.; Stello, D.; Chaplin, W. J.;
D'Antona, F.; Montalbán, J.; Basu, S.; Bressan, A.; Grundahl,
F.; Pinsonneault, M.; Serenelli, A. M.; Elsworth, Y.; Hekker, S.;
Kallinger, T.; Mosser, B.; Ventura, P.; Bonanno, A.; Noels, A.;
Silva Aguirre, V.; Szabo, R.; Li, J.; McCauliff, S.; Middour, C. K.;
Kjeldsen, H.
2012MNRAS.419.2077M Altcode: 2011arXiv1109.4376M; 2011MNRAS.tmp.1877M
Mass-loss of red giant branch (RGB) stars is still poorly determined,
despite its crucial role in the chemical enrichment of galaxies. Thanks
to the recent detection of solar-like oscillations in G-K giants
in open clusters with Kepler, we can now directly determine stellar
masses for a statistically significant sample of stars in the old open
clusters NGC 6791 and 6819. The aim of this work is to constrain the
integrated RGB mass-loss by comparing the average mass of stars in
the red clump (RC) with that of stars in the low-luminosity portion of
the RGB [i.e. stars with L≲L(RC)]. Stellar masses were determined by
combining the available seismic parameters ν<SUB>max</SUB> and Δν
with additional photometric constraints and with independent distance
estimates. We measured the masses of 40 stars on the RGB and 19 in the
RC of the old metal-rich cluster NGC 6791. We find that the difference
between the average mass of RGB and RC stars is small, but significant
[? (random) ±0.04 (systematic) M<SUB>⊙</SUB>]. Interestingly, such
a small ? does not support scenarios of an extreme mass-loss for this
metal-rich cluster. If we describe the mass-loss rate with Reimers
prescription, a first comparison with isochrones suggests that the
observed ? is compatible with a mass-loss efficiency parameter in the
range 0.1 ≲η≲ 0.3. Less stringent constraints on the RGB mass-loss
rate are set by the analysis of the ∼2 Gyr old NGC 6819, largely due
to the lower mass-loss expected for this cluster, and to the lack of an
independent and accurate distance determination. In the near future,
additional constraints from frequencies of individual pulsation modes
and spectroscopic effective temperatures will allow further stringent
tests of the Δν and ν<SUB>max</SUB> scaling relations, which provide
a novel, and potentially very accurate, means of determining stellar
radii and masses.
---------------------------------------------------------
Title: Fundamental properties of five Kepler stars using global
asteroseismic quantities and ground-based observations
Authors: Creevey, O. L.; Doǧan, G.; Frasca, A.; Thygesen, A. O.;
Basu, S.; Bhattacharya, J.; Biazzo, K.; Brandão, I. M.; Bruntt, H.;
Mazumdar, A.; Niemczura, E.; Shrotriya, T.; Sousa, S. G.; Stello, D.;
Subramaniam, A.; Campante, T. L.; Handberg, R.; Mathur, S.; Bedding,
T. R.; García, R. A.; Régulo, C.; Salabert, D.; Molenda-Żakowicz,
J.; Quirion, P. -O.; White, T. R.; Bonanno, A.; Chaplin, W. J.;
Christensen-Dalsgaard, J.; Christiansen, J. L.; Elsworth, Y.; Fanelli,
M. N.; Karoff, C.; Kinemuchi, K.; Kjeldsen, H.; Gai, N.; Monteiro,
M. J. P. F. G.; Suárez, J. C.
2012A&A...537A.111C Altcode: 2011arXiv1111.4615C
We present an asteroseismic study of the solar-like stars KIC 11395018,
KIC 10273246, KIC 10920273, KIC 10339342, and KIC 11234888 using
short-cadence time series of more than eight months from the Kepler
satellite. For four of these stars, we derive atmospheric parameters
from spectra acquired with the Nordic Optical Telescope. The global
seismic quantities (average largefrequency separation and frequency
of maximum power), combined with the atmospheric parameters, yield
the mean density and surface gravity with precisions of 2% and ~0.03
dex, respectively. We also determine the radius, mass, and age with
precisions of 2-5%, 7-11%, and ~35%, respectively, using grid-based
analyses. Coupling the stellar parameters with photometric data yields
an asteroseismic distance with a precision better than 10%. A vsini
measurement provides a rotational period-inclination correlation, and
using the rotational periods from the recent literature, we constrain
the stellar inclination for three of the stars. An Li abundance analysis
yields an independent estimate of the age, but this is inconsistent
with the asteroseismically determined age for one of the stars. We
assess the performance of five grid-based analysis methods and find
them all to provide consistent values of the surface gravity to ~0.03
dex when both atmospheric and seismic constraints are at hand. The
different grid-based analyses all yield fitted values of radius and
mass to within 2.4σ, and taking the mean of these results reduces
it to 1.5σ. The absence of a metallicity constraint when the average
large frequency separation is measured with a precision of 1% biases
the fitted radius and mass for the stars with non-solar metallicity
(metal-rich KIC 11395018 and metal-poor KIC 10273246), while including
a metallicity constraint reduces the uncertainties in both of these
parameters by almost a factor of two. We found that including the
average small frequency separation improves the determination of the
age only for KIC 11395018 and KIC 11234888, and for the latter this
improvement was due to the lack of strong atmospheric constraints.
---------------------------------------------------------
Title: Characterization of the power excess of solar-like oscillations
in red giants with Kepler
Authors: Mosser, B.; Elsworth, Y.; Hekker, S.; Huber, D.; Kallinger,
T.; Mathur, S.; Belkacem, K.; Goupil, M. J.; Samadi, R.; Barban, C.;
Bedding, T. R.; Chaplin, W. J.; García, R. A.; Stello, D.; De Ridder,
J.; Middour, C. K.; Morris, R. L.; Quintana, E. V.
2012A&A...537A..30M Altcode: 2011arXiv1110.0980M
Context. The space mission Kepler provides us with long and
uninterrupted photometric time series of red giants. This allows
us to examine their seismic global properties and to compare these
with theoretical predictions. <BR /> Aims: We aim to describe the
oscillation power excess observed in red giant oscillation spectra
with global seismic parameters, and to investigate empirical scaling
relations governing these parameters. From these scalings relations,
we derive new physical properties of red giant oscillations. <BR />
Methods: Various different methods were compared in order to validate
the processes and to derive reliable output values. For consistency,
a single method was then used to determine scaling relations for the
relevant global asteroseismic parameters: mean mode height, mean height
of the background signal superimposed on the oscillation power excess,
width of the power excess, bolometric amplitude of the radial modes
and visibility of non-radial modes. A method for deriving oscillation
amplitudes is proposed, which relies on the complete identification
of the red giant oscillation spectrum. <BR /> Results: The comparison
of the different methods has shown the important role of the way the
background is modelled. The convergence reached by the collaborative
work enables us to derive significant results concerning the oscillation
power excess. We obtain several scaling relations, and identify the
influence of the stellar mass and the evolutionary status. The effect
of helium burning on the red giant interior structure is confirmed: it
yields a strong mass-radius relation for clump stars. We find that none
of the amplitude scaling relations motivated by physical considerations
predict the observed mode amplitudes of red giant stars. In parallel,
the degree-dependent mode visibility exhibits important variations. Both
effects seem related to the significant influence of the high mode
mass of non-radial mixed modes. A family of red giants with very weak
dipole modes is identified, and its properties are analyzed. <BR />
Conclusions: The clear correlation between the power densities of the
background signal and of the stellar oscillation induces important
consequences to be considered for deriving a reliable theoretical
relation of the mode amplitude. As a by-product of this work, we have
verified that red giant asteroseismology delivers new insights for
stellar and Galactic physics, given the evidence for mass loss at the
tip of the red giant branch. <P />Appendices are available in electronic
form at <A href="http://www.aanda.org">http://www.aanda.org</A>
---------------------------------------------------------
Title: Oscillation mode linewidths of main-sequence and subgiant
stars observed by Kepler
Authors: Appourchaux, T.; Benomar, O.; Gruberbauer, M.; Chaplin,
W. J.; García, R. A.; Handberg, R.; Verner, G. A.; Antia, H. M.;
Campante, T. L.; Davies, G. R.; Deheuvels, S.; Hekker, S.; Howe,
R.; Salabert, D.; Bedding, T. R.; White, T. R.; Houdek, G.; Silva
Aguirre, V.; Elsworth, Y. P.; van Cleve, J.; Clarke, B. D.; Hall,
J. R.; Kjeldsen, H.
2012A&A...537A.134A Altcode: 2011arXiv1112.3295A
Context. Solar-like oscillations have been observed by Kepler and CoRoT
in several solar-type stars. <BR /> Aims: We study the variations in the
stellar p-mode linewidth as a function of effective temperature. <BR
/> Methods: We study a time series of nine months of Kepler data. We
analyse the power spectra of 42 cool main-sequence stars and subgiants
using both maximum likelihood estimators and Bayesian estimators
to recover individual mode characteristics such as frequencies,
linewidths, and mode heights. <BR /> Results: We report on the mode
linewidth at both maximum power and maximum mode height for these 42
stars as a function of effective temperature. <BR /> Conclusions: We
show that the mode linewidth at either maximum mode height or maximum
amplitude follows a scaling relation with effective temperature,
which is a combination of a power law and a lower bound. The typical
power-law index is about 13 for the linewidth derived from the maximum
mode height, and about 16 for the linewidth derived from the maximum
amplitude, while the lower bound is about 0.3 μHz and 0.7 μHz,
respectively. We stress that this scaling relation is only valid for
cool main-sequence stars and subgiants, and does not have any predictive
power outside the temperature range of these stars.
---------------------------------------------------------
Title: Testing Scaling Relations for Solar-like Oscillations from
the Main Sequence to Red Giants Using Kepler Data
Authors: Huber, D.; Bedding, T. R.; Stello, D.; Hekker, S.; Mathur,
S.; Mosser, B.; Verner, G. A.; Bonanno, A.; Buzasi, D. L.; Campante,
T. L.; Elsworth, Y. P.; Hale, S. J.; Kallinger, T.; Silva Aguirre,
V.; Chaplin, W. J.; De Ridder, J.; García, R. A.; Appourchaux,
T.; Frandsen, S.; Houdek, G.; Molenda-Żakowicz, J.; Monteiro,
M. J. P. F. G.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Kawaler,
S. D.; Kjeldsen, H.; Broomhall, A. M.; Corsaro, E.; Salabert, D.;
Sanderfer, D. T.; Seader, S. E.; Smith, J. C.
2011ApJ...743..143H Altcode: 2011arXiv1109.3460H
We have analyzed solar-like oscillations in ~1700 stars observed by the
Kepler Mission, spanning from the main sequence to the red clump. Using
evolutionary models, we test asteroseismic scaling relations for the
frequency of maximum power (ν<SUB>max</SUB>), the large frequency
separation (Δν), and oscillation amplitudes. We show that the
difference of the Δν-ν<SUB>max</SUB> relation for unevolved and
evolved stars can be explained by different distributions in effective
temperature and stellar mass, in agreement with what is expected from
scaling relations. For oscillation amplitudes, we show that neither
(L/M)<SUP> s </SUP> scaling nor the revised scaling relation by Kjeldsen
& Bedding is accurate for red-giant stars, and demonstrate that a
revised scaling relation with a separate luminosity-mass dependence can
be used to calculate amplitudes from the main sequence to red giants
to a precision of ~25%. The residuals show an offset particularly for
unevolved stars, suggesting that an additional physical dependency is
necessary to fully reproduce the observed amplitudes. We investigate
correlations between amplitudes and stellar activity, and find evidence
that the effect of amplitude suppression is most pronounced for subgiant
stars. Finally, we test the location of the cool edge of the instability
strip in the Hertzsprung-Russell diagram using solar-like oscillations
and find the detections in the hottest stars compatible with a domain
of hybrid stochastically excited and opacity driven pulsation.
---------------------------------------------------------
Title: Frequency dependence of the large frequency separation of
solar-like oscillators: influence of the helium second-ionization zone
Authors: Hekker, S.; Basu, Sarbani; Elsworth, Y.; Chaplin, W. J.
2011MNRAS.418L.119H Altcode: 2011arXiv1109.2595H
The large frequency separation (Δν) between modes of the same degree
and consecutive orders in a star is approximately proportional to the
square root of its mean density. To determine Δν as accurately as
possible, a mean large frequency separation (<Δν>) computed over
several orders is often used. It is, however, known that Δν varies
with frequency in a second-order effect. From observations, it has been
shown that this frequency dependence is more important for main-sequence
stars than it is for red giant stars. Here we use YREC models to verify
and explain this observational result. We find that for stars with R
≳ 8 R<SUB>⊙</SUB>, the effect of the helium second-ionization zone
(He II zone) is relatively small. For these stars, the deep location
of the He II zone induces a frequency modulation covering only a few
Δν, while the amplitude of the modulation is low due to the relatively
weak and extended He II layer, causing a shallow wide depression in the
first adiabatic exponent (Γ<SUB>1</SUB>). For less evolved stars, the
He II zone is located closer to the surface, and it is more confined,
i.e. a deep narrow depression in Γ<SUB>1</SUB>. This causes frequency
modulations with relatively high amplitudes covering up to about 20Δν,
inducing a relatively large frequency modulation. Additionally, we
find that for less evolved stars, the He II zone is stronger and more
localized for more massive stars and for stars with low metallicities
further increasing the amplitude of the frequency modulation.
---------------------------------------------------------
Title: Granulation in Red Giants: Observations by the Kepler Mission
and Three-dimensional Convection Simulations
Authors: Mathur, S.; Hekker, S.; Trampedach, R.; Ballot, J.; Kallinger,
T.; Buzasi, D.; García, R. A.; Huber, D.; Jiménez, A.; Mosser, B.;
Bedding, T. R.; Elsworth, Y.; Régulo, C.; Stello, D.; Chaplin, W. J.;
De Ridder, J.; Hale, S. J.; Kinemuchi, K.; Kjeldsen, H.; Mullally,
F.; Thompson, S. E.
2011ApJ...741..119M Altcode: 2011arXiv1109.1194M
The granulation pattern that we observe on the surface of the Sun is
due to hot plasma rising to the photosphere where it cools down and
descends back into the interior at the edges of granules. This is the
visible manifestation of convection taking place in the outer part of
the solar convection zone. Because red giants have deeper convection
zones than the Sun, we cannot a priori assume that their granulation is
a scaled version of solar granulation. Until now, neither observations
nor one-dimensional analytical convection models could put constraints
on granulation in red giants. With asteroseismology, this study can
now be performed. We analyze ~1000 red giants that have been observed
by Kepler during 13 months. We fit the power spectra with Harvey-like
profiles to retrieve the characteristics of the granulation (timescale
τ<SUB>gran</SUB> and power P <SUB>gran</SUB>). We search for a
correlation between these parameters and the global acoustic-mode
parameter (the position of maximum power, ν<SUB>max</SUB>) as
well as with stellar parameters (mass, radius, surface gravity
(log g), and effective temperature (T <SUB>eff</SUB>)). We show
that τ<SUB>eff</SUB>vpropν<SUP>-0.89</SUP> <SUB>max</SUB> and
P <SUB>gran</SUB>vpropν<SUP>-1.90</SUP> <SUB>max</SUB>, which
is consistent with the theoretical predictions. We find that
the granulation timescales of stars that belong to the red clump
have similar values while the timescales of stars in the red giant
branch are spread in a wider range. Finally, we show that realistic
three-dimensional simulations of the surface convection in stars,
spanning the (T <SUB>eff</SUB>, log g) range of our sample of red
giants, match the Kepler observations well in terms of trends.
---------------------------------------------------------
Title: Asteroseismic Diagrams from a Survey of Solar-like Oscillations
with Kepler
Authors: White, Timothy R.; Bedding, Timothy R.; Stello, Dennis;
Appourchaux, Thierry; Ballot, Jérôme; Benomar, Othman; Bonanno,
Alfio; Broomhall, Anne-Marie; Campante, Tiago L.; Chaplin, William
J.; Christensen-Dalsgaard, Jørgen; Corsaro, Enrico; Doǧan, Gülnur;
Elsworth, Yvonne P.; Fletcher, Stephen T.; García, Rafael A.; Gaulme,
Patrick; Handberg, Rasmus; Hekker, Saskia; Huber, Daniel; Karoff,
Christoffer; Kjeldsen, Hans; Mathur, Savita; Mosser, Benoit; Monteiro,
Mario J. P. F. G.; Régulo, Clara; Salabert, David; Silva Aguirre,
Victor; Thompson, Michael J.; Verner, Graham; Morris, Robert L.;
Sanderfer, Dwight T.; Seader, Shawn E.
2011ApJ...742L...3W Altcode: 2011arXiv1110.1375W
Photometric observations made by the NASA Kepler Mission have led to a
dramatic increase in the number of main-sequence and subgiant stars with
detected solar-like oscillations. We present an ensemble asteroseismic
analysis of 76 solar-type stars. Using frequencies determined from the
Kepler time-series photometry, we have measured three asteroseismic
parameters that characterize the oscillations: the large frequency
separation (Δν), the small frequency separation between modes of
l = 0 and l = 2 (δν<SUB>02</SUB>), and the dimensionless offset
(epsilon). These measurements allow us to construct asteroseismic
diagrams, namely the so-called Christensen-Dalsgaard diagram of
δν<SUB>02</SUB> versus Δν, and the recently re-introduced epsilon
diagram. We compare the Kepler results with previously observed
solar-type stars and with theoretical models. The positions of
stars in these diagrams places constraints on their masses and
ages. Additionally, we confirm the observational relationship
between epsilon and T <SUB>eff</SUB> that allows for the unambiguous
determination of radial order and should help resolve the problem of
mode identification in F stars.
---------------------------------------------------------
Title: Kepler Mission Stellar and Instrument Noise Properties
Authors: Gilliland, Ronald L.; Chaplin, William J.; Dunham, Edward
W.; Argabright, Vic S.; Borucki, William J.; Basri, Gibor; Bryson,
Stephen T.; Buzasi, Derek L.; Caldwell, Douglas A.; Elsworth, Yvonne
P.; Jenkins, Jon M.; Koch, David G.; Kolodziejczak, Jeffrey; Miglio,
Andrea; van Cleve, Jeffrey; Walkowicz, Lucianne M.; Welsh, William F.
2011ApJS..197....6G Altcode: 2011arXiv1107.5207G
Kepler mission results are rapidly contributing to fundamentally new
discoveries in both the exoplanet and asteroseismology fields. The
data returned from Kepler are unique in terms of the number of stars
observed, precision of photometry for time series observations, and
the temporal extent of high duty cycle observations. As the first
mission to provide extensive time series measurements on thousands
of stars over months to years at a level hitherto possible only for
the Sun, the results from Kepler will vastly increase our knowledge
of stellar variability for quiet solar-type stars. Here, we report
on the stellar noise inferred on the timescale of a few hours of
most interest for detection of exoplanets via transits. By design the
data from moderately bright Kepler stars are expected to have roughly
comparable levels of noise intrinsic to the stars and arising from a
combination of fundamental limitations such as Poisson statistics and
any instrument noise. The noise levels attained by Kepler on-orbit
exceed by some 50% the target levels for solar-type, quiet stars. We
provide a decomposition of observed noise for an ensemble of 12th
magnitude stars arising from fundamental terms (Poisson and readout
noise), added noise due to the instrument and that intrinsic to the
stars. The largest factor in the modestly higher than anticipated
noise follows from intrinsic stellar noise. We show that using stellar
parameters from galactic stellar synthesis models, and projections
to stellar rotation, activity, and hence noise levels reproduce the
primary intrinsic stellar noise features.
---------------------------------------------------------
Title: Constructing a One-solar-mass Evolutionary Sequence Using
Asteroseismic Data from Kepler
Authors: Silva Aguirre, V.; Chaplin, W. J.; Ballot, J.; Basu,
S.; Bedding, T. R.; Serenelli, A. M.; Verner, G. A.; Miglio, A.;
Monteiro, M. J. P. F. G.; Weiss, A.; Appourchaux, T.; Bonanno,
A.; Broomhall, A. M.; Bruntt, H.; Campante, T. L.; Casagrande, L.;
Corsaro, E.; Elsworth, Y.; García, R. A.; Gaulme, P.; Handberg,
R.; Hekker, S.; Huber, D.; Karoff, C.; Mathur, S.; Mosser, B.;
Salabert, D.; Schönrich, R.; Sousa, S. G.; Stello, D.; White, T. R.;
Christensen-Dalsgaard, J.; Gilliland, R. L.; Kawaler, S. D.; Kjeldsen,
H.; Houdek, G.; Metcalfe, T. S.; Molenda-Żakowicz, J.; Thompson,
M. J.; Caldwell, D. A.; Christiansen, J. L.; Wohler, B.
2011ApJ...740L...2S Altcode: 2011arXiv1108.2031S
Asteroseismology of solar-type stars has entered a new era of
large surveys with the success of the NASA Kepler mission, which
is providing exquisite data on oscillations of stars across the
Hertzsprung-Russell diagram. From the time-series photometry, the two
seismic parameters that can be most readily extracted are the large
frequency separation (Δν) and the frequency of maximum oscillation
power (ν<SUB>max</SUB>). After the survey phase, these quantities
are available for hundreds of solar-type stars. By scaling from solar
values, we use these two asteroseismic observables to identify for the
first time an evolutionary sequence of 1 M <SUB>sun</SUB> field stars,
without the need for further information from stellar models. Comparison
of our determinations with the few available spectroscopic results
shows an excellent level of agreement. We discuss the potential of the
method for differential analysis throughout the main-sequence evolution
and the possibility of detecting twins of very well-known stars.
---------------------------------------------------------
Title: Asteroseismology from multi-month Kepler photometry: the
evolved Sun-like stars KIC 10273246 and KIC 10920273
Authors: Campante, T. L.; Handberg, R.; Mathur, S.; Appourchaux, T.;
Bedding, T. R.; Chaplin, W. J.; García, R. A.; Mosser, B.; Benomar,
O.; Bonanno, A.; Corsaro, E.; Fletcher, S. T.; Gaulme, P.; Hekker, S.;
Karoff, C.; Régulo, C.; Salabert, D.; Verner, G. A.; White, T. R.;
Houdek, G.; Brandão, I. M.; Creevey, O. L.; Doǧan, G.; Bazot,
M.; Christensen-Dalsgaard, J.; Cunha, M. S.; Elsworth, Y.; Huber,
D.; Kjeldsen, H.; Lundkvist, M.; Molenda-Żakowicz, J.; Monteiro,
M. J. P. F. G.; Stello, D.; Clarke, B. D.; Girouard, F. R.; Hall, J. R.
2011A&A...534A...6C Altcode: 2011arXiv1108.3807C
Context. The evolved main-sequence Sun-like stars KIC 10273246 (F-type)
and KIC 10920273 (G-type) were observed with the NASA Kepler satellite
for approximately ten months with a duty cycle in excess of 90%. Such
continuous and long observations are unprecedented for solar-type
stars other than the Sun. <BR /> Aims: We aimed mainly at extracting
estimates of p-mode frequencies - as well as of other individual mode
parameters - from the power spectra of the light curves of both stars,
thus providing scope for a full seismic characterization. <BR />
Methods: The light curves were corrected for instrumental effects in
a manner independent of the Kepler science pipeline. Estimation of
individual mode parameters was based both on the maximization of the
likelihood of a model describing the power spectrum and on a classic
prewhitening method. Finally, we employed a procedure for selecting
frequency lists to be used in stellar modeling. <BR /> Results: A
total of 30 and 21 modes of degree l = 0,1,2 - spanning at least eight
radial orders - have been identified for KIC 10273246 and KIC 10920273,
respectively. Two avoided crossings (l = 1 ridge) have been identified
for KIC 10273246, whereas one avoided crossing plus another likely
one have been identified for KIC 10920273. Good agreement is found
between observed and predicted mode amplitudes for the F-type star KIC
10273246, based on a revised scaling relation. Estimates are given of
the rotational periods, the parameters describing stellar granulation
and the global asteroseismic parameters Δν and ν<SUB>max</SUB>.
---------------------------------------------------------
Title: Observational Constraints, Stellar Models, and Kepler Data
for theta Cyg, the Brightest Star Observable by Kepler
Authors: Guzik, J. A.; Houdek, G.; Chaplin, W. J.; Kurtz, D.;
Gilliland, R. L.; Mullally, F.; Rowe, J. F.; Haas, M. R.; Bryson,
S. T.; Still, M. D.; Boyajian, T.
2011arXiv1110.2120G Altcode:
The V=4.48 F4 main-sequence star theta Cyg is the brightest star
observable in the Kepler spacecraft field-of-view. Short-cadence
(58.8 s) photometric data were obtained by Kepler during 2010
June-September. Preliminary analysis shows solar-like oscillations in
the frequency range 1200- 2500 microHz. To interpret these data and to
motivate further observations, we use observational constraints from
the literature to construct stellar evolution and pulsation models
for this star. We compare the observed large frequency separation of
the solar-like oscillations with the model predictions, and discuss
the prospects for gamma Doradus-like g-mode pulsations, given the
observational constraints. We discuss the value of angular diameter
measurements from optical interferometry for constraining stellar
properties and the implications for asteroseismology.
---------------------------------------------------------
Title: An Asteroseismic Membership Study of the Red Giants in Three
Open Clusters Observed by Kepler: NGC 6791, NGC 6819, and NGC 6811
Authors: Stello, Dennis; Meibom, Søren; Gilliland, Ronald L.;
Grundahl, Frank; Hekker, Saskia; Mosser, Benoît; Kallinger, Thomas;
Mathur, Savita; García, Rafael A.; Huber, Daniel; Basu, Sarbani;
Bedding, Timothy R.; Brogaard, Karsten; Chaplin, William J.; Elsworth,
Yvonne P.; Molenda-Żakowicz, Joanna; Szabó, Robert; Still, Martin;
Jenkins, Jon M.; Christensen-Dalsgaard, Jørgen; Kjeldsen, Hans;
Serenelli, Aldo M.; Wohler, Bill
2011ApJ...739...13S Altcode: 2011arXiv1107.1234S
Studying star clusters offers significant advances in stellar
astrophysics due to the combined power of having many stars with
essentially the same distance, age, and initial composition. This
makes clusters excellent test benches for verification of stellar
evolution theory. To fully exploit this potential, it is vital that
the star sample is uncontaminated by stars that are not members of
the cluster. Techniques for determining cluster membership therefore
play a key role in the investigation of clusters. We present results
on three clusters in the Kepler field of view based on a newly
established technique that uses asteroseismology to identify fore-
or background stars in the field, which demonstrates advantages over
classical methods such as kinematic and photometry measurements. Four
previously identified seismic non-members in NGC 6819 are confirmed
in this study, and three additional non-members are found—two in
NGC 6819 and one in NGC 6791. We further highlight which stars are,
or might be, affected by blending, which needs to be taken into account
when analyzing these Kepler data.
---------------------------------------------------------
Title: Assessing the Nature and Impact of Observed Stellar Variability
on Kepler’s Ability to Detect Earth-Size Planets
Authors: Jenkins, Jon Michael; Dunham, E. W.; Argabright, V. S.;
Borucki, W. J.; Caldwell, D. A.; Chaplin, W. J.; Christiansen, J. L.;
Gautier, T. N.; Gilliland, R. L.; Kolodziejczak, J.; Machalek, P.;
Van Cleve, J.; Basri, G.; Buzasi, D. L.; Haas, M. R.; Howell, S. B.;
Tenenbaum, P.; Walkowicz, L. M.; Welsh, W. F.
2011ESS.....2.1914J Altcode:
The Kepler spacecraft was launched on March 6 2009 on a 3.5-year mission
to determine the frequency of Earth-size and larger planets in or near
the habitable zones of their stars. Kepler has been observing 160,000
stars to detect transiting planets for over two years and has discovered
more than 16 confirmed or validated planets and has identified over
1200 candidate planets. There is sufficient data and experience with the
photometer to characterize Kepler’s ability to detect weak signatures
of small, terrestrial planets. The photometer’s sensitivity depends
on the total combined differential photometric precision (CDPP) and on
the mission lifetime. These driving requirements for Kepler called for
a total CDPP of 20 ppm for 12th magnitude G2 dwarf stars in 6.5 hours,
and a mission lifetime of 3.5 years. The noise budget includes 14 ppm
for shot noise, 10 ppm for instrument noise and 10 ppm adopted for
intrinsic stellar variability. The CDPP requirement was necessarily set
without knowledge of actual typical levels of stellar variability. We
find that Kepler’s noise metrics for 12th magnitude dwarf stars
are dominated by stellar variability and the overall combined noise
is ∼50% higher than the required value. While this does reduce
Kepler’s ability to achieve its scientific objectives, Kepler’s
originally envisioned capability to detect terrestrial planets can be
recovered by extending the duration of the flight mission to 8 years.
---------------------------------------------------------
Title: Verification of the Kepler Input Catalog from Asteroseismology
of Solar-type Stars
Authors: Verner, G. A.; Chaplin, W. J.; Basu, S.; Brown, T. M.;
Hekker, S.; Huber, D.; Karoff, C.; Mathur, S.; Metcalfe, T. S.;
Mosser, B.; Quirion, P. -O.; Appourchaux, T.; Bedding, T. R.; Bruntt,
H.; Campante, T. L.; Elsworth, Y.; García, R. A.; Handberg, R.;
Régulo, C.; Roxburgh, I. W.; Stello, D.; Christensen-Dalsgaard, J.;
Gilliland, R. L.; Kawaler, S. D.; Kjeldsen, H.; Allen, C.; Clarke,
B. D.; Girouard, F. R.
2011ApJ...738L..28V Altcode: 2011arXiv1109.0869V
We calculate precise stellar radii and surface gravities from the
asteroseismic analysis of over 500 solar-type pulsating stars observed
by the Kepler space telescope. These physical stellar properties
are compared with those given in the Kepler Input Catalog (KIC),
determined from ground-based multi-color photometry. For the stars
in our sample, we find general agreement but we detect an average
overestimation bias of 0.23 dex in the KIC determination of log (g)
for stars with log (g)<SUB>KIC</SUB> > 4.0 dex, and a resultant
underestimation bias of up to 50% in the KIC radii estimates for stars
with R <SUB>KIC</SUB> < 2 R <SUB>sun</SUB>. Part of the difference
may arise from selection bias in the asteroseismic sample; nevertheless,
this result implies there may be fewer stars characterized in the KIC
with R ~ 1 R <SUB>sun</SUB> than is suggested by the physical properties
in the KIC. Furthermore, if the radius estimates are taken from the
KIC for these affected stars and then used to calculate the size of
transiting planets, a similar underestimation bias may be applied to
the planetary radii.
---------------------------------------------------------
Title: Amplitudes of Solar-like Oscillations: Constraints from Red
Giants in Open Clusters Observed by Kepler
Authors: Stello, Dennis; Huber, Daniel; Kallinger, Thomas; Basu,
Sarbani; Mosser, Benoît; Hekker, Saskia; Mathur, Savita; García,
Rafael A.; Bedding, Timothy R.; Kjeldsen, Hans; Gilliland, Ronald L.;
Verner, Graham A.; Chaplin, William J.; Benomar, Othman; Meibom,
Søren; Grundahl, Frank; Elsworth, Yvonne P.; Molenda-Żakowicz,
Joanna; Szabó, Robert; Christensen-Dalsgaard, Jørgen; Tenenbaum,
Peter; Twicken, Joseph D.; Uddin, Kamal
2011ApJ...737L..10S Altcode: 2011arXiv1107.0490S
Scaling relations that link asteroseismic quantities to global stellar
properties are important for gaining understanding of the intricate
physics that underpins stellar pulsations. The common notion that all
stars in an open cluster have essentially the same distance, age, and
initial composition implies that the stellar parameters can be measured
to much higher precision than what is usually achievable for single
stars. This makes clusters ideal for exploring the relation between
the mode amplitude of solar-like oscillations and the global stellar
properties. We have analyzed data obtained with NASA's Kepler space
telescope to study solar-like oscillations in 100 red giant stars
located in either of the three open clusters, NGC 6791, NGC 6819,
and NGC 6811. By fitting the measured amplitudes to predictions from
simple scaling relations that depend on luminosity, mass, and effective
temperature, we find that the data cannot be described by any power
of the luminosity-to-mass ratio as previously assumed. As a result
we provide a new improved empirical relation which treats luminosity
and mass separately. This relation turns out to also work remarkably
well for main-sequence and subgiant stars. In addition, the measured
amplitudes reveal the potential presence of a number of previously
unknown unresolved binaries in the red clump in NGC 6791 and NGC 6819,
pointing to an interesting new application for asteroseismology as a
probe into the formation history of open clusters.
---------------------------------------------------------
Title: Global asteroseismic properties of solar-like oscillations
observed by Kepler: a comparison of complementary analysis methods
Authors: Verner, G. A.; Elsworth, Y.; Chaplin, W. J.; Campante,
T. L.; Corsaro, E.; Gaulme, P.; Hekker, S.; Huber, D.; Karoff, C.;
Mathur, S.; Mosser, B.; Appourchaux, T.; Ballot, J.; Bedding, T. R.;
Bonanno, A.; Broomhall, A. -M.; García, R. A.; Handberg, R.; New,
R.; Stello, D.; Régulo, C.; Roxburgh, I. W.; Salabert, D.; White,
T. R.; Caldwell, D. A.; Christiansen, J. L.; Fanelli, M. N.
2011MNRAS.415.3539V Altcode: 2011MNRAS.tmp..892V; 2011arXiv1105.0571V
We present the asteroseismic analysis of 1948 F-, G- and K-type
main-sequence and subgiant stars observed by the National Aeronautics
and Space Administration Kepler mission. We detect and characterize
solar-like oscillations in 642 of these stars. This represents the
largest cohort of main-sequence and subgiant solar-like oscillators
observed to date. The photometric observations are analysed using the
methods developed by nine independent research teams. The results are
combined to validate the determined global asteroseismic parameters
and calculate the relative precision by which the parameters can be
obtained. We correlate the relative number of detected solar-like
oscillators with stellar parameters from the Kepler Input Catalogue
and find a deficiency for stars with effective temperatures in the
range 5300 ≲T<SUB>eff</SUB>≲ 5700 K and a drop-off in detected
oscillations in stars approaching the red edge of the classical
instability strip. We compare the power-law relationships between the
frequency of peak power, ν<SUB>max</SUB>, the mean large frequency
separation, Δν, and the maximum mode amplitude, A<SUB>max</SUB>,
and show that there are significant method-dependent differences in the
results obtained. This illustrates the need for multiple complementary
analysis methods to be used to assess the robustness and reproducibility
of results derived from global asteroseismic parameters.
---------------------------------------------------------
Title: A new efficient method for determining weighted power spectra:
detection of low-frequency solar p-modes by analysis of BiSON data
Authors: Fletcher, S. T.; Broomhall, A. -M.; Chaplin, W. J.; Elsworth,
Y.; New, R.
2011MNRAS.415.1310F Altcode: 2011arXiv1104.5355F; 2011MNRAS.tmp..724F
We present a new and highly efficient algorithm for computing
a power spectrum made from evenly spaced data which combines the
noise-reducing advantages of the weighted fit with the computational
advantages of the fast Fourier transform. We apply this method to
a 10-yr data set of the solar p-mode oscillations obtained by the
Birmingham Solar Oscillations Network (BiSON) and thereby uncover
three new low-frequency modes. These are the ℓ= 2, n= 5 and n=
7 modes and the ℓ= 3, n=7 mode. In the case of the ℓ= 2, n= 5
mode, this is believed to be the first such identification of this
mode in the literature. The statistical weights needed for the method
are derived from a combination of the real data and a sophisticated
simulation of the instrument performance. Variations in the weights
are due mainly to the differences in the noise characteristics of the
various BiSON instruments, the change in those characteristics over
time and the changing line-of-sight velocity between the stations and
the Sun. It should be noted that a weighted data set will have a more
time-dependent signal than an unweighted set and that, consequently,
its frequency spectrum will be more susceptible to aliasing.
---------------------------------------------------------
Title: Characterization of red giant stars in the public Kepler data
Authors: Hekker, S.; Gilliland, R. L.; Elsworth, Y.; Chaplin, W. J.;
De Ridder, J.; Stello, D.; Kallinger, T.; Ibrahim, K. A.; Klaus,
T. C.; Li, J.
2011MNRAS.414.2594H Altcode: 2011MNRAS.tmp..559H; 2011arXiv1103.0141H
The first public release of long-cadence stellar photometric data
collected by the NASA Kepler mission has now been made available. In
this paper, we characterize the red giant (G-K) stars in this large
sample in terms of their solar-like oscillations. We use published
methods and well-known scaling relations in the analysis. Just over 70
per cent of the red giants in the sample show detectable solar-like
oscillations, and from these oscillations we are able to estimate
the fundamental properties of the stars. This asteroseismic analysis
reveals different populations: low-luminosity H-shell burning red giant
branch stars, cool high-luminosity red giants on the red giant branch
and He-core burning clump and secondary-clump giants.
---------------------------------------------------------
Title: Solar-like Oscillations in KIC 11395018 and KIC 11234888 from
8 Months of Kepler Data
Authors: Mathur, S.; Handberg, R.; Campante, T. L.; García, R. A.;
Appourchaux, T.; Bedding, T. R.; Mosser, B.; Chaplin, W. J.; Ballot,
J.; Benomar, O.; Bonanno, A.; Corsaro, E.; Gaulme, P.; Hekker,
S.; Régulo, C.; Salabert, D.; Verner, G.; White, T. R.; Brandão,
I. M.; Creevey, O. L.; Doǧan, G.; Elsworth, Y.; Huber, D.; Hale,
S. J.; Houdek, G.; Karoff, C.; Metcalfe, T. S.; Molenda-Żakowicz,
J.; Monteiro, M. J. P. F. G.; Thompson, M. J.; Christensen-Dalsgaard,
J.; Gilliland, R. L.; Kawaler, S. D.; Kjeldsen, H.; Quintana, E. V.;
Sanderfer, D. T.; Seader, S. E.
2011ApJ...733...95M Altcode: 2011arXiv1103.4085M
We analyze the photometric short-cadence data obtained with the Kepler
mission during the first 8 months of observations of two solar-type
stars of spectral types G and F: KIC 11395018 and KIC 11234888,
respectively, the latter having a lower signal-to-noise ratio (S/N)
compared with the former. We estimate global parameters of the acoustic
(p) modes such as the average large and small frequency separations, the
frequency of the maximum of the p-mode envelope, and the average line
width of the acoustic modes. We were able to identify and to measure
22 p-mode frequencies for the first star and 16 for the second one
even though the S/N of these stars are rather low. We also derive some
information about the stellar rotation periods from the analyses of the
low-frequency parts of the power spectral densities. A model-independent
estimation of the mean density, mass, and radius is obtained using the
scaling laws. We emphasize the importance of continued observations
for the stars with low S/N for an improved characterization of the
oscillation modes. Our results offer a preview of what will be possible
for many stars with the long data sets obtained during the remainder
of the mission.
---------------------------------------------------------
Title: Preparation of Kepler light curves for asteroseismic analyses
Authors: García, R. A.; Hekker, S.; Stello, D.; Gutiérrez-Soto,
J.; Handberg, R.; Huber, D.; Karoff, C.; Uytterhoeven, K.;
Appourchaux, T.; Chaplin, W. J.; Elsworth, Y.; Mathur, S.; Ballot,
J.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Houdek, G.; Jenkins,
J. M.; Kjeldsen, H.; McCauliff, S.; Metcalfe, T.; Middour, C. K.;
Molenda-Zakowicz, J.; Monteiro, M. J. P. F. G.; Smith, J. C.; Thompson,
M. J.
2011MNRAS.414L...6G Altcode: 2011arXiv1103.0382G
The Kepler mission is providing photometric data of exquisite
quality for the asteroseismic study of different classes of pulsating
stars. These analyses place particular demands on the pre-processing
of the data, over a range of time-scales from minutes to months. Here,
we describe processing procedures developed by the Kepler Asteroseismic
Science Consortium to prepare light curves that are optimized for the
asteroseismic study of solar-like oscillating stars in which outliers,
jumps and drifts are corrected.
---------------------------------------------------------
Title: Asteroseismic inferences on red giants in open clusters NGC
6791, NGC 6819, and NGC 6811 using Kepler
Authors: Hekker, S.; Basu, S.; Stello, D.; Kallinger, T.; Grundahl,
F.; Mathur, S.; García, R. A.; Mosser, B.; Huber, D.; Bedding, T. R.;
Szabó, R.; De Ridder, J.; Chaplin, W. J.; Elsworth, Y.; Hale, S. J.;
Christensen-Dalsgaard, J.; Gilliland, R. L.; Still, M.; McCauliff,
S.; Quintana, E. V.
2011A&A...530A.100H Altcode: 2011arXiv1104.4393H
Context. Four open clusters are present in the Kepler field of view
and timeseries of nearly a year in length are now available. These
timeseries allow us to derive asteroseismic global oscillation
parameters of red-giant stars in the three open clusters NGC 6791, NGC
6819 and NGC 6811. From these parameters and effective temperatures,
we derive masses, radii and luminosities for the clusters as well as
field red giants. <BR /> Aims: We study the influence of evolution and
metallicity on the observed red-giant populations. <BR /> Methods: The
global oscillation parameters are derived using different published
methods and the effective temperatures are derived from 2MASS
colours. The observational results are compared with BaSTI evolution
models. <BR /> Results: We find that the mass has significant influence
on the asteroseismic quantities Δν vs. ν<SUB>max</SUB> relation,
while the influence of metallicity is negligible, under the assumption
that the metallicity does not affect the excitation/damping of the
oscillations. The positions of the stars in the H-R diagram depend on
both mass and metallicity. Furthermore, the stellar masses derived for
the field stars are bracketed by those of the cluster stars. <BR />
Conclusions: Both the mass and metallicity contribute to the observed
difference in locations in the H-R diagram of the old metal-rich cluster
NGC 6791 and the middle-aged solar-metallicity cluster NGC 6819. For
the young cluster NGC 6811, the explanation of the position of the stars
in the H-R diagram challenges the assumption of solar metallicity, and
this open cluster might have significantly lower metallicity [Fe/H]
in the range - 0.3 to - 0.7 dex. Also, nearly all the observed field
stars seem to be older than NGC 6811 and younger than NGC 6791.
---------------------------------------------------------
Title: Accurate p-mode measurements of the G0V metal-rich CoRoT
target HD 52265
Authors: Ballot, J.; Gizon, L.; Samadi, R.; Vauclair, G.; Benomar, O.;
Bruntt, H.; Mosser, B.; Stahn, T.; Verner, G. A.; Campante, T. L.;
García, R. A.; Mathur, S.; Salabert, D.; Gaulme, P.; Régulo, C.;
Roxburgh, I. W.; Appourchaux, T.; Baudin, F.; Catala, C.; Chaplin,
W. J.; Deheuvels, S.; Michel, E.; Bazot, M.; Creevey, O.; Dolez, N.;
Elsworth, Y.; Sato, K. H.; Vauclair, S.; Auvergne, M.; Baglin, A.
2011A&A...530A..97B Altcode: 2011arXiv1105.3551B
Context. The star <ASTROBJ>HD 52265</ASTROBJ> is a G0V metal-rich
exoplanet-host star observed in the seismology field of the CoRoT
space telescope from November 2008 to March 2009. The satellite
collected 117 days of high-precision photometric data on this star,
showing that it presents solar-like oscillations. HD 52265 was also
observed in spectroscopy with the Narval spectrograph at the same
epoch. <BR /> Aims: We characterise HD 52265 using both spectroscopic
and seismic data. <BR /> Methods: The fundamental stellar parameters
of HD 52265 were derived with the semi-automatic software VWA, and
the projected rotational velocity was estimated by fitting synthetic
profiles to isolated lines in the observed spectrum. The parameters
of the observed p modes were determined with a maximum-likelihood
estimation. We performed a global fit of the oscillation spectrum,
over about ten radial orders, for degrees l = 0 to 2. We also derived
the properties of the granulation, and analysed a signature of the
rotation induced by the photospheric magnetic activity. <BR /> Results:
Precise determinations of fundamental parameters have been obtained:
T<SUB>eff</SUB> = 6100 ± 60 K, log g = 4.35 ± 0.09, [M/H] = 0.19 ±
0.05, as well as vsini=3.6<SUP>+0.3</SUP><SUB>-1.0kms</SUB>. We have
measured a mean rotation period P<SUB>rot</SUB> = 12.3 ± 0.15 days,
and find a signature of differential rotation. The frequencies of 31
modes are reported in the range 1500-2550 μHz. The large separation
exhibits a clear modulation around the mean value Dnu=98.3 ± 0.1
μHz. Mode widths vary with frequency along an S-shape with a clear
local maximum around 1800 μHz. We deduce lifetimes ranging between
0.5 and 3 days for these modes. Finally, we find a maximal bolometric
amplitude of about 3.96 ± 0.24 ppm for radial modes. <P />The CoRoT
space mission, launched on December 27th 2006, has been developed
and is operated by CNES, with the contribution of Austria, Belgium,
Brazil, ESA (RSSD and Science Programme), Germany and Spain.
---------------------------------------------------------
Title: Solar-cycle variations of large frequency separations of
acoustic modes: implications for asteroseismology
Authors: Broomhall, A. -M.; Chaplin, W. J.; Elsworth, Y.; New, R.
2011MNRAS.413.2978B Altcode: 2011MNRAS.tmp..428B; 2011arXiv1102.0906B
We have studied solar-cycle changes in the large frequency separations
that can be observed in Birmingham Solar Oscillations Network
(BiSON) data. The large frequency separation is often one of the
first outputs from asteroseismic studies because it can help constrain
stellar properties like mass and radius. We have used three methods for
estimating the large separations: use of individual p-mode frequencies,
computation of the autocorrelation of frequency-power spectra, and
computation of the power spectrum of the power spectrum. The values
of the large separations obtained by the different methods are offset
from each other and have differing sensitivities to the realization
noise. A simple model was used to predict solar-cycle variations
in the large separations, indicating that the variations are due to
the well-known solar-cycle changes to mode frequency. However, this
model is only valid over a restricted frequency range. We discuss the
implications of these results for asteroseismology.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Solar-like oscillations in Kepler
red giants (Hekker+, 2011)
Authors: Hekker, S.; Elsworth, Y.; De Ridder, J.; Mosser, B.; Garcia,
R. A.; Kallinger, T.; Mathur, S.; Huber, D.; Buzasi, D. L.; Preston,
H. L.; Hale, S. J.; Ballot, J.; Chaplin, W. J.; Regulo, C.; Bedding,
T. R.; Stello, D.; Borucki, W. J.; Koch, D. G.; Jenkins, J.; Allen,
C.; Gilliland, R. L.; Kjeldsen, H.; Christensen-Dalsgaard, J.
2011yCat..35250131H Altcode: 2011yCat..35259131H
For this investigation we use Kepler data obtained during the first four
months of operation. These data have been analysed by different groups
using already published methods and the results are compared. We also
performed simulations to investigate the uncertainty on the resulting
parameters due to different realizations of the stochastic signal. <P
/>(1 data file).
---------------------------------------------------------
Title: The OCTAVE automated pipeline for extracting individual mode
parameters of solar-like oscillations in main-sequence stars
Authors: Fletcher, S. T.; Broomhall, A. -M.; Chaplin, W. J.; Elsworth,
Y.; Hekker, S.; New, R.
2011MNRAS.413..359F Altcode: 2011MNRAS.tmp..197F
With the launch of the NASA Kepler spacecraft, the number of solar-like
stars for which there are high-precision photometric observations
available has increased considerably. In order to analyse the data
from a large number of stars in a reasonable amount of time, automated
pipelines are desirable. Here we present an extension of the OCTAVE
(Birmingham-Sheffield Hallam) pipeline, which has been developed as
part of the AsteroFLAG collaboration. While the first parts of the
pipeline extracted overall oscillation parameters of the stars, here
we present a significant extension to that pipeline designed in order
to extract individual mode frequencies and amplitudes. The pipeline
also attempts to label the detected modes by straightening and then
identifying the ridges within the echelle diagrams in an automated
manner. Tests have been performed on artificial stars and the pipeline
is shown to return estimates of the mode frequencies that are in line
with the input parameters. There does appear to be some positive bias
in the returned value of the mode amplitudes which must be accounted
for when employing the pipeline for real data.
---------------------------------------------------------
Title: Helioseismic Studies With Multi-wavelength Data From HMI And
AIA Onboard SDO
Authors: Hill, Frank; Jain, K.; Tripathy, S.; Kholikov, S.; Gonzalez
Hernandez, I.; Leibacher, J.; Howe, R.; Baudin, F.; Carlsson, M.;
Chaplin, W.; Tarbell, T.
2011SPD....42.2111H Altcode: 2011BAAS..43S.2111H
The successful launch of the Solar Dynamics Observatory (SDO) in
February 2010 opens important, new possibilities for helioseismic
exploration of the solar interior and atmosphere using multi-wavelength
observations from multiple instruments. In order to better understand
the solar interior and atmosphere, as well as the physics of the
helioseismic modes and waves themselves, we exploit the potential of
the Atmospheric Imaging Assembly (AIA) 1600 and 1700 Angstrom continuum
measurements and the contemporaneous Helioseismic and Magnetic Imager
(HMI) Fe I 6173.3 Angstrom velocity and intensity observations. Standard
techniques of helioseismology e.g Sun-as-a-star, spherical harmonic
analysis, ring diagrams, and time- distance analysis are applied to
obtain acoustic mode parameters and other characteristics. Here we
present our preliminary results, and interpret these in the context
of the differences in the heights of formation of the lines.
---------------------------------------------------------
Title: Predicting the Detectability of Oscillations in Solar-type
Stars Observed by Kepler
Authors: Chaplin, W. J.; Kjeldsen, H.; Bedding, T. R.;
Christensen-Dalsgaard, J.; Gilliland, R. L.; Kawaler, S. D.;
Appourchaux, T.; Elsworth, Y.; García, R. A.; Houdek, G.; Karoff, C.;
Metcalfe, T. S.; Molenda-Żakowicz, J.; Monteiro, M. J. P. F. G.;
Thompson, M. J.; Verner, G. A.; Batalha, N.; Borucki, W. J.;
Brown, T. M.; Bryson, S. T.; Christiansen, J. L.; Clarke, B. D.;
Jenkins, J. M.; Klaus, T. C.; Koch, D.; An, D.; Ballot, J.; Basu,
S.; Benomar, O.; Bonanno, A.; Broomhall, A. -M.; Campante, T. L.;
Corsaro, E.; Creevey, O. L.; Esch, L.; Gai, N.; Gaulme, P.; Hale,
S. J.; Handberg, R.; Hekker, S.; Huber, D.; Mathur, S.; Mosser, B.;
New, R.; Pinsonneault, M. H.; Pricopi, D.; Quirion, P. -O.; Régulo,
C.; Roxburgh, I. W.; Salabert, D.; Stello, D.; Suran, M. D.
2011ApJ...732...54C Altcode: 2011arXiv1103.0702C
Asteroseismology of solar-type stars has an important part to play
in the exoplanet program of the NASA Kepler Mission. Precise and
accurate inferences on the stellar properties that are made possible
by the seismic data allow very tight constraints to be placed on the
exoplanetary systems. Here, we outline how to make an estimate of the
detectability of solar-like oscillations in any given Kepler target,
using rough estimates of the temperature and radius, and the Kepler
apparent magnitude.
---------------------------------------------------------
Title: Evidence for the Impact of Stellar Activity on the
Detectability of Solar-like Oscillations Observed by Kepler
Authors: Chaplin, W. J.; Bedding, T. R.; Bonanno, A.; Broomhall,
A. -M.; García, R. A.; Hekker, S.; Huber, D.; Verner, G. A.;
Basu, S.; Elsworth, Y.; Houdek, G.; Mathur, S.; Mosser, B.; New,
R.; Stevens, I. R.; Appourchaux, T.; Karoff, C.; Metcalfe, T. S.;
Molenda-Żakowicz, J.; Monteiro, M. J. P. F. G.; Thompson, M. J.;
Christensen-Dalsgaard, J.; Gilliland, R. L.; Kawaler, S. D.; Kjeldsen,
H.; Ballot, J.; Benomar, O.; Corsaro, E.; Campante, T. L.; Gaulme,
P.; Hale, S. J.; Handberg, R.; Jarvis, E.; Régulo, C.; Roxburgh,
I. W.; Salabert, D.; Stello, D.; Mullally, F.; Li, J.; Wohler, W.
2011ApJ...732L...5C Altcode: 2011arXiv1103.5570C
We use photometric observations of solar-type stars, made by the NASA
Kepler Mission, to conduct a statistical study of the impact of stellar
surface activity on the detectability of solar-like oscillations. We
find that the number of stars with detected oscillations falls
significantly with increasing levels of activity. The results present
strong evidence for the impact of magnetic activity on the properties
of near-surface convection in the stars, which appears to inhibit
the amplitudes of the stochastically excited, intrinsically damped
solar-like oscillations.
---------------------------------------------------------
Title: Ensemble Asteroseismology of Solar-Type Stars with the NASA
Kepler Mission
Authors: Chaplin, W. J.; Kjeldsen, H.; Christensen-Dalsgaard, J.;
Basu, S.; Miglio, A.; Appourchaux, T.; Bedding, T. R.; Elsworth, Y.;
García, R. A.; Gilliland, R. L.; Girardi, L.; Houdek, G.; Karoff,
C.; Kawaler, S. D.; Metcalfe, T. S.; Molenda-Żakowicz, J.; Monteiro,
M. J. P. F. G.; Thompson, M. J.; Verner, G. A.; Ballot, J.; Bonanno,
A.; Brandão, I. M.; Broomhall, A. -M.; Bruntt, H.; Campante, T. L.;
Corsaro, E.; Creevey, O. L.; Doğan, G.; Esch, L.; Gai, N.; Gaulme,
P.; Hale, S. J.; Handberg, R.; Hekker, S.; Huber, D.; Jiménez, A.;
Mathur, S.; Mazumdar, A.; Mosser, B.; New, R.; Pinsonneault, M. H.;
Pricopi, D.; Quirion, P. -O.; Régulo, C.; Salabert, D.; Serenelli,
A. M.; Silva Aguirre, V.; Sousa, S. G.; Stello, D.; Stevens, I. R.;
Suran, M. D.; Uytterhoeven, K.; White, T. R.; Borucki, W. J.; Brown,
T. M.; Jenkins, J. M.; Kinemuchi, K.; Van Cleve, J.; Klaus, T. C.
2011Sci...332..213C Altcode: 2011arXiv1109.4723C
In addition to its search for extrasolar planets, the NASA Kepler
mission provides exquisite data on stellar oscillations. We report the
detections of oscillations in 500 solar-type stars in the Kepler field
of view, an ensemble that is large enough to allow statistical studies
of intrinsic stellar properties (such as mass, radius, and age) and
to test theories of stellar evolution. We find that the distribution
of observed masses of these stars shows intriguing differences to
predictions from models of synthetic stellar populations in the Galaxy.
---------------------------------------------------------
Title: An In-depth Study of Grid-based Asteroseismic Analysis
Authors: Gai, Ning; Basu, Sarbani; Chaplin, William J.; Elsworth,
Yvonne
2011ApJ...730...63G Altcode: 2010arXiv1009.3018G
NASA's Kepler mission is providing basic asteroseismic data for
hundreds of stars. One of the more common ways of determining
stellar characteristics from these data is by the so-called
grid-based modeling. We have made a detailed study of grid-based
analysis techniques to study the errors (and error correlations)
involved. As had been reported earlier, we find that it is relatively
easy to get very precise values of stellar radii using grid-based
techniques. However, we find that there are small, but significant,
biases that can result because of the grid of models used. The biases
can be minimized if metallicity is known. Masses cannot be determined
as precisely as the radii and suffer from larger systematic effects. We
also find that the errors in mass and radius are correlated. A positive
consequence of this correlation is that log g can be determined both
precisely and accurately with almost no systematic biases. Radii and
log g can be determined with almost no model dependence to within 5%
for realistic estimates of errors in asteroseismic and conventional
observations. Errors in mass can be somewhat higher unless accurate
metallicity estimates are available. Age estimates of individual stars
are the most model dependent. The errors are larger, too. However, we
find that for star clusters, it is possible to get a relatively precise
age if one assumes that all stars in a given cluster have the same age.
---------------------------------------------------------
Title: Kepler Detected Gravity-Mode Period Spacings in a Red
Giant Star
Authors: Beck, P. G.; Bedding, T. R.; Mosser, B.; Stello, D.; Garcia,
R. A.; Kallinger, T.; Hekker, S.; Elsworth, Y.; Frandsen, S.; Carrier,
F.; De Ridder, J.; Aerts, C.; White, T. R.; Huber, D.; Dupret, M. -A.;
Montalbán, J.; Miglio, A.; Noels, A.; Chaplin, W. J.; Kjeldsen, H.;
Christensen-Dalsgaard, J.; Gilliland, R. L.; Brown, T. M.; Kawaler,
S. D.; Mathur, S.; Jenkins, J. M.
2011Sci...332..205B Altcode:
Stellar interiors are inaccessible through direct observations. For
this reason, helioseismologists made use of the Sun’s acoustic
oscillation modes to tune models of its structure. The quest to detect
modes that probe the solar core has been ongoing for decades. We
report the detection of mixed modes penetrating all the way to the
core of an evolved star from 320 days of observations with the Kepler
satellite. The period spacings of these mixed modes are directly
dependent on the density gradient between the core region and the
convective envelope.
---------------------------------------------------------
Title: Sounding Open Clusters: Asteroseismic Constraints from Kepler
on the Properties of NGC 6791 and NGC 6819
Authors: Basu, Sarbani; Grundahl, Frank; Stello, Dennis; Kallinger,
Thomas; Hekker, Saskia; Mosser, Benoit; García, Rafael A.; Mathur,
Savita; Brogaard, Karsten; Bruntt, Hans; Chaplin, William J.; Gai,
Ning; Elsworth, Yvonne; Esch, Lisa; Ballot, Jerome; Bedding, Timothy
R.; Gruberbauer, Michael; Huber, Daniel; Miglio, Andrea; Yildiz, Mutlu;
Kjeldsen, Hans; Christensen-Dalsgaard, Jørgen; Gilliland, Ronald L.;
Fanelli, Michael M.; Ibrahim, Khadeejah A.; Smith, Jeffrey C.
2011ApJ...729L..10B Altcode: 2011arXiv1102.2231B
We present initial results on some of the properties of open clusters
NGC 6791 and NGC 6819 derived from asteroseismic data obtained by
NASA's Kepler mission. In addition to estimating the mass, radius,
and log g of stars on the red giant branch (RGB) of these clusters,
we estimate the distance to the clusters and their ages. Our
model-independent estimate of the distance modulus of NGC 6791 is
(m - M)<SUB>0</SUB> = 13.11 ± 0.06. We find (m - M)<SUB>0</SUB> =
11.85 ± 0.05 for NGC 6819. The average mass of stars on the RGB of
NGC 6791 is 1.20 ± 0.01 M <SUB>sun</SUB>, while that of NGC 6819 is
1.68 ± 0.03 M <SUB>sun</SUB>. It should be noted that we do not have
data that cover the entire RGB and the actual mass will be somewhat
lower. We have determined model-dependent estimates of ages of these
clusters. We find ages between 6.8 and 8.6 Gyr for NGC 6791, however,
most sets of models give ages around 7 Gyr. We obtain ages between 2
and 2.4 Gyr for NGC 6819.
---------------------------------------------------------
Title: Gravity modes as a way to distinguish between hydrogen-
and helium-burning red giant stars
Authors: Bedding, Timothy R.; Mosser, Benoit; Huber, Daniel;
Montalbán, Josefina; Beck, Paul; Christensen-Dalsgaard, Jørgen;
Elsworth, Yvonne P.; García, Rafael A.; Miglio, Andrea; Stello,
Dennis; White, Timothy R.; De Ridder, Joris; Hekker, Saskia; Aerts,
Conny; Barban, Caroline; Belkacem, Kevin; Broomhall, Anne-Marie;
Brown, Timothy M.; Buzasi, Derek L.; Carrier, Fabien; Chaplin,
William J.; di Mauro, Maria Pia; Dupret, Marc-Antoine; Frandsen,
Søren; Gilliland, Ronald L.; Goupil, Marie-Jo; Jenkins, Jon M.;
Kallinger, Thomas; Kawaler, Steven; Kjeldsen, Hans; Mathur, Savita;
Noels, Arlette; Silva Aguirre, Victor; Ventura, Paolo
2011Natur.471..608B Altcode: 2011arXiv1103.5805B
Red giants are evolved stars that have exhausted the supply of hydrogen
in their cores and instead burn hydrogen in a surrounding shell. Once a
red giant is sufficiently evolved, the helium in the core also undergoes
fusion. Outstanding issues in our understanding of red giants include
uncertainties in the amount of mass lost at the surface before helium
ignition and the amount of internal mixing from rotation and other
processes. Progress is hampered by our inability to distinguish between
red giants burning helium in the core and those still only burning
hydrogen in a shell. Asteroseismology offers a way forward, being
a powerful tool for probing the internal structures of stars using
their natural oscillation frequencies. Here we report observations of
gravity-mode period spacings in red giants that permit a distinction
between evolutionary stages to be made. We use high-precision
photometry obtained by the Kepler spacecraft over more than a year
to measure oscillations in several hundred red giants. We find many
stars whose dipole modes show sequences with approximately regular
period spacings. These stars fall into two clear groups, allowing us
to distinguish unambiguously between hydrogen-shell-burning stars
(period spacing mostly ~50seconds) and those that are also burning
helium (period spacing ~100 to 300 seconds).
---------------------------------------------------------
Title: Variations of the amplitudes of oscillation of the Be star
Achernar
Authors: Goss, K. J. F.; Karoff, C.; Chaplin, W. J.; Elsworth, Y.;
Stevens, I. R.
2011MNRAS.411..162G Altcode: 2010arXiv1010.0834G; 2010MNRAS.tmp.1668G
We report on finding variations in amplitude of the two main oscillation
frequencies found in the Be star Achernar, over a period of 5 yr. They
were uncovered by analysing photometric data of the star from the Solar
Mass Ejection Imager (SMEI) instrument. The two frequencies observed,
0.775 and 0.725 d<SUP>-1</SUP>, were analysed in detail and their
amplitudes were found to increase and decrease significantly over the
5-yr period, with the amplitude of the 0.725 d<SUP>-1</SUP> frequency
changing by up to a factor of 8. The nature of this event has yet to
be properly understood, but the possibility of it being due to the
effects of a stellar outburst or a stellar cycle are discussed.
---------------------------------------------------------
Title: The radius and mass of the close solar twin 18 Scorpii derived
from asteroseismology and interferometry
Authors: Bazot, M.; Ireland, M. J.; Huber, D.; Bedding, T. R.;
Broomhall, A. -M.; Campante, T. L.; Carfantan, H.; Chaplin, W. J.;
Elsworth, Y.; Meléndez, J.; Petit, P.; Théado, S.; Van Grootel,
V.; Arentoft, T.; Asplund, M.; Castro, M.; Christensen-Dalsgaard,
J.; Do Nascimento, J. D.; Dintrans, B.; Dumusque, X.; Kjeldsen, H.;
McAlister, H. A.; Metcalfe, T. S.; Monteiro, M. J. P. F. G.; Santos,
N. C.; Sousa, S.; Sturmann, J.; Sturmann, L.; ten Brummelaar, T. A.;
Turner, N.; Vauclair, S.
2011A&A...526L...4B Altcode: 2012arXiv1209.0217B
The growing interest in solar twins is motivated by the possibility of
comparing them directly to the Sun. To carry on this kind of analysis,
we need to know their physical characteristics with precision. Our
first objective is to use asteroseismology and interferometry on
the brightest of them: 18 Sco. We observed the star during 12 nights
with HARPS for seismology and used the PAVO beam-combiner at CHARA
for interferometry. An average large frequency separation 134.4 ±
0.3 μHz and angular and linear radiuses of 0.6759 ± 0.0062 mas and
1.010 ± 0.009 R<SUB>⊙</SUB> were estimated. We used these values
to derive the mass of the star, 1.02 ± 0.03 M<SUB>⊙</SUB>. <P
/>Based on observations collected at the European Southern Observatory
(ID 183.D-0729(A)) and at the CHARA Array, operated by Georgia State
University.
---------------------------------------------------------
Title: Are short-term variations in solar oscillation frequencies
the signature of a second solar dynamo?
Authors: Broomhall, Anne-Marie; Fletcher, Stephen T.; Salabert, David;
Basu, Sarbani; Chaplin, William J.; Elsworth, Yvonne; García, Rafael
A.; Jiménez, Antonio; New, Roger
2011JPhCS.271a2025B Altcode: 2010arXiv1012.4933B
In addition to the well-known 11-year solar cycle, the Sun's magnetic
activity also shows significant variation on shorter time scales,
e.g. between one and two years. We observe a quasi-biennial (2-year)
signal in the solar p-mode oscillation frequencies, which are sensitive
probes of the solar interior. The signal is visible in Sun-as-a-star
data observed by different instruments and here we describe the results
obtained using BiSON, GOLF, and VIRGO data. Our results imply that the
2-year signal is susceptible to the influence of the main 11-year solar
cycle. However, the source of the signal appears to be separate from
that of the 11-year cycle. We speculate as to whether it might be the
signature of a second dynamo, located in the region of near-surface
rotational shear.
---------------------------------------------------------
Title: Solar-like oscillations in red giants observed with Kepler:
comparison of global oscillation parameters from different methods
Authors: Hekker, S.; Elsworth, Y.; De Ridder, J.; Mosser, B.; García,
R. A.; Kallinger, T.; Mathur, S.; Huber, D.; Buzasi, D. L.; Preston,
H. L.; Hale, S. J.; Ballot, J.; Chaplin, W. J.; Régulo, C.; Bedding,
T. R.; Stello, D.; Borucki, W. J.; Koch, D. G.; Jenkins, J.; Allen,
C.; Gilliland, R. L.; Kjeldsen, H.; Christensen-Dalsgaard, J.
2011A&A...525A.131H Altcode: 2010arXiv1008.2959H
Context. The large number of stars for which uninterrupted
high-precision photometric timeseries data are being collected with
Kepler and CoRoT initiated the development of automated methods to
analyse the stochastically excited oscillations in main-sequence,
subgiant and red-giant stars. <BR /> Aims: We investigate the
differences in results for global oscillation parameters of G and K
red-giant stars due to different methods and definitions. We also
investigate uncertainties originating from the stochastic nature
of the oscillations. <BR /> Methods: For this investigation we use
Kepler data obtained during the first four months of operation. These
data have been analysed by different groups using already published
methods and the results are compared. We also performed simulations
to investigate the uncertainty on the resulting parameters due to
different realizations of the stochastic signal. <BR /> Results:
We obtain results for the frequency of maximum oscillation power
(ν_max) and the mean large separation (<Δν>) from different
methods for over one thousand red-giant stars. The results for these
parameters agree within a few percent and seem therefore robust to the
different analysis methods and definitions used here. The uncertainties
for ν_max and <Δν> due to differences in realization noise are
not negligible and should be taken into account when using these results
for stellar modelling. <P />Table 7 is only available in electronic
form at <A href="http://www.aanda.org">http://www.aanda.org</A>
---------------------------------------------------------
Title: Low-degree helioseismology with AIA
Authors: Howe, R.; Hill, F.; Komm, R.; Broomhall, A. -M.; Chaplin,
W. J.; Elsworth, Y.
2011JPhCS.271a2058H Altcode:
We form unresolved-sun time series from the 1600 and 1700 Angstrom
images produced by the Atmospheric Imaging Assembly, and find a clean
low-degree p-mode spectrum at each wavelength. The time series and
spectra are compared with Doppler velocity and continuum intensity
time series from the Helioseismic and Magnetic Imager and velocity
series from the Birmingham Solar Oscillation Network. The UV data
have a slight phase shift with respect to the velocity, and show more
sensitivity to high-frequency and less to low-frequency modes. Unlike
the HMI (visible) continuum observations, the UV spectra show little
or no granulation noise at low frequencies and thus potentially allow
more low-frequency modes to be recovered. These results suggest that
asteroseismology at near-UV wavelengths should be very feasible and
even an improvement on visible-wavelength intensity measurements,
at least in low-activity stars.
---------------------------------------------------------
Title: Asteroseismology of solar-type stars with Kepler I: Data
analysis
Authors: Karoff, C.; Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.;
Garcia, R. A.; Houdek, G.; Metcalfe, T. S.; Molenda-Żakowicz, J.;
Monteiro, M. J. P. F. G.; Thompson, M. J.; Christensen-Dalsgaard, J.;
Gilliland, R. L.; Kjeldsen, H.; Basu, S.; Bedding, T. R.; Campante,
T. L.; Eggenberger, P.; Fletcher, S. T.; Gaulme, P.; Handberg, R.;
Hekker, S.; Martic, M.; Mathur, S.; Mosser, B.; Regulo, C.; Roxburgh,
I. W.; Salabert, D.; Stello, D.; Verner, G. A.; Belkacem, K.; Biazzo,
K.; Cunha, M. S.; Gruberbauer, M.; Guzik, J. A.; Kupka, F.; Leroy,
B.; Ludwig, H. -G.; Mathis, S.; Noels, A.; Noyes, R. W.; Roca Cortes,
T.; Roth, M.; Sato, K. H.; Schmitt, J.; Suran, M. D.; Trampedach,
R.; Uytterhoeven, K.; Ventura, R.
2010AN....331..972K Altcode: 2010arXiv1005.0507K
We report on the first asteroseismic analysis of solar-type stars
observed by Kepler. Observations of three G-type stars, made at
one-minute cadence during the first 33.5 days of science operations,
reveal high signal-to-noise solar-like oscillation spectra in all three
stars: About 20 modes of oscillation can clearly be distinguished
in each star. We discuss the appearance of the oscillation spectra,
including the presence of a possible signature of faculae, and the
presence of mixed modes in one of the three stars.
---------------------------------------------------------
Title: Asteroseismology of solar-type stars with Kepler: II. Stellar
modeling
Authors: Metcalfe, T. S.; Monteiro, M. J. P. F. G.; Thompson, M. J.;
Chaplin, W. J.; Basu, S.; Bonanno, A.; Di Mauro, M. P.; Doğan, G.;
Eggenberger, P.; Karoff, C.; Stello, D.; WG1, KASC
2010AN....331..977M Altcode: 2010arXiv1006.5695M
Observations from the Kepler satellite were recently published for
three bright G-type stars, which were monitored during the first 33.5
days of science operations. One of these stars, KIC 11026764, exhibits
a characteristic pattern of oscillation frequencies suggesting that the
star has evolved significantly. We have derived initial estimates of the
properties of KIC 11026764 from the oscillation frequencies observed
by Kepler, combined with ground-based spectroscopic data. We present
preliminary results from detailed modeling of this star, employing a
variety of independent codes and analyses that attempt to match the
asteroseismic and spectroscopic constraints simultaneously.
---------------------------------------------------------
Title: Challenges and opportunities for helio- and asteroseismology
Authors: Chaplin, W. J.
2010AN....331.1090C Altcode: 2010arXiv1006.5320C
I consider some of the challenges and opportunities facing helio-
and asteroseismology, which reflect major themes of presentation and
discussion from the HELAS IV international conference “Seismological
Challenges for Stellar Structure”. I concentrate in particular on
the exciting prospects for asteroseismology, now that the field is
being provided with data of unprecedented quality and in unprecedented
volumes.
---------------------------------------------------------
Title: Solar-like oscillations in cluster stars
Authors: Stello, D.; Basu, S.; Bedding, T. R.; Brogaard, K.; Bruntt,
H.; Chaplin, W. J.; Christensen-Dalsgaard, J.; Demarque, P.; Elsworth,
Y. P.; García, R. A.; Gilliland, R. L.; Hekker, S.; Huber, D.;
Karoff, C.; Kjeldsen, H.; Lebreton, Y.; Mathur, S.; Meibom, S.;
Molenda-Żakowicz, J.; Noels, A.; Roxburgh, I. W.; Silva Aguirre,
V.; Sterken, C.; Szabó, R.
2010AN....331..985S Altcode: 2010arXiv1007.0009S
This article summaries a talk given at the HELAS IV international
meeting We present a brief overview of the history of attempts to
obtain a clear detection of solar-like oscillations in cluster stars,
and discuss the results on the first clear detection, which was made
by the Kepler Asteroseismic Science Consortium (KASC) Working Group
2. <P />Data from Kepler.
---------------------------------------------------------
Title: Asteroseismology of Red Giants from the First Four Months of
Kepler Data: Global Oscillation Parameters for 800 Stars
Authors: Huber, D.; Bedding, T. R.; Stello, D.; Mosser, B.; Mathur,
S.; Kallinger, T.; Hekker, S.; Elsworth, Y. P.; Buzasi, D. L.; De
Ridder, J.; Gilliland, R. L.; Kjeldsen, H.; Chaplin, W. J.; García,
R. A.; Hale, S. J.; Preston, H. L.; White, T. R.; Borucki, W. J.;
Christensen-Dalsgaard, J.; Clarke, B. D.; Jenkins, J. M.; Koch, D.
2010ApJ...723.1607H Altcode: 2010arXiv1010.4566H
We have studied solar-like oscillations in ~800 red giant stars
using Kepler long-cadence photometry. The sample includes stars
ranging in evolution from the lower part of the red giant branch to
the helium main sequence. We investigate the relation between the
large frequency separation (Δν) and the frequency of maximum power
(ν<SUB>max</SUB>) and show that it is different for red giants than
for main-sequence stars, which is consistent with evolutionary models
and scaling relations. The distributions of ν<SUB>max</SUB> and Δν
are in qualitative agreement with a simple stellar population model
of the Kepler field, including the first evidence for a secondary
clump population characterized by M >~ 2 M <SUB>sun</SUB> and
ν<SUB>max</SUB> ~= 40-110 μHz. We measured the small frequency
separations δν<SUB>02</SUB> and δν<SUB>01</SUB> in over 400
stars and δν<SUB>03</SUB> in over 40. We present C-D diagrams
for l = 1, 2, and 3 and show that the frequency separation ratios
δν<SUB>02</SUB>/Δν and δν<SUB>01</SUB>/Δν have opposite trends
as a function of Δν. The data show a narrowing of the l = 1 ridge
toward lower ν<SUB>max</SUB>, in agreement with models predicting
more efficient mode trapping in stars with higher luminosity. We
investigate the offset epsilon in the asymptotic relation and find
a clear correlation with Δν, demonstrating that it is related
to fundamental stellar parameters. Finally, we present the first
amplitude-ν<SUB>max</SUB> relation for Kepler red giants. We observe
a lack of low-amplitude stars for ν<SUB>max</SUB> >~ 110 μHz
and find that, for a given ν<SUB>max</SUB> between 40 and 110 μHz,
stars with lower Δν (and consequently higher mass) tend to show
lower amplitudes than stars with higher Δν.
---------------------------------------------------------
Title: A Precise Asteroseismic Age and Radius for the Evolved Sun-like
Star KIC 11026764
Authors: Metcalfe, T. S.; Monteiro, M. J. P. F. G.; Thompson, M. J.;
Molenda-Żakowicz, J.; Appourchaux, T.; Chaplin, W. J.; Doǧan, G.;
Eggenberger, P.; Bedding, T. R.; Bruntt, H.; Creevey, O. L.; Quirion,
P. -O.; Stello, D.; Bonanno, A.; Silva Aguirre, V.; Basu, S.; Esch,
L.; Gai, N.; Di Mauro, M. P.; Kosovichev, A. G.; Kitiashvili, I. N.;
Suárez, J. C.; Moya, A.; Piau, L.; García, R. A.; Marques, J. P.;
Frasca, A.; Biazzo, K.; Sousa, S. G.; Dreizler, S.; Bazot, M.; Karoff,
C.; Frandsen, S.; Wilson, P. A.; Brown, T. M.; Christensen-Dalsgaard,
J.; Gilliland, R. L.; Kjeldsen, H.; Campante, T. L.; Fletcher, S. T.;
Handberg, R.; Régulo, C.; Salabert, D.; Schou, J.; Verner, G. A.;
Ballot, J.; Broomhall, A. -M.; Elsworth, Y.; Hekker, S.; Huber, D.;
Mathur, S.; New, R.; Roxburgh, I. W.; Sato, K. H.; White, T. R.;
Borucki, W. J.; Koch, D. G.; Jenkins, J. M.
2010ApJ...723.1583M Altcode: 2010arXiv1010.4329M
The primary science goal of the Kepler Mission is to provide
a census of exoplanets in the solar neighborhood, including the
identification and characterization of habitable Earth-like planets. The
asteroseismic capabilities of the mission are being used to determine
precise radii and ages for the target stars from their solar-like
oscillations. Chaplin et al. published observations of three bright
G-type stars, which were monitored during the first 33.5 days of science
operations. One of these stars, the subgiant KIC 11026764, exhibits a
characteristic pattern of oscillation frequencies suggesting that it
has evolved significantly. We have derived asteroseismic estimates of
the properties of KIC 11026764 from Kepler photometry combined with
ground-based spectroscopic data. We present the results of detailed
modeling for this star, employing a variety of independent codes and
analyses that attempt to match the asteroseismic and spectroscopic
constraints simultaneously. We determine both the radius and the age
of KIC 11026764 with a precision near 1%, and an accuracy near 2%
for the radius and 15% for the age. Continued observations of this
star promise to reveal additional oscillation frequencies that will
further improve the determination of its fundamental properties.
---------------------------------------------------------
Title: Asteroseismology of red giants from the first four months of
Kepler data: Fundamental stellar parameters
Authors: Kallinger, T.; Mosser, B.; Hekker, S.; Huber, D.; Stello,
D.; Mathur, S.; Basu, S.; Bedding, T. R.; Chaplin, W. J.; De Ridder,
J.; Elsworth, Y. P.; Frandsen, S.; García, R. A.; Gruberbauer, M.;
Matthews, J. M.; Borucki, W. J.; Bruntt, H.; Christensen-Dalsgaard,
J.; Gilliland, R. L.; Kjeldsen, H.; Koch, D. G.
2010A&A...522A...1K Altcode: 2010arXiv1010.4589K
Context. Clear power excess in a frequency range typical for solar-type
oscillations in red giants has been detected in more than 1000 stars,
which have been observed during the first 138 days of the science
operation of the NASA Kepler satellite. This sample includes stars in
a wide mass and radius range with spectral types G and K, extending
in luminosity from the bottom of the giant branch up to high-luminous
red giants, including the red bump and clump. The high-precision
asteroseismic observations with Kepler provide a perfect source
for testing stellar structure and evolutionary models, as well as
investigating the stellar population in our Galaxy. <BR /> Aims:
We aim to extract accurate seismic parameters from the Kepler time
series and use them to infer asteroseismic fundamental parameters
from scaling relations and a comparison with red-giant models. <BR />
Methods: We fit a global model to the observed power density spectra,
which allows us to accurately estimate the granulation background
signal and the global oscillation parameters, such as the frequency
of maximum oscillation power. We find regular patterns of radial and
non-radial oscillation modes and use a new technique to automatically
identify the mode degree and the characteristic frequency separations
between consecutive modes of the same spherical degree. In most
cases, we can also measure the small separation between l = 0, 1,
and 2 modes. Subsequently, the seismic parameters are used to estimate
stellar masses and radii and to place the stars in an H-R diagram by
using an extensive grid of stellar models that covers a wide parameter
range. Using Bayesian techniques throughout our entire analysis allows
us to determine reliable uncertainties for all parameters. <BR />
Results: We provide accurate seismic parameters and their uncertainties
for a large sample of red giants and determine their asteroseismic
fundamental parameters. We investigate the influence of the stars'
metallicities on their positions in the H-R diagram. Finally, we study
the red-giant populations in the red clump and bump and compare them
to a synthetic population. We find a mass and metallicity gradient in
the red clump and clear evidence of a secondary-clump population.
---------------------------------------------------------
Title: Modelling the autocovariance of the power spectrum of a
solar-type oscillator
Authors: Campante, T. L.; Karoff, C.; Chaplin, W. J.; Elsworth, Y. P.;
Handberg, R.; Hekker, S.
2010MNRAS.408..542C Altcode: 2010arXiv1006.0925C; 2010MNRAS.tmp.1125C
Asteroseismology is able to conduct studies on the interiors of
solar-type stars from the analysis of stellar acoustic spectra. However,
such an analysis process often has to rely upon subjective choices made
throughout. A recurring problem is to determine whether a signal in the
acoustic spectrum originates from a radial or a dipolar oscillation
mode. In order to overcome this problem, we present a procedure for
modelling and fitting the autocovariance of the power spectrum which
can be used to obtain global seismic parameters of solar-type stars,
doing so in an automated fashion without the need to make subjective
choices. From the set of retrievable global seismic parameters we
emphasize the mean small frequency separation and, depending on the
intrinsic characteristics of the power spectrum, the mean rotational
frequency splitting. Since this procedure is automated, it can serve
as a useful tool in the analysis of the more than 1000 solar-type
stars expected to be observed as part of the Kepler Asteroseismic
Investigation (KAI). We apply the aforementioned procedure to
simulations of the Sun. Assuming different apparent magnitudes, we
address the issues of how accurately and how precisely we can retrieve
the several global seismic parameters were the Sun to be observed as
part of the KAI.
---------------------------------------------------------
Title: Oscillation mode lifetimes of red giants observed during the
initial and first anticentre long run of CoRoT
Authors: Hekker, S.; Barban, C.; Baudin, F.; De Ridder, J.; Kallinger,
T.; Morel, T.; Chaplin, W. J.; Elsworth, Y.
2010A&A...520A..60H Altcode: 2010arXiv1006.4284H
Context. Long timeseries of data increase the frequency resolution in
the power spectrum. This allows for resolving stochastically excited
modes with long mode lifetimes, as well as features that are close
together in frequency. The CoRoT fields observed during the initial
run and second long run partly overlap, and stars in this overlapping
field observed in both runs are used to create timeseries with a
longer timespan than available from the individual runs. <BR /> Aims:
We aim to measure the mode lifetimes of red giants and compare them
with theoretical predictions. We also investigate the dependence of
the mode lifetimes on frequency and the degree of the oscillation
modes. <BR /> Methods: We perform simulations to investigate the
influence of the gap in the data between the initial and second long
run, the total length of the run and the signal-to-noise ratio on the
measured mode lifetime. This provides us with a correction factor to
apply to the mode lifetimes measured from a maximum likelihood fit to
the oscillation frequencies. <BR /> Results: We find that the length
of the timeseries, the signal-to-noise ratio and possible gaps do
have a non-negligible effect on the measurements of the mode lifetime
of stochastically excited oscillation modes, but we can correct for
it. For the four stars for which we can perform a fit of the oscillation
frequencies, we find that the mode lifetimes depend on frequency and
on degree of the mode, which quantitatively agrees with theoretical
predictions. <P />The CoRoT space mission which was developed and
is operated by the French space agency CNES, with participation of
ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany,
and Spain. Light curves can be retrieved from the CoRoT archive: <A
href="http://idoc-corot.ias.u-psud.fr.">http://idoc-corot.ias.u-psud.fr.</A>
---------------------------------------------------------
Title: A comparison of frequentist and Bayesian inference: searching
for low-frequency p modes and g modes in Sun-as-a-star data
Authors: Broomhall, A. -M.; Chaplin, W. J.; Elsworth, Y.; Appourchaux,
T.; New, R.
2010MNRAS.406..767B Altcode: 2010MNRAS.tmp..680B; 2010arXiv1004.4505B
We describe and use two different statistical approaches to
try and detect low-frequency solar oscillations in Sun-as-a-star
data: a frequentist approach and a Bayesian approach. We have used
frequentist statistics to search contemporaneous Sun-as-a-star data
for coincident, statistically prominent features. However, we find
that this approach leads to numerous false detections. We have also
used Bayesian statistics to search for evidence of low-frequency p
modes and g modes in Sun-as-a-star data. We describe how Bayesian
statistics can be used to search near-contemporaneous data for
coincident prominent features. Near-contemporaneous data were
used to circumvent the difficulties in deriving probabilities that
occur when common noise is present in the data. We find that the
Bayesian approach, which is reliant on the assumptions made when
determining the posterior probability, leads to significantly fewer
false detections and those that are observed can be discredited using
a priori knowledge. Therefore, we have more confidence in the mode
candidates found with Bayesian statistics.
---------------------------------------------------------
Title: A Seismic Signature of a Second Dynamo?
Authors: Fletcher, Stephen T.; Broomhall, Anne-Marie; Salabert, David;
Basu, Sarbani; Chaplin, William J.; Elsworth, Yvonne; Garcia, Rafael
A.; New, Roger
2010ApJ...718L..19F Altcode: 2010arXiv1006.4305F
The Sun is a variable star whose magnetic activity varies most
perceptibly on a timescale of approximately 11 years. However,
significant variation is also observed on much shorter timescales. We
observe a quasi-biennial (2 year) signal in the natural oscillation
frequencies of the Sun. The oscillation frequencies are sensitive probes
of the solar interior and so by studying them we can gain information
about conditions beneath the solar surface. Our results strongly point
to the 2 year signal being distinct and separate from, but nevertheless
susceptible to the influence of, the main 11 year solar cycle.
---------------------------------------------------------
Title: Determining stellar radii using large separations: an error
analysis
Authors: Basu, Sarbani; Chaplin, William J.; Elsworth, Yvonne
2010Ap&SS.328...79B Altcode: 2009Ap&SS.tmp..185B
The Kepler mission will provide large separations for many stars. One
of the tasks of Kepler Asteroseismic Consortium is to determine radii
of the observed stars from the large separations and other catalogued
“classical” data such as effective temperature, metallicities,
brightness, distance etc. We present the results of a detailed analysis
of errors in the radius estimates caused by errors in the input
parameters. This exercise enables us to determine which parameters
will benefit from follow-up observations of the interesting cases.
---------------------------------------------------------
Title: The solar-like CoRoT target HD 170987: spectroscopic and
seismic observations
Authors: Mathur, S.; García, R. A.; Catala, C.; Bruntt, H.; Mosser,
B.; Appourchaux, T.; Ballot, J.; Creevey, O. L.; Gaulme, P.; Hekker,
S.; Huber, D.; Karoff, C.; Piau, L.; Régulo, C.; Roxburgh, I. W.;
Salabert, D.; Verner, G. A.; Auvergne, M.; Baglin, A.; Chaplin, W. J.;
Elsworth, Y.; Michel, E.; Samadi, R.; Sato, K.; Stello, D.
2010A&A...518A..53M Altcode: 2010arXiv1004.4891M
Context. The CoRoT mission is in its third year of observation and the
data from the second long run in the galactic centre direction are being
analysed. The solar-like oscillating stars that have been observed up
to now have given some interesting results, specially concerning the
amplitudes that are lower than predicted. We present here the results
from the analysis of the star HD 170987. <BR /> Aims: The goal of this
research work is to characterise the global parameters of HD 170987. We
look for global seismic parameters such as the mean large separation,
maximum amplitude of the modes, and surface rotation because the
signal-to-noise ratio in the observations does not allow us to measure
individual modes. We also aim to retrieve the parameters of the star
and its chemical composition. <BR /> Methods: We studied the chemical
composition of the star through ground-based observations performed
with the NARVAL spectrograph. We used several methods to calculate
the global parameters from the acoustic oscillations based on CoRoT
data. The light curve of the star has been interpolated with inpainting
algorithms to reduce the effect of data gaps. <BR /> Results: We found
the power excess related to p modes in the range [400-1200] μHz with
a mean large separation of 55.2 ± 0.8 μHz with a probability above
95 % that increases to 55.9 ± 0.2 μHz in a higher frequency range
[500-1250] μHz and a rejection level of 1%. A hint of the variation of
this quantity with frequency was also found. The rotation period of the
star is estimated to be around 4.3 days with an inclination axis of i =
50° <SUP>+20</SUP><SUB>-13</SUB>. We measured a bolometric amplitude
per radial mode in a range [2.4-2.9] ppm around 1000 μHz. Finally
we estimate the stellar mass with a grid of models, M = 1.43 ± 0.05
M_⊙, the radius, R = 1.96 ± 0.046 R_⊙, and the age ~2.4 Gyr. <P
/>The CoRoT space mission, launched on 2006 December 27, has been
developed and is operated by CNES, with the contribution of Austria,
Belgium, Brazil, ESA (RSSD and Science Programme), Germany and Spain.
---------------------------------------------------------
Title: Differences Between the Current Solar Minimum and Earlier
Minima
Authors: Basu, S.; Broomhall, A. -M.; Chaplin, W. J.; Elsworth, Y.;
Fletcher, S.; New, R.
2010ASPC..428...37B Altcode: 2010arXiv1003.4262B
The Birmingham Solar-Oscillations Network (BiSON) has collected
helioseismic data over three solar cycles. We use these data to
determine how the internal properties of the Sun during this minimum
differ from the previous two minima. The Cycle 24 data show oscillatory
differences with respect to the other two sets, indicating relatively
localized changes in the solar interior. Analysis of MDI data from
Cycle 23 and Cycle 24 also show significant signs of differences.
---------------------------------------------------------
Title: The New Solar Minimum: How Deep does the Problem Go?
Authors: Fletcher, S.; New, R.; Broomhall, A. -M.; Chaplin, W.;
Elsworth, Y.
2010ASPC..428...43F Altcode: 2010arXiv1003.4228F
Although there are now some tentative signs that the start of cycle 24
has begun there is still considerable interest in the somewhat unusual
behavior of the current solar minimum and the apparent delay in the
true start of the next cycle. While this behavior is easily tracked
by observing the change in surface activity, a question can also be
asked about what is happening beneath the surface where the magnetic
activity ultimately originates. In order to try to answer this question
we can look at the behavior of the frequencies of the Sun's natural
seismic modes of oscillation—the p modes. These seismic frequencies
also respond to changes in activity and are probes of conditions in
the solar interior.<BR /> The Birmingham Solar Oscillations Network
(BiSON) has made measurements of low-degree (low-l) p mode frequencies
over the last three solar cycles, and so is in a unique position to
explore the current unusual and extended solar minimum. We compare the
frequency shifts in the low-l p-modes obtained from the BiSON data with
the change in surface activity as measured by different proxies and
show there are significant differences especially during the declining
phase of solar cycle 23 and into the current minimum. We also observe
quasi-biennial periodic behavior in the p mode frequencies over the
last two cycles that, unlike in the surface measurements, seems to be
present at mid- and low-activity levels. Additionally we look at the
frequency shifts of individual l modes.
---------------------------------------------------------
Title: Detection of Solar-like Oscillations from Kepler Photometry
of the Open Cluster NGC 6819
Authors: Stello, Dennis; Basu, Sarbani; Bruntt, Hans; Mosser, Benoît;
Stevens, Ian R.; Brown, Timothy M.; Christensen-Dalsgaard, Jørgen;
Gilliland, Ronald L.; Kjeldsen, Hans; Arentoft, Torben; Ballot,
Jérôme; Barban, Caroline; Bedding, Timothy R.; Chaplin, William
J.; Elsworth, Yvonne P.; García, Rafael A.; Goupil, Marie-Jo;
Hekker, Saskia; Huber, Daniel; Mathur, Savita; Meibom, Søren;
Sangaralingam, Vinothini; Baldner, Charles S.; Belkacem, Kevin;
Biazzo, Katia; Brogaard, Karsten; Suárez, Juan Carlos; D'Antona,
Francesca; Demarque, Pierre; Esch, Lisa; Gai, Ning; Grundahl, Frank;
Lebreton, Yveline; Jiang, Biwei; Jevtic, Nada; Karoff, Christoffer;
Miglio, Andrea; Molenda-Żakowicz, Joanna; Montalbán, Josefina; Noels,
Arlette; Roca Cortés, Teodoro; Roxburgh, Ian W.; Serenelli, Aldo M.;
Silva Aguirre, Victor; Sterken, Christiaan; Stine, Peter; Szabó,
Robert; Weiss, Achim; Borucki, William J.; Koch, David; Jenkins, Jon M.
2010ApJ...713L.182S Altcode: 2010arXiv1001.0026S
Asteroseismology of stars in clusters has been a long-sought goal
because the assumption of a common age, distance, and initial chemical
composition allows strong tests of the theory of stellar evolution. We
report results from the first 34 days of science data from the Kepler
Mission for the open cluster NGC 6819—one of the four clusters in
the field of view. We obtain the first clear detections of solar-like
oscillations in the cluster red giants and are able to measure
the large frequency separation, Δν, and the frequency of maximum
oscillation power, ν<SUB>max</SUB>. We find that the asteroseismic
parameters allow us to test cluster membership of the stars, and
even with the limited seismic data in hand, we can already identify
four possible non-members despite their having a better than 80%
membership probability from radial velocity measurements. We are also
able to determine the oscillation amplitudes for stars that span about
2 orders of magnitude in luminosity and find good agreement with the
prediction that oscillation amplitudes scale as the luminosity to the
power of 0.7. These early results demonstrate the unique potential of
asteroseismology of the stellar clusters observed by Kepler.
---------------------------------------------------------
Title: Solar-like Oscillations in Low-luminosity Red Giants: First
Results from Kepler
Authors: Bedding, T. R.; Huber, D.; Stello, D.; Elsworth, Y. P.;
Hekker, S.; Kallinger, T.; Mathur, S.; Mosser, B.; Preston, H. L.;
Ballot, J.; Barban, C.; Broomhall, A. M.; Buzasi, D. L.; Chaplin,
W. J.; García, R. A.; Gruberbauer, M.; Hale, S. J.; De Ridder, J.;
Frandsen, S.; Borucki, W. J.; Brown, T.; Christensen-Dalsgaard, J.;
Gilliland, R. L.; Jenkins, J. M.; Kjeldsen, H.; Koch, D.; Belkacem,
K.; Bildsten, L.; Bruntt, H.; Campante, T. L.; Deheuvels, S.; Derekas,
A.; Dupret, M. -A.; Goupil, M. -J.; Hatzes, A.; Houdek, G.; Ireland,
M. J.; Jiang, C.; Karoff, C.; Kiss, L. L.; Lebreton, Y.; Miglio,
A.; Montalbán, J.; Noels, A.; Roxburgh, I. W.; Sangaralingam, V.;
Stevens, I. R.; Suran, M. D.; Tarrant, N. J.; Weiss, A.
2010ApJ...713L.176B Altcode: 2010arXiv1001.0229B
We have measured solar-like oscillations in red giants using
time-series photometry from the first 34 days of science operations
of the Kepler Mission. The light curves, obtained with 30 minute
sampling, reveal clear oscillations in a large sample of G and K
giants, extending in luminosity from the red clump down to the bottom
of the giant branch. We confirm a strong correlation between the large
separation of the oscillations (Δν) and the frequency of maximum power
(ν<SUB>max</SUB>). We focus on a sample of 50 low-luminosity stars
(ν<SUB>max</SUB> > 100 μHz, L <~ 30 L <SUB>sun</SUB>) having
high signal-to-noise ratios and showing the unambiguous signature
of solar-like oscillations. These are H-shell-burning stars, whose
oscillations should be valuable for testing models of stellar evolution
and for constraining the star formation rate in the local disk. We use a
new technique to compare stars on a single échelle diagram by scaling
their frequencies and find well-defined ridges corresponding to radial
and non-radial oscillations, including clear evidence for modes with
angular degree l = 3. Measuring the small separation between l = 0 and
l = 2 allows us to plot the so-called C-D diagram of δν<SUB>02</SUB>
versus Δν. The small separation δν<SUB>01</SUB> of l = 1 from
the midpoint of adjacent l = 0 modes is negative, contrary to the Sun
and solar-type stars. The ridge for l = 1 is notably broadened, which
we attribute to mixed modes, confirming theoretical predictions for
low-luminosity giants. Overall, the results demonstrate the tremendous
potential of Kepler data for asteroseismology of red giants.
---------------------------------------------------------
Title: A Multi-Site Campaign to Measure Solar-Like Oscillations in
Procyon. II. Mode Frequencies
Authors: Bedding, Timothy R.; Kjeldsen, Hans; Campante, Tiago L.;
Appourchaux, Thierry; Bonanno, Alfio; Chaplin, William J.; Garcia,
Rafael A.; Martić, Milena; Mosser, Benoit; Butler, R. Paul; Bruntt,
Hans; Kiss, László L.; O'Toole, Simon J.; Kambe, Eiji; Ando,
Hiroyasu; Izumiura, Hideyuki; Sato, Bun'ei; Hartmann, Michael;
Hatzes, Artie; Barban, Caroline; Berthomieu, Gabrielle; Michel,
Eric; Provost, Janine; Turck-Chièze, Sylvaine; Lebrun, Jean-Claude;
Schmitt, Jerome; Bertaux, Jean-Loup; Benatti, Serena; Claudi, Riccardo
U.; Cosentino, Rosario; Leccia, Silvio; Frandsen, Søren; Brogaard,
Karsten; Glowienka, Lars; Grundahl, Frank; Stempels, Eric; Arentoft,
Torben; Bazot, Michaël; Christensen-Dalsgaard, Jørgen; Dall, Thomas
H.; Karoff, Christoffer; Lundgreen-Nielsen, Jens; Carrier, Fabien;
Eggenberger, Patrick; Sosnowska, Danuta; Wittenmyer, Robert A.; Endl,
Michael; Metcalfe, Travis S.; Hekker, Saskia; Reffert, Sabine
2010ApJ...713..935B Altcode: 2010arXiv1003.0052B
We have analyzed data from a multi-site campaign to observe oscillations
in the F5 star Procyon. The data consist of high-precision velocities
that we obtained over more than three weeks with 11 telescopes. A
new method for adjusting the data weights allows us to suppress the
sidelobes in the power spectrum. Stacking the power spectrum in a
so-called échelle diagram reveals two clear ridges, which we identify
with even and odd values of the angular degree (l = 0 and 2, and l =
1 and 3, respectively). We interpret a strong, narrow peak at 446 μHz
that lies close to the l = 1 ridge as a mode with mixed character. We
show that the frequencies of the ridge centroids and their separations
are useful diagnostics for asteroseismology. In particular, variations
in the large separation appear to indicate a glitch in the sound-speed
profile at an acoustic depth of ~1000 s. We list frequencies for 55
modes extracted from the data spanning 20 radial orders, a range
comparable to the best solar data, which will provide valuable
constraints for theoretical models. A preliminary comparison with
published models shows that the offset between observed and calculated
frequencies for the radial modes is very different for Procyon than
for the Sun and other cool stars. We find the mean lifetime of the
modes in Procyon to be 1.29<SUP>+0.55</SUP> <SUB>-0.49</SUB> days,
which is significantly shorter than the 2-4 days seen in the Sun.
---------------------------------------------------------
Title: The Asteroseismic Potential of Kepler: First Results for
Solar-Type Stars
Authors: Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; García,
R. A.; Houdek, G.; Karoff, C.; Metcalfe, T. S.; Molenda-Żakowicz,
J.; Monteiro, M. J. P. F. G.; Thompson, M. J.; Brown, T. M.;
Christensen-Dalsgaard, J.; Gilliland, R. L.; Kjeldsen, H.; Borucki,
W. J.; Koch, D.; Jenkins, J. M.; Ballot, J.; Basu, S.; Bazot, M.;
Bedding, T. R.; Benomar, O.; Bonanno, A.; Brandão, I. M.; Bruntt,
H.; Campante, T. L.; Creevey, O. L.; Di Mauro, M. P.; Doǧan,
G.; Dreizler, S.; Eggenberger, P.; Esch, L.; Fletcher, S. T.;
Frandsen, S.; Gai, N.; Gaulme, P.; Handberg, R.; Hekker, S.; Howe,
R.; Huber, D.; Korzennik, S. G.; Lebrun, J. C.; Leccia, S.; Martic,
M.; Mathur, S.; Mosser, B.; New, R.; Quirion, P. -O.; Régulo, C.;
Roxburgh, I. W.; Salabert, D.; Schou, J.; Sousa, S. G.; Stello, D.;
Verner, G. A.; Arentoft, T.; Barban, C.; Belkacem, K.; Benatti, S.;
Biazzo, K.; Boumier, P.; Bradley, P. A.; Broomhall, A. -M.; Buzasi,
D. L.; Claudi, R. U.; Cunha, M. S.; D'Antona, F.; Deheuvels, S.;
Derekas, A.; García Hernández, A.; Giampapa, M. S.; Goupil, M. J.;
Gruberbauer, M.; Guzik, J. A.; Hale, S. J.; Ireland, M. J.; Kiss,
L. L.; Kitiashvili, I. N.; Kolenberg, K.; Korhonen, H.; Kosovichev,
A. G.; Kupka, F.; Lebreton, Y.; Leroy, B.; Ludwig, H. -G.; Mathis, S.;
Michel, E.; Miglio, A.; Montalbán, J.; Moya, A.; Noels, A.; Noyes,
R. W.; Pallé, P. L.; Piau, L.; Preston, H. L.; Roca Cortés, T.;
Roth, M.; Sato, K. H.; Schmitt, J.; Serenelli, A. M.; Silva Aguirre,
V.; Stevens, I. R.; Suárez, J. C.; Suran, M. D.; Trampedach, R.;
Turck-Chièze, S.; Uytterhoeven, K.; Ventura, R.; Wilson, P. A.
2010ApJ...713L.169C Altcode: 2010arXiv1001.0506C
We present preliminary asteroseismic results from Kepler on three G-type
stars. The observations, made at one-minute cadence during the first
33.5 days of science operations, reveal high signal-to-noise solar-like
oscillation spectra in all three stars: about 20 modes of oscillation
may be clearly distinguished in each star. We discuss the appearance of
the oscillation spectra, use the frequencies and frequency separations
to provide first results on the radii, masses, and ages of the stars,
and comment in the light of these results on prospects for inference
on other solar-type stars that Kepler will observe.
---------------------------------------------------------
Title: Discovery of a Red Giant with Solar-like Oscillations in an
Eclipsing Binary System from Kepler Space-based Photometry
Authors: Hekker, S.; Debosscher, J.; Huber, D.; Hidas, M. G.; De
Ridder, J.; Aerts, C.; Stello, D.; Bedding, T. R.; Gilliland, R. L.;
Christensen-Dalsgaard, J.; Brown, T. M.; Kjeldsen, H.; Borucki, W. J.;
Koch, D.; Jenkins, J. M.; Van Winckel, H.; Beck, P. G.; Blomme,
J.; Southworth, J.; Pigulski, A.; Chaplin, W. J.; Elsworth, Y. P.;
Stevens, I. R.; Dreizler, S.; Kurtz, D. W.; Maceroni, C.; Cardini,
D.; Derekas, A.; Suran, M. D.
2010ApJ...713L.187H Altcode: 2010arXiv1001.0399H
Oscillating stars in binary systems are among the most interesting
stellar laboratories, as these can provide information on the stellar
parameters and stellar internal structures. Here we present a red
giant with solar-like oscillations in an eclipsing binary observed
with the NASA Kepler satellite. We compute stellar parameters of the
red giant from spectra and the asteroseismic mass and radius from
the oscillations. Although only one eclipse has been observed so far,
we can already determine that the secondary is a main-sequence F star
in an eccentric orbit with a semi-major axis larger than 0.5 AU and
orbital period longer than 75 days.
---------------------------------------------------------
Title: The Octave (Birmingham-Sheffield Hallam) automated pipeline for
extracting oscillation parameters of solar-like main-sequence stars
Authors: Hekker, S.; Broomhall, A. -M.; Chaplin, W. J.; Elsworth,
Y. P.; Fletcher, S. T.; New, R.; Arentoft, T.; Quirion, P. -O.;
Kjeldsen, H.
2010MNRAS.402.2049H Altcode: 2009MNRAS.tmp.1945H; 2009arXiv0911.2612H
The number of main-sequence stars for which we can observe
solar-like oscillations is expected to increase considerably with the
short-cadence high-precision photometric observations from the NASA
Kepler satellite. Because of this increase in the number of stars,
automated tools are needed to analyse these data in a reasonable amount
of time. In the framework of the asteroFLAG consortium, we present an
automated pipeline which extracts frequencies and other parameters
of solar-like oscillations in main-sequence and subgiant stars. The
pipeline uses only the time series data as input and does not require
any other input information. Tests on 353 artificial stars reveal
that we can obtain accurate frequencies and oscillation parameters
for about three quarters of the stars. We conclude that our methods
are well suited for the analysis of main-sequence stars, which show
mainly p-mode oscillations.
---------------------------------------------------------
Title: Automated Asteroseismic Analysis of Solar-type Stars
Authors: Karoff, C.; Campante, T. L.; Chaplin, W. J.
2010arXiv1003.4167K Altcode:
The rapidly increasing volume of asteroseismic observations on
solar-type stars has revealed a need for automated analysis tools. The
reason for this is not only that individual analyses of single stars are
rather time consuming, but more importantly that these large volumes
of observations open the possibility to do population studies on
large samples of stars and such population studies demand a consistent
analysis. By consistent analysis we understand an analysis that can be
performed without the need to make any subjective choices on e.g. mode
identification and an analysis where the uncertainties are calculated
in a consistent way. Here we present a set of automated asterosesimic
analysis tools. The main engine of these set of tools is an algorithm
for modelling the autocovariance spectra of the stellar acoustic spectra
allowing us to measure not only the frequency of maximum power and the
large frequency separation, but also the small frequency separation and
potentially the mean rotational rate and the inclination. The measured
large and small frequency separations and the frequency of maximum power
are used as input to an algorithm that estimates fundamental stellar
parameters such as mass, radius, luminosity, effective temperature,
surface gravity and age based on grid modeling. All the tools take
into account the window function of the observations which means that
they work equally well for space-based photometry observations from
e.g. the NASA Kepler satellite and ground-based velocity observations
from e.g. the ESO HARPS spectrograph.
---------------------------------------------------------
Title: Kepler Asteroseismology Program: Introduction and First Results
Authors: Gilliland, Ronald L.; Brown, Timothy M.;
Christensen-Dalsgaard, Jørgen; Kjeldsen, Hans; Aerts, Conny;
Appourchaux, Thierry; Basu, Sarbani; Bedding, Timothy R.; Chaplin,
William J.; Cunha, Margarida S.; De Cat, Peter; De Ridder, Joris;
Guzik, Joyce A.; Handler, Gerald; Kawaler, Steven; Kiss, László;
Kolenberg, Katrien; Kurtz, Donald W.; Metcalfe, Travis S.; Monteiro,
Mario J. P. F. G.; Szabó, Robert; Arentoft, Torben; Balona, Luis;
Debosscher, Jonas; Elsworth, Yvonne P.; Quirion, Pierre-Olivier;
Stello, Dennis; Suárez, Juan Carlos; Borucki, William J.; Jenkins,
Jon M.; Koch, David; Kondo, Yoji; Latham, David W.; Rowe, Jason F.;
Steffen, Jason H.
2010PASP..122..131G Altcode: 2010arXiv1001.0139G
Asteroseismology involves probing the interiors of stars and quantifying
their global properties, such as radius and age, through observations of
normal modes of oscillation. The technical requirements for conducting
asteroseismology include ultrahigh precision measured in photometry
in parts per million, as well as nearly continuous time series over
weeks to years, and cadences rapid enough to sample oscillations with
periods as short as a few minutes. We report on results from the first
43 days of observations, in which the unique capabilities of Kepler
in providing a revolutionary advance in asteroseismology are already
well in evidence. The Kepler asteroseismology program holds intrinsic
importance in supporting the core planetary search program through
greatly enhanced knowledge of host star properties, and extends well
beyond this to rich applications in stellar astrophysics.
---------------------------------------------------------
Title: Sounding stellar cycles with Kepler - preliminary results
from ground-based chromospheric activity measurements†
Authors: Karoff, C.; Metcalfe, T. S.; Chaplin, W. J.; Frandsen,
S.; Grundahl, F.; Kjeldsen, H.; Buzasi, D.; Arentoft, T.;
Christensen-Dalsgaard, J.
2010IAUS..264...57K Altcode: 2009arXiv0910.1436K
Due to its unique long-term coverage and high photometric precision,
observations from the Kepler asteroseismic investigation will provide us
with the possibility to sound stellar cycles in a number of solar-type
stars with asteroseismology. By comparing these measurements with
conventional ground-based chromospheric activity measurements we
might be able to increase our understanding of the relation between
the chromospheric changes and the changes in the eigenmodes. <P />In
parallel with the Kepler observations we have therefore started a
programme at the Nordic Optical Telescope to observe and monitor
chromospheric activity in the stars that are most likely to be
selected for observations for the whole satellite mission. The
ground-based observations presented here can be used both to guide
the selection of the special Kepler targets and as the first step in
a monitoring programme for stellar cycles. Also, the chromospheric
activity measurements obtained from the ground-based observations can
be compared with stellar parameters such as ages and rotation in order
to improve stellar evolution models.
---------------------------------------------------------
Title: Determining global parameters of the oscillations of solar-like
stars
Authors: Mathur, S.; García, R. A.; Régulo, C.; Creevey, O. L.;
Ballot, J.; Salabert, D.; Arentoft, T.; Quirion, P. -O.; Chaplin,
W. J.; Kjeldsen, H.
2010A&A...511A..46M Altcode: 2009arXiv0912.3367M
Context. Helioseismology has enabled us to better understand the solar
interior, while also allowing us to better constrain solar models. But
now is a tremendous epoch for asteroseismology as space missions
dedicated to studying stellar oscillations have been launched within
the last years (MOST and CoRoT). CoRoT has already proved valuable
results for many types of stars, while Kepler, which was launched in
March 2009, will provide us with a huge number of seismic data very
soon. This is an opportunity to better constrain stellar models and
to finally understand stellar structure and evolution. <BR /> Aims:
The goal of this research work is to estimate the global parameters
of any solar-like oscillating target in an automatic manner. We
want to determine the global parameters of the acoustic modes (large
separation, range of excited pressure modes, maximum amplitude, and
its corresponding frequency), retrieve the surface rotation period
of the star and use these results to estimate the global parameters
of the star (radius and mass). <BR /> Methods: To prepare for the
arrival and the analysis of hundreds of solar-like oscillating
stars, we have developed a robust and automatic pipeline, which was
partially adapted from helioseismic methods. The pipeline consists of
data analysis techniques, such as Fast Fourier Transform, wavelets,
autocorrelation, as well as the application of minimisation algorithms
for stellar-modelling. <BR /> Results: We apply our pipeline to some
simulated lightcurves from the asteroFLAG team and the Aarhus-asteroFLAG
simulator, and obtain results that are consistent with the input data
to the simulations. Our strategy gives correct results for stars with
magnitudes below 11 with only a few 10% of bad determinations among
the reliable results. We then apply the pipeline to the Sun and three
CoRoT targets. In particular we determine the large separation and
radius of the Sun, HD49933, HD181906, and HD181420.
---------------------------------------------------------
Title: Determination of Stellar Radii from Asteroseismic Data
Authors: Basu, Sarbani; Chaplin, William J.; Elsworth, Yvonne
2010ApJ...710.1596B Altcode: 2009arXiv0909.0506B
The NASA Kepler mission is designed to find planets through
transits. Accurate and precise radii of the detected planets
depend on knowing the radius of the host star accurately, which
is difficult unless the temperature and luminosity of the star are
known precisely. Kepler, however, has an asteroseismology program
that will provide seismic variables that can characterize stellar
radii easily, accurately, and extremely precisely. In this paper,
we describe the Yale-Birmingham (YB) method to determine stellar
radii using a combination of seismic and conventional variables and
analyze the effect of these variables on the result. We find that for
main-sequence stars, a knowledge of the parallax is not important to get
accurate radii using the YB method: we can get results to an accuracy
and precision of better than a few percent if we know the effective
temperature and the seismic parameters for these stars. Metallicity
does not make much difference either. However, good estimates of the
effective temperature and metallicity, along with those of the seismic
parameters, are essential to determine radii of subgiants properly. On
the other hand, for red giants we find that determining radii properly
is not possible without a good estimate of the parallax. We find that
the so-called "surface term" in the seismic data has minimal effect
on the inferred radii. Uncertainties in the convective mixing length
can matter under some circumstances and can cause a systematic shift
in the inferred radii. Blind tests with data simulated to match those
expected from the asteroseismic survey phase of Kepler show that it
will be possible to infer stellar radii successfully using our method.
---------------------------------------------------------
Title: The quest for the solar g modes
Authors: Appourchaux, T.; Belkacem, K.; Broomhall, A. -M.; Chaplin,
W. J.; Gough, D. O.; Houdek, G.; Provost, J.; Baudin, F.; Boumier,
P.; Elsworth, Y.; García, R. A.; Andersen, B. N.; Finsterle, W.;
Fröhlich, C.; Gabriel, A.; Grec, G.; Jiménez, A.; Kosovichev, A.;
Sekii, T.; Toutain, T.; Turck-Chièze, S.
2010A&ARv..18..197A Altcode: 2010A&ARv.tmp....1A; 2009arXiv0910.0848A
Solar gravity modes (or g modes)—oscillations of the solar interior
on which buoyancy acts as the restoring force—have the potential
to provide unprecedented inference on the structure and dynamics of
the solar core, inference that is not possible with the well-observed
acoustic modes (or p modes). The relative high amplitude of the g-mode
eigenfunctions in the core and the evanesence of the modes in the
convection zone make the modes particularly sensitive to the physical
and dynamical conditions in the core. Owing to the existence of the
convection zone, the g modes have very low amplitudes at photospheric
levels, which makes the modes extremely hard to detect. In this article,
we review the current state of play regarding attempts to detect g
modes. We review the theory of g modes, including theoretical estimation
of the g-mode frequencies, amplitudes and damping rates. Then we go
on to discuss the techniques that have been used to try to detect g
modes. We review results in the literature, and finish by looking to
the future, and the potential advances that can be made—from both
data and data-analysis perspectives—to give unambiguous detections
of individual g modes. The review ends by concluding that, at the time
of writing, there is indeed a consensus amongst the authors that there
is currently no undisputed detection of solar g modes.
---------------------------------------------------------
Title: The Inhomogeneous Response Across the Solar Disc of Unresolved
Doppler Velocity Observations
Authors: Broomhall, A. -M.; Chaplin, W. J.; Elsworth, Y.; New, R.
2009ASPC..416..245B Altcode: 2008arXiv0810.3856B
Unresolved Doppler velocity measurements are not homogeneous across
the solar disc (Brookes et al. 1978). We consider one cause of the
inhomogeneity that originates from the BiSON instrumentation itself:
the intensity of light observed from a region on the solar disc is
dependent on the distance between that region on the image of the
solar disc formed in the instrument and the detector. The non-uniform
weighting affects the realization of the solar noise and the amplitudes
of the solar oscillations observed by a detector. An "offset velocity",
which varies with time, is observed in BiSON data and has consequences
for the long-term stability of observations. We have attempted to
model, in terms of the inhomogeneous weighting, the average observed
offset velocity.
---------------------------------------------------------
Title: Are Low-Degree p-Mode Frequencies Predictable from One Cycle
to the Next?
Authors: Broomhall, A. -M.; Chaplin, W. J.; Elsworth, Y.; New, R.;
Verner, G. A.
2009ASPC..416..183B Altcode: 2008arXiv0810.3591B
The Birmingham Solar-Oscillations Network (BiSON) has been collecting
data for over 30 yrs and so observations span nearly three eleven yr
solar activity cycles. This allows us to address important questions
concerning the solar cycle and its effect on solar oscillations,
such as: how consistent is the acoustic behavior from one cycle to the
next? We have used the p-mode frequencies observed in BiSON data from
one solar activity cycle (cycle 22) to predict the mode frequencies
that were observed in the next activity cycle (cycle 23). Some bias in
the predicted frequencies was observed when short 108 days time series
were used to make the predictions. We also found that the accuracy of
the predictions was dependent on which activity proxy was used to make
the predictions and on the length of the relevant time series.
---------------------------------------------------------
Title: Pseudo-Global Fitting of Gapped Helioseismic Data
Authors: Fletcher, S.; New, R.; Chaplin, W.; Elsworth, Y.
2009ASPC..416..519F Altcode: 2009arXiv0904.4126F
Mode fitting or "peak-bagging" is an important procedure in
helioseismology allowing one to determine the various mode parameters of
solar oscillations. We have recently developed a new "pseudo-global"
fitting algorithm as a way of reducing the systematic bias in the
fits of certain mode parameters that are seen when using "local"
fitting techniques to analyze "Sun-as-a-star" p-mode data. This new
algorithm has been designed specifically to gain the advantages of
fitting the entire power spectrum, while retaining the efficiency of
local fitting techniques. <P />Using simulated data with a full fill we
have previously shown that the pseudo-global routine reduces the bias
in estimates of the frequencies and asymmetries and in the estimates
of the solar background when compared with a traditional fitting
technique. Here we present results that show that the pseudo-global
routine is also effective in reducing bias in the parameter estimates
when the time-series has significant gaps. As such we are now able to
employ the routine in order to fit ground-based helioseismic data such
as that collected by the Birmingham Solar Oscillations Network (BiSON).
---------------------------------------------------------
Title: Analysis of GOLF Power Spectra Weighted to Account for Noise
Variations Through the Data Set
Authors: New, R.; Fletcher, S.; Chaplin, W.; Elsworth, Y.; García,
R. A.
2009ASPC..416..325N Altcode:
It has been established that the noise in Doppler velocity measurements
obtained by resonant scattering spectrometers varies with season of the
year and, of course, with instrument conditions. For example, recent
analysis has characterized the noise in data taken by the Global
Oscillations at Low Frequencies (GOLF) instrument on the ESA/NASA
satellite SoHO, which shows seasonal variation and a secular increase
associated with the degradation of GOLF's photomultiplier tubes. Using
the noise characteristics it is possible to generate power spectra using
the weighted sine-wave fit technique often employed in asteroseismic
work. This paper presents the first analyses of such weighted power
spectra, which have been generated from several years of GOLF data,
and compares the results generated by more commonly employed unweighted
transform techniques.
---------------------------------------------------------
Title: BiSON Update
Authors: Allison, J.; Barnes, I.; Broomhall, A. -M.; Chaplin, W.;
Davies, G.; Elsworth, Y.; Hale, S.; Jackson, B.; Miller, B.; New,
R.; Fletcher, S.
2009ASPC..416..227A Altcode:
We present an update on the operation of the Birmingham Solar
Oscillations Network (BiSON) network including our various running
statistics such as duty cycle. We also give an update regarding our
status and briefly outline the foreseeable future of the network.
---------------------------------------------------------
Title: The Simulation of Realistic BiSON-like Helioseismic Data
Authors: Fletcher, S.; New, R.; Broomhall, A. -M.; Chaplin, W.;
Elsworth, Y.
2009ASPC..416..337F Altcode: 2009arXiv0903.3486F
When simulating full-disc helioseismic data, instrumental noise has
traditionally been treated as time-independent. However, in reality,
instrumental noise will often vary to some degree over time due to
line-of-sight velocity variations and possibly degrading hardware. <P
/>Here we present a new technique for simulating Birmingham Solar
Oscillations Network (BiSON) helioseismic data with a more realistic
analogue for instrumental noise. This is achieved by simulating
the potassium solar Fraunhofer line as observed by the BiSON
instruments. Intensity measurements in the red and blue wing of the
line can then be simulated and appropriate time-dependent instrumental
noise can be added. The simulated time-series can then be formed in
the same way as with real data. Here we present the simulation method
and the first generation of a BiSON-like instrumental-noise time series.
---------------------------------------------------------
Title: The relation between Δν and ν<SUB>max</SUB> for solar-like
oscillations
Authors: Stello, D.; Chaplin, W. J.; Basu, S.; Elsworth, Y.; Bedding,
T. R.
2009MNRAS.400L..80S Altcode: 2009MNRAS.tmpL.341S; 2009arXiv0909.5193S; 2009MNRAS.tmpL.349S
Establishing relations between global stellar parameters and
asteroseismic quantities can help improve our understanding of stellar
astrophysics and facilitate the interpretation of observations. We
present an observed relation between the large frequency separation,
Δν, and the frequency of maximum power, ν<SUB>max</SUB>. We find
that Δν ~ ν<SUP>0.77</SUP><SUB>max</SUB>, allowing prediction
of Δν to about 15 per cent given ν<SUB>max</SUB>. Our result
is further supported by established scaling relations for Δν and
ν<SUB>max</SUB> and by extended stellar model calculations, which
confirm that Δν can be estimated using this relation for basically
any star showing solar-like oscillations in the investigated range
(0.5 < M/M <SUB>solar</SUB> < 4.0).
---------------------------------------------------------
Title: A fresh look at the seismic spectrum of HD49933: analysis of
180 days of CoRoT photometry
Authors: Benomar, O.; Baudin, F.; Campante, T. L.; Chaplin, W. J.;
García, R. A.; Gaulme, P.; Toutain, T.; Verner, G. A.; Appourchaux,
T.; Ballot, J.; Barban, C.; Elsworth, Y.; Mathur, S.; Mosser, B.;
Régulo, C.; Roxburgh, I. W.; Auvergne, M.; Baglin, A.; Catala, C.;
Michel, E.; Samadi, R.
2009A&A...507L..13B Altcode: 2009arXiv0910.3060B
Context: Solar-like oscillations have now been observed in several
stars, thanks to ground-based spectroscopic observations and space-borne
photometry. CoRoT, which has been in orbit since December 2006, has
observed the star HD49933 twice. The oscillation spectrum of this
star has proven difficult to interpret. <BR />Aims: Thanks to a new
timeseries provided by CoRoT, we aim to provide a robust description
of the oscillations in HD49933, i.e., to identify the degrees of the
observed modes, and to measure mode frequencies, widths, amplitudes
and the average rotational splitting. <BR />Methods: Several methods
were used to model the Fourier spectrum: Maximum Likelihood Estimators
and Bayesian analysis using Markov Chain Monte-Carlo techniques. <BR
/>Results: The different methods yield consistent result, and allow us
to make a robust identification of the modes and to extract precise
mode parameters. Only the rotational splitting remains difficult to
estimate precisely, but is clearly relatively large (several μHz in
size). <P />The CoRoT space mission, launched on 2006 December 27,
was developed and is operated by the CNES, with participation of
the Science Programs of ESA, ESA's RSSD, Austria, Belgium, Brazil,
Germany and Spain. <P />Figures 5-9 and Table 2 are only available in
electronic form at http://www.aanda.org
---------------------------------------------------------
Title: Automated extraction of oscillation parameters for Kepler
observations of solar-type stars
Authors: Huber, D.; Stello, D.; Bedding, T. R.; Chaplin, W. J.;
Arentoft, T.; Quirion, P. -O.; Kjeldsen, H.
2009CoAst.160...74H Altcode: 2009arXiv0910.2764H
The recent launch of the Kepler space telescope brings the opportunity
to study oscillations systematically in large numbers of solar-like
stars. In the framework of the asteroFLAG project, we have developed an
automated pipeline to estimate global oscillation parameters, such as
the frequency of maximum power (νmax ) and the large frequency spacing
(Δν), for a large number of time series. We present an effective
method based on the autocorrelation function to find excess power and
use a scaling relation to estimate granulation timescales as initial
conditions for background modelling. We derive reliable uncertainties
for νmax and Δν through extensive simulations. We have tested the
pipeline on about 2000 simulated Kepler stars with magnitudes of V ∼
7-12 and were able to correctly determine νmax and Δν for about half
of the sample. For about 20%, the returned large frequency spacing
is accurate enough to determine stellar radii to a 1% precision. We
conclude that the methods presented here are a promising approach to
process the large amount of data expected from Kepler.
---------------------------------------------------------
Title: Solar-like oscillations in HD 181420: data analysis of 156
days of CoRoT data
Authors: Barban, C.; Deheuvels, S.; Baudin, F.; Appourchaux, T.;
Auvergne, M.; Ballot, J.; Boumier, P.; Chaplin, W. J.; García,
R. A.; Gaulme, P.; Michel, E.; Mosser, B.; Régulo, C.; Roxburgh,
I. W.; Verner, G.; Baglin, A.; Catala, C.; Samadi, R.; Bruntt, H.;
Elsworth, Y.; Mathur, S.
2009A&A...506...51B Altcode:
Context: The estimate of solar-like oscillation properties, such
as their frequencies, amplitudes and lifetimes, is challenging
because of their low amplitudes and will benefit from long and
uninterrupted observing runs. The space telescope CoRoT allows us
to obtain high-performance photometric data over a long and quasi
continuous period. Among its main targets are stars for which we expect
solar-like oscillations. <BR />Aims: HD 181420, an F2 main sequence
star, has been observed by CoRoT during its first long run covering
about 156 days. With this unprecedently high-quality set of data,
our aim is to derive the p-mode parameters that can be used to probe
the stellar interior. <BR />Methods: The CoRoT data obtained on HD
181420 is analysed using a classical Fourier approach for the search
for the p mode signature. The p-mode parameters are then derived using
global fitting of the power spectrum by a Lorentzian model, as used
widely in the solar case. <BR />Results: From the p-mode frequencies,
the mean value of the large spacing is estimated to be 75 {μ Hz}. The
p-mode amplitudes are slightly less than 4 ppm with a line width of
about 8 {μ Hz} at the maximum of the p modes. The inclination angle is
estimated to be around 45 °. The large mode line-width combined with
the observed mode spacing make it difficult to identify the ℓ=2 modes
and to estimate the rotational splitting. We explore two scenarios
for the identification of the modes. <P />The CoRoT space mission,
launched on 2006 December 27, was delopped and is operated by the
CNES with participation of the Science Programs of ESA; ESA's RSSD,
Austria, Belgium, Brazil, Germany and Spain.
---------------------------------------------------------
Title: Solar-like oscillations with low amplitude in the CoRoT target
HD 181906
Authors: García, R. A.; Régulo, C.; Samadi, R.; Ballot, J.; Barban,
C.; Benomar, O.; Chaplin, W. J.; Gaulme, P.; Appourchaux, T.; Mathur,
S.; Mosser, B.; Toutain, T.; Verner, G. A.; Auvergne, M.; Baglin,
A.; Baudin, F.; Boumier, P.; Bruntt, H.; Catala, C.; Deheuvels, S.;
Elsworth, Y.; Jiménez-Reyes, S. J.; Michel, E.; Pérez Hernández,
F.; Roxburgh, I. W.; Salabert, D.
2009A&A...506...41G Altcode: 2009arXiv0907.0608G
Context: The F8 star HD 181906 (effective temperature ∼6300 K) was
observed for 156 days by the CoRoT satellite during the first long
run in the direction of the galactic centre. Analysis of the data
reveals a spectrum of solar-like acoustic oscillations. However, the
faintness of the target (m<SUB>v</SUB> = 7.65) means the signal-to-noise
(S/N) in the acoustic modes is quite low, and this low S/N leads to
complications in the analysis. <BR />Aims: We extract global variables
of the star, as well as key parameters of the p modes observed in the
power spectrum of the lightcurve. <BR />Methods: The power spectrum
of the lightcurve, a wavelet transform and spot fitting were used
to obtain the average rotation rate of the star and its inclination
angle. Then, the autocorrelation of the power spectrum and the power
spectrum of the power spectrum were used to properly determine the
large separation. Finally, estimations of the mode parameters were
done by maximizing the likelihood of a global fit, where several modes
were fit simultaneously. <BR />Results: We have been able to infer the
mean surface rotation rate of the star (~4 μHz) with indications of
the presence of surface differential rotation, the large separation
of the p modes (~87 μHz), hence also the “ridges” corresponding
to overtones of the acoustic modes. <P />CoRoT (Convection, Rotation
and planetary Transits) is a minisatellite developed by the French
Space agency CNES in collaboration with the Science Programmes of ESA,
Austria, Belgium, Brazil, Germany and Spain.
---------------------------------------------------------
Title: Sounding stellar cycles with Kepler - I. Strategy for
selecting targets
Authors: Karoff, C.; Metcalfe, T. S.; Chaplin, W. J.; Elsworth, Y.;
Kjeldsen, H.; Arentoft, T.; Buzasi, D.
2009MNRAS.399..914K Altcode: 2009arXiv0906.5441K; 2009MNRAS.tmp.1226K
The long-term monitoring and high photometric precision of the Kepler
satellite will provide a unique opportunity to sound the stellar cycles
of many solar-type stars using asteroseismology. This can be achieved
by studying periodic changes in the amplitudes and frequencies of
the oscillation modes observed in these stars. By comparing these
measurements with conventional ground-based chromospheric activity
indices, we can improve our understanding of the relationship between
chromospheric changes and those taking place deep in the interior
throughout the stellar activity cycle. In addition, asteroseismic
measurements of the convection zone depth and differential rotation
may help us determine whether stellar cycles are driven at the top
or at the base of the convection zone. In this paper, we analyse
the precision that will be possible using Kepler to measure stellar
cycles, convection zone depths and differential rotation. Based on
this analysis, we describe a strategy for selecting specific targets
to be observed by the Kepler Asteroseismic Investigation for the
full length of the mission, to optimize their suitability for probing
stellar cycles in a wide variety of solar-type stars.
---------------------------------------------------------
Title: Analysing Solar-like Oscillations with an Automatic Pipeline
Authors: Mathur, S.; García, R. A.; Régulo, C.; Ballot, J.; Salabert,
D.; Chaplin, W. J.
2009AIPC.1170..540M Altcode: 2009arXiv0907.1139M
The Kepler mission will provide a huge amount of asteroseismic data
during the next few years, among which hundreds of solar-like stars will
be targeted. The amount of stars and their observation length represent
a step forward in the comprehension of the stellar evolution that has
already been initiated by CoRoT and MOST missions. Up to now, the slow
cadence of observed targets allowed an individual and personalized
analysis of each star. During the survey phase of Kepler, this will
be impossible. This is the reason why, within the AsteroFLAG team,
we have been developing automatic pipelines for the Kepler solar-like
oscillation stars. Our code starts by finding the frequency-range
where p-mode power is present and, after fitting the background,
it looks for the mode amplitudes as well as the central frequency of
the p-mode hump. A good estimation of the large separation can thus
be inferred in this region. If the signal to noise is high enough,
the code obtains the characteristics of the p modes by doing a global
fitting on the power spectrum. Here, we will first describe a few
features of this pipeline and its application to AsteroFLAG synthetic
data to check the validity of the code.
---------------------------------------------------------
Title: Corrections of Sun-as-a-star p-mode frequencies for effects
of the solar cycle
Authors: Broomhall, A. -M.; Chaplin, W. J.; Elsworth, Y.; Fletcher,
S. T.; New, R.
2009A&A...503..241B Altcode: 2009arXiv0907.2855B
Solar p-mode frequencies vary with solar activity. It is important
to take this into account when comparing the frequencies observed
from epochs that span different regions of the solar cycle. We present
details of how to correct observed p-mode frequencies for the effects of
the solar cycle. We describe three types of correction. The first allows
mode frequencies to be corrected to a nominal activity level, such as
the canonical quiet-Sun level. The second accounts for the effect on the
observed mode frequencies, powers, and damping rates of the continually
varying solar cycle and is pertinent to frequencies obtained from very
long data sets. The third corrects for Sun-as-a-star observations not
seeing all components of the modes. Suitable combinations of the three
correction procedures allow the frequencies obtained from different
sets of data to be compared and enable activity-independent inversions
of the solar interior. As an example of how to apply the corrections
we describe those used to produce a set of definitive Sun-as-a-star
frequencies.
---------------------------------------------------------
Title: Is the Current Lack of Solar Activity Only Skin Deep?
Authors: Broomhall, A. -M.; Chaplin, W. J.; Elsworth, Y.; Fletcher,
S. T.; New, R.
2009ApJ...700L.162B Altcode: 2009arXiv0907.3417B
The Sun is a variable star whose magnetic activity and total
irradiance vary on a timescale of approximately 11 years. The current
activity minimum has attracted considerable interest because of its
unusual duration and depth. This raises the question: what might be
happening beneath the surface where the magnetic activity ultimately
originates? The surface activity can be linked to the conditions in
the solar interior by the observation and analysis of the frequencies
of the Sun's natural seismic modes of oscillation—the p modes. These
seismic frequencies respond to changes in activity and are probes of
conditions within the Sun. The Birmingham Solar-Oscillations Network
(BiSON) has made measurements of p-mode frequencies over the last three
solar activity cycles, and so is in a unique position to explore the
current unusual and extended solar minimum. We show that the BiSON data
reveal significant variations of the p-mode frequencies during the
current minimum. This is in marked contrast to the surface activity
observations, which show little variation over the same period. The
level of the minimum is significantly deeper in the p-mode frequencies
than in the surface observations. We observe a quasi-biennial signal in
the p-mode frequencies, which has not previously been observed at mid-
and low-activity levels. The stark differences in the behavior of the
frequencies and the surface activity measures point to activity-related
processes occurring in the solar interior, which are yet to reach the
surface, where they may be attenuated.
---------------------------------------------------------
Title: Radius Determination of Solar-type Stars Using
Asteroseismology: What to Expect from the Kepler Mission
Authors: Stello, Dennis; Chaplin, William J.; Bruntt, Hans; Creevey,
Orlagh L.; García-Hernández, Antonio; Monteiro, Mario J. P. F. G.;
Moya, Andrés; Quirion, Pierre-Olivier; Sousa, Sergio G.; Suárez,
Juan-Carlos; Appourchaux, Thierry; Arentoft, Torben; Ballot, Jerome;
Bedding, Timothy R.; Christensen-Dalsgaard, Jørgen; Elsworth,
Yvonne; Fletcher, Stephen T.; García, Rafael A.; Houdek, Günter;
Jiménez-Reyes, Sebastian J.; Kjeldsen, Hans; New, Roger; Régulo,
Clara; Salabert, David; Toutain, Thierry
2009ApJ...700.1589S Altcode: 2009arXiv0906.0766S
For distant stars, as observed by the NASA Kepler satellite,
parallax information is currently of fairly low quality and is not
complete. This limits the precision with which the absolute sizes of
the stars and their potential transiting planets can be determined by
traditional methods. Asteroseismology will be used to aid the radius
determination of stars observed during NASA's Kepler mission. We
report on the recent asteroFLAG hare-and-hounds Exercise#2, where
a group of "hares" simulated data of F-K main-sequence stars that a
group of "hounds" sought to analyze, aimed at determining the stellar
radii. We investigated stars in the range 9 < V < 15, both
with and without parallaxes. We further test different uncertainties
in T <SUB>eff</SUB>, and compare results with and without using
asteroseismic constraints. Based on the asteroseismic large frequency
spacing, obtained from simulations of 4 yr time series data from
the Kepler mission, we demonstrate that the stellar radii can be
correctly and precisely determined, when combined with traditional
stellar parameters from the Kepler Input Catalogue. The radii found
by the various methods used by each independent hound generally agree
with the true values of the artificial stars to within 3%, when the
large frequency spacing is used. This is 5-10 times better than the
results where seismology is not applied. These results give strong
confidence that radius estimation can be performed to better than 3%
for solar-like stars using automatic pipeline reduction. Even when the
stellar distance and luminosity are unknown we can obtain the same level
of agreement. Given the uncertainties used for this exercise we find
that the input log g and parallax do not help to constrain the radius,
and that T <SUB>eff</SUB> and metallicity are the only parameters we
need in addition to the large frequency spacing. It is the uncertainty
in the metallicity that dominates the uncertainty in the radius.
---------------------------------------------------------
Title: New aspects of Doppler imaging in Sun-as-a-star observations
Authors: Broomhall, A. M.; Chaplin, W. J.; Elsworth, Y.; New, R.
2009MNRAS.397..793B Altcode: 2009MNRAS.tmp..780B; 2009arXiv0904.4122B; 2009MNRAS.tmp..750B
Birmingham Solar Oscillations Network (BiSON) instruments use
resonant scattering spectrometers to make unresolved Doppler velocity
observations of the Sun. Unresolved measurements are not homogenous
across the solar disc and so the observed data do not represent
a uniform average over the entire surface. The influence on the
inhomogeneity of the solar rotation and limb darkening has been
considered previously and is well understood. Here, we consider a
further effect that originates from the instrumentation itself. The
intensity of light observed from a particular region on the solar disc
is dependent on the distance between that region on the image of the
solar disc formed in the instrument and the detector. The majority of
BiSON instruments have two detectors positioned on opposite sides of
the image of the solar disc and the observations made by each detector
are weighted towards differing regions of the disc. Therefore, the
visibility and amplitudes of the solar oscillations and the realization
of the solar noise observed by each detector will differ. We find
that the modelled bias is sensitive to many different parameters such
as the width of solar absorption lines, the strength of the magnetic
field in the resonant scattering spectrometer, the orientation of the
Sun's rotation axis, the size of the image observed by the instrument
and the optical depth in the vapour cell. We find that the modelled
results best match the observations when the optical depth at the
centre of the vapour cell is 0.55. The inhomogeneous weighting means
that a `velocity offset' is introduced into unresolved Doppler velocity
observations of the Sun, which varies with time, and so has an impact
on the long-term stability of the observations.
---------------------------------------------------------
Title: Fresh Insights on the Structure of the Solar Core
Authors: Basu, Sarbani; Chaplin, William J.; Elsworth, Yvonne; New,
Roger; Serenelli, Aldo M.
2009ApJ...699.1403B Altcode: 2009arXiv0905.0651B
We present new results on the structure of the solar core, obtained
with new sets of frequencies of solar low-degree p modes obtained from
the BiSON network. We find that different methods used in extracting
the different sets of frequencies cause shifts in frequencies, but
the shifts are not large enough to affect solar structure results. We
find that the BiSON frequencies show that the solar sound speed in the
core is slightly larger than that inferred from data from Michelson
Doppler Imager low-degree modes, and the uncertainties on the inversion
results are smaller. Density results also change by a larger amount,
and we find that solar models now tend to show smaller differences
in density compared to the Sun. The result is seen at all radii,
a result of the fact that conservation of mass implies that density
differences in one region have to cancel out density differences in
others, since our models are constructed to have the same mass as the
Sun. The uncertainties on the density results are much smaller too. We
attribute the change in results to having more, and lower frequency,
low-degree mode frequencies available. These modes provide greater
sensitivity to conditions in the core.
---------------------------------------------------------
Title: Definitive Sun-as-a-star p-mode frequencies: 23 years of
BiSON observations
Authors: Broomhall, A. -M.; Chaplin, W. J.; Davies, G. R.; Elsworth,
Y.; Fletcher, S. T.; Hale, S. J.; Miller, B.; New, R.
2009MNRAS.396L.100B Altcode: 2009MNRAS.tmpL.242B; 2009arXiv0903.5219B
We present a list of `best possible' estimates of low-degree p-mode
frequencies from 8640 days of observations made by the Birmingham
Solar-Oscillations Network (BiSON). This is the longest stretch of
helioseismic data ever used for this purpose, giving exquisite precision
in the estimated frequencies. Every effort has been made in the analysis
to ensure that the frequency estimates are also accurate. In addition
to presenting the raw best-fitting frequencies from our `peak-bagging'
analysis, we also provide tables of corrected frequencies pertinent
to the quiet-Sun and an intermediate level of solar activity.
---------------------------------------------------------
Title: Mode lifetimes of stellar oscillations. Implications for
asteroseismology
Authors: Chaplin, W. J.; Houdek, G.; Karoff, C.; Elsworth, Y.; New, R.
2009A&A...500L..21C Altcode: 2009arXiv0905.1722C
Context: Successful inference from asteroseismology relies on at least
two factors: that the oscillations in the stars have amplitudes large
enough to be clearly observable, and that the oscillations themselves
be stable enough to enable precise measurements of mode frequencies
and other parameters. Solar-like p modes are damped by convection,
and hence the stability of the modes depends on the lifetime. <BR
/>Aims: We seek a simple scaling relation between the mean lifetime of
the most prominent solar-like p modes in stars, and the fundamental
stellar parameters. <BR />Methods: We base our search for a relation
on the use of stellar equilibrium and pulsation computations of a grid
of stellar models, and the first asteroseismic results on lifetimes
of main-sequence, sub-giant and red-giant stars. <BR />Results:
We find that the mean lifetimes of all three classes of solar-like
stars scale like T_eff<SUP>-4</SUP> (where T_eff is the effective
temperature). When this relation is combined with the well-known scaling
relation of Kjeldsen & Bedding for mode amplitudes observed in
narrow-band intensity observations, we obtain the unexpected result
that the height (the maximum power spectral density) of mode peaks in
the frequency power spectrum scales as g<SUP>-2</SUP> (where g is the
surface gravity). As it is the mode height (and not the amplitude) that
fixes the S/N at which the modes can be measured, and as g changes only
slowly along the main sequence, this suggests that stars cooler than
the Sun might be as good targets for asteroseismology as their hotter
counterparts. When observations are instead made in Doppler velocity,
our results imply that mode height does increase with increasing
effective temperature.
---------------------------------------------------------
Title: Efficient Pseudo-Global Fitting for Helioseismic Data
Authors: Fletcher, S. T.; Chaplin, W. J.; Elsworth, Y.; New, Roger
2009ApJ...694..144F Altcode: 2009arXiv0902.4427F
Mode fitting or "peak bagging" is an important procedure in
helioseismology allowing one to determine the various mode parameters of
solar oscillations. Here we describe a way of reducing the systematic
bias in the fits of certain mode parameters that are seen when using
"local" fitting techniques to analyze the Sun-as-a-star p-mode
power spectrum. To do this we have developed a new "pseudo-global"
fitting algorithm designed to gain the advantages of fitting the
entire power spectrum, but without the problems involved in fitting a
model incorporating many hundreds of parameters. We have performed a
comparative analysis between the local and pseudo-global peak-bagging
techniques by fitting the "limit" profiles of simulated helioseismic
data. Results show that for asymmetric modes the traditional fitting
technique returns systematically biased estimates of the central
frequency parameter. This bias is significantly reduced when employing
the pseudo-global routine. Similarly, we show that estimates of the
background returned from the pseudo-global routine match the input
values much more closely than the estimates from the local fitting
method. We have also used the two fitting techniques to analyze a
set of real solar data collected by the Global Oscillations at Low
Frequencies instrument on board the ESA/NASA Solar and Heliospheric
Observatory spacecraft. Similar differences between the estimated
frequencies returned by the two techniques are seen when fitting both
the real and simulated data. We show that the background fits returned
by the pseudo-global routine more closely match the estimate of the
background one can infer from interpolating between fits to the high
and low frequency ends of the p-mode power spectrum.
---------------------------------------------------------
Title: Excitation and Damping of p-Mode Oscillations of α Cen B
Authors: Chaplin, W. J.; Houdek, G.; Elsworth, Y.; New, R.; Bedding,
T. R.; Kjeldsen, H.
2009ApJ...692..531C Altcode: 2008arXiv0810.5022C
This paper presents an analysis of observational data on the p-mode
spectrum of the star α Cen B, and a comparison with theoretical
computations of the stochastic excitation and damping of the modes. We
find that at frequencies gsim4500 μHz, the model damping rates appear
to be too weak to explain the observed shape of the power spectral
density of α Cen B. The conclusion rests on the assumption that most
of the disagreement is due to problems modeling the damping rates,
not the excitation rates, of the modes. This assumption is supported
by a parallel analysis of BiSON Sun-as-a-star data, for which it
is possible to use analysis of very long timeseries to place tight
constraints on the assumption. The BiSON analysis shows that there is a
similar high-frequency disagreement between theory and observation in
the Sun. We demonstrate that by using suitable comparisons of theory
and observation it is possible to make inference on the dependence of
the p-mode linewidths on frequency, without directly measuring those
linewidths, even though the α Cen B dataset is only a few nights
long. Use of independent measures from a previous study of the α Cen
B linewidths in two parts of its spectrum also allows us to calibrate
our linewidth estimates for the star. The resulting calibrated linewidth
curve looks similar to a frequency-scaled version of its solar cousin,
with the scaling factor equal to the ratio of the respective acoustic
cut-off frequencies of the two stars. The ratio of the frequencies at
which the onset of high-frequency problems is seen in both stars is
also given approximately by the same scaling factor.
---------------------------------------------------------
Title: SMEI observations of previously unseen pulsation frequencies
in γ Doradus
Authors: Tarrant, N. J.; Chaplin, W. J.; Elsworth, Y. P.; Spreckley,
S. A.; Stevens, I. R.
2008A&A...492..167T Altcode: 2008arXiv0810.0612T
Aims: As g-mode pulsators, gamma-Doradus-class stars may naïvely be
expected to show a large number of modes. Taking advantage of the long
photometric time-series generated by the solar mass ejection imager
(SMEI) instrument, we have studied the star gamma Doradus to determine
whether any other modes than the three already known are present at
observable amplitude. <BR />Methods: High-precision photometric data
from SMEI taken between April 2003 and March 2006 were subjected to
periodogram analysis with the PERIOD04 package. <BR />Results: We
confidently determine three additional frequencies at 1.39, 1.87, and
2.743 d<SUP>-1</SUP>. These are above and beyond the known frequencies
of 1.320, 1.364, and 1.47 d<SUP>-1</SUP>. <BR />Conclusions: Two of
the new frequencies, at 1.39 and 1.87 d<SUP>-1</SUP>, are speculated
to be additional modes of oscillation, with the third frequency at
2.743<SUP>-1</SUP> a possible combination frequency.
---------------------------------------------------------
Title: Asteroseismology of Red Giant stars
Authors: Tarrant, N. J.; Chaplin, W. J.; Elsworth, Y. P.; Spreckley,
S. A.; Stevens, I. R.
2008CoAst.157...92T Altcode: 2008arXiv0810.3839T
Sun-like oscillations, that is p-modes excited stochastically by
convective noise, have now been observed in a number of Red Giant
stars. Compared to those seen in the Sun, these modes are of large
amplitude and long period, making the oscillations attractive prospects
for observation. However, the low Q-factor of these modes, and issues
relating to the rising background at low frequencies, present some
interesting challenges for identifying modes and determining the related
asteroseismic parameters. We report on the analysis procedure adopted
for peak-bagging by our group at Birming- ham, and the techniques
used to robustly ensure these are not a product of noise. I also show
results from a number of giants extracted from multi-year observations
with the SMEI instrument
---------------------------------------------------------
Title: Reliability of P mode event classification using
contemporaneous BiSON and GOLF observations
Authors: Simoniello, R.; Chaplin, W. J.; Elsworth, Y. P.; García,
R. A.
2008JPhCS.118a2088S Altcode: 2008arXiv0808.1668S
We carried out a comparison of the signals seen in contemporaneous
BiSON and GOLF data sets. Both instruments perform Doppler shift
velocity measurements in integrated sunlight, although BiSON perform
measurements from the two wings of potassium absorption line and GOLF
from one wing of the NaD1 line. Discrepancies between the two datasets
have been observed. We show,in fact, that the relative power depends
on the wing in which GOLF data observes. During the blue wing period,
the relative power is mugh higher than in BiSON datasets, while a good
agreement has been observed during the red period.
---------------------------------------------------------
Title: solarFLAG hare and hounds: estimation of p-mode frequencies
from Sun-as-star helioseismology data
Authors: Jiménez-Reyes, S. J.; Chaplin, W. J.; García, R. A.;
Appourchaux, T.; Baudin, F.; Boumier, P.; Elsworth, Y.; Fletcher,
S. T.; Lazrek, M.; Leibacher, J. W.; Lochard, J.; New, R.; Régulo,
C.; Salabert, D.; Toutain, T.; Verner, G. A.; Wachter, R.
2008MNRAS.389.1780J Altcode: 2008arXiv0807.0989J; 2008MNRAS.tmp..954J; 2008MNRAS.tmp.1026J
We report on the results of the latest solarFLAG hare-and-hounds
exercise, which was concerned with testing methods for extraction
of frequencies of low-degree solar p modes from data collected
by Sun-as-a-star observations. We have used the new solarFLAG
simulator, which includes the effects of correlated mode excitation and
correlations with background noise, to make artificial time-series data
that mimic Doppler velocity observations of the Sun-as-a-star. The
correlations give rise to asymmetry of mode peaks in the frequency
power spectrum. 10 members of the group (the hounds) applied their
`peak-bagging' codes to a 3456-d data set, and the estimated
mode frequencies were returned to the hare (who was WJC) for
comparison. Analysis of the results reveals a systematic bias in the
estimated frequencies of modes above ~1.8mHz. The bias is negative,
meaning the estimated frequencies systematically underestimate the
input frequencies. <P />We identify two sources that are the dominant
contributions to the frequency bias. Both sources involve failure to
model accurately subtle aspects of the observed power spectral density
in the part (window) of the frequency power spectrum that is being
fitted. One source of bias arises from a failure to account for the
power spectral density coming from all those modes whose frequencies lie
outside the fitting windows. The other source arises from a failure to
account for the power spectral density of the weak l = 4 and 5 modes,
which are often ignored in Sun-as-a-star analysis. The Sun-as-a-star
peak-bagging codes need to allow for both sources, otherwise the
frequencies are likely to be biased.
---------------------------------------------------------
Title: AsteroFLAG — from the Sun to the stars
Authors: Chaplin, W. J.; Appourchaux, T.; Arentoft, T.; Ballot, J.;
Baudin, F.; Bazot, M.; Bedding, T. R.; Christensen-Dalsgaard, J.;
Creevey, O. L.; Duez, V.; Elsworth, Y.; Fletcher, S. T.; García,
R. A.; Gough, D. O.; Jiménez, A.; Jiménez-Reyes, S. J.; Houdek, G.;
Kjeldsen, H.; Lazrek, M.; Leibacher, J. W.; Monteiro, M. J. P. F. G.;
Neiner, C.; New, R.; Régulo, C.; Salabert, D.; Samadi, R.; Sekii,
T.; Sousa, S. G.; Toutain, T.; Turck-Chièze, S.
2008JPhCS.118a2048C Altcode:
We stand on the threshold of a critical expansion of asteroseismology
of Sun-like stars, the study of stellar interiors by observation
and analysis of their global acoustic modes of oscillation. The
Sun-like oscillations give a very rich spectrum allowing the internal
structure and dynamics to be probed down into the stellar cores to
very high precision. Asteroseismic observations of many stars will
allow multiple-point tests of crucial aspects of stellar evolution
and dynamo theory. The aims of the asteroFLAG collaboration are to
help the community to refine existing, and to develop new, methods
for analysis of the asteroseismic data on the Sun-like oscillators.
---------------------------------------------------------
Title: Perspectives in Global Helioseismology and the Road Ahead
Authors: Chaplin, William J.; Basu, Sarbani
2008SoPh..251...53C Altcode: 2008arXiv0801.4213C; 2008SoPh..tmp...36C
We review the impact of global helioseismology on key questions
concerning the internal structure and dynamics of the Sun and consider
the exciting challenges the field faces as it enters a fourth decade
of science exploitation. We do so with an eye on the past, looking at
the perspectives global helioseismology offered in its earlier phases,
in particular the mid-to-late 1970s and the 1980s. We look at how
modern, higher quality, longer datasets coupled with new developments in
analysis have altered, refined, and changed some of those perspectives
and opened others that were not previously available for study. We
finish by discussing outstanding challenges and questions for the field.
---------------------------------------------------------
Title: CoRoT sounds the stars: p-mode parameters of Sun-like
oscillations on HD 49933
Authors: Appourchaux, T.; Michel, E.; Auvergne, M.; Baglin, A.;
Toutain, T.; Baudin, F.; Benomar, O.; Chaplin, W. J.; Deheuvels, S.;
Samadi, R.; Verner, G. A.; Boumier, P.; García, R. A.; Mosser, B.;
Hulot, J. -C.; Ballot, J.; Barban, C.; Elsworth, Y.; Jiménez-Reyes,
S. J.; Kjeldsen, H.; Régulo, C.; Roxburgh, I. W.
2008A&A...488..705A Altcode:
Context: The first asteroseismology results from CoRoT are presented,
on a star showing Sun-like oscillations. We have analyzed a 60 day
lightcurve of high-quality photometric data collected by CoRoT on the
F5 V star HD 49933. The data reveal a rich spectrum of overtones of
low-degree p modes. <BR />Aims: Our aim was to extract robust estimates
of the key parameters of the p modes observed in the power spectrum of
the lightcurve. <BR />Methods: Estimation of the mode parameters was
performed using maximum likelihood estimation of the power spectrum. A
global fitting strategy was adopted whereby 15 mode orders of the
mode spectrum (45 modes) were fitted simultaneously. <BR />Results:
The parameter estimates that we list include mode frequencies,
peak linewidths, mode amplitudes, and a mean rotational frequency
splitting. We find that the average large frequency (overtone) spacing
derived from the fitted mode frequencies is 85.9 ± 0.15 μHz. The
frequency of maximum amplitude of the radial modes is at 1760 μHz,
where the observed rms mode amplitude is 3.75 ± 0.23 ppm. The mean
rotational splitting of the non-radial modes appears to be in the
range ≈2.7 μHz to ≈3.4 μHz. The angle of inclination offered by
the star, as determined by fits to the amplitude ratios of the modes,
appears to be in the range ≈50 degrees to ≈62 degrees. <P />The
CoRoT space mission, launched on <P />2006 December 27, was developed
and is operated by the CNES, with <P />participation of the Science
Programs of ESA, ESA's RSSD, Austria, <P />Belgium, Brazil, Germany
and Spain.
---------------------------------------------------------
Title: Uncovering the Bias in Low-Degree p-Mode Linewidth Fitting
Authors: Chaplin, W. J.; Elsworth, Y.; Miller, B. A.; New, R.; Verner,
G. A.
2008SoPh..251..189C Altcode: 2008SoPh..tmp..115C
Obtaining reliable estimates of linewidths in the power spectra of
low-degree p modes is problematic at low frequency. In this regime,
the mode coherence time increases with decreasing frequency, often
causing the modes to be unresolved in relatively long duration
spectra. The signal-to-noise ratio is also less favourable at low
frequency, resulting in fits to power spectra underestimating the
true linewidth of the p modes owing to the tails of the Lorentzian
peaks becoming dominated by the background noise. We use a numerical
simulation approach to assess the effect of this bias on the fitted
widths of p-mode peaks and calculate observational duration limits
required to obtain an unbiased estimate of the p-mode linewidth as a
function of frequency. This is done in four different cases, where
the precision of the artificial data is set at 0.25, 0.50, 0.75,
and 1.00 m s<SUP>−1</SUP> by adding random scatter to increase the
sample standard deviation per 40-second measurement. In all cases, the
observational duration required to accurately obtain width estimates
increases beyond that required for sufficient spectral resolution
below a certain threshold frequency. For modes at ≈ 1500 μHz, with
an amplitude of approximately ten times the background, observations
of up to 972 days are required to obtain an unbiased estimate of the
linewidth. This is equivalent to ≈ 18 times the coherence time of
the corresponding p modes.
---------------------------------------------------------
Title: The Amplitude of Solar Oscillations Using Stellar Techniques
Authors: Kjeldsen, Hans; Bedding, Timothy R.; Arentoft, Torben; Butler,
R. Paul; Dall, Thomas H.; Karoff, Christoffer; Kiss, László L.;
Tinney, C. G.; Chaplin, William J.
2008ApJ...682.1370K Altcode: 2008arXiv0804.1182K
The amplitudes of solar-like oscillations depend on the excitation
and damping, both of which are controlled by convection. Comparing
observations with theory should therefore improve our understanding
of the underlying physics. However, theoretical models invariably
compute oscillation amplitudes relative to the Sun, and it is
therefore vital to have a good calibration of the solar amplitude
using stellar techniques. We have used daytime spectra of the Sun,
obtained with HARPS and UCLES, to measure the solar oscillations
and made a detailed comparison with observations using the BiSON
helioseismology instrument. We find that the mean solar amplitude
measured using stellar techniques, averaged over one full solar cycle,
is 18.7 +/- 0.7 cm s<SUP>-1</SUP> for the strongest radial modes (l =
0) and 25.2 +/- 0.9 cm s<SUP>-1</SUP> for l = 1. In addition, we use
simulations to establish an equation that estimates the uncertainty
of amplitude measurements that are made of other stars, given that the
mode lifetime is known. Finally, we also give amplitudes of solar-like
oscillations for three stars that we measured from a series of short
observations with HARPS (γ Ser, β Aql, and α For), together with
revised amplitudes for five other stars for which we have previously
published results (α Cen A, α Cen B, β Hyi, ν Ind, and δ Pav).
---------------------------------------------------------
Title: Challenges for asteroseismic analysis of Sun-like stars
Authors: Chaplin, W. J.; Houdek, G.; Appourchaux, T.; Elsworth, Y.;
New, R.; Toutain, T.
2008A&A...485..813C Altcode: 2008arXiv0804.4371C
Context: Asteroseismology of Sun-like stars is undergoing rapid
expansion with, for example, new data from the CoRoT mission and
continuation of ground-based campaigns. There is also the exciting
upcoming prospect of NASA's Kepler mission, which will allow the
asteroseismic study of several hundred Sun-like targets, in some cases
for periods lasting up to a few years. <BR />Aims: The seismic mode
parameters are the input data needed for making inference on stars
and their internal structures. In this paper we discuss the ease with
which it will be possible to extract estimates of individual mode
parameters, dependent on the mass, age, and visual brightness of the
star. Our results are generally applicable; however, we look at mode
detectability in the context of the upcoming Kepler observations. <BR
/>Methods: To inform our discussions we make predictions of various
seismic parameters. To do this we use simple empirical scaling relations
and detailed pulsation computations of the stochastic excitation and
damping characteristics of the Sun-like p modes. <BR />Results: The
issues related to parameter extraction on individual p modes discussed
here are mode detectability, the detectability and impact of stellar
activity cycles, and the ability to measure properties of rotationally
split components, which is dependent on the relative importance of
the rotational characteristics of the star and the damping of the
stochastically excited p modes.
---------------------------------------------------------
Title: Oscillations in β Ursae Minoris. Observations with SMEI
Authors: Tarrant, N. J.; Chaplin, W. J.; Elsworth, Y.; Spreckley,
S. A.; Stevens, I. R.
2008A&A...483L..43T Altcode: 2008arXiv0804.3253T
Aims: From observations of the K4III star β UMi we attempt to determine
whether oscillations or any other form of variability is present. <BR
/>Methods: A high-quality photometric time series of ≈1000 days in
length obtained from the SMEI instrument on the Coriolis satellite is
analysed. Various statistical tests were performed to determine the
significance of features seen in the power density spectrum of the
light curve. <BR />Results: Two oscillations with frequencies 2.44
and 2.92 μHz have been identified. We interpret these oscillations
as consecutive overtones of an acoustic spectrum, implying a large
frequency spacing of 0.48 μHz. Using derived asteroseismic parameters
in combination with known astrophysical parameters, we estimate
the mass of β UMi to be 1.3 ± 0.3 {M}<SUB>⊙</SUB>. Peaks of the
oscillations in the power density spectrum show width, implying that
modes are stochastically excited and damped by convection. The mode
lifetime is estimated at 18±9 days.
---------------------------------------------------------
Title: A modified peak-bagging technique for fitting low-ℓ solar
p-modes
Authors: Fletcher, S. T.; Chaplin, W. J.; Elsworth, Y.; New, R.
2008AN....329..447F Altcode: 2008arXiv0803.3033F
We introduce a modified version of a standard power spectrum
`peak-bagging' technique which is designed to gain some of the
advantages that fitting the entire low-degree p-mode power spectrum
simultaneously would bring, but without the problems involved in
fitting a model incorporating many hundreds of parameters. Employing
Monte-Carlo simulations we show that by using this modified fitting code
it is possible to determine the true background level in the vicinity
of the p-mode peaks. In addition to this we show how small biases in
other mode parameters, which are related to inaccurate estimates of
the true background, are also consequently removed.
---------------------------------------------------------
Title: A framework for describing correlated excitation of solar
p-modes
Authors: Chaplin, W. J.; Elsworth, Y.; Toutain, T.
2008AN....329..440C Altcode: 2008arXiv0804.3338C
In a previous paper we suggested that, for a given p mode, the
excitation function is the same as the component of the solar background
noise that has an identical surface spherical harmonic projection
(over the corresponding range of temporal frequency). An important
consequence of this surmise is that the excitation of overtones
of a given angular degree and azimuthal order will be correlated in
time. In this note, we introduce the basic principles and a mathematical
description of correlated mode excitation. We use simple, illustrative
examples, involving two modes. Our treatment suggests that in the
real observations, any signatures of the correlation would not appear
as a correlation of the output amplitudes of overtones, but rather
as subtle modifications to the power spectral density at frequencies
between the central frequencies of the overtones. These modifications
give a contribution to the observed peak asymmetries.
---------------------------------------------------------
Title: AsteroFLAG: First results from hare-and-hounds Exercise #1
Authors: Chaplin, W. J.; Appourchaux, T.; Arentoft, T.; Ballot, J.;
Christensen-Dalsgaard, J.; Creevey, O. L.; Elsworth, Y.; Fletcher,
S. T.; García, R. A.; Houdek, G.; Jiménez-Reyes, S. J.; Kjeldsen,
H.; New, R.; Régulo, C.; Salabert, D.; Sekii, T.; Sousa, S. G.;
Toutain, T.; rest of asteroFLAG Group
2008AN....329..549C Altcode: 2008arXiv0803.4143C
We report on initial results from the first phase of Exercise #1 of the
asteroFLAG hare and hounds. The asteroFLAG group is helping to prepare
for the asteroseismology component of NASA's Kepler mission, and the
first phase of Exercise #1 is concerned with testing extraction of
estimates of the large and small frequency spacings of the low-degree p
modes from Kepler-like artificial data. These seismic frequency spacings
will provide key input for complementing the exoplanet search data.
---------------------------------------------------------
Title: The visibility of low-frequency solar acoustic modes
Authors: Broomhall, A. M.; Chaplin, W. J.; Elsworth, Y.; Fletcher,
S. T.
2008AN....329..461B Altcode: 2008arXiv0802.1418B
We make predictions of the detectability of low-frequency
p modes. Estimates of the powers and damping times of these
low-frequency modes are found by extrapolating the observed powers and
widths of higher-frequency modes with large observed signal-to-noise
ratios. The extrapolations predict that the low-frequency modes will
have small signal-to-noise ratios and narrow widths in a frequency-power
spectrum. Monte Carlo simulations were then performed where timeseries
containing mode signals and normally distributed Gaussian noise were
produced. The mode signals were simulated to have the powers and damping
times predicted by the extrapolations. Various statistical tests were
then performed on the frequency-amplitude spectra formed from these
timeseries to investigate the fraction of spectra in which the modes
could be detected. The results of these simulations were then compared
to the number of p-modes candidates observed in real Sun-as-a-star data
at low frequencies. The fraction of simulated spectra in which modes
were detected decreases rapidly as the frequency of modes decreases
and so the fraction of simulations in which the low-frequency modes
were detected was very small. However, increasing the signal-to-noise
(S/N) ratio of the low-frequency modes by a factor of 2 above the
extrapolated values led to significantly more detections. Therefore
efforts should continue to further improve the quality of solar data
that is currently available.
---------------------------------------------------------
Title: A devil in the detail: parameter cross-talk from the solar
cycle and estimation of solar p-mode frequencies
Authors: Chaplin, W. J.; Jiménez-Reyes, S. J.; Eff-Darwich, A.;
Elsworth, Y.; New, R.
2008MNRAS.385.1605C Altcode: 2008MNRAS.tmp..261C; 2008arXiv0801.1431C
Frequencies, powers and damping rates of the solar p modes are all
observed to vary over the 11-yr solar activity cycle. Here, we show
that simultaneous variations in these parameters give rise to a
subtle cross-talk effect, which we call the `devil in the detail',
that biases p-mode frequencies estimated from analysis of long power
frequency spectra. We also show that the resonant peaks observed in the
power frequency spectra show small distortions due to the effect. Most
of our paper is devoted to a study of the effect for Sun-as-a-star
observations of the low-l p modes. We show that for these data the
significance of the effect is marginal. We also touch briefly on the
likely l dependence of the effect, and discuss the implications of
these results for solar structure inversions.
---------------------------------------------------------
Title: Distortion of the p-mode peak profiles by the solar-cycle
frequency shifts: do we need to worry?
Authors: Chaplin, W. J.; Elsworth, Y.; New, R.; Toutain, T.
2008MNRAS.384.1668C Altcode: 2007arXiv0712.2931C; 2008MNRAS.tmp..140C
We seek to address whether solar-cycle frequency shifts of the Sun's
low-l p modes `distort' the underlying shapes of the mode peaks, when
those peaks are observed in power frequency spectra made from data
spanning large fractions, or more, of the cycle period. We present
analytical descriptions of the expected profiles, and validate the
predictions through use of artificial seismic time-series data, in which
temporal variations of the oscillator frequencies are introduced. Our
main finding is that for the Sun-like frequency shifts the distortion
of the asymmetrical Lorentzian-like profiles is very small, but also
just detectible. Our analysis indicates that by fitting modes to the
usual Lorentzian-like models - which do not allow for the distortion -
rather than new models we derive, there is a bias in the mode height and
linewidth parameters that is comparable in size to the observational
uncertainties given by multi-year data sets. Bias in the frequency
parameter gives much less cause for worry, being over an order of
magnitude smaller than the corresponding frequency uncertainties. The
distortion discussed in this paper may need to be considered when
multiyear Sun-like asteroseismic data sets are analysed on stars
showing strong activity cycles.
---------------------------------------------------------
Title: Asteroseismology of red giants: photometric observations of
Arcturus by SMEI
Authors: Tarrant, N. J.; Chaplin, W. J.; Elsworth, Y.; Spreckley,
S. A.; Stevens, I. R.
2007MNRAS.382L..48T Altcode: 2007MNRAS.tmpL.110T; 2007arXiv0706.3346T
We present new results on oscillations of the K1.5III giant Arcturus
(α Boo), from analysis of just over 2.5 yr of precise photometric
observations made by the Solar Mass Ejection Imager on board the
Coriolis satellite. A strong mode of oscillation is uncovered by the
analysis, having frequency 3.51 +/- 0.03μHz. By fitting its mode peak,
we are able to offer a highly constrained direct estimate of the damping
time (τ = 24 +/- 1d). The data also hint at the possible presence of
several radial-mode overtones, and maybe some non-radial modes. We are
also able to measure the properties of the granulation on the star,
with the characteristic time-scale for the granulation estimated to
be ~0.50 +/- 0.05 d.
---------------------------------------------------------
Title: Solar Heavy-Element Abundance: Constraints from Frequency
Separation Ratios of Low-Degree p-Modes
Authors: Chaplin, William J.; Serenelli, Aldo M.; Basu, Sarbani;
Elsworth, Yvonne; New, Roger; Verner, Graham A.
2007ApJ...670..872C Altcode: 2007arXiv0705.3154C
We use very precise frequencies of low-degree solar-oscillation
modes measured from 4752 days of data collected by the Birmingham
Solar-Oscillations Network to derive seismic information on the solar
core. We compare these observations to results from a large Monte Carlo
simulation of standard solar models, and use the results to constrain
the mean molecular weight of the solar core and the metallicity of
the solar convection zone. We find that only a high value of solar
metallicity is consistent with the seismic observations. We can
determine the mean molecular weight of the solar core to a very high
precision, and, depending on the sequence of Monte Carlo models used, we
find that the average mean molecular weight in the inner 20% by radius
of the Sun ranges from 0.7209 to 0.7231, with uncertainties of less than
0.5% on each value. Our lowest seismic estimate of solar metallicity
is Z=0.0187, and our highest is Z=0.0239, with uncertainties in the
range of 12%-19%. Our results indicate that the discrepancies between
solar models constructed with low metallicity and the helioseismic
observations extend to the solar core, and thus cannot be attributed
to deficiencies in the modeling of the solar convection zone.
---------------------------------------------------------
Title: Needles in haystacks: how to use contemporaneous data in the
search for low-frequency modes of oscillation of the Sun
Authors: Broomhall, A. M.; Chaplin, W. J.; Elsworth, Y.; Appourchaux,
T.
2007MNRAS.379....2B Altcode: 2007MNRAS.tmp..525B
We show how to take advantage of contemporaneous data from two different
instruments in the search for low-frequency modes of oscillation of
the Sun. Contemporaneous data allow searches to be made for prominent,
sharp concentrations of power which are coincident in frequency. Crucial
to determining objective measures of the joint probability of the
random occurrence of such features, which are potential candidates
for modes, is a good understanding of the characteristics of the
background noise. In this paper we show how to make proper allowance,
in the calculation of the probability, for noise that is common to data
from different instruments. This common noise is solar in origin, and
comes from the solar granulation. Its presence makes calculation of the
probability a non-trivial problem. We demonstrate application of the
technique in searches for low-frequency p modes. The data we searched
comprised 3071 d of contemporaneous Sun-as-a-star Doppler velocity
observations made by the ground-based Birmingham Solar-Oscillations
Network (BiSON), and the GOLF instrument onboard the ESA/NASA SOHO
spacecraft.
---------------------------------------------------------
Title: On understanding the meaning of l = 2 and 3 p-mode frequencies
as measured by various helioseismic instruments
Authors: Appourchaux, T.; Chaplin, W. J.
2007A&A...469.1151A Altcode:
Aims:Frequencies of the low-degree p-mode oscillations of the Sun
may be extracted either from data collected by instruments that make
full-disc observations of the Sun as a star, or from data collected
by instruments that resolve, or image, the Sun's surface onto many
detector elements. The two methods can show marked differences in
their sensitivity to modes having certain combinations of degree and
azimuthal order. These different sensitivities lead to differences
in measurements of the central frequencies of the modes, which must
be properly accounted for if data from two different instruments
are to be compared, or combined. <BR />Methods: We perform an
analytical derivation of the p-mode frequency offsets expected between
contemporaneous Sun-as-a-star and resolved-Sun data. <BR />Results:
Here, we demonstrate that the empirical factors derived by Chaplin et
al. (2004, A&A, 424, 713) are reproduced by our analysis, but with
a more marked dependence upon the mode linewidth.
---------------------------------------------------------
Title: On prospects for sounding activity cycles of Sun-like stars
with acoustic modes
Authors: Chaplin, W. J.; Elsworth, Y.; Houdek, G.; New, R.
2007MNRAS.377...17C Altcode: 2007MNRAS.tmp..170C
Data are now available on the Sun-like, p-mode oscillations of a growing
number of late-type stars. With extension of these observations to
dedicated, long-term campaigns, it will soon become possible to probe
acoustically magnetic activity, and stellar cycles, by observation of
systematic shifts in the mode frequencies giving additional information
to the stellar dynamo theorists. Here, we use model computations
of the damping rates of stochastically excited radial p modes to
make predictions of the precision with which it will be possible
to measure stellar-cycle frequency shifts of Sun-like stars along
the lower main sequence. We assume the first analyses will average
shifts across the most prominent modes to reduce uncertainties. We
also make some predictions of the expected frequency shifts, based on
existing stellar CaII H& K data. Our main conclusion is that the
basic properties of the acoustic signatures of the cycles should be
measurable to reasonably high precision given only a few multimonth
segments of data. It should also be possible to make inference on the
surface distribution of the activity, through measurement of shifts of
modes of different degree. Our computations also reveal an interesting
feature in the predicted appearance of the acoustic mode spectra of
stars cooler than about 5400K: the modelled power spectral density
of the modes shows two maxima, at different frequencies. By computing
average shifts of modes across the two maxima, where the signal-to-noise
ratio is highest, it should be possible to get the first measures of
the frequency dependence of the p-mode shifts. This dependence provides
information on the mechanism responsible for driving these shifts.
---------------------------------------------------------
Title: Solar p-Mode Frequencies over Three Solar Cycles
Authors: Chaplin, W. J.; Elsworth, Y.; Miller, B. A.; Verner, G. A.;
New, R.
2007ApJ...659.1749C Altcode:
We analyze thirty years of solar oscillations data collected by the
Birmingham Solar Oscillations Network (BiSON). Estimates of the mean
frequency shifts of low-degree p-modes have been extracted over a
period spanning solar cycles 21-23. Two methods of analysis are used
to extract the frequency shifts: one method uses results on fitted
frequencies of individual modes, which are then averaged to give mean
frequency shifts; the other method uses cross-correlations of power
frequency spectra made from subsets of the data shifted in time. The
frequency shifts are correlated against six proxies of solar activity,
which are sensitive to magnetic and irradiance variability at a range
of locations from the photosphere to the corona. We find proxies
that have good sensitivity to the effects of weak-component magnetic
flux-which is more widely distributed in latitude than the strong flux
in the active regions-are those that follow the frequency shifts most
consistently over the three cycles. This list includes the Mg II H and
K core-to-wing data, the 10.7 cm radio flux, and the He I equivalent
width data. While the two methods of analysis give consistent results,
use of the cross-correlation function to measure mean frequency shifts
returns less precise values in cases in which the duty cycle is greater
than 30%. Estimation of uncertainties from the cross-correlation method
also requires that proper allowance be made for strong correlations
in the data.
---------------------------------------------------------
Title: Sun-as-a-star observations: evidence for degree dependence
of changes in damping of low-ℓ p modes along the solar cycle
Authors: Salabert, D.; Chaplin, W. J.; Elsworth, Y.; New, R.; Verner,
G. A.
2007A&A...463.1181S Altcode: 2006astro.ph..9156S
Aims:We use 9.5-yr of BiSON Sun-as-a-star data to search for dependence
of solar-cycle parameter changes on the angular degree, ℓ, of the
data. The nature of the Sun-as-a-star observations is such that for
changes measured at fixed frequency, or for changes averaged across the
same range in frequency, any ℓ dependence present carries information
on the latitudinal distribution of the agent (i.e., the activity)
responsible for those changes. <BR />Methods: We split the 9.5-yr
timeseries into contiguous 108-d pieces, and determine mean changes
in the damping of, power in, and energy supplied to the modes through
the solar cycle. We also apply a careful correction to account for the
deleterious effects of the ground-based BiSON window function on the
results. <BR />Results: From our full analysis we obtain a marginally
significant result for the damping parameter, where the mean change
is found to be weakest at ℓ=0. The other parameters show hints
of some dependence in ℓ. <BR />Conclusions: .Our main conclusion
is that the mean fractional solar-cycle change in the ℓ=0 damping
rates is approximately 50% smaller than was previously assumed. It
had been common practice to use an average over all low-ℓ modes;
our downward revision of the radial-mode value has implications for
comparisons with models of the global solar cycle changes, which are
usually based on a spherically symmetric geometry.
---------------------------------------------------------
Title: Solar Abundances and Helioseismology: Fine-Structure Spacings
and Separation Ratios of Low-Degree p-Modes
Authors: Basu, Sarbani; Chaplin, William J.; Elsworth, Yvonne; New,
Roger; Serenelli, Aldo M.; Verner, Graham A.
2007ApJ...655..660B Altcode: 2006astro.ph.10052B
We have used 4752 days of data collected by the Birmingham Solar
Oscillations Network (BiSON) to determine very precise oscillation
frequencies of acoustic low-degree modes that probe the solar core. We
compare the fine (small frequency) spacings and frequency separation
ratios formed from these data with those of different solar models. We
find that models constructed with low metallicity are incompatible with
the observations. The results provide strong support for lowering the
theoretical uncertainties on the neutrino fluxes. These uncertainties
were recently raised due to the controversy over solar abundances.
---------------------------------------------------------
Title: On the Variation of the Peak Asymmetry of Low-l Solar p Modes
Authors: Jiménez-Reyes, S. J.; Chaplin, W. J.; Elsworth, Y.; García,
R. A.; Howe, R.; Socas-Navarro, H.; Toutain, T.
2007ApJ...654.1135J Altcode:
The resonant peaks of solar p modes show small amounts of asymmetry in
frequency. Here, we use five independent sets of contemporaneous data,
collected over a ~=8 yr period, to investigate whether peak asymmetry in
low angular degree p modes changes over the solar activity cycle. Three
of the data sets are from instruments on board the ESA/NASA SOHO
spacecraft (GOLF, MDI, and VIRGO/SPM); and two are from ground-based
networks (BiSON and GONG). Evidence for variation in asymmetry, well
correlated with the activity cycle, is uncovered in the GOLF and BiSON
Doppler velocity data. Suggestions of a similar trend are present in
the GONG Doppler velocity data. Apparent changes in the MDI Doppler
velocity data are somewhat less significant. Meanwhile, analysis of
the SPM intensity data failed to uncover any evidence for significant
change of the asymmetry parameter.
---------------------------------------------------------
Title: BiSON update
Authors: Allison, J.; Barnes, I.; Chaplin, W. J.; Elsworth, Y. P.;
Hale, S. J.; Jackson, B.; Miller, B. A.; Verner, G. A.; New, R.
2006ESASP.624E..99A Altcode: 2006soho...18E..99A
No abstract at ADS
---------------------------------------------------------
Title: Analysis of velocity-noise variations arising from photon-noise
in data from the GOLF instrument
Authors: New, R.; Chaplin, W. J.; Elsworth, Y. P.; García, R. A.;
Jiménez-Reyes, S. J.
2006ESASP.624E.100N Altcode: 2006soho...18E.100N
No abstract at ADS
---------------------------------------------------------
Title: The seismic Sun over three activity cycles
Authors: Chaplin, W. J.; Elsworth, Y.; Hale, S. J.; Miller, B. A.;
Verner, G. A.; New, R.
2006ESASP.624E...8C Altcode: 2006soho...18E...8C
No abstract at ADS
---------------------------------------------------------
Title: Helioseismology with low-degree observations: where we stand,
and what the future holds
Authors: Chaplin, W. J.
2006ESASP.624E..21C Altcode: 2006soho...18E..21C
No abstract at ADS
---------------------------------------------------------
Title: A study of the role of phase evolution in the amplitudes of
low-degree solar p-modes
Authors: Simoniello, R.; Chaplin, W. J.; Elsworth, Y.; New, R.
2006ESASP.624E.106S Altcode: 2006soho...18E.106S
No abstract at ADS
---------------------------------------------------------
Title: Are the shapes of the p-mode peaks `distorted' by the solar
cycle when they are observed in long, multi-year power frequency
spectra?
Authors: Chaplin, W. J.; Elsworth, Y.; New, R.; Toutain, T.
2006ESASP.624E..91C Altcode: 2006soho...18E..91C
No abstract at ADS
---------------------------------------------------------
Title: Frequency, splitting, linewidth and amplitude estimates of
low-l p modes of alpha Cen A: analysis of WIRE photometry
Authors: Fletcher, S. T.; Chaplin, W. J.; Elsworth, Y.; Schou, J.;
Buzasi, D.
2006ESASP.624E..27F Altcode: 2006soho...18E..27F
No abstract at ADS
---------------------------------------------------------
Title: The internal structure of the Sun inferred from g modes and
low-frequency p modes
Authors: Elsworth, Y. P.; Baudin, F.; Chaplin, W; Andersen, B;
Appourchaux, T.; Boumier, P.; Broomhall, A. -M.; Corbard, T.;
Finsterle, W.; Fröhlich, C.; Gabriel, A.; García, R. A.; Gough,
D. O.; Grec, G.; Jiménez, A.; Kosovichev, A.; Provost, J.; Sekii,
T.; Toutain, T.; Turck-Chièze, S.
2006ESASP.624E..22E Altcode: 2006soho...18E..22E
The Phoebus group is an international collaboration of
helioseismologists, its aim being to detect low-frequency solar g
modes. Here, we report on recent work, including the development and
application of new techniques based on the detection of coincidences
in contemporaneous datasets and the asymptotic properties of the g-mode
frequencies. The length of the time series available to the community is
now more than ten years, and this has reduced significantly the upper
detection limits on the g-mode amplitudes. Furthermore, low-degree p
modes can now be detected clearly at frequencies below 1000 μHz.
---------------------------------------------------------
Title: Peak asymmetry of solar p modes: a framework to explain the
effects of the correlated noise from the acoustic source
Authors: Toutain, T.; Elsworth, Y.; Chaplin, W. J.
2006MNRAS.371.1731T Altcode: 2006MNRAS.tmp..904T
It is well known that in the power spectrum solar p modes have
asymmetric profiles, which depart from a Lorentzian shape. We present
a framework to explain the contribution of correlated background noise,
from the acoustic source, to this asymmetry. An important prediction is
that observed peak asymmetry may differ depending on the way the p-mode
observations are made, and on how the data are prepared. Furthermore,
if valid, the proposed framework may provide the basis for separating
the contribution of the correlated noise from that of the source
location and properties.
---------------------------------------------------------
Title: On the prospects for sounding activity cycles on Sun-like stars
Authors: Chaplin, W. J.; Elsworth, Y.; Houdek, G.; New, R.
2006ESASP.624E.112C Altcode: 2006soho...18E.112C
No abstract at ADS
---------------------------------------------------------
Title: Rotation inversions of artificial solarFLAG Sun-as-a-star data
Authors: Chaplin, W. J.; Sekii, T.; Appourchaux, T.; Baudin, F.;
Boumier, P.; Corbard, T.; Elsworth, Y.; Fletcher, S. T.; Garcia,
R. A.; Jiménez-Reyes, S. J.; Lazrek, M.; New, R.; Salabert, D.;
Toutain, T.; Wachter, R.
2006ESASP.624E..82C Altcode: 2006soho...18E..82C
No abstract at ADS
---------------------------------------------------------
Title: Reliable analysis of power and phase features as seen from
BiSON and GOLF observations
Authors: Simoniello, R.; Elsworth, Y. P.; Chaplin, W. J.; García, R.
2006ESASP.624E.101S Altcode: 2006soho...18E.101S
No abstract at ADS
---------------------------------------------------------
Title: Evidence for degree dependence of changes in p-mode damping
along the solar cycle in Sun-as-a-star data
Authors: Salabert, D.; Chaplin, W. J.; Elsworth, Y.; New, R.; Verner,
G. A.
2006ESASP.624E.113S Altcode: 2006soho...18E.113S
No abstract at ADS
---------------------------------------------------------
Title: Needles in haystacks: how to use contemporaneous data in the
search for g-modes
Authors: Broomhall, A. M.; Chaplin, W. J.; Elsworth, Y.
2006ESASP.624E..96B Altcode: 2006soho...18E..96B
No abstract at ADS
---------------------------------------------------------
Title: Frequency, splitting, linewidth and amplitude estimates
of low-ℓ p modes of α Cen A: analysis of Wide-Field Infrared
Explorer photometry
Authors: Fletcher, S. T.; Chaplin, W. J.; Elsworth, Y.; Schou, J.;
Buzasi, D.
2006MNRAS.371..935F Altcode: 2006astro.ph..7172F; 2006MNRAS.tmp..824F
We present results of fitting the 50-d time series of photometry of α
Cen A taken by the Wide-Field Infrared Explorer (WIRE) satellite in
1999. Both power spectrum and autocovariance function (ACF) fitting
techniques were used in an attempt to determine mode frequencies,
rotational splittings, lifetimes and amplitudes of low-l p modes. In
all, using both techniques, we managed to fit 18 modes (seven l = 0,
eight l = 1 and three l = 2) with frequencies determined to within
1-2 μHz. These estimates are shown to be 0.6 +/- 0.3 μHz lower, on
average, than the frequencies determined from two other more recent
studies, which used data gathered about 19 months after the WIRE
observations. This could be indicative of an activity cycle, although
due to the large uncertainty, more data would be needed to confirm
this. <P />Over a range of 1700-2650 μHz, we were also able to use
the ACF fitting to determine an average lifetime of 3.9 +/- 1.4 d,
and an average rotational splitting of 0.54 +/- 0.22 μHz, which is
the first ever reliable estimate of this parameter. In contrast to
the ACF, the power spectrum fitting was shown to return significantly
biased results for these parameters.
---------------------------------------------------------
Title: Recent Progresses on g-Mode Search
Authors: Appourchaux, T.; Andersen, B.; Baudin, F.; Boumier, P.;
Broomhall, A. -M.; Chaplin, W.; Corbard, T.; Elsworth, Y.; Finsterle,
W.; Fröhlich, C.; Gabriel, A.; Garcia, R.; Gough, D. O.; Grec, G.;
Jiménez, A.; Kosovichev, A.; Provost, J.; Sekii, T.; Toutain, T.;
Turck-Chièze, S.
2006ESASP.617E...2A Altcode: 2006soho...17E...2A
No abstract at ADS
---------------------------------------------------------
Title: Anomalous variations in low-degree helioseismic mode
frequencies
Authors: Howe, R.; Chaplin, W. J.; Elsworth, Y.; Hill, F.; Komm,
R. W.; Isaak, G. R.; New, R.
2006MNRAS.369..933H Altcode: 2006MNRAS.tmp..504H
We compare changes in the frequencies of solar acoustic modes with
degree between 0 and 2, as derived from Global Oscillation Network Group
(GONG), Birmingham Solar Oscillations Network (BiSON) and Michelson
Doppler Imager (MDI) spectra obtained between 1995 and 2003. We find
that, after the solar-activity dependence has been removed from the
frequencies, there remain variations that appear to be significant,
and are often well correlated between the different data sets. We
consider possible explanations for these fluctuations, and conclude
that they are likely to be related to the stochastic excitation of the
modes. The existence of such fluctuations has possible relevance to
the analysis of other low-degree acoustic mode spectra such as those
from solar-type stars.
---------------------------------------------------------
Title: Solar FLAG hare and hounds: on the extraction of rotational
p-mode splittings from seismic, Sun-as-a-star data
Authors: Chaplin, W. J.; Appourchaux, T.; Baudin, F.; Boumier, P.;
Elsworth, Y.; Fletcher, S. T.; Fossat, E.; García, R. A.; Isaak,
G. R.; Jiménez, A.; Jiménez-Reyes, S. J.; Lazrek, M.; Leibacher,
J. W.; Lochard, J.; New, R.; Pallé, P.; Régulo, C.; Salabert, D.;
Seghouani, N.; Toutain, T.; Wachter, R.
2006MNRAS.369..985C Altcode: 2006MNRAS.tmp..515C; 2006astro.ph..6748C
We report on results from the first solar Fitting at Low-Angular
degree Group (solar FLAG) hare-and-hounds exercise. The group
is concerned with the development of methods for extracting the
parameters of low-l solar p-mode data (`peak bagging'), collected by
Sun-as-a-star observations. Accurate and precise estimation of the
fundamental parameters of the p modes is a vital pre-requisite of all
subsequent studies. Nine members of the FLAG (the `hounds') fitted
an artificial 3456-d data set. The data set was made by the `hare'
(WJC) to simulate full-disc Doppler velocity observations of the
Sun. The rotational frequency splittings of the l = 1, 2 and 3 modes
were the first parameter estimates chosen for scrutiny. Significant
differences were uncovered at l = 2 and 3 between the fitted splittings
of the hounds. Evidence is presented that suggests this unwanted bias
had its origins in several effects. The most important came from the
different way in which the hounds modelled the visibility ratio of
the different rotationally split components. Our results suggest that
accurate modelling of the ratios is vital to avoid the introduction of
significant bias in the estimated splittings. This is of importance
not only for studies of the Sun, but also of the solar analogues
that will be targets for asteroseismic campaigns. <P />Solar FLAG
URL: http://bison.ph.bham.ac.uk/~wjc/Research/FLAG.html <P />E-mail:
wjc@bison.ph.bham.ac.uk ‡ <P />George Isaak passed away in 2005 June
5, prior to the completion of this work. He is greatly missed by us all.
---------------------------------------------------------
Title: BiSON Data Show Change in Solar Structure with Magnetic
Activity
Authors: Verner, G. A.; Chaplin, W. J.; Elsworth, Y.
2006ApJ...640L..95V Altcode:
We find evidence for an activity-dependent change in solar structure
at the second helium ionization zone (~0.98 R<SUB>solar</SUB>). We use
low-degree p-mode frequencies obtained from 13 years of observations
by the Birmingham Solar Oscillations Network (BiSON) to track changes
in the amplitude of the rapid-variation signature imposed by the bump
in the adiabatic exponent, Γ<SUB>1</SUB>, at the He II ionization
zone. This is the first indication of structural change detected using
only low-degree data and confirms the recent results of high-degree
and local helioseismic studies.
---------------------------------------------------------
Title: The Detectability of Signatures of Rapid Variation in
Low-Degree Stellar p-Mode Oscillation Frequencies
Authors: Verner, G. A.; Chaplin, W. J.; Elsworth, Y.
2006ApJ...638..440V Altcode:
Regions of rapid variation in stellar interiors introduce
characteristic periodic signatures into the frequencies of their p-mode
oscillations. These signatures have previously been isolated in solar
data and have been used to estimate the level of convective overshoot
and the envelope helium abundance in the Sun. Precise asteroseismic
data are now becoming available for a number of distant Sun-like stars,
and the techniques developed for low-degree solar data can be used in
the stellar case. In this paper, we address the observational duration
required to isolate and examine these rapid-variation signatures through
the use of low-degree solar data as a Sun-like stellar analog. We also
outline the difficulties involved and bias introduced when using a
limited number of poorly constrained mode frequencies. The signature
resulting from the region of the second ionization of helium is found
to be detectable in spectra of shorter duration than those required to
isolate the smaller amplitude signature arising from the base of the
convective envelope. Observations of just 84 days may be sufficient to
extract reliable information on the acoustic depth and extent of the He
II ionization zone, although longer observations are required to obtain
sufficient precision to estimate the envelope helium abundance. The
acoustic radius of the base of the convective envelope and the amplitude
of the signature are reliably isolated in spectra of at least 182 days.
---------------------------------------------------------
Title: Impact of the Solar Activity Cycle on Frequency Separation
Ratios in Helioseismology
Authors: Chaplin, W. J.; Elsworth, Y.; Miller, B. A.; New, R.; Verner,
G. A.
2005ApJ...635L.105C Altcode:
Roxburgh & Vorontsov have recently proposed the use of ratios of
small to large frequency separations of low angular degree p-modes as
a means of eliminating from asteroseismic data the unwanted influence
of the structure of the near-surface layers of stars. Here we have
studied the impact of the solar activity cycle on the magnitude of
these so-called frequency separation ratios using data collected by
Sun-as-a-star observations. The ratios are observed to change with the
shifting level of global solar activity. The effect, which we detect
in BiSON Doppler velocity data at a marginal level of significance,
is shown to be a consequence of the influence of acoustic asphericity
from the surface activity on the azimuthally dependent Sun-as-a-star
frequencies. The results suggest that any analysis that makes use of
ratios formed from long helioseismic data sets may therefore show
effects of bias. While the effect is less significant in shorter
data sets, of length similar to what will soon be available from
asteroseismic campaigns, an approximate doubling of the effects from
the solar asphericity may be sufficient to cause complications for
stellar analyses.
---------------------------------------------------------
Title: Chaplin, Ballai: Helioseismology: The sound of the Sun
Authors: Chaplin, W. J.; Ballai, I.
2005A&G....46d..27C Altcode:
Observations of resonant phenomena on the Sun are now being made that
have their origins not only in the interior, but also in structures in
the tenuous solar atmosphere. The challenge for solar researchers is to
reconcile the flood of observations and theory from these varied scales
and locations to further improve our understanding of the Sun. Here,
we look at some of the exciting challenges facing researchers delving
into the seismology of the Sun.
---------------------------------------------------------
Title: Seismology of the Sun: from the inner core to the corona
Authors: Ballai, I.; Chaplin, W.
2005Obs...125..224B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On model predictions of the power spectral density of radial
solar p modes
Authors: Chaplin, W. J.; Houdek, G.; Elsworth, Y.; Gough, D. O.;
Isaak, G. R.; New, R.
2005MNRAS.360..859C Altcode: 2005MNRAS.tmp..510C
We investigate the frequency dependence of the power spectral density
of low-degree solar p modes by comparing measurements with the results
of a stochastic-excitation model. In the past it was common practice
to use the total power in such investigations. Using the maximum of
the power spectral density instead provides a direct comparison with
the measured mode heights in the observed power spectrum. This method
permits a more careful calibration of the adjustable parameters in the
excitation model, a model which we present here, for the first time,
in a format that precisely and unambiguously relates the amplitudes
of the modes of oscillation to the Reynolds stress in the equilibrium
model. We find that errors in the theory of the linear mode damping
rates, particularly at low frequency, have a dramatic impact on
the predictions of the mode heights in the spectral density, whereas
parameter changes in the stochastic excitation model, within a plausible
domain of parameter space, have a comparatively small effect.
---------------------------------------------------------
Title: Towards the future - Birmingham UKSP 2005
Authors: Chaplin, W. J.; Erdélyi, R.
2005A&G....46c..15C Altcode:
This year's annual UK Solar Physics Meeting was held in parallel with
the National Astronomy Meeting in Birmingham, from 4-8 April 2005. Bill
Chaplin and Robert Erdélyi report on proceedings.
---------------------------------------------------------
Title: Noise characteristics of full-disc helioseismic observations
made by resonant scattering spectrometers
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Miller, B. A.;
New, R.; Pintér, B.
2005MNRAS.359..607C Altcode: 2005MNRAS.tmp..294C
Resonant scattering spectrometers (RSSs) have been used to make
high-precision full-disc helioseismic observations since the 1970s. They
are capable of very high-precision determinations of line-shift, meaning
that they are used to obtain precise velocity measurements, and, for
suitably configured RSSs, the disc-averaged longitudinal magnetic field
(SMMF). In order to exploit fully the very extensive high-precision
data sets, it is essential to understand the noise characteristics of
the instruments. This paper re-examines the consequences for velocity
and SMMF determinations of there being noise on the scattered light
signals measured by an RSS. It presents a theoretical description,
and analysis of simulations, which match well the noise variations
found recently in both BiSON velocity and SMMF observations. It also
outlines a method for using the differences between the power spectra
of redundant channels to analyse instrumental noise characteristics.
---------------------------------------------------------
Title: Monte Carlo simulation of solar p-mode profiles revisited:
Bias and uncertainty estimation from one, not many, fits
Authors: Toutain, T.; Elsworth, Y.; Chaplin, W. J.
2005A&A...433..713T Altcode:
It is quite common in helioseismology to use extensive Monte Carlo
simulations to investigate the bias and associated uncertainties in
fitted p-mode parameters. This can, however, be very time-intensive
if the fitting problem is complicated or large datasets (in time or
resolution) are involved. Here, we show that it is often possible to
reduce significantly the task by taking advantage of the statistical
properties of the p-mode profiles.
---------------------------------------------------------
Title: Inferred acoustic rates of solar p modes from several
helioseismic instruments
Authors: Baudin, F.; Samadi, R.; Goupil, M. -J.; Appourchaux, T.;
Barban, C.; Boumier, P.; Chaplin, W. J.; Gouttebroze, P.
2005A&A...433..349B Altcode:
Acoustic rates of excitation of solar p modes can be estimated from
observations in order to place constraints on the modelling of the
excitation process and the layers where it occurs in the star. For
several reasons (including a poor signal to noise ratio and mode
overlap), this estimation is difficult. In this work, we use three
completely independent datasets to obtain robust estimates in the
solar case for ℓ=1 modes. We also show that the height in the solar
atmosphere where the modes are observed must be taken into account. Our
three sets of results are shown to be consistent, particularly in
the lower part of the p-mode spectrum (from 1.8 mHz to 2.8 mHz). At
higher frequencies, the agreement is not as good, because of a larger
dispersion of the measurements and also because of some systematic
differences which might be due to observation height estimation or to
a systematic influence of the noise.
---------------------------------------------------------
Title: The Search for Correlation between BiSON SMMF Data and
CME Events
Authors: Chaplin, William J.; Dumbill, Andrew M.; Elsworth, Yvonne
P.; Isaak, George R.; McLeod, Clive P.; Miller, Brek A.; New, Roger;
Pintér, Balázs
2005HiA....13..141C Altcode:
The Birmingham Solar Oscillation Network (BiSON) has acquired high
precision solar mean magnetic field (SMMF) data on a 40-second
cadence for a decade. We present first attempts to compare such data
from recent years with the occurence of CME's as recorded by LASCO
using correlation techniques applied to measurements from different
BiSON instruments to maximise the sensitivity to CME related SMMF
responses. SMMF measurements were recorded at the time of occurence
of several hundreds CME's.
---------------------------------------------------------
Title: On the detectability of a rotation-rate gradient in the
solar core
Authors: Chaplin, W. J.; Sekii, T.; Elsworth, Y.; Gough, D. O.
2004MNRAS.355..535C Altcode: 2004MNRAS.tmp..451C
We consider the problem of uncovering a possible gradient of rotation
in the solar core using seismic frequency splittings of low-degree
p-modes. The data are presumed to come from full-disc observations of
the Sun. In particular, we formulate an approach for determining the
diagnostic potential of a low-l splitting set to uncover, by inversion,
a difference in rotation between two target radii: one deep in the core,
the other in the mid-regions of the radiative zone. Our formulation
assumes the underlying rotation rate to be flat in the outer part
of the zone, but to vary linearly in the core (with the breakpoint
in behaviour located between the two target radii). Artificial data
are used to test the formulation, and to investigate the relative
importance at low l of deeply penetrating, high-order modes and
relatively shallow, low-order modes. Our results suggest that in
order to detect a significant difference between the rotation at r=
0.1R and 0.35R- with the input splitting data coming from a 10-yr
set of high-quality observations - that difference would need to be
a significant fraction of the rotation rate itself.
---------------------------------------------------------
Title: Phase Variation as a New Tool in the Investigation of the
Excitation and Damping of Solar p-modes
Authors: Simoniello, R.; Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.;
New, R.
2004ApJ...616..594S Altcode:
We report on a novel way of using the phase evolution in solar
oscillation data as a tool in the study of p-mode excitation and
damping. A mathematical formalism is presented, backed by extensive
simulations, that enables the determination of the line width of
modes close to the peak of the solar oscillation spectrum. The method
potentially avoids the usual problem of strong correlation between the
width and the height of the modes. We also identify further possible
uses of the technique.
---------------------------------------------------------
Title: Flag Hare-And Exercise: on the Extraction of Sectoral Mode
Splittings from Full-Disc Sun-As Data
Authors: Chaplin, W. J.; Appourchaux, T.; Baudin, F.; Boumier, P.;
Elsworth, Y.; Fletcher, S. T.; Fossat, E.; García, R. A.; Isaak,
G. R.; Jiménez, A.; Jiménez-Reyes, S. J.; Lazrek, M.; Lochard, J.;
New, R.; Pallé, P.; Régulo, C.; Salabert, D.; Toutain, T.
2004ESASP.559..356C Altcode: 2004soho...14..356C
No abstract at ADS
---------------------------------------------------------
Title: Impact of Observational Duty Cycle on P-Mode Eigenfrequencies
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Miller, B. A.;
New, R.; Salabert, D.
2004ESASP.559..364C Altcode: 2004soho...14..364C
No abstract at ADS
---------------------------------------------------------
Title: Twenty-Eight Years of BISON Data
Authors: Miller, B. A.; Hale, S. J.; Elsworth, Y.; Chaplin, W. J.;
Isaak, G. R.; New, R.
2004ESASP.559..571M Altcode: 2004soho...14..571M
No abstract at ADS
---------------------------------------------------------
Title: The Phase of Global Solar Oscillations
Authors: Simoniello, R.; Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.;
Miller, B. A.; New, R.
2004ESASP.559..251S Altcode: 2004soho...14..251S
No abstract at ADS
---------------------------------------------------------
Title: Exploring P-Modes Big Excitations Using 10 Years of BISON Data
Authors: Simoniello, R.; Chaplin, W. J.; Elsworth, Y. P.
2004ESASP.559..631S Altcode: 2004soho...14..631S
No abstract at ADS
---------------------------------------------------------
Title: Novel Techniques for the Identification of Noise Contributions
to Full-Disc Helioseismic Power Spectra
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Miller, B. A.;
New, R.; Pintér, B.
2004ESASP.559..360C Altcode: 2004soho...14..360C
No abstract at ADS
---------------------------------------------------------
Title: Low-Degree Helioseismology: the State of Play on its Silver
Anniversary. Analysis and Measurement of LOW-l Solar P-Mode Parameters
in the
Authors: Chaplin, W. J.
2004ESASP.559...34C Altcode: 2004soho...14...34C
No abstract at ADS
---------------------------------------------------------
Title: Time-Domain
Authors: Fletcher, S. T.; Chaplin, W. J.; Elsworth, Y.
2004ESASP.559...44F Altcode: 2004soho...14...44F
No abstract at ADS
---------------------------------------------------------
Title: On comparing estimates of low-l solar p-mode frequencies from
Sun-as-a-star and resolved observations
Authors: Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; Isaak, G. R.;
Miller, B. A.; New, R.
2004A&A...424..713C Altcode:
Low-angular-degree (low-l) solar p modes provide a sensitive probe
of the radiative interior and core of the Sun. Estimates of their
centroid frequencies can be used to constrain the spherically symmetric
structure of these deep-lying layers. The required data can be extracted
from two types of observation: one where the modes are detected in
integrated sunlight, i.e., a Sun-as-a-star view; and a second where
the visible disc is imaged onto many pixels, and the collected images
then decomposed into their constituent spherical harmonics. While the
imaging strategy provides access to all of the individual components
of a multiplet, the Sun-as-a-star technique is sensitive to only
about two thirds of these (average over l=0 to 3) with those modes
that are detected having different levels of visibility. Because
the various components can have contrasting spatial structure over
the solar surface, they can respond very differently to changes in
activity along the solar cycle. Since the Sun-as-a-star and resolved
analyses take as input a different “subset” of modes, the extracted
frequency estimates are expected to differ depending upon the phase
of the cycle. Differences also arise from the types of models used to
fit the modes. Here, we present expressions that allow the sizes of
these differences to be predicted.
---------------------------------------------------------
Title: Impact of observational duty cycle on the measurement of
low-ℓ solar p-mode frequencies
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Miller, B. A.;
New, R.; Salabert, D.
2004A&A...424..301C Altcode:
We investigate the impact of a multi-site, ground-based observational
window function on the extraction of estimates of the frequencies
of low-angular-degree (low-ℓ) solar p modes from decade-long
datasets. To effect this study we have made use of some ≈10 yr of
full-disc, “Sun-as-a-star” Doppler velocity data collected by the
Birmingham-Solar Oscillations Network (BiSON). A coherent combination
of observations made by all six BiSON sites provided the principal
time series of data. This set was then modulated by a whole series
of different window functions and the resulting sets analyzed. The
windows were made from different combinations and numbers of BiSON
stations. We find that for the majority of low-ℓ modes the bias in
the frequencies given by the effects of the window function is not
significant. However, for modes above ≈3300 μ Hz, and some ℓ=2
modes near ≈2500 μ Hz, the bias is important when the frequencies
are extracted from long datasets. <P />Appendix A is only available
in electronic form at http://www.edpsciences.org
---------------------------------------------------------
Title: The solar cycle as seen by low-l p-mode frequencies: comparison
with global and decomposed activity proxies
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Miller, B. A.;
New, R.
2004MNRAS.352.1102C Altcode: 2004MNRAS.tmp..158C
We present a detailed study of variations observed in low-angular
degree solar p-mode frequencies during solar cycles 22 and 23,
and their relation to global and spatially decomposed proxies of
the surface activity. To do so, we have analysed 11yr of unresolved
(Sun-as-a-star) Doppler velocity observations of the solar disc made by
the Birmingham Solar-Oscillations Network (BiSON). The sensitivity of
these observations to different azimuthal orders, m, is such that for
the degree range studied (0 <=l<= 2) extracted frequencies can be
regarded as providing a measure of the response of the sectoral modes
(with |m| =l). <P />After allowing for the dependence of the frequency
shifts on mode frequency and inertia, we find the average l= 0 shift is
significantly weaker than that at l= 2; the magnitude of the average l=
1 shift lies in between the two. The comparative sizes of the shifts
are observed to match those of the corresponding spherical harmonic
(Legendre) components of both the Kitt Peak magnetogram (KPMI) and
HeI equivalent width activity indices, and reflect, therefore, the
sensitivity of the observed mode components to the distribution of
activity over the solar surface (i.e. a `spatial' contribution to the
shifts). When the falling and rising parts of the cycles are analysed
independently, we uncover a significant difference in behaviour at l=
1. Possible reasons for this are discussed.
---------------------------------------------------------
Title: On the Spatial Dependence of Low-Degree Solar p-Mode Frequency
Shifts from Full-Disk and Resolved-Sun Observations
Authors: Jiménez-Reyes, S. J.; García, R. A.; Chaplin, W. J.;
Korzennik, S. G.
2004ApJ...610L..65J Altcode:
We have analyzed low angular degree (low-l) solar p-mode frequency
shifts extracted from two types of observations, both made by
instruments on board the ESA/NASA Solar and Heliospheric Observatory
satellite during a period that covers the rising phase of activity,
cycle 23 (1995-2002). The first are full-disk (Sun-as-a-star) averages
made in Doppler velocity by the Global Oscillations at Low Frequency
spectrophotometer; the second are Doppler velocity observations made
with high spatial resolution by the Michelson Doppler Imager. We compare
the eigenfrequency shifts from both sets of data and find that they are
consistent at the level of precision of the observations. Furthermore,
the sizes of the shifts uncovered for different mode components are
found to scale in proportion to the corresponding spherical harmonic
components of the observed line-of-sight surface magnetic field, with
the sectoral mode components showing (as expected) the largest shifts.
---------------------------------------------------------
Title: Search for solar cycle changes in the signature of rapid
variation in BiSON data
Authors: Verner, G. A.; Chaplin, W. J.; Elsworth, Y.
2004MNRAS.351..311V Altcode:
The second helium ionization zone and the base of the convective
envelope are regions of rapid variation of solar structure which
introduce characteristic signatures into the frequencies of p-mode
oscillations. These signals provide a direct seismological method
to probe the acoustic properties of these regions. In this work we
isolate these signatures in over 9 yr of low-degree BiSON data and
extract information on the acoustic depth and local properties from each
signal. Any temporal variations are investigated by fitting the signals
extracted from 432, 864 and 1728-d spectra. The extracted parameters
are found to be in agreement over the different length spectra and
within one formal standard deviation of the values obtained for model
`S'. There is no evidence found for any systematic variation in the
acoustic depth, width or magnitude of the second helium ionization
zone, which suggests any activity-dependent disturbance to the near
surface layers does not propagate down to this layer. The convection
zone signal does show some temporal variation that may be correlated
with solar activity, although further analysis with current data is
required. The isolation of these signatures in low-degree data confirms
that this method can be used to provide structural information on
Sun-like stars once similar asteroseismic data become available.
---------------------------------------------------------
Title: Extended search for correlation between solar mean magnetic
field BiSON data and coronal mass ejections
Authors: Chaplin, William J.; Dumbill, Andrew M.; Elsworth, Yvonne
P.; Isaak, George R.; McLeod, Clive P.; Miller, Brek A.; New, Roger;
Pintér, Balázs
2004SoPh..220..307C Altcode:
The Birmingham Solar-Oscillations Network (BiSON) has acquired
high-precision solar mean magnetic field (SMMF) data on a 40-s
cadence for a decade. We present attempts to compare such data
from recent years with the occurrence of coronal mass ejections
(CMEs) as recorded by LASCO, using correlation techniques applied
to measurements from different BiSON instruments to maximise the
sensitivity to CME-related SMMF responses. SMMF measurements were
recorded at the time of occurrence of several hundred CMEs. No CME
event shows a convincing response in our SMMF data at short periods
setting a threshold amplitude of 12 mG. By averaging data sets we are
able to set lower thresholds, which depend somewhat on the distribution
of response strengths. A brief summary of the very first results of
this study is also given in Chaplin et al.
---------------------------------------------------------
Title: A comparison of the use of genetic and hill-climbing algorithms
to fit low-l solar p-mode spectra
Authors: Fletcher, S. T.; Chaplin, W. J.; Elsworth, Y.
2004SoPh..220..361F Altcode:
We present a comparative study of low-l solar p-mode parameters
extracted by genetic-algorithm and `standard' hill-climbing minimisation
routines. To effect this we make use of observations made in integrated
sunlight by the Birmingham Solar-Oscillations Network (BiSON) and
the GOLF instrument on board the ESA/NASA SOHO satellite, in addition
to artificial data. We find that over the central part of the p-mode
range the two fitting routines return similar results. However, at low
frequencies — where the S/N in the modes is low and their resonant
peaks narrow — we find that the genetic routine appears to offer
more robust estimates of the underlying parameters.
---------------------------------------------------------
Title: About the rotation of the solar radiative interior
Authors: García, R. A.; Corbard, T.; Chaplin, W. J.; Couvidat, S.;
Eff-Darwich, A.; Jiménez-Reyes, S. J.; Korzennik, S. G.; Ballot,
J.; Boumier, P.; Fossat, E.; Henney, C. J.; Howe, R.; Lazrek, M.;
Lochard, J.; Pallé, P. L.; Turck-Chièze, S.
2004SoPh..220..269G Altcode:
In the modern era of helioseismology we have a wealth of high-quality
data available, e.g., more than 6 years of data collected by the various
instruments on board the SOHO mission, and an even more extensive
ground-based set of observations covering a full solar cycle. Thanks
to this effort a detailed picture of the internal rotation of the Sun
has been constructed. In this paper we present some of the actions
that should be done to improve our knowledge of the inner rotation
profile discussed during the workshop organized at Saclay on June 2003
on this topic. In particular we will concentrate on the extraction of
the rotational frequency splittings of low- and medium-degree modes
and their influence on the rotation of deeper layers. Furthermore,
for the first time a full set of individual |m|-component rotational
splittings is computed for modes ℓ≤4 and 1<ν<2 mHz, opening
new studies on the latitudinal dependence of the rotation rate in the
radiative interior. It will also be shown that these splittings have
the footprints of the differential rotation of the convective zone
which can be extremely useful to study the differential rotation of
other stars where only these low-degree modes will be available.
---------------------------------------------------------
Title: Tracing the “Acoustic” Solar Cycle: A Direct Comparison of
BiSON and GOLF Low-l p-Mode Variations
Authors: Jiménez-Reyes, S. J.; Chaplin, W. J.; Elsworth, Y.; García,
R. A.
2004ApJ...604..969J Altcode:
We present a detailed, comparative study of low angular degree
solar p-mode variations extracted by analyses of two sets of
observational data. These were collected by the ground-based Birmingham
Solar-Oscillations Network (BiSON) and the Global Oscillations at Low
Frequency (GOLF) instrument on board the ESA/NASA SOHO satellite. The
~5.5 yr period analyzed covers the complete rising phase of solar
activity cycle 23 (1996-2002). We find an excellent level of agreement
in the uncovered variations, indicating that the two data sets are
highly correlated and dominated by the same mode realization noise (the
signature of the stochastic forcing of the resonances). The results lend
further support to the surmise that changes in damping alone may account
for observed variations in mode power and damping. While significant
variations in peak asymmetry are uncovered in the near-continuous GOLF
set, a similar analysis of the BiSON database yields a null result. This
reflects the deleterious impact of its ground-based window function
on the precision with which the asymmetry can be determined. As such
we are unable to rule out the possibility that variations of magnitude
similar to those in GOLF may be present in the BiSON observations.
---------------------------------------------------------
Title: Solar p-mode frequencies at ℓ=2: What do analyses of
unresolved observations actually measure?
Authors: Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; Isaak, G. R.;
Miller, B. A.; New, R.; Toutain, T.
2004A&A...416..341C Altcode:
We have studied in detail the extraction of estimates of ℓ=2 p-mode
frequencies from unresolved observations of the visible disc of the
Sun. Examples of data of this type include ground-based observations
made by the Birmingham Solar-Oscillations Network (BiSON), and
space-borne observations made by the GOLF and VIRGO/SPM instruments
on board the ESA/NASA SOHO satellite. The fitting of the modes is
complicated in practice by the asymmetric arrangement in frequency
of the three components (m=-2, 0 and 2) that are prominent in such
data. In order to investigate the effect of this we used a series of
10-yr artificial datasets into which varying degrees of asymmetry were
introduced. The sets were designed to mimic the characteristics of the
BiSON and GOLF data, and were analyzed both with and without the BiSON
window function from the period 1992 through 2001. Since reliable
estimates of the asymmetry have only recently been extracted from
unresolved observations (Chaplin et al. \cite{Chaplin03}a) it has for a
long time been standard practice to fit the ℓ=2 modes to a model that
assumes a symmetrically arranged multiplet. We have tested the impact
of this on the accuracy of the extracted frequencies. Furthermore,
we demonstrate that asymmetric models can be successfully applied,
provided the data are of sufficient length and quality. We also discuss
the implications of our simulations for analyses of real solar data.
---------------------------------------------------------
Title: Use of genetic algorithms to determine low-l rotational p-mode
splittings at high frequencies
Authors: Fletcher, S. T.; Chaplin, W. J.; Elsworth, Y.
2003MNRAS.346..825F Altcode:
We present a comparative study of genetic and standard fitting routines
applied to the task of extracting reliable estimates of the rotational
splitting of full-disc, low-angular-degree (low-l) solar p-mode data
at high frequencies. 100 artificial proxies of a 10-yr data base of
observations made by the Birmingham Solar-Oscillations Network (BiSON)
were used to test the two approaches. All sets were analysed over the
frequency range from 3000 to 4000 μHz. <P />Previous work, based
on non-linear `hill-climbing' fitting techniques, has demonstrated
the unfortunate tendency for full-disc estimates of the splitting to
overestimate the true, underlying values at high frequencies. Here,
we show that the resulting bias is less severe when a genetic-fitting
approach is adopted. This is largely the result of the number of
erroneous `null-valued' estimates of the splitting being considerably
reduced: these estimates are, in effect, re-introduced into the expected
normal distribution of fitted splittings. We also illustrate the diverse
control one has when using a genetic algorithm as a fitting routine;
this diversity is shown to allow further refinement in the estimate
of the rotational splitting. <P />Finally, we address the issue of
the reliability of the formal splitting uncertainties returned by
the mode fitting, and find that complications arising from the strong
anticorrelation between the splittings and their error estimates are
not alleviated by the use of the genetic technique.
---------------------------------------------------------
Title: Excitation and Damping of Low-Degree Solar p-Modes during
Activity Cycle 23: Analysis of GOLF and VIRGO Sun Photometer Data
Authors: Jiménez-Reyes, S. J.; García, R. A.; Jiménez, A.; Chaplin,
W. J.
2003ApJ...595..446J Altcode:
We have used observations made by the Global Oscillations at Low
Frequency (GOLF) and the Variability of Irradiance and Gravity
Oscillations Sun Photometer (VIRGO/SPM) instruments on board the
ESA/NASA Solar and Heliospheric Observatory satellite to study
variations in the excitation and damping of low angular degree (low-l)
solar p-modes on the rising phase of activity cycle 23. Our analysis
includes a correction procedure that for the first time allows GOLF data
to be “treated” as a single homogeneous set, thereby compensating
for the change of operational configuration partway through the
mission. Over the range 2.5<=ν<=3.5mHz, we uncover an increase
in damping and decrease in mode power that is consistent with previous
findings. Furthermore, an excellent level of agreement is found between
the variations extracted from the GOLF and VIRGO/SPM data. We find
no net long-term changes to the modal energy supply rate. However,
an analysis of the residuals uncovers the presence of a quasi-periodic
signature of period ~1.5 yr (most pronounced for SPM). While it is true
that several workers claim to have uncovered similar periodicities in
other phenomena related to the near-surface layers of the Sun here, we
are at present more inclined to attribute our finding to an artifact of
the mode-fitting procedure. We also uncover a significant change in the
asymmetry of mode peaks in the GOLF data, as found in previous studies
of much longer data sets. These assumed that the dominant contribution
to this arose from the switch in operating configuration partway
through the mission (which altered the depth in the solar atmosphere
sampled by the instrument). However, our preliminary analysis of data
collected over the 100 day period beginning 2002 November 19-when the
instrument switched back to its original configuration-suggests that
this change may have a solar cycle component.
---------------------------------------------------------
Title: Studies of the solar mean magnetic field with the Birmingham
Solar-Oscillations Network (BiSON)
Authors: Chaplin, W. J.; Dumbill, A. M.; Elsworth, Y.; Isaak, G. R.;
McLeod, C. P.; Miller, B. A.; New, R.; Pintér, B.
2003MNRAS.343..813C Altcode:
The first analysis of 10 yr of solar mean magnetic field data
from the Birmingham Solar-Oscillations Network (BiSON) instrument
at Sutherland, SA is presented. Long-period (>1 d) variations
correlate well with those observed by the Stanford group, but our
daily mean values have a statistical precision over 10 times better
than previous work. Differences between the absolute values determined
from Sutherland and Stanford are discussed, as are systematic annual
variations of the order of 15 per cent. At high frequencies (>0.5
mHz), the mean noise spectral density for our decade of observations
is 0.53 G<SUP>2</SUP> Hz<SUP>-1</SUP>, setting a lower limit to the
noise level than that obtained from brief observations by GOLF on
board the ESA/NASA satellite SOHO in 1996. The high-frequency mean
noise spectral density is different in different years. The lowest
annual value, obtained for 1997, is 0.22 G<SUP>2</SUP> Hz<SUP>-1</SUP>,
whilst the highest, for 1995, is 1.46 G<SUP>2</SUP> Hz<SUP>-1</SUP>. It
is not yet clear whether these variations are related to solar activity.
---------------------------------------------------------
Title: Observation of, and temporal variations in, solar p-mode
multiplet frequency asymmetries at l= 2
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Miller, B. A.;
New, R.; Thiery, S.; Boumier, P.; Gabriel, A. H.
2003MNRAS.343..343C Altcode:
The predominant contribution to the frequency splitting of low-l solar
p modes arises from the rotation of the solar interior and this lifts
the frequency degeneracy in l to give a symmetric pattern where the
observed (synodic) separation between adjacent m (i.e. for |Δm|= 1)
is ~400 nHz. Magnetic fields can also contribute to the splitting, but
they do so in such a way as to introduce asymmetries in the arrangement
of the components within each multiplet. In disc-integrated data this
effect may become apparent when l>= 2. Here, we attempt to extract
estimates of the frequency asymmetries at l= 2 from the analysis
of disc-integrated data collected by the ground-based Birmingham
Solar Oscillations Network (BiSON) and the GOLF instrument on board
the ESA/NASA SOHO satellite. Our analyses demonstrate that we have
evidence for there being non-zero asymmetries present (significance
~3-4σ) during an epoch coincident with high levels of surface
activity close to the maximum of solar cycle 23. The asymmetries are
indistinguishable from zero at minimum levels of activity near the cycle
22/23 boundary. <P />We also compare the observed asymmetries with those
calculated from a model that is based upon the recent predictions of
Moreno-Insertis & Solanki. While the level of agreement between
the two is found to be reasonable, the observations suggest (though
with poor constraints placed upon this) that the influence on the
mode frequencies of high-latitude activity may not be as strong as in
the model.
---------------------------------------------------------
Title: A Comparison of Low-Degree Solar p-Mode Parameters from BiSON
and GONG: Underlying Values and Temporal Variations
Authors: Howe, R.; Chaplin, W. J.; Elsworth, Y. P.; Hill, F.; Komm,
R.; Isaak, G. R.; New, R.
2003ApJ...588.1204H Altcode:
Approximately 5 years of the l=0 time series from the GONG project
have been analyzed using the algorithm developed for the BiSON
zero-dimensional data. The data cover the period 1995-2000. The results
are compared with those from a parallel analysis of contemporaneous
BiSON data and also with the results of the traditional GONG analysis
of the low-degree time series. The spectra analyzed were prepared
using the multitaper spectral analysis technique used in the recent
reanalysis of the GONG data. We consider both solar cycle trends
and temporally averaged values for mode frequencies, line widths,
amplitudes, and asymmetry parameters.
---------------------------------------------------------
Title: Using the BiSON signal to probe the photosphere
Authors: McCarty, B.; Chaplin, W. J.; Elsworth, Y.
2003ESASP.517..349M Altcode: 2003soho...12..349M
Red and blue-wing velocity residuals have been generated from each side
of the 770-nm potassium line profile as observed by BiSON. Analysis of
these single-sided residuals allows an estimate of the velocity scale
height, H, to be made. An initial investigation using data from one
BiSON station gives a value of H ~ 530±45 km.
---------------------------------------------------------
Title: Degree dependence of mode parameters with solar activity in
BiSON data
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; New, R.
2003ESASP.517..119C Altcode: 2003soho...12..119C
The line-width, velocity power and rate of supply of energy to the
low-degree p modes of the Sun are investigated over falling phase of
cycle 22 and the rising phase of cycle 23 by fitting in the Fourier
transform domain. We see that for the first time for low-degree modes
we are able to parameterise the solar activity dependence as a function
of the angular degree of the mode.
---------------------------------------------------------
Title: Probing the solar core with BiSON: the challenge at low l
and low frequency
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Miller, B. A.;
New, R.; Pintér, B.
2003ESASP.517..183C Altcode: 2003soho...12..183C
In this contribution we touch upon a few issues of relevance to the
current status of low-angular-degree (low-l) p-mode Helioseismology. In
particular: the precision in frequency, both historic and current,
achievable at low l; the quest to extend the low-frequency detection
threshold nearer to the p-mode fundamental; and the level of agreement
between frequencies extracted from different data using various
analysis techniques.
---------------------------------------------------------
Title: Amplitude modulation of low degree p-modes - comparison of
BISON and VIRGO
Authors: Andersen, Bo; Leifsen, Torben; Chaplin, William J.; Elsworth,
Yvonne
2003ESASP.517..151A Altcode: 2003soho...12..151A
Using both VIRGO and MDI data we have previously studied the amplitude
variation of the l=0 p-modes for radial orders 12 to 32. In this study
we extend the investigation backward in time to 1992 by including
data from the BISON network. For the large amplitude modes there is a
strong correlation between the space based radiance measurements from
VIRGO and the ground based Doppler shift measurements from BISON. The
extreme rotational modulation of l=0, n=22 is confirmed to be a
phenomenon confined to the period of minimum solar activity. Also with
neighbouring l=1, n=21 a clear modulation is seen at slightly lower
frequency. Some persistent frequencies occur in other l=0,1 modes,
but not to the same level in time and amplitude.
---------------------------------------------------------
Title: Comparing results from the GONG l = 0 and BiSON time series
Authors: Howe, R.; Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Komm,
R. W.; New, R.
2003ESASP.517..303H Altcode: 2003soho...12..303H
Approximately 5 years of the l = 0 time series from the GONG project
have been analysed using the algorithm developed for the BiSON
0-dimensional data. The data cover the period 1995-2000. The results
are compared with those from a parallel analysis of contemporaneous
BiSON data, and also with the results of the traditional GONG analysis
of the low-degree time series. The spectra analysed were prepared
using the multitaper spectral analysis technique used in the recent
re-analysis of the GONG data. We consider both solar-cycle trends
and temporally averaged values for mode frequencies, linewidths,
amplitudes and asymmetry parameters.
---------------------------------------------------------
Title: High-frequency interference peaks in BiSON data
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Marchenkov,
K. I.; Miller, B. A.; New, R.
2003ESASP.517..247C Altcode: 2003soho...12..247C
We have analyzed 9 yr of non-imaged Doppler velocity observations of
the visible disc of the Sun in an effort to search for pseudo-mode-like
structure in the data above the acoustic cut-off frequency of the solar
atmosphere (≍5400 μHz). These data were collected by the ground-based
Birmingham Solar-Oscillations Network (BiSON) over the period 1992
January through 2000 December. Our analysis uncovers the presence of a
pseudo-mode-like structure above the acoustic cut-off frequency that
persists up to ≍8500 μHz, with a spacing between adjacent peaks
(or troughs) of ~68 μHz. The signature - which disappears at higher
frequencies - has a slightly different repeat period (i.e., frequency
separation between successive peaks or troughs) to that found by Garcia
et al. (1998) in full-disc GOLF data.
---------------------------------------------------------
Title: The Search for Correlation Between BISON Smmf Data and Cme's
Authors: Chaplin, William J.; Dumbill, Andy M.; Elsworth, Yvonne;
Isaak, George R.; McLeod, Clive P.; Miller, Brek A.; New, Roger;
Pinter, Balazs
2003IAUJD...3E..30C Altcode:
The Birmingham Solar Oscillation Network (BiSON) has acquired high
precision solar mean magnetic field (SMMF) data on a 40-second
cadence for a decade. We present first attempts to compare such data
from recent years with the occurence of CME's as recorded by LASCO
using correlation techniques applied to measurements from different
BiSON instruments to maximise the sensitivity to CME related SMMF
responses. SMMF measurements were recorded at the time of occurence
of several hundreds CME's.
---------------------------------------------------------
Title: Time Variation of the Low Degree P-Mode Parameters
Authors: Jimenez-Reyes, Sebastian J.; Garcia, Rafael A.; Jimenez,
Antonio; Chaplin, W. J.
2003IAUJD..12E..20J Altcode:
High quality data collected from GOLF VIRGO and MDI from the SoHO
satellite and from the BiSON ground based network have been used to
analyze the low degree (<= 3) p-mode parameters during the increasing
phase of solar cycle 23. The variations of amplitudes frequencies
linewidth asymmetries velocity power and energy supply rate will be
showed and discussed. Special attention will be given to two of these
parameters: the asymmetries and the energy supply rate. <P />The average
of velocity line profile asymmetries of p-modes between 2.5 and 3.5
mHz appears very well correlated with the solar activity cycle while
no clear correlation in average appears in intensity measurements. An
individual analysis of the different degrees will be also shown and
possible consequences on the location of the excitation source will
be discussed. <P />It is well known that the energy supply rate is
roughly constant in average during the solar cycle. Our results agree
with this conclusion but a clear 1.5 years modulation appears and with
slightly larger amplitude for the intensity observation.
---------------------------------------------------------
Title: On the measurement bias of low-l solar p-mode excitation
parameters: The impact of a ground-based window function
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Miller, B. A.;
New, R.; Pintér, B.; Thiery, S.
2003A&A...398..305C Altcode:
We present a study of the impact of a ground-based, multi-station window
function on estimates of the power and damping of low-l solar p modes
extracted from fits to resonant structure in the frequency domain. The
window functions come from six-site observations made by the Birmingham
Solar-Oscillations Network (BiSON) over the 10-yr period beginning 1991
January. Two strategies were adopted. In the first, we used an 800-d
time series of continuous observations made by the GOLF instrument
on board the ESA/NASA SOHO satellite. These data were modulated by a
variety of BiSON window functions, with fractional duty cycles ranging
from ~ 0.4 to ~ 0.8, and the resulting series analyzed. In the second
we generated artificial 10-yr time series and studied the effect on
these of the complete BiSON window.
---------------------------------------------------------
Title: Does the Energy Supplied to Low-l Solar p-Modes Vary over
the Activity Cycle?
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Miller, B. A.;
New, R.; Toutain, T.
2003ApJ...582L.115C Altcode:
We report on the average behavior of the excitation and damping of
low angular degree (low l) solar p-mode oscillations over the decade
from 1991 to 2000 using both long and short time duration Fourier
transforms. The data in question were collected by the ground-based
Birmingham Solar Oscillations Network. Throughout most of the
period under study, the energy supply rate to the modes remains
roughly constant-implying a near-constant level of forcing-while the
damping and velocity power show a fairly smooth increase and decrease,
respectively, in response to increasing levels of solar activity (in
line with previous findings). However, here we uncover evidence of
there being a sharp increase in the mode velocity power over a brief
period of approximately 100 days centered on 1998 late March. The
magnitude and sign of this are contrary to the expectation based on
the long-timescale, solar-cycle trend; such unusual behavior is absent
in the damping. This implies that the forcing of, or rate of energy
supplied to, the modes increased in magnitude over this period.
---------------------------------------------------------
Title: Peak finding at low signal-to-noise ratio: low-ℓ solar
acoustic eigenmodes at n≤9 from the analysis of BiSON data
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Marchenkov,
K. I.; Miller, B. A.; New, R.; Pinter, B.; Appourchaux, T.
2002MNRAS.336..979C Altcode:
We make use of 9 yr of full-disc helioseismic data - as collected by
the ground-based Birmingham Solar-Oscillations Network (BiSON) - to
search for low-frequency, low-angular-degree (low-l) acoustic modes. A
range of tests are applied to the power spectrum of the observations
that search for prominent mode-like structure: strong spikes, structure
spanning several bins signifying the presence of width (from damping),
and the occurrence of prominent multiplet structure at l>= 1 arising
principally from the solar rotation and made from several spikes
separated suitably in frequency. For each test we present analytical
expressions that allow the probability that the uncovered structure is
part of the broad-band noise background to be assessed. These make use
of the cumulative binomial (Bernoulli) distribution and serve to provide
an objective measure of the significance of the detections. This work
has to date uncovered nine significant detections of non-broad-band
origin that we have identified as low-l modes with radial overtone
numbers n<= 9.
---------------------------------------------------------
Title: Observation of, and variations in, multiplet frequency
asymmetries at low l
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Marchenkov,
K. I.; Miller, B. A.; New, R.; Pinter, B.; Thiery, S.
2002ESASP.508...71C Altcode: 2002soho...11...71C
The predominant contribution to the frequency splitting of low-l solar
p modes arises from the rotation of the solar interior and this lifts
the frequency degeneracy in l to give a symmetric pattern where the
observed (synodic) separation between adjacent m (i.e., for |Δm| = 1)
is ~400nHz. Magnetic fields can also contribute to the splitting, but
they do so in such a way as to introduce asymmetries in the arrangement
of the components within each multiplet. In full-disc data this effect
may become apparent when l >= 2. Here, we extract estimates of the
frequency asymmetry for l = 2, investigate variations over the activity
cycle and compare the results with the near-surface predictions of
Dziembowski et al. (2000) which are based upon observations from
higher l.
---------------------------------------------------------
Title: Does the energy supply rate to the p modes vary over the
solar cycle?
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; New, R.
2002ESASP.508...33C Altcode: 2002soho...11...33C
The rate of supply of energy to the low-degree p modes of the Sun
is investigated using both long and short time-duration Fourier
transforms. We see that, although on average the energy supply rate to
the modes is independent of solar activity, there is a period of high
solar activity where the energy-supply rate is increased. Furthermore
we see that the correlations between the mode line width and the power
in the modes are different on the falling phase of cycle 22 and the
rising phase of cycle 23 with a strong correlation between the energy
supply rate and the mode power on the rising phase of cycle 23.
---------------------------------------------------------
Title: On the measurement precision of solar p-mode eigenfrequencies
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Miller, B. A.;
New, R.
2002MNRAS.330..731C Altcode:
We make use of 3456d of observations of the low-l p-mode oscillations
of the Sun in order to study the evolution over time of the measurement
precision of the radial eigenfrequencies. These data were collected by
the ground-based Birmingham Solar-Oscillations Network (BiSON) between
1991 January and 2000 June. When the power spectrum of the complete
time series is fitted, the analysis yields frequency uncertainties
that are close to those expected from the returned coherence times of
the modes. The slightly elevated levels compared with the prediction
appear to be consistent with a degradation of the signal-to-noise
ratio in the spectrum that is the result of the influence of the
window function of the observations (duty cycle 71 per cent). The
fractional frequency precision reaches levels of a several parts in
10<SUP>6</SUP> for many of the modes. The corresponding errors reported
from observations made by the GOLF instrument on board the ESA/NASA
SOHO satellite, when extrapolated to the length of the BiSON data set,
are shown to be (on average) about ~25 per cent smaller than their BiSON
counterparts owing to the uninterrupted nature of the data from which
they were derived. <P />An analysis of the BiSON data in contiguous
segments of different lengths, T, demonstrates that the frequency
uncertainties scale as T<SUP>-1/2</SUP>. This is to be expected in the
regime where the coherence (life) times of the modes, τ<SUB>nl</SUB>,
are smaller than the observing time T (the `oversampled' regime). We
show that mode detections are only now beginning to encroach on the
`undersampled' regime (where T<τ<SUB>nl</SUB>).
---------------------------------------------------------
Title: Variation of acoustic mode centroid frequencies over the
solar cycle
Authors: Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; Isaak, G. R.;
New, R.
2002AdSpR..29.1881C Altcode:
Together with a brief historical overview, we use high-quality
helioseismic data collected by three different observational
programmes during the declining phase of activity cycle 22, and a
substantial portion of the rising phase of the current cycle (23),
to study the phenomenological nature of the cycle-induced (centroid)
eigenfrequencies. Our analyses (for 1600 ≤ ν ≤ 4000 μHz) make
use of observations made by the ground-based GONG over the angular
degree range 4 ≤ l ≤ 150; the ground-based BiSON over 0 ≤ l ≤
2; and the VIRGO/LOI instrument on board the ESA/NASA SOHO satellite
over 0 ≤ l ≤ 8. We show that GONG shifts averaged over different
ranges in l, together with the BiSON and LOI data averaged over
their full quoted ranges, all scale at a given frequency with the
normalized mode inertia ratio Q<SUB>nl</SUB> (Christensen-Dalsgaard
& Berthomieu 1991). This is to be expected if the time-dependent
perturbation affecting the modes is confined in the surface layers;
the excellent agreement also reflects favourably on the external
consistency of the different observations. We have also analyzed
the frequency dependence of the shifts by fitting a power-law of the
form δν <SUB>nl</SUB> ∝ (ν <SUB>nl</SUB>/ E<SUB>nl</SUB> to the
data (where the E<SUB>nl</SUB> are the mode inertias, and α is the
power-law index to be extracted). Previous studies have suggested that
a relation with α = 0 provides an adequate description of the shifts
up to ν ≈ 3500 μHz. However, here we show that while nevertheless
describing the shifts well up to ∼ 2500 μHz, the linear scaling
breaks down conspicuously at higher frequencies. Above this threshold,
the shifts follow a power-law dependence with α ∼ 2.
---------------------------------------------------------
Title: Rigid rotation of the solar core? On the reliable extraction
of low-l rotational p-mode splittings from full-disc observations
of the Sun
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Marchenkov,
K. I.; Miller, B. A.; New, R.
2001MNRAS.327.1127C Altcode:
We present low-l rotational p-mode splittings from the analysis
of 8yr of observations made by the Birmingham Solar-Oscillations
Network (BiSON) of the full solar disc. These data are presented
in the light of a thorough investigation of the fitting techniques
used to extract them. Particular attention is paid to both the origin
and magnitude of bias present in these estimates. An extensive Monte
Carlo strategy has been adopted to facilitate this study - in all,
several thousand complete, artificial proxies of the 96-month data
set have been generated to test the analysis of real `full-disc'
data. These simulations allow for an assessment of any complications
in the analysis which might arise from variations in the properties
of the p modes over the 11-yr solar activity cycle. The use of such
an extended data set affords greater precision in the splittings,
and by implication the rotation rate inferred from these data, and
reduces bias inherent in the analysis, thereby giving a more accurate
determination of the rotation. The grand, weighted sidereal average
of the BiSON set is 434+/-2nHz, a value consistent with that expected
were the deep radiative interior (r/R<0.5) to rotate at the same
frequency, and in the same `rigid' manner, as the more precisely and
accurately studied outer part of the radiative zone.
---------------------------------------------------------
Title: Changes in convective properties over the solar cycle: effect
on p-mode damping rates
Authors: Houdek, G.; Chaplin, W. J.; Appourchaux, T.;
Christensen-Dalsgaard, J.; Däppen, W.; Elsworth, Y.; Gough, D. O.;
Isaak, G. R.; New, R.; Rabello-Soares, M. C.
2001MNRAS.327..483H Altcode:
Measurements of both solar irradiance and p-mode oscillation
frequencies indicate that the structure of the Sun changes with
the solar cycle. Balmforth, Gough & Merryfield investigated the
effect of symmetrical thermal disturbances on the solar structure
and the resulting pulsation frequency changes. They concluded that
thermal perturbations alone cannot account for the variations in both
irradiance and p-mode frequencies, and that the presence of a magnetic
field affecting acoustical propagation is the most likely explanation
of the frequency change, in the manner suggested earlier by Gough &
Thompson and by Goldreich et al. Numerical simulations of Boussinesq
convection in a magnetic field have shown that at high Rayleigh number
the magnetic field can modify the preferred horizontal length scale
of the convective flow. Here, we investigate the effect of changing
the horizontal length scale of convective eddies on the linewidths
of the acoustic resonant mode peaks observed in helioseismic power
spectra. The turbulent fluxes in these model computations are obtained
from a time-dependent, non-local generalization of the mixing-length
formalism. The modelled variations are compared with p-mode linewidth
changes revealed by the analysis of helioseismic data collected by
the Birmingham Solar-Oscillations Network (BiSON); these low-degree
(low-l) observations cover the complete falling phase of solar activity
cycle 22. The results are also discussed in the light of observations
of solar-cycle variations of the horizontal size of granules and with
results from 2D simulations by Steffen of convective granules.
---------------------------------------------------------
Title: The phenomenology of solar-cycle-induced acoustic
eigenfrequency variations: a comparative and complementary analysis
of GONG, BiSON and VIRGO/LOI data
Authors: Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; Isaak, G. R.;
New, R.
2001MNRAS.324..910C Altcode:
We use high-quality helioseismic data collected by three different
observational programmes during the declining phase of activity
cycle 22,Q7 and a substantial portion of the rising phase of the
current cycle (23), to study the phenomenological nature of the
cycle-induced (centroid) eigenfrequency variations. We have analysed
the frequency dependence of the shifts by fitting a power law of the
form δν<SUB>nl</SUB>~(ν<SUB>nl</SUB>)<SUP>α</SUP>/E<SUB>nl</SUB>
to the data (where the E<SUB>nl</SUB> are the mode inertias, and
α is the power-law index to be extracted). Previous studies have
suggested that a relation with α=0 provides an adequate description
of the shifts up to ν~3500μHz. However, here we show that while
nevertheless describing the shifts well up to ~2500μHz, the linear
scaling breaks down conspicuously at higher frequencies. Above this
threshold, the shifts follow a power-law dependence with α~2. Our
analyses (for 1600<=ν<=4000μHz) make use of observations made
by the ground-based GONG over the angular degree range 4<=l<=150
the ground-based BiSON over 0<=l<=2 and the VIRGO/LOI instrument
on board the ESA/NASA SOHO satellite over 0<=l<=8. We show that
GONG shifts averaged over different ranges in l, together with the BiSON
and LOI data averaged over their full quoted ranges, all scale at fixed
frequency with the normalized mode inertia ratio Q<SUB>nl</SUB>Q1. This
is to be expected if the solar-cycle perturbation affecting the modes
is confined in the surface layers; the excellent agreement also reflects
favourably on the external consistency of the different observations.
---------------------------------------------------------
Title: Changes to low-ll solar p-mode frequencies over the solar
cycle: correlations on different time-scales
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Marchenkov,
K. I.; Miller, B. A.; New, R.
2001MNRAS.322...22C Altcode:
We have studied variations in the frequencies of low-l solar p modes
through the analysis of nine years of helioseismic data collected
by the Birmingham Solar Oscillations Network (BiSON)†. This is the
first time that such a long data set has been explored with the extra
accuracy afforded by fitting the modes to asymmetric profiles. The epoch
covered (1991-99) spans the declining activity phase of solar cycle 22,
and a substantial portion of the initial activity increase during cycle
23. The complete time series has been split into contiguous segments of
length 27, 54, 108 and 216d in order to facilitate the study of changes
occurring on different time-scales. Further, we have characterized the
observed shifts as a function of six well-known indicators of solar
activity. These indices reflect changes taking place in the photosphere,
chromosphere and corona, but only over the visible hemisphere of the
Sun. Since the low-l eigenfrequencies respond to global variations
in activity, we discuss the implications of this mismatch for the
analyses performed. We demonstrate that, as expected, the low-l modes
adjust to changes in the activity measures on time-scales as short as
a few months. Our analysis indicates that all six proxies correlate
equally well (at the level of precision of the data) with the measured
shifts. Further, the sensitivity of the shifts to changes in five of
the activity indices is the same, to within ~15per cent (1σ) or so,
on the falling and rising phases considered. There is, however, a
slight suggestion that the sensitivity to changes in the disc-averaged
line-of-sight magnetic field component (as determined from daily Kitt
Peak magnetograms) may be higher on the rising phase of the cycle.
---------------------------------------------------------
Title: Non linear inversion for the sound speed in the solar interior
using BiSON and SOI/MDI p-mode frequencies
Authors: Marchenkov, K. I.; Roxburgh, I. W.; Vorontsov, S. V.; Chaplin,
W. J.; Elsworth, Y.; Isaak, G. R.; New, R.
2001ESASP.464..531M Altcode: 2001soho...10..531M
The results of the global sound-speed inversion obtained with solar
p-mode frequencies provided by the recent high-quality observational
data (BiSON, SOI/MDI) are presented and discussed. The iterative
nonlinear inversion technique used here is a generalization (for the
case of exact solution of the adiabatic oscillation equations) of the
Born quasiasymptotic approximate inversion developed by Marchenkov et
al. (2000).
---------------------------------------------------------
Title: BiSON
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Marchenkov, K.;
Miller, B. A.; New, R.; Pinter, B.
2001ESASP.464..313C Altcode: 2001soho...10..313C
The current status of the Birmingham Solar Oscillation Network (BiSON)
is discussed.
---------------------------------------------------------
Title: Helioseismic signatures of localized structural discontinuities
in BiSON and GONG data
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; New, R.
2001ESASP.464...79C Altcode: 2001soho...10...79C
We use high-quality helioseismic data collected by BiSON and GONG in
an attempt to search for variations over time of the influence on the
acoustic mode frequencies of localized structural perturbations located
beneath the solar surface. Our analysis of the BiSON data is aimed at
a study of the effects of the He II ionization zone. We use GONG data
(4 <= l <= 140) to extract estimates of the solar-cycle-induced
eigenfrequency shifts over the range 1600 <= ν <= 4000
μHz. A careful analysis of these data may have uncovered tentative
evidence for an oscillatory behaviour that would be the signature of
a time-dependent solar cycle perturbation located approximately ~20
Mm beneath the photosphere.
---------------------------------------------------------
Title: A long-term look at acoustic modes with a nine-year BiSON
spectrum
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Marchenkov, K.;
Miller, B. A.; New, R.; Pinter, B.
2001ESASP.464...51C Altcode: 2001soho...10...51C
We present data taken from BiSON to illuminate solar-activity related
changes in the oscillation parameters. We also use the full dataset
to hunt for low order p-modes.
---------------------------------------------------------
Title: Does the excitation and damping of the acoustic eigenmodes
vary over the solar cycle? An insight from LOI observations
Authors: Chaplin, W. J.; Appourchaux, T.
2001ESASP.464..601C Altcode: 2001soho...10..601C
We have used observations made by the LOI instrument on board the
ESA/NASA SOHO satellite in order to try and uncover variations in
the excitation and damping of the low-angular-degree solar acoustic
eigenmodes over the solar cycle. These data were collected on the rising
phase of activity cycle 23. We have divided the dataset into independent
136-d and 1-yr time series and fitted the modes in the complex Fourier
(frequency) domain to yield estimates of the line widths and amplitudes
of the modes. The extracted parameters have then been analyzed in order
to search for solar-cycle-induced variations. Over the range 2600 <=
ν <= 3600μHz, we uncover a mean implied activity minimum-to-maximum
increase in the frequency-domain line widths of 21+/-3 per cent; a mean
decrease of 37+/-3 per cent decrease in the mode heights; and a mean
decrease of 18+/-4 per cent in the mode powers. Our analysis indicates
that - at the level of precision of the available data - the rate
at which energy is supplied to the modes remains constant (uncovered
variation 3+/-5 per cent). These results are in reasonable agreement
with recent claims by Chaplin et al. (2000) and Komm, Howe and Hill
(2000) from analyses of BiSON and GONG data respectively. Furthermore,
the signs and relative magnitudes of the extracted changes are
consistent with the speculation made by Chaplin et al. that it is
alterations in the damping, and not the forcing, of the modes that
gives rise to the variations observed over the solar activity cycle.
---------------------------------------------------------
Title: Characteristics of full-disc BiSON power spectra above the
acoustic cut-off frequency of the solar atmosphere
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Marchenkov,
K. I.; Miller, B. A.; New, R.
2001ESASP.464..191C Altcode: 2001soho...10..191C
We have analyzed 60 months of non-imaged Doppler velocity
observations of the visible disc of the Sun in an effort to search
for pseudo-mode-like structure in the data above the acoustic cut-off
frequency of the solar atmosphere (≍5400 μHz). These data were
collected by the ground-based Birmingham Solar-Oscillations Network
(BiSON). Our analysis uncovers marginally significant evidence for
the presence of a pseudo-mode-like structure in the range 5900 <=
ν <= 6600 μHz, with a spacing between adjacent peaks (or troughs)
of ~70 μHz. The signature - which, owing to the low signal to noise,
disappears at higher frequencies - has a similar repeat period and phase
to that found by Garcia et al. (1998) in full-disc GOLF data. However,
the zero-to-peak power is a factor of ~10 weaker in strength.
---------------------------------------------------------
Title: Probing the solar cycle: a comparative and complementary
analysis of GONG BiSON and VIRGO/LOI eigenfrequency shifts
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; New, R.;
Appourchaux, T.
2001ESASP.464...83C Altcode: 2001soho...10...83C
We use high-quality helioseismic data collected by GONG (over 4 <=
l <= 140), BiSON (0 <= l <= 2) and VIRGO/LOI (0 <= l <=
8) to study the phenomenological nature of the cycle-induced (centroid)
eigenfrequency variations. We have analyzed the frequency dependence
of the shifts by fitting a power-law of the form δν<SUB>nl</SUB> ~
(ν<SUB>nl</SUB>)<SUP>α</SUP>/E<SUB>nl</SUB> to the data (where the
E<SUB>nl</SUB> are the mode inertias, and α is the power-law index to
be extracted). Previous studies have suggested that a relation with
α = 0 provides an adequate description of the shifts up to ν ≍
3500 μHz. However, here we show that while nevertheless describing
the shifts well up to ~2500 μHz, the linear scaling breaks down
conspicuously at higher frequencies. Above this threshold, the shifts
follow a power-law dependence with α ~ 2. We also ahow that GONG
shifts, averaged over different ranges in l together with the BiSON
and LOI data averaged over their full quoted ranges, all scale at
fixed frequency with the normalized mode inertia ratio Q<SUB>nl</SUB>
(Christensen-Dalsgaard & Berthomieu 1991). This is to be expected
if the solar-cycle perturbation affecting the modes is confined in
the surface layers; the excellent agreement also reflects favourably
on the external consistency of the different observations.
---------------------------------------------------------
Title: g-mode detection: Where do we stand?
Authors: Appourchaux, T.; Andersen, B.; Berthomieu, G.; Chaplin, W.;
Elsworth, Y.; Finsterle, W.; Frölich, C.; Gough, D. O.; Hoeksema,
T.; Isaak, G.; Kosovichev, A.; Provost, J.; Scherrer, P.; Sekii, T.;
Toutain, T.
2001ESASP.464..467A Altcode: 2001soho...10..467A
We review the recent developments in determining the upper limits to
g-mode amplitudes obtained by SOHO instruments, GONG and BiSON. We
address how this limit can be improved by way of new helioseismic
instruments and/or new collaborations, hopefully providing in the not
too distant future unambiguous g-mode detection.
---------------------------------------------------------
Title: Observational Upper Limits to Low-Degree Solar g-Modes
Authors: Appourchaux, T.; Fröhlich, C.; Andersen, B.; Berthomieu, G.;
Chaplin, W. J.; Elsworth, Y.; Finsterle, W.; Gough, D. O.; Hoeksema,
J. T.; Isaak, G. R.; Kosovichev, A. G.; Provost, J.; Scherrer, P. H.;
Sekii, T.; Toutain, T.
2000ApJ...538..401A Altcode:
Observations made by the Michelson Doppler Imager (MDI) and Variability
of solar IRradiance and Gravity Oscillations (VIRGO) on the Solar and
Heliospheric Observatory (SOHO) and by the ground-based Birmingham
Solar Oscillations Network (BiSON) and Global Oscillations Network
Group (GONG) have been used in a concerted effort to search for solar
gravity oscillations. All spectra are dominated by solar noise in the
frequency region from 100 to 1000 μHz, where g-modes are expected to be
found. Several methods have been used in an effort to extract any g-mode
signal present. These include (1) the correlation of data-both full-disk
and imaged (with different spatial-mask properties)-collected over
different time intervals from the same instrument, (2) the correlation
of near-contemporaneous data from different instruments, and (3) the
extraction-through the application of complex filtering techniques-of
the coherent part of data collected at different heights in the solar
atmosphere. The detection limit is set by the loss of coherence
caused by the temporal evolution and the motion (e.g., rotation)
of superficial structures. Although we cannot identify any g-mode
signature, we have nevertheless set a firm upper limit to the amplitudes
of the modes: at 200 μHz, they are below 10 mm s<SUP>-1</SUP> in
velocity, and below 0.5 parts per million in intensity. The velocity
limit corresponds very approximately to a peak-to-peak vertical
displacement of δR/R<SUB>solar</SUB>=2.3×10<SUP>-8</SUP> at the
solar surface. These levels which are much lower than prior claims,
are consistent with theoretical predictions.
---------------------------------------------------------
Title: Source of excitation of low-l solar p modes: characteristics
and solar-cycle variations
Authors: Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; Isaak, G. R.;
Miller, B. A.; New, R.
2000MNRAS.314...75C Altcode:
We investigate various properties of the excitation source that
is responsible for driving the acoustic p-mode oscillations of the
Sun. Current prejudice places this in the superadiabatic layer of
the convection zone. We consider in detail how the precise nature of
the resonant mode spectrum is modified: (i) as a result of the impact
of different source-multipole mixtures; and (ii) as a function of the
radial extent of the source. To do this, we model the observed resonant
spectra with the solutions to a simple, one-dimensional wave equation
which is intended to describe the essential elements of the solar
resonant acoustic cavity. Further, we also fit these models to the
low-l peaks in a high-resolution power spectrum generated from data
collected by the Birmingham Solar-Oscillations Network (BiSON). We
also use the extensive BiSON data set to search for variations in the
source characteristics over the solar cycle.
---------------------------------------------------------
Title: Variations in the excitation and damping of low-l solar p
modes over the solar activity cycle<SUP>*</SUP>
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Miller, B. A.;
New, R.
2000MNRAS.313...32C Altcode:
We have searched helioseismic data collected by the Birmingham Solar
Oscillations Network (BiSON) for solar-cycle changes to those low-l
p-mode parameters that relate to the excitation and damping of the
resonances. These data - collected between 1991 and 1997 - cover the
complete declining phase of solar activity cycle 22 (up to and including
the cycle 22/23 boundary). Over the range 2600<=ν<=3600μHz,
we uncover a mean 24+/-3per cent increase in the frequency-domain
linewidths; a mean decrease of 46+/-5per cent decrease in the mode
heights, and a mean decrease of 22+/-3per cent in the modal velocity
powers. The rate at which energy is supplied to the modes remains
constant, at the level of precision of the observations (measured
change 0+/-4per cent). We use expressions derived from the equation of
a damped harmonic oscillator to illustrate the diagnostic properties
of the observables: these indicate that both the signs and relative
sizes of the extracted variations can arise from changes solely to
the net damping; the net forcing of the modes need not change. The
results possibly hint at the changes being maximal at frequencies near
~3100μHz. They might therefore suggest an origin for the observed
variations that is peaked in the superadiabatic layer of the convection
zone, which couples most strongly to the eigenfunctions of modes at
the centre of the p-mode spectrum.
---------------------------------------------------------
Title: Depth of excitation and reversal of asymmetry of low-l
solar P modes: a complementary analysis of BiSON<SUP>*</SUP> and
VIRGO/SPM† data
Authors: Chaplin, W. J.; Appourchaux, T.
1999MNRAS.309..761C Altcode:
We use the solutions to a simple, one-dimensional wave equation -
which is intended to describe the essential elements of the solar
resonant acoustic cavity - as formalistic models to which to fit
low-l modes in observational helioseismic power spectra. We have
analysed data collected in velocity, by the ground-based Birmingham
Solar-Oscillations Network (BiSON), and in intensity, by the full-disc
VIRGO Sun photometers (SPM) on board the ESA/NASA SOHO satellite. Our
analysis extracts, as a function of the modal radial overtone number
n, direct estimates of: the location of the excitation source of the
acoustic resonances; and the size of the component of the convective
granulation that is correlated to the observations of the resonances,
and is responsible for the reversal of asymmetry of the mode profiles
when different observation techniques are applied (i.e. intensity
or Doppler velocity measurements). This information is coded in the
complicated forms of the observed, resonant profiles.
---------------------------------------------------------
Title: Skew-symmetric solar P modes in low-l BiSON ^* data
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Miller, B. A.;
New, R.
1999MNRAS.308..424C Altcode:
The p-mode oscillations of the Sun are manifestations of resonantly
trapped acoustic waves propagating within its interior. The effective
size of the resulting resonant cavity changes with the properties of
the modes - the interaction of this phenomenon with a highly localized
excitation source in the upper layers of the convection zone gives
rise to skew-symmetric resonant profiles whose degree of asymmetry
changes with frequency. Here, we have fitted low-angular-degree (low-l)
resonant p-mode peaks - in a power spectrum generated from 32 months
of BiSON Doppler velocity observations of the visible solar disc -
to a skew-symmetric formalism to account for this effect. We present
the fitted frequencies, fine-structure spacings [d_0(n) and d_1(n)]
and mode-skewness estimates; and discuss the quantitative impact of
fitting a skew, rather than symmetric, limit model. We also consider
the reliability of the extracted parameters through the application
of a useful statistical test, and extensive Monte Carlo fits to
artificial data.
---------------------------------------------------------
Title: Rotation of the solar core from BiSON and LOWL frequency
observations
Authors: Chaplin, W. J.; Christensen-Dalsgaard, J.; Elsworth, Y.;
Howe, R.; Isaak, G. R.; Larsen, R. M.; New, R.; Schou, J.; Thompson,
M. J.; Tomczyk, S.
1999MNRAS.308..405C Altcode:
Determination of the rotation of the solar core requires very accurate
data on splittings for the low-degree modes which penetrate to the core,
as well as for modes of higher degree to suppress the contributions
from the rest of the Sun to the splittings of the low-degree modes. Here
we combine low-degree data based on 32 months of observations with the
BiSON network and data from the LOWL instrument. The data are analysed
with a technique that specifically aims at obtaining an inference of
rotation that is localized to the core. Our analysis provides what we
believe is the most stringent constraint to date on the rotation of
the deep solar interior.
---------------------------------------------------------
Title: An analysis of solar p-mode frequencies extracted from BiSON
data: 1991-1996
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Lines, R.;
McLeod, C. P.; Miller, B. A.; New, R.
1998MNRAS.300.1077C Altcode:
We present a comprehensive frequency analysis of Doppler velocity
observations of the visible solar disc made by the Birmingham Solar
Oscillations Network (BiSON) from 1990-1996, i.e. covering the
falling phase of activity cycle 22, up to and including the cycle
22/23 boundary. We have fitted low-degree (low-l) solar p modes in
a variety of power spectra of differing lengths generated from these
data. The analysis of the extracted frequencies reveals the expected
clear solar-cycle dependence; in addition, there is now sufficient
accuracy in the data to show that the low-l modal eigenfrequencies are
less affected by the solar cycle than their higher l counterparts. The
observed low-degree frequency shifts up to ~3900muHz are consistent
- at the level of precision of the data - with an inverse mode-mass
scaling. At frequencies above this, the blending of modes adjacent in
frequency space makes it increasingly difficult to extract reliable
frequency estimates. However, our data show indications of a turnover
and possibly also an eventual sign change in the solar cycle shifts
at frequencies above ~4000muHz, as seen in higher l data. We have
parametrized the observed shifts as a function of the 10.7-cm radio
flux, and produced an activity-corrected, average frequency table
which incorporates eigenfrequencies from 18 4-month and 9 8-month
spectra. We also present the fitted frequencies from a 32-month
power spectrum, generated from data collected at or close to solar
minimum. In addition, we also searched for frequency asymmetries in
the l=2 mode multiplets. These could result from strong near-surface
magnetic activity, or a buried magnetic field. Our fits merely place
an upper limit to any mean asymmetry - over the range 10<=n<=21 -
of between ~-80 and ~170nHz (3sigma).
---------------------------------------------------------
Title: Solar p-mode excitation: further insight from recent low-l
BiSON helioseismological data
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Lines, R.;
McLeod, C. P.; Miller, B. A.; New, R.
1998MNRAS.298L...7C Altcode:
We present measurements of low-degree solar p-mode velocity powers,
energies and energy supply rates between ~1600muHz and ~4700muHz,
as derived from the analysis of several years of high-quality
helioseismological data collected by the Birmingham Solar-Oscillations
Network (BiSON). For the radial (l=0) modes, we find that the total
energy E per mode (kinetic plus potential) peaks at ~3200muHz,
reaching ~10^28erg. The rate at which energy is supplied to the
modes E=2piDeltanu.E, where Deltanu is the FWHM modal line width, is
observed to plateau between ~3000 and ~4000muHz, reaching a maximum of
~10^23ergs^-1. At frequencies below the plateau, the supply rate follows
a simple power law with a dependence of E~nu^7.0+/-0.4 and at very-high
frequencies the data follow E~nu^-4.5+/-1.1. These assume modal inertias
normalized at T=T_eff with the mode-mass calculation normalized at
the optical depth of the BiSON observations, the fitted power laws in
E are approximately ~nu^6.5+/-1.1 and ~nu^-6.2+/-1.1 respectively.
---------------------------------------------------------
Title: Solar p-mode Excitation: Further Insights from Recent Low-l
BiSON Helioseismological Data
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Lines, R.;
McLeod, C. P.; Miller, B. A.; New, R.
1998ESASP.418..879C Altcode: 1998soho....6..879C
We present measurements of low-degree solar p-mode velocity powers,
energies and energy supply rates between ~1600 μ Hz and ~4700 μ
Hz, as derived from the analysis of several years of high-quality
helioseismological data collected by the Birmingham Solar-Oscillations
Network (BiSON). For the radial (ell = 0) modes, we find that the
total energy E per mode (kinetic plus potential) peaks at ~3200 μ Hz,
reaching ~10<SUP>28</SUP> ergs. The rate at which energy is supplied
to the modes dot{E} = 2pi Δ ν cdot E, where Δ ν is the fwhm modal
line width, is observed to plateau between ~3000 μ Hz and ~4000 μ
Hz, reaching a maximum of ~10<SUP>23</SUP> ergs s<SUP>-1</SUP>. At
frequencies below the plateau, the supply rate follows a simple
power law with a dependence of dot{E} propto nu<SUP>7.0 plus or minus
0.4</SUP>; and at very-high frequencies the data follow dot{E} propto
nu<SUP>-4.5 plus or minus 1.1</SUP>.
---------------------------------------------------------
Title: Low Degree p-mode solar cycle trends from BISON data
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; McLeod, C. P.;
Miller, B. A.; New, R.
1998IAUS..185..171C Altcode:
The resonant p-mode oscillations of the Sun are manifestations of
trapped, standing sound waves in the solar interior. The frequencies
of the discrete spectrum of sustained modes are consequently modified
by the mechanical properties of the layers through which the waves
traverse. Quasi-periodic changes to the solar structure -- on an 11
(22)-year timescale -- result in certain measurable mode properties
being affected. Here, we have used high-quality Doppler velocity data,
collected in integrated sunlight by the Birmingham Solar-Oscillations
Network (BiSON), in order to assess the resulting impact on the
low-degree modes of oscillation over the falling phase of solar cycle
22, and the beginning of cycle 23.
---------------------------------------------------------
Title: Further inside into p-mode excitation and damping from recent
BiSON data
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; McLeod, C. P.;
Miller, B. A.; New, R.
1998IAUS..185..221C Altcode:
The resonant p-mode oscillations of the Sun are believed to be excited
stochastically in its outer layers. Here, we seek to gain additional
insight into the p-mode excitation and damping problem by following
the power evolution, with time, of individual low-degree (low-ell)
multiplets. Sine-wave fits have been performed -- at the appropriate
frequencies -- on short stretches of high-quality Doppler velocity data,
collected in integrated sunlight by the Birmingham Solar-Oscillations
Network (BiSON). The results of these analyses will be presented
and discussed.
---------------------------------------------------------
Title: Observational Upper Limits for Low-Degree Solar g-modes
Authors: Fröhlich, C.; Finsterle, W.; Andersen, B.; Appourchaux, T.;
Chaplin, W. J.; Elsworth, Y.; D. O. Gough; Hoeksema, J. T.; Isaak,
G. R.; Kosovichev, A. G.; Provost, J.; Scherrer, P. H.; Sekii, T.;
Toutain, T.
1998ESASP.418...67F Altcode: 1998soho....6...67F
No abstract at ADS
---------------------------------------------------------
Title: Touching on the effects of an imperfect Window Function
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; McLeod, C. P.;
Miller, B. A.; New, R.
1998IAUS..185...47C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A comparison of low-degree solar p-mode frquencies from BISON
and LOI
Authors: Appourchaux, T.; Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.;
McLeod, C. P.; Miller, B. A.; New, R.
1998IAUS..185...45A Altcode:
Here, we compare the low-degree solar p-mode frequencies returned from
the analysis of two, contemporaneous, independent helioseismological
data sets collected during 1996. The first comprises Doppler velocity
observations of the 770-nm line of potassium, made in integrated
sunlight by the six-station, terrestrial Birmingham Solar-Oscillations
Network (BiSON). The second consists of irradiance distribution
measurements of the solar disc, made at 500rm nm, by the Luminosity
Oscillations Imager (LOI), which is part of the VIRGO experiment on
the ESA/NASA SOHO satellite.
---------------------------------------------------------
Title: Comparative Studies of Low-Order and Low-Degree Solar p Modes
Authors: Appourchaux, T.; Andersen, B.; Chaplin, W.; Elsworth, Y.;
Finsterle, W.; Frohlich, C.; Gough, D.; Hoeksema, J. T.; Isaak, G.;
Kosovichev, A.; Provost, J.; Scherrer, P.; Sekii, T.; Toutain, T.
1998ESASP.418...95A Altcode: 1998soho....6...95A
The amplitudes of solar p-modes decrease steeply with decreasing
radial order below about 17. The background solar signal (solar noise)
in general increases steadily with decreasing frequency. For the
irradiance and radiance measurements with VIRGO or SOI/MDI on SOHO this
combination makes it difficult to detect low degree modes below about
1.8 mHz. The solar noise as observed in velocity with SOI/MDI or the
ground based BISON network is significantly lower in this region than
in intensity measurements. This allows low degree modes to be observed
close to 1 mHz. We present results of detection and charaterization
of the lowest order observable p-modes both in velocity and intensity
measurements. Where applicable the properties of the modes observed
with the two methods are compared.
---------------------------------------------------------
Title: The Extraction of Rotational Splittings from Monte Carlo
Simulations of Unresolved Low-l Data
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Miller, B. A.;
New, R.
1998ESASP.418..135C Altcode: 1998soho....6..135C
The rotation of the Sun lifts the frequency degeneracy in ell of the
acoustic eigenmode spectrum. The extraction of reliable estimates
of these splittings is a particularly challenging task. Here, we
address the problem in the context of the analysis of full-disc
helioseismological data. In essence, a set of “zero-dimensional”
data are collected. Consequently: (i) a power spectrum of the data will
consist of many closely spaced resonant peaks, with the most prominent
aspect being an alternating quadrupole-monopole and octupole-dipole
mode-pair structure; (ii) the data cannot be spatially filtered to
extract “single-mode” power spectra -- however, this does mean that
they are unaffected by spatial sideband leakage (which presents its
own set of problems for resolved data); and (iii) the composition of
the power spectrum may be further complicated by the introduction
of temporal sidebands and other window-function-aliased power as a
result of an imperfect observational duty cycle. At low frequencies,
the modes are very weak -- however, their long coherence times give
sharp, well defined resonant peaks in the frequency domain, enabling
the m-dependent structure of the mode to be well resolved (given a
sufficiently long integration time). At higher frequencies, despite
increased signal-to-noise, the increasing mode line widths lead to a
substantial blending of adjacent features in the frequency domain -- as
the frequency-domain line widths increase still further, so the problems
associated with extracting reliable estimates of the mode splittings
become ever more severe. Here, we have used artificial p-mode data --
generated by a model which is based upon a randomly forced, damped
harmonic oscillator -- to assess the veracity of maximum-likelihood
fitting approaches for different parts of the low-ell spectrum. Among
other points of interest, the results of these simulations reveal a
clear tendency for the formal uncertainty of the fitted splitting to
be anti-correlated with the magnitude of the splitting for modes at
higher n.
---------------------------------------------------------
Title: A search l=2 asymmetries in BISON data
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; McLeod, C. P.;
Miller, B. A.; New, R.
1998IAUS..185..169C Altcode:
The rotation of the Sun lifts the frequency degeneracy in the angular
degree ell of the resonant p-mode oscillations of the solar cavity,
giving rise to a multiplet structure, each resulting component being
identified by an azimuthal order m. A buried magnetic field will
perturb these frequencies still further via the Lorentz force. Here,
we have used low-degree solar p-mode data, collected by the Birmingham
Solar-Oscillations Network (BiSON) in integrated sunlight, in an effort
to search for such an effect in modes of degree ell=2. The Lorentz
perturbation will shift the outer, sectoral (m=pm 2) components in
the same sense, while the m=0 component remains unaffected, giving the
integrated-sunlight-observed ell=2 multiplet an asymmetric frequency
structure. The degree of asymmetry is expected to change with the solar
cycle. Results obtained by attempting to fit explicitly the asymmetric
structure, and by overlaying many independent mode realizations,
will be presented and discussed.
---------------------------------------------------------
Title: Solar internal sound speed as inferred from combined BiSON
and LOWL oscillation frequencies
Authors: Basu, Sarbani; Christensen-Dalsgaard, J.; Chaplin, W. J.;
Elsworth, Y.; Isaak, G. R.; New, R.; Schou, J.; Thompson, M. J.;
Tomczyk, S.
1997MNRAS.292..243B Altcode: 1997astro.ph..2105B
Observations of the Sun with the LOWL instrument provide a homogeneous
set of solar p-mode frequencies from low to intermediate degree that
allow one to determine the structure of much of the solar interior
avoiding systematic errors that are introduced when different data sets
are combined, i.e., principally the effects of solar cycle changes on
the frequencies. Unfortunately, the LOWL data set contains very few of
the lowest-degree modes, which are essential for determining reliably
the structure of the solar core - in addition, these lowest-degree data
have fairly large associated uncertainties. However, observations made
by the Birmingham Solar-Oscillations Network (BiSON) in integrated
sunlight provide high-accuracy measurements of a large number of
low-degree modes. In this paper we demonstrate that the low-degree mode
set of the LOWL data can be successfully combined with the more accurate
BiSON data, provided the observations are contemporaneous for those
frequencies where the solar cycle induced effects are important. We
show that this leads to a factor of 2 decrease in the error on the
inferred sound speed in the solar core. We find that the solar sound
speed is higher than in solar models for r<0.2Rsolar. The density
of the solar core is, however, lower than that in solar models.
---------------------------------------------------------
Title: Techniques used in the analysis of data collected by the
Birmingham Solar-Oscillations Network (BiSON). II. Frequency domain
analysis & data merging
Authors: Chaplin, W. J.; Elsworth, Y.; Howe, R.; Isaak, G. R.; McLeod,
C. P.; Miller, B. A.; New, R.
1997A&AS..125..195C Altcode:
The Birmingham Solar-Oscillations Network (BiSON) consists of 6
solar observatories dedicated to the collection of full-disc solar
Doppler velocity data -- these data are sensitive to the lowest spatial
degrees of oscillation (0 <= l <= 4). In Paper I of this series,
we described the calibration of raw data from the BiSON instruments
to produce solar velocity residuals representing the oscillations
of the Sun's surface. In this paper, we discuss the combination of
velocity residuals into time series -- including a thorough discussion
of the treatment of data overlaps between sites -- and the analysis
of the power spectra computed from such time series to derive the
characteristics of the acoustic modes.
---------------------------------------------------------
Title: A Key to Understanding the Sun and Stars: The Birmingham
Solar-Oscillations Network (BiSON)
Authors: Chaplin, W. J.
1997IrAJ...24..103C Altcode:
The Birmingham Solar-Oscillations Network (BiSON) consists of six
semi- and fully-automatic observatories, dedicated to the continuous
observation of the low-degree, globally coherent, p-mode oscillations
of the Sun. These resonant modes are manifestations of trapped,
standing sound waves that penetrate into the core of the Sun and
which consequently provide a sensitive probe of its deep radiative
interior. Here, we discuss briefly the nature of the oscillations,
introduce BiSON, and touch upon some of the important science extracted
by the network which has, among other topics, impacted upon: solar
and stellar physics; stellar evolutionary theory; the solar neutrino
problem; and cosmology.
---------------------------------------------------------
Title: Solar p-mode linewidths from recent BiSON helioseismological
data
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; McLeod, C. P.;
Miller, B. A.; New, R.
1997MNRAS.288..623C Altcode:
We present low-degree solar p-mode linewidths from the analysis of
several high-resolution frequency spectra generated from high-quality
Doppler velocity data collected - in integrated sunlight - by the
Birmingham Solar-Oscillations Network (BiSON) between 1991 July and
1995 July. We have used linewidths, Deltanu, measured in a 32-month
frequency spectrum, to test the power-law dependence of the widths
at low frequencies. Over the range 1473<=nu<=1822Hz, we find
Deltanu~nu^7.0+/-1.5. If an effort is made to correct for finite
observing time systematics, the fitted index increases to 7.3
(and even higher, to 7.8, if a naive, single-bin-width correction
is applied). This is somewhat steeper than reported in previous
observations of intermediate-degree modes, and is more in line
with theoretical calculations which predict Deltanu~nu^8 over this
frequency range. If one assumes that the steep dependence reported
here persists down to lower frequencies, low-degree-mode coherence
(e-folding) times at 800Hz of >14yr, and at 300 muHz (i.e. near
the frequency expected for the fundamental) of >13000yr are implied.
---------------------------------------------------------
Title: The observation and simulation of stochastically excited
solar p modes
Authors: Chaplin, W. J.; Elsworth, Y.; Howe, R.; Isaak, G. R.; McLeod,
C. P.; Miller, B. A.; New, R.
1997MNRAS.287...51C Altcode:
We use low-degree p-mode data, collected in integrated sunlight by
the Birmingham Solar-Oscillations Network (BiSON), to derive the
distribution of the observed strengths of the solar oscillations. We
demonstrate that certain features of the observations cannot be
explained by a model of the oscillations that is based upon a
stochastically forced, damped harmonic oscillator. The solution of
the equation of motion of the oscillator, as derived by the use of the
Laplace transform, is presented, and its application to the simulation
of real p-mode data, in the form of a coded algorithm, is discussed. A
variety of tests are applied - both in the time and in the frequency
domains - to artificially generated time series. These confirm that
the model serves both as a useful diagnostic tool and for providing
additional insight into the p-mode excitation and damping problem.
---------------------------------------------------------
Title: The Solar Core: New Low-l p-Mode Fine-Spacing Results from
BiSON
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; McLeod, C. P.;
Miller, B. A.; New, R.
1997ApJ...480L..75C Altcode: 1997astro.ph..2141C
The fine-structure spacing d<SUB>l</SUB>(n) = ν<SUB>l,n</SUB>
- ν<SUB>l+2,n-1</SUB> for low-degree solar p modes of angular
degree l and radial order n is sensitive to conditions in the deep
radiative interior of the Sun. Here we present fine-structure spacings
derived from the analysis of nearly 5 years of helioseismological data
collected between 1991 July and 1996 February by the Birmingham Solar
Oscillations Network (BiSON). These data cover 9 <= n <= 28 for
d<SUB>0</SUB>(n), and 11 <= n <= 27 for d<SUB>1</SUB>(n). The
measured spacings are much more precise and cover a greater range
than earlier measurements from BiSON data (Elsworth et al. 1990a). The
predicted fine-structure spacings for a “standard” solar model are
clearly excluded by the BiSON data (at ~10 σ) models that include
helium and heavy-element settling provide a much better match to the
observed spacings (see also Elsworth et al. 1995). Since the inclusion
of core settling in solar models will tend to increase slightly
the predicted neutrino flux, the BiSON fine-structure data appear
to reinforce previous conclusions, i.e., an astrophysical solution
to the solar neutrino problem seems unlikely. <P />Birmingham Solar
Oscillations Network; http://bison.ph.bham.ac.uk.
---------------------------------------------------------
Title: Solar core rotation from low-degree BiSON p-mode splittings:
1981-95
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; McLeod, C. P.;
Miller, B. A.; New, R.
1996MNRAS.283L..31C Altcode:
In this paper, we present an analysis of the rotational splittings of
low-degree solar p modes, as measured in full-disc helioseismological
data collected by the Birmingham Solar-Oscillations Network (BiSON)
between 1981 and 1995. These data provide coverage over solar
activity cycles 21 and 22. Rotationally split multiplets were fitted
in two 4-month and seven 8-month frequency spectra with a technique
that minimizes a maximum-likelihood function consistent with chi^2
2-d.o.f. statistics. The fitted modes used in the analysis map the
range 1<=l<=3 and 2.0<=nu<=3.1mHz. The lower limit to the
analysed frequency range was determined by the poorer quality of the
pre-1990 data; the upper, very conservative, cut-off was imposed in
order to avoid using data where the linewidths of the modes begin to
increase substantially above 1muHz. Global splitting averages (for
1<=l<=3) were computed over the quoted mode-frequency range by:
(i) weighting each datum according to the scatter observed in the
sectoral splittings as a function of l and (ii) weighting each datum
according to its formal uncertainty, as computed by the mode-fitting
procedure. The l-weighted averages show a slight decline over the period
1981-95: however, the gradient is only significant at the ~2sigma
level (-3.8+/-1.8nHz yr^-1). If one were to interpret any trends in
the low-degree splittings as being indicative of a modification of
the rotational behaviour of the solar core (for r/R_solar<=0.25),
we would estimate that a ~60 per cent change in the core rotation rate
is excluded at the 3sigma level by the l-weighted data. The `formally'
weighted averages imply a very significant change with epoch. However,
an analysis of the data appears to show that the formal uncertainties
may somewhat underestimate the actual errors on the measured splittings,
leading to an overestimation of the significance of any inferred change
with epoch.
---------------------------------------------------------
Title: Low-frequency, low-degree solar p-mode measurements from
recent BiSON* data
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Lines, R.;
McLeod, C. P.; Miller, B. A.; New, R.
1996MNRAS.282L..15C Altcode:
We present high-quality measurements of the frequencies of some
acoustic modes of oscillation of the Sun, as determined from recent
full-disc BiSON data. These cover the range 0<=<~<=3 and
7<=<e1>n<=</e1>14. Several of the mode frequencies
have been measured to accuracies as high as 5 parts in 10^6, as
determined by the formal mode-fitting uncertainties. When compared
with the model frequencies of the AARHUS group (model OPAL1 from
Basu et al.) in which the Livermore equation of state, the Livermore
opacities and both helium and heavy element diffusion and settling
have been incorporated, the frequency differences (in the sense BiSON
minus OPAL1) are typically of the order of only ~-0.1 muHz over this
frequency region.
---------------------------------------------------------
Title: BiSON Performance
Authors: Chaplin, William J.; Elsworth, Yvonne; Howe, Rachel; Isaak,
George R.; McLeod, Clive P.; Miller, Brek A.; van der Raay, H. B.;
Wheeler, Sarah J.; New, Roger
1996SoPh..168....1C Altcode:
Since 1981 we have been operating the Birmingham Solar-Oscillations
Network (BiSON), a global network of resonant-scattering spectrometers,
observing the low-l solar p modes. Here we discuss historical
developments, culminating in the establishment of a 6-station network
in 1992 September, and the subsequent performance of that network. The
data record of each station from 1992 to 1994 has been analysed in terms
of weather and equipment breakdowns. Our early experience suggests that
the best long-term coverage possible with a 6-station network is limited
in practice to about 80%, which falls short of previous predictions.
---------------------------------------------------------
Title: Low-degree, L=4 modes in full-disc BiSON* helioseismological
data
Authors: Chaplin, W. J.; Elsworth, Y.; Howe, R.; Isaak, G. R.; McLeod,
C. P.; Miller, B. A.; New, R.
1996MNRAS.280.1162C Altcode:
We demonstrate that some L=4 acoustic eigenmodes of the Sun are clearly
distinguishable in long power spectra generated from Doppler velocity
residuals collected in unimaged sunlight by the six-station Birmingham
Solar Oscillations Network (BiSON). Modes covering the range n=17
to 21 have been measured in 16-month-long power spectra. They have
typical amplitudes -when measured in full-disc Doppler velocity data
- of less than ~1 cm s^-1 per root bin, and their frequencies have
been determined to fractional accuracies of the order of 3 parts in
10^5. The sensitivity of the whole-disc observations to these modes -
as implied by the data - appears to be approximately a factor of 2
greater than the theoretical predictions of Christensen-Dalsgaard.
---------------------------------------------------------
Title: Solar core rotation: low-degree solar p-mode rotational
splitting results from BiSON*
Authors: Chaplin, W. J.; Elsworth, Y.; Howe, R.; Isaak, G. R.; McLeod,
C. P.; Miller, B. A.; New, R.
1996MNRAS.280..849C Altcode:
In a recent paper (Elsworth et al.), we presented rotational splitting
measurements of low-degree, low-frequency solar p modes, which, for
the first time, show visually well-separated components at frequencies
as low as ~1.5 mHz. At the present time, these data appear to rule out
a rapidly rotating solar core. Here, we expand our analysis of these
data to a full discussion of the statistical properties of the measured
splittings. We have considered two fully independent Fourier spectra,
generated from Doppler velocity residuals collected by the six-station
Birmingham Solar-Oscillations Network (BiSON) between 1992 January 1 and
1994 August 23 (Fourier spectra 16A and 16C from Elsworth et al.). We
present formal uncertainties from maximum-likelihood fits to the mode
multiplets, analyse and compare the statistical properties of the sets,
and search for possible trends in the splitting measures with n.
---------------------------------------------------------
Title: Recent results from the Birmingham Solar-Oscillations Network
(BiSON).
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; McLeod, C. P.;
Miller, B. A.; New, R.
1996BAAS...28..936C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Recent Results from the Birmingham Solar-Oscillations Network
(BiSON)
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; McLeod, C. P.;
Miller, B. A.; New, R.
1996AAS...188.6904C Altcode: 1996BAAS...28R.936C
The Birmingham Solar-Oscillations Network (BiSON) consists of 6
semi and fully automatic observatories, dedicated to the collection
of low-degree solar oscillations data in integrated sunlight. The
network was established in 1981 with two permanent stations; the
addition of several more sites culminated with the addition of a
sixth in 1992. Here, we give an update on the current status of the
network. In addition, we discuss recent important scientific results
from analysed data, including: low-degree rotational splitting results
covering the period 1981 to 1995; and the measurement of low-frequency
modes, down to ~ 1.2mHz, in a power spectrum generated from 32 months
of recent BiSON data.
---------------------------------------------------------
Title: The Recent Performance of the 6-STATION BISON Network
Authors: Chaplin, W. J.; Elsworth, Y.; Howe, R.; Isaak, G. R.; McLeod,
C. P.; Miller, B. A.; van der Raay, H. B.
1995ESASP.376b.391C Altcode: 1995help.confP.391C; 1995soho....2..391C
No abstract at ADS
---------------------------------------------------------
Title: Some Notes on the Calibration of Doppler Velocity Residuals
Collected by a Resonant Scattering Spectrometer
Authors: Chaplin, W. J.; Elsworth, Y.; Howe, R.; Isaak, G. R.; McLeod,
C. P.; Miller, B. A.; New, R.
1995ESASP.376b.163C Altcode: 1995soho....2..163C; 1995help.confP.163C
Discusses three alternative calibration techniques for Doppler velocity
data collected by a resonant-scattering spectrometer viewing the
unimaged solar disc, that allow long-term, low-frequency information
to be preserved. In the first, the effects of curvature in the solar
reference line are removed by normalizing the observed ratio, R(v) -
the difference between the resonantly-scattered intensities in the blue
and red wings of the source line, normalized by the scattered sum -
by a function that reflects the variation of the total intensity over
the instrument bandwidth. In the second method, a linearized function is
formed from a power series of R(v). A straight forward example of this
technique appears to be subject to systematic, low-frequency errors
of the order of ≡1 to 2 m s<SUP>-1</SUP>. And in the third method,
Doppler velocity data collected over a full observing season could,
in principle, form an internal reference - a look-up curve.
---------------------------------------------------------
Title: The Measurement of L = 4 Modes in Full-Disc BISON Data
Authors: Chaplin, W. J.; Elsworth, Y.; Howe, R.; Isaak, G. R.; McLeod,
C. P.; Miller, B. A.
1995ESASP.376b.387C Altcode: 1995help.confP.387C; 1995soho....2..387C
No abstract at ADS
---------------------------------------------------------
Title: An Investigation of the Correlation Between Unusually Large
Amplitude P-Modes and Solar Activity
Authors: Chaplin, W. J.; Elsworth, Y.; Howe, R.; Isaak, G. R.; McLeod,
C. P.; Miller, B. A.; New, R.
1995ESASP.376b.335C Altcode: 1995help.confP.335C; 1995soho....2..335C
No abstract at ADS
---------------------------------------------------------
Title: A search for small-amplitude, acoustic, p-mode oscillations
on alpha CMi
Authors: Bedford, D. K.; Chaplin, W. J.; Coates, D. W.; Davies, A. R.;
Innis, J. L.; Isaak, G. R.; Speake, C. C.
1995MNRAS.273..367B Altcode:
We have searched for small-amplitude, acoustic, p-mode oscillations
on the F5 IV-V subgiant alpha CMi (HR 2943) in high-quality
Doppler velocity measurements made in 1991, 1992 and 1993 with a
magneto-optical-filter spectrometer. An internal precision of 0.13
m^-2 s^-2 muHz^-1 (1 sigma) has been achieved in one of the 1993
data sets. Conclusive evidence for the presence of a p-mode spectrum
may be established by extracting the mean first-order-half spacing
1/2Deltav. Fourier analysis of the 1991 and 1992 data appears
to indicate the presence of a strong concentration of periodic
power. However, the analysis of substantially higher quality 1993 data
fails to reveal a strong peak; we are therefore forced to conclude
tentatively that we have, at present, failed to find conclusive evidence
for an acoustic oscillation spectrum on alpha CMi.
---------------------------------------------------------
Title: High-precision, longitudinal, disc-averaged magnetic field
measurements of α Canis Minoris and β Leporis.
Authors: Bedford, D. K.; Chaplin, W. J.; Davies, A. R.; Innis, J. L.;
Isaak, G. R.; Speake, C. C.
1995A&A...293..377B Altcode:
High-precision longitudinal, disc-averaged magnetic field measurements
have been made on two late-type stars, α CMi (HR 2943) and β Lep (HR
1829). A magneto-optical filter has been used to measure the degree
of circular polarization in the wings of a line of neutral potassium
(7699 A) formed in the atmosphere of the target star. From 10 nights
of data taken on α CMi on the 1.9-m reflector at the South African
Astronomical Observatory (SAAO) in 1993 January, an upper limit to
any net longitudinal field component present - assuming the field to
be constant over the period of observation - of -0.40+/-0.26G was
established. Similarly, upper limits for β Lep of -4.3+/-6.4G and
-0.7+/-1.6G were established, from 4 and 10 nights of data taken
in 1992 and 1993 January respectively. No significant, periodic,
day-to-day variations were seen in the three time series of data.
---------------------------------------------------------
Title: High-precision velocity observations of Procyon A -
II. Measurement of the orbital motion of Procyon A during 1986-90.
Authors: Innis, J. L.; Isaak, G. R.; Speake, C. C.; Chaplin, W. J.;
Brazier, R. I.; Jones, A. R.
1994MNRAS.271..573I Altcode:
Radial velocity observations of high internal precision have been
obtained, with the Birmingham stellar spectrometer, of the F5 IV-V star
Procyon A. The velocities have been derived using a `null technique' by
determining the time when the topocentric velocity of Procyon A passes
through zero (which occurs in January each year). At this time, the
barycentric velocity of the star is equal to the barycentric velocity
of the instrument, which can be calculated to a high accuracy. Seven
such velocities have been determined from five observing runs during
the years 1986 to 1990 inclusive. The internal precision and external
errors (e.g. our zero-point) cannot be uniquely determined from so
few points but the former appears to be in the range 10 to 40 m s-
. We have compared our data with the orbit of Procyon recently derived
by Irwin et al. The mean annual acceleration of Procyon A over the two
years 1988 to 1990, according to the orbit of Irwin et al., is 133 m
s- yr . Our measured value is 122 m s1 yr , with an error of the order
oft 10 m s- , in reasonable agreement with the value obtained by Irwin
et al. A detailed comparison will be possible when several more years
of data have been obtained. Key words: techniques: radial velocities -
binaries: spectroscopic - stars: individual: Procyon.
---------------------------------------------------------
Title: The longitudinal magnetic field of Procyon.
Authors: Bedford, D. K.; Chaplin, W. J.; Innis, J. L.; Isaak, G. R.;
McLeod, C. P.; Speake, C. C.
1994MNRAS.269..639B Altcode:
An upper limit of 4.3 G (3 u) on the longitudinal magnetic field, and
its variation, of the bright star Procyon is placed by the extended
measurement of the circular polarization in the blue and red wings
of the 770-nm absorption line of neutral potassium. Key words: line:
profiles - polarization - stars: individual: Procyon - stars: magnetic
fields.
---------------------------------------------------------
Title: A high-precision determination of the radial velocity of the
G5 II giant beta Lep.
Authors: Bedford, D. K.; Chaplin, W. J.; Davies, A. R.; Innis, J. L.;
Isaak, G. R.; Speake, C. C.
1994MNRAS.269..435B Altcode:
We apply a null technique to measure to a high accuracy the
barycentric radial velocity of the G5 II giant P Lep (HR 1829). We use a
magneto-optical filter as a spectroscopic bridge to determine the time
at which the geocentric velocity of the star passes through zero. From
data taken on the 1.9-m reflector at the South African Astronomical
Observatory (SAAO) in 1992 and 1993 January, the barycentric radial
velocity of P Lep is calculated to be -13.6+0.2 and -13.576+0.040 km
s ' respectively. Key words: techniques: radial velocities - stars:
individual: P Lep - stars: oscillations.
---------------------------------------------------------
Title: High-precision velocity and magnetic measurements of bright
stars with a magneto-optical filter
Authors: Chaplin, William James Bill
1994PhDT.......304C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Metal epoxy-coated mirrors for stellar seismology
Authors: Bedford, David K.; Chaplin, W. J.; Isaak, G. R.
1993SPIE.1931...96B Altcode:
A 0.9 m diameter f/1.8 paraboloidal mirror of moderate quality
(approximately 2 arcmin) has been produced by spinning an epoxy- coated
spherical substrate. This mirror has been used to build a prototype
flux collector for stellar seismology. The objective is to produce 2
m mirrors for this application.
---------------------------------------------------------
Title: High Precision Velocity Measurements of the Star Procyon -
a Possible Stellar Signal
Authors: Bedford, D. K.; Chaplin, W. J.; Davies, A. R.; Innis, J. L.;
Isaak, G. R.; Speake, C. C.
1993ASPC...42..383B Altcode: 1993gong.conf..383B
No abstract at ADS
