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Author name code: palle
ADS astronomy entries on 2022-09-14
author:"Palle, Pere"
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Title: Magnetic activities on two single-lined RS Canum Venaticorum
binaries IM Pegasi and σ Geminorum
Authors: Cao, Dongtao; Gu, Shenghong; Grundahl, F.; Pallé, P. L.
2022MNRAS.514.4190C Altcode: 2022MNRAS.tmp.1527C
We present the study on continuous high-resolution spectroscopic
observations of two long-period single-lined RS Canum Venaticorum
(RS CVn) binary stars IM Pegasi (IM Peg) and σ Geminorum (σ
Gem), obtained with the Hertzsprung SONG telescope during the
2015-2016 season. Chromospheric activity indicators H<SUB>α</SUB>,
$\rm{Na\,\,{\small I}}$ D<SUB>1</SUB>, D<SUB>2</SUB> doublet,
$\rm{He\,\,{\small I}}$ D<SUB>3</SUB>, and H<SUB>β</SUB> lines
have been analysed by using the spectral subtraction technique. The
expected chromospheric emission features in the H<SUB>α</SUB>,
$\rm{Na\,\,{\small I}}$ D<SUB>1</SUB>, D<SUB>2</SUB> doublet, and
H<SUB>β</SUB> lines confirm that both of two stars are very active
systems. In the spectra, the $\rm{He\,\,{\small I}}$ D<SUB>3</SUB>
line had been always detected in absorption feature. Although the
behaviour of chromospheric activity indicators is very similar for both
stars, the activity level of IM Peg is much stronger than that of σ
Gem. Moreover, the equivalent width variations of the H<SUB>α</SUB>,
$\rm{He\,\,{\small I}}$ D<SUB>3</SUB>, and H<SUB>β</SUB> line
subtractions correlate well and show different behaviour among different
orbital cycles, which indicates the presence and evolution of activity
longitudes over the surface of two stars. Furthermore, the subtracted
H<SUB>α</SUB> line profile is usually asymmetric. The red-shifted
excess absorption features could be interpreted as a strong down-flow
of cool absorbing material, while the blue-shifted emission component is
probably caused by up-flow of hot materials through microflare events.
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Title: Parameters of the eclipsing binary α Draconis observed by
TESS and SONG
Authors: Hey, Daniel R.; Kochoska, Angela; Monier, Richard;
Kochukhov, Oleg; Johnston, Cole; Bedding, Timothy R.; Murphy, Simon
J.; Abdul-Masih, Michael; Southworth, John; Andersen, Mads Fredslund;
Grundahl, Frank; Pallé, Pere L.
2022MNRAS.511.2648H Altcode: 2022MNRAS.tmp..117H
We present an analysis of the eclipsing single-lined spectroscopic
binary system α Dra based on photometry from the Transiting Exoplanet
Survey Satellite (TESS) mission and newly acquired spectroscopic
measurements. Recently discovered to have eclipses in the TESS data,
at a magnitude of V = 3.7, α Dra is now one of the brightest detached
eclipsing binary (EB) systems known. We obtain the parameters of this
system by simultaneously fitting the TESS light curve in conjunction
with radial velocities (RVs) acquired from the SONG spectrograph. We
determine the fractional radii (R/a) for the primary and secondary
components of the system to be 0.0479 $\, \pm \,$ 0.0003 and 0.0226
$\, \pm \,$ 0.0005, respectively. We constrain the temperature, mass,
and luminosity (log(L/L<SUB>⊙</SUB>)) of the primary to be $9975\,
\pm \, 125$ K, $3.7\, \pm \, 0.1$ M<SUB>⊙</SUB>, and $2.49\, \pm \,
0.02$, respectively, using isochrone fitting. Although the secondary
is too faint to appear in the spectra, the obtained mass function and
observed inclination yields a secondary minimum mass of $M_2=2.5\,
\pm \, 0.1$ M<SUB>⊙</SUB>, which suggests that it is an A2V type
star. We were unable to obtain RVs of the secondary, and are only
able to see a weak highly rotationally broadened absorption line,
indicating that the secondary is rapidly rotating (vsin i ~ 200 km
s<SUP>-1</SUP>). We also perform an abundance analysis of the primary
star for 21 chemical elements. We find a complex abundance pattern,
with a few elements having mild underabundances while the majority have
solar abundances. We make available the PYTHON code used in this paper
to facilitate future modelling of EBs. https://github.com/danhey/adra
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Title: VizieR Online Data Catalog: Radial velocity and transit
photometry of TOI-1431 (Addison+, 2021)
Authors: Addison, B. C.; Knudstrup, E.; Wong, I.; Hebrard, G.; Dorval,
P.; Snellen, I.; Albrecht, S.; Bello-Arufe, A.; Almenara, J. -M.;
Boisse, I.; Bonfils, X.; Dalal, S.; Demangeon, O. D. S.; Hoyer, S.;
Kiefer, F.; Santos, N. C.; Nowak, G.; Luque, R.; Stangret, M.; Palle,
E.; Tronsgaard, R.; Antoci, V.; Buchhave, L. A.; Gunther, M. N.;
Daylan, T.; Murgas, F.; Parviainen, H.; Esparza-Borges, E.; Crouzet,
N.; Narita, N.; Fukui, A.; Kawauchi, K.; Watanabe, N.; Rabus, M.;
Johnson, M. C.; Otten, G. P. P. L.; Talens, G. J.; Cabot, S. H. C.;
Fischer, D. A.; Grundahl, F.; Fredslund Andersen, M.; Jessen-Hansen,
J.; Palle, P.; Shporer, A.; Ciardi, D. R.; Clark, J. T.; Wittenmyer,
R. A.; Wright, D. J.; Horner, J.; Collins, K. A.; Jensen, E. L. N.;
Kielkopf, J. F.; Schwarz, R. P.; Srdoc, G.; Yilmaz, M.; Senavci,
H. V.; Diamond, B.; Harbeck, D.; Komacek, T. D.; Smith, J. C.; Wang,
S.; Eastman, J. D.; Stassun, K. G.; Latham, D. W.; Vanderspek, R.;
Seager, S.; Winn, J. N.; Jenkins, J. M.; Louie, D. R.; Bouma, L. G.;
Twicken, J. D.; Levine, A. M.; McLean, B.
2022yCat..51620292A Altcode:
The star TOI-1431 was observed in Sectors 15 (on Camera 2 and CCD chip
number 4) and 16 (on Camera 2 and CCD chip number 3) by Transiting
Exoplanet Survey Satellite (TESS) in 2min cadence mode nearly
continuously between 2019 August 15 and 2019 October 7. <P />One full
transit of TOI-1431b was observed on 2019 December 24-25 with the
CDK14 telescope at Howard Community College. The observations were
taken using alternating 10s exposures in the Sloan g'an d z filters,
starting at 23:02 UT on December 24 at an airmass of 1.2 and finishing
at 02:56 UT on December 25 at an airmass of 2.4. Two full transits of
TOI-1431b were observed with MuSCAT2, one on 2020 May 16 and a second
one on 2020 May 24, using simultaneous multicolor photometry in g',r',
i' and z bands. A full transit of TOI-1431b was observed with the
0.8m Prof. Dr. Berahitdin Albayrak Telescope (T80) at the AUKR on
2020 June 16 in the Sloan z band. We used the 0.3m telescope at the
Kotizarovci Observatory near Viskovo, Croatia, to observe a full transit
of TOI-1431b on 2020 August 8. On 2020 September 20, we observed a full
transit of TOI-1431b from the 0.6m ULMT at Mt Lemmon using the Sloan z'
filter. A full transit of TOI-1431b was observed on 2020 October 14
from the LCOGT 1.0m network node at McDonald Observatory near Fort
Davis, Texas (LCO-McD), in PANSTARRS Y band. <P />High-resolution
spectroscopic observations of TOI-1431 were obtained using the robotic
Stellar Observations Network Group (SONG) 1m Hertzsprung telescope
at the Teide Observatory in Tenerife. (R=90000 between 4400 and
6900Å). TOI-1431 was observed with the fiber-fed SOPHIE HR echelle
spectrograph on the 1.93m telescope at the Haute-Provence Observatory
between 2019 December 18 and 2020 January 12. (R=75000 at 5500Å). We
acquired 52 spectra of TOI-1431 using the Fibre-fed Echelle Spectrograph
(FIES) at the 2.56m Nordic Optical Telescope (NOT) of Roque de los
Muchachos Observatory (La Palma, Spain). (R=67000 at 3760-8220Å). We
triggered observations of TOI-1431 on the Network of Robotic Echelle
Spectrographs (NRES) operated by the LCOGT. (R=53000 between 380 and
860nm). We observed TOI-1431 with the Extreme Precision Spectrometer
(EXPRES), which was recently commissioned at the 4.3m Lowell Discovery
Telescope. (R~137500 between 380 and 780nm). <P />(4 data files).
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Title: HiRISE - High-Resolution Imaging and Spectroscopy Explorer
- Ultrahigh resolution, interferometric and external occulting
coronagraphic science
Authors: Erdélyi, Robertus; Damé, Luc; Fludra, Andrzej; Mathioudakis,
Mihalis; Amari, T.; Belucz, B.; Berrilli, F.; Bogachev, S.; Bolsée,
D.; Bothmer, V.; Brun, S.; Dewitte, S.; de Wit, T. Dudok; Faurobert,
M.; Gizon, L.; Gyenge, N.; Korsós, M. B.; Labrosse, N.; Matthews,
S.; Meftah, M.; Morgan, H.; Pallé, P.; Rochus, P.; Rozanov, E.;
Schmieder, B.; Tsinganos, K.; Verwichte, E.; Zharkov, S.; Zuccarello,
F.; Wimmer-Schweingruber, R.
2022ExA...tmp...21E Altcode:
Recent solar physics missions have shown the definite role of waves and
magnetic fields deep in the inner corona, at the chromosphere-corona
interface, where dramatic and physically dominant changes occur. HiRISE
(High Resolution Imaging and Spectroscopy Explorer), the ambitious new
generation ultra-high resolution, interferometric, and coronagraphic,
solar physics mission, proposed in response to the ESA Voyage 2050
Call, would address these issues and provide the best-ever and most
complete solar observatory, capable of ultra-high spatial, spectral,
and temporal resolution observations of the solar atmosphere, from the
photosphere to the corona, and of new insights of the solar interior
from the core to the photosphere. HiRISE, at the L1 Lagrangian
point, would provide meter class FUV imaging and spectro-imaging,
EUV and XUV imaging and spectroscopy, magnetic fields measurements,
and ambitious and comprehensive coronagraphy by a remote external
occulter (two satellites formation flying 375 m apart, with a
coronagraph on a chaser satellite). This major and state-of-the-art
payload would allow us to characterize temperatures, densities, and
velocities in the solar upper chromosphere, transition zone, and inner
corona with, in particular, 2D very high resolution multi-spectral
imaging-spectroscopy, and, direct coronal magnetic field measurement,
thus providing a unique set of tools to understand the structure and
onset of coronal heating. HiRISE's objectives are natural complements
to the Parker Solar Probe and Solar Orbiter-type missions. We present
the science case for HiRISE which will address: i) the fine structure
of the chromosphere-corona interface by 2D spectroscopy in FUV at
very high resolution; ii) coronal heating roots in the inner corona by
ambitious externally-occulted coronagraphy; iii) resolved and global
helioseismology thanks to continuity and stability of observing at the
L1 Lagrange point; and iv) solar variability and space climate with,
in addition, a global comprehensive view of UV variability.
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Title: No swan song for Sun-as-a-star helioseismology: Performances
of the Solar-SONG prototype for individual mode characterisation
Authors: Breton, S. N.; Pallé, P. L.; García, R. A.; Fredslund
Andersen, M.; Grundahl, F.; Christensen-Dalsgaard, J.; Kjeldsen, H.;
Mathur, S.
2022A&A...658A..27B Altcode: 2021arXiv211012698B
The GOLF instrument on board SoHO has been in operation for almost 25
years, but the ageing of the instrument has now strongly affected its
performance, especially in the low-frequency pressure-mode (p-mode)
region. At the end of the SoHO mission, the ground-based network
BiSON will remain the only facility able to perform Sun-integrated
helioseismic observations. Therefore, we want to assess the helioseismic
performances of an échelle spectrograph such as SONG. The high
precision of such an instrument and the quality of the data acquired
for asteroseismic purposes call for an evaluation of the instrument's
ability to perform global radial-velocity measurements of the solar
disk. Data acquired during the Solar-SONG 2018 observation campaign
at the Teide Observatory are used to study mid- and low-frequency
p modes. A Solar-SONG time series of 30 days in duration is reduced
with a combination of the traditional IDL iSONG pipeline and a new
Python pipeline described in this paper. A mode fitting method built
around a Bayesian approach is then performed on the Solar-SONG and
contemporaneous GOLF, BiSON, and HMI data. For this contemporaneous time
series, Solar-SONG is able to characterise p modes at a lower frequency
than BiSON or GOLF (1750 μHz versus 1946 and 2157 μHz, respectively),
while for HMI it is possible to characterise a mode at 1686 μHz. The
decrease in GOLF sensitivity is then evaluated through the evolution
of its low-frequency p-mode characterisation abilities over the years:
a set of 30-day-long GOLF time series, considered at the same period
of the year from 1996 to 2017, is analysed. We show that it is more
difficult to accurately characterise p modes in the range 1680 to 2160
μHz when considering the most recent time series. By comparing the
global power level of different frequency regions, we also observe that
the Solar-SONG noise level in the 1000 to 1500 μHz region is lower
than for any GOLF subseries considered in this work. While the global
p-mode power-level ratio is larger for GOLF during the first years
of the mission, this ratio decreases over the years and is bested by
Solar-SONG for every time series after 2000. All these observations
strongly suggest that efforts should be made towards deploying more
Solar-SONG nodes in order to acquire longer time series with better
duty cycles.
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Title: Analysing Kepler stellar surface rotation and activity
with ROOSTER
Authors: Breton, S. N.; Santos, A. R. G.; Mathur, S.; García, R. A.;
Bugnet, L.; Pallé, P. L.
2021sf2a.conf..363B Altcode:
It is crucial for our knowledge of stellar evolution to be able to
efficiently determine stellar surface rotation periods in large stellar
samples. Random forest (RF) learning abilities are exploited to automate
the extraction of rotation periods in Kepler light curves. We train
three different classifiers: one to detect if rotational modulation is
present in the light curve; one to select the rotation period among
estimates provided by ACF and wavelet analysis methods; and finally
one to flag classical pulsators or close binary candidates that can
bias our rotation-period determination. We test our machine learning
pipeline, ROOSTER, on the Kepler K and M dwarf sample using the most
up-to-date reference catalog. We show that we are able to detect
rotational modulations with an accuracy of 94.2% and to retrieve final
rotation periods with an accuracy of 95.3%. This value is raised to
99.5% after visually inspecting 25.2% of the stars. Over the two main
analysis steps, the pipeline yields a global accuracy of 92.1% before
visual checks, 96.9% after. The method is then applied to analyse the
F and G stars observed by Kepler. The methodology presented here can
be adapted to extract surface rotation periods for stars observed by
other missions, like K2, TESS, and PLATO.
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Title: TOI-1431b/MASCARA-5b: A Highly Irradiated Ultrahot Jupiter
Orbiting One of the Hottest and Brightest Known Exoplanet Host Stars
Authors: Addison, Brett C.; Knudstrup, Emil; Wong, Ian; Hébrard,
Guillaume; Dorval, Patrick; Snellen, Ignas; Albrecht, Simon;
Bello-Arufe, Aaron; Almenara, Jose-Manuel; Boisse, Isabelle; Bonfils,
Xavier; Dalal, Shweta; Demangeon, Olivier D. S.; Hoyer, Sergio; Kiefer,
Flavien; Santos, N. C.; Nowak, Grzegorz; Luque, Rafael; Stangret,
Monika; Palle, Enric; Tronsgaard, René; Antoci, Victoria; Buchhave,
Lars A.; Günther, Maximilian N.; Daylan, Tansu; Murgas, Felipe;
Parviainen, Hannu; Esparza-Borges, Emma; Crouzet, Nicolas; Narita,
Norio; Fukui, Akihiko; Kawauchi, Kiyoe; Watanabe, Noriharu; Rabus,
Markus; Johnson, Marshall C.; Otten, Gilles P. P. L.; Jan Talens,
Geert; Cabot, Samuel H. C.; Fischer, Debra A.; Grundahl, Frank;
Fredslund Andersen, Mads; Jessen-Hansen, Jens; Pallé, Pere; Shporer,
Avi; Ciardi, David R.; Clark, Jake T.; Wittenmyer, Robert A.; Wright,
Duncan J.; Horner, Jonathan; Collins, Karen A.; Jensen, Eric L. N.;
Kielkopf, John F.; Schwarz, Richard P.; Srdoc, Gregor; Yilmaz, Mesut;
Senavci, Hakan Volkan; Diamond, Brendan; Harbeck, Daniel; Komacek,
Thaddeus D.; Smith, Jeffrey C.; Wang, Songhu; Eastman, Jason D.;
Stassun, Keivan G.; Latham, David W.; Vanderspek, Roland; Seager,
Sara; Winn, Joshua N.; Jenkins, Jon M.; Louie, Dana R.; Bouma, Luke
G.; Twicken, Joseph D.; Levine, Alan M.; McLean, Brian
2021AJ....162..292A Altcode: 2021arXiv210412078A
We present the discovery of a highly irradiated and moderately inflated
ultrahot Jupiter, TOI-1431b/MASCARA-5 b (HD 201033b), first detected
by NASA's Transiting Exoplanet Survey Satellite mission (TESS) and
the Multi-site All-Sky Camera (MASCARA). The signal was established to
be of planetary origin through radial velocity measurements obtained
using SONG, SOPHIE, FIES, NRES, and EXPRES, which show a reflex motion
of K = 294.1 ± 1.1 m s<SUP>-1</SUP>. A joint analysis of the TESS and
ground-based photometry and radial velocity measurements reveals that
TOI-1431b has a mass of M <SUB>p</SUB> = 3.12 ± 0.18 M <SUB>J</SUB>
(990 ± 60 M <SUB>⊕</SUB>), an inflated radius of R <SUB>p</SUB>
= 1.49 ± 0.05 R <SUB>J</SUB> (16.7 ± 0.6 R <SUB>⊕</SUB>), and
an orbital period of P = 2.650237 ± 0.000003 days. Analysis of the
spectral energy distribution of the host star reveals that the planet
orbits a bright (V = 8.049 mag) and young ( ${0.29}_{-0.19}^{+0.32}$
Gyr) Am type star with ${T}_{\mathrm{eff}}={7690}_{-250}^{+400}$
K, resulting in a highly irradiated planet with an incident flux of
$\langle F\rangle ={7.24}_{-0.64}^{+0.68}\times $ 10<SUP>9</SUP> erg
s<SUP>-1</SUP> cm<SUP>-2</SUP> ( ${5300}_{-470}^{+500}\,{S}_{\oplus
}$ ) and an equilibrium temperature of T <SUB>eq</SUB> = 2370 ± 70
K. TESS photometry also reveals a secondary eclipse with a depth
of ${127}_{-5}^{+4}$ ppm as well as the full phase curve of the
planet's thermal emission in the red-optical. This has allowed us to
measure the dayside and nightside temperature of its atmosphere as T
<SUB>day</SUB> = 3004 ± 64 K and T <SUB>night</SUB> = 2583 ± 63 K,
the second hottest measured nightside temperature. The planet's low
day/night temperature contrast (~420 K) suggests very efficient heat
transport between the dayside and nightside hemispheres. Given the host
star brightness and estimated secondary eclipse depth of ~1000 ppm in
the K band, the secondary eclipse is potentially detectable at near-IR
wavelengths with ground-based facilities, and the planet is ideal for
intensive atmospheric characterization through transmission and emission
spectroscopy from space missions such as the James Webb Space Telescope
and the Atmospheric Remote-sensing Infrared Exoplanet Large-survey.
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Title: ROOSTER, a machine learning tool to determine stellar surface
rotation periods in Kepler data
Authors: Breton, S. N.; Santos, A. R. G.; Mathur, S.; García, R. A.;
Pallé, P. L.; Bugnet, L.
2021plat.confE..27B Altcode:
The Kepler and, to a lesser extent, the CoRoT missions opened
the era of large-scale photometric stellar surveys with space
instruments. Corotating dark spots and bright faculae on the stellar
surface lead to brightness variations and therefore those long-term
photometric surveys provide ideal datasets to measure stellar surface
rotation periods and build stellar rotation catalogs. Such catalogs
can then be used to constrain gyrochronology models or to study the
interplay between rotation and magnetic activity. Taking the best
possible advantage of those large-scale surveys, the main challenge
that we face today is finding efficient methods to analyse the large
amount of data. It has been shown that a combination of methods
(auto-correlation function, time-frequency analysis) applied on light
curves with different high-pass filtering provide reliable rotation
estimates. However, the results yielded by those methods require a
significant amount of visual inspection. <P />In the work presented
here, random forest learning abilities are exploited to automate the
extraction of rotation periods and magnetic activity index in Kepler
light curves and to reduce the number of required visual inspections
in the dataset. We train three different classifiers: one to detect
if rotation modulations are present in the light curve, one to flag
classical pulsators or close binary candidates that can bias our
rotation-period determination, and finally one classifier to provide the
final rotation period. We test our machine learning pipeline, ROOSTER
(Breton et al. 2021), on the Kepler K and M dwarf sample using the
reference catalog of Santos et al (2019). We show that we are able to
detect rotation modulations with an accuracy of 94.2% and to retrieve
final rotation periods with an accuracy of 95.3%. This value is raised
to 99.5% after visually inspecting 25.2% of the stars. Over the two
main analysis steps, the pipeline yields a global accuracy of 92.1%
before visual checks, 96.9% after. The method is then applied to
analyse the F and G Kepler sample (Santos et al. 2021). This allowed
us to derive the largest catalog of surface rotation periods for the
Kepler targets with more than 55,000 entries. The work we performed
used only time series from the Kepler mission, but the methodology
presented here could be adapted to extract surface rotation periods
for stars observed by other missions, like K2, TESS, or PLATO.
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Title: Precise radial velocities of giant stars. XV. Mysterious nearly
periodic radial velocity variations in the eccentric binary ε Cygni
Authors: Heeren, Paul; Reffert, Sabine; Trifonov, Trifon; Wong, Ka
Ho; Lee, Man Hoi; Lillo-Box, Jorge; Quirrenbach, Andreas; Arentoft,
Torben; Albrecht, Simon; Grundahl, Frank; Andersen, Mads Fredslund;
Antoci, Victoria; Pallé, Pere L.
2021A&A...647A.160H Altcode: 2021arXiv210201999H
Context. Using the Hamilton Échelle Spectrograph at Lick Observatory,
we have obtained precise radial velocities (RVs) of a sample of 373
G- and K-giant stars over more than 12 yr, leading to the discovery
of several single and multiple planetary systems. The RVs of the
long-period (~53 yr) spectroscopic binary ε Cyg (HIP 102488) are found
to exhibit additional regular variations with a much shorter period
(~291 days). <BR /> Aims: We intend to improve the orbital solution
of the ε Cyg system and attempt to identify the cause of the nearly
periodic shorter period variations, which might be due to an additional
substellar companion. <BR /> Methods: We used precise RV measurements
of the K-giant star ε Cyg from Lick Observatory, in combination with
a large set of RVs collected more recently with the SONG telescope,
as well as archival data sets. We fit Keplerian and fully dynamical
N-body models to the RVs in order to explore the properties of a
previously known spectroscopic stellar companion and to investigate
whether there is an additional planetary companion in the system. To
search for long-term stable regions in the parameter space around the
orbit of this putative planet, we ran a stability analysis using an
N-body code. Furthermore, we explored the possibility of co-orbital
bodies to the planet with a demodulation technique. We tested the
hypothesis of ε Cyg being a hierarchical stellar triple by using
a modified version of the N-body code. Alternative causes for the
observed RV variations, such as stellar spots and oscillations, were
examined by analyzing photometric data of the system and by comparing
its properties to known variable stars with long secondary periods and
heartbeat stars from the literature. <BR /> Results: Our Keplerian
model characterizes the orbit of the spectroscopic binary to higher
precision than achieved previously, resulting in a semi-major axis of
a = 15.8 AU, an eccentricity of e = 0.93, and a minimum mass of the
secondary of msini = 0.265 M<SUB>⊙</SUB>. Additional short-period
RV variations closely resemble the signal of a Jupiter-mass planet
orbiting the evolved primary component with a period of 291 d,
but the period and amplitude of the putative orbit change strongly
over time. Furthermore, in our stability analysis of the system,
no stable orbits could be found in a large region around the best
fit. Both of these findings deem a planetary cause of the RV variations
unlikely. Most of the investigated alternative scenarios also fail
to explain the observed variability convincingly. Due to its very
eccentric binary orbit, it seems possible, however, that ε Cyg could
be an extreme example of a heartbeat system. <P />RV data (Tables
A.1 and A.2) are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">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/647/A160">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/647/A160</A>
<P />Based on observations collected at the Lick Observatory,
University of California. <P />Based on observations collected with
the Hertzsprung SONG telescope at the Spanish Observatorio del Teide,
Tenerife. <P />Based on data collected by the BRITE Constellation
satellite mission, designed, built, launched, operated, and supported
by the Austrian Research Promotion Agency (FFG), the University of
Vienna, the Technical University of Graz, the University of Innsbruck,
the Canadian Space Agency (CSA), the University of Toronto Institute
for Aerospace Studies (UTIAS), the Foundation for Polish Science &
Technology (FNiTP MNiSW), and National Science Centre (NCN).
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Title: ROOSTER: a machine-learning analysis tool for Kepler stellar
rotation periods
Authors: Breton, S. N.; Santos, A. R. G.; Bugnet, L.; Mathur, S.;
García, R. A.; Pallé, P. L.
2021A&A...647A.125B Altcode: 2021arXiv210110152B
In order to understand stellar evolution, it is crucial to efficiently
determine stellar surface rotation periods. Indeed, while they are of
great importance in stellar models, angular momentum transport processes
inside stars are still poorly understood today. Surface rotation,
which is linked to the age of the star, is one of the constraints
needed to improve the way those processes are modelled. Statistics of
the surface rotation periods for a large sample of stars of different
spectral types are thus necessary. An efficient tool to automatically
determine reliable rotation periods is needed when dealing with large
samples of stellar photometric datasets. The objective of this work is
to develop such a tool. For this purpose, machine learning classifiers
constitute relevant bases to build our new methodology. Random
forest learning abilities are exploited to automate the extraction
of rotation periods in Kepler light curves. Rotation periods and
complementary parameters are obtained via three different methods:
a wavelet analysis, the autocorrelation function of the light curve,
and the composite spectrum. We trained three different classifiers:
one to detect if rotational modulations are present in the light curve,
one to flag close binary or classical pulsators candidates that can
bias our rotation period determination, and finally one classifier
to provide the final rotation period. We tested our machine learning
pipeline on 23 431 stars of the Kepler K and M dwarf reference rotation
catalogue for which 60% of the stars have been visually inspected. For
the sample of 21 707 stars where all the input parameters are provided
to the algorithm, 94.2% of them are correctly classified (as rotating
or not). Among the stars that have a rotation period in the reference
catalogue, the machine learning provides a period that agrees within
10% of the reference value for 95.3% of the stars. Moreover, the
yield of correct rotation periods is raised to 99.5% after visually
inspecting 25.2% of the stars. Over the two main analysis steps,
rotation classification and period selection, the pipeline yields a
global agreement with the reference values of 92.1% and 96.9% before and
after visual inspection. Random forest classifiers are efficient tools
to determine reliable rotation periods in large samples of stars. The
methodology presented here could be easily adapted to extract surface
rotation periods for stars with different spectral types or observed
by other instruments such as K2, TESS or by PLATO in the near future.
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Title: Observing the changing surface structures of the active K
giant σ Geminorum with SONG
Authors: Korhonen, H.; Roettenbacher, R. M.; Gu, S.; Grundahl, F.;
Andersen, M. F.; Henry, G. W.; Jessen-Hansen, J.; Antoci, V.; Pallé,
P. L.
2021A&A...646A...6K Altcode: 2020arXiv201215177K
<BR /> Aims: We aim to study the spot evolution and differential
rotation in the magnetically active cool K-type giant star σ Gem
from broadband photometry and continuous spectroscopic observations
that span 150 nights. <BR /> Methods: We use high-resolution,
high signal-to-noise ratio spectra obtained with the Hertzsprung
SONG telescope to reconstruct surface (photospheric) temperature
maps with Doppler imaging techniques. The 303 observations span
150 nights and allow for a detailed analysis of the spot evolution
and surface differential rotation. The Doppler imaging results are
compared to simultaneous broadband photometry from the Tennessee State
University T3 0.4 m Automated Photometric Telescope. The activity from
the stellar chromosphere, which is higher in the stellar atmosphere,
is also studied using SONG observations of Balmer Hα line profiles
and correlated with the photospheric activity. <BR /> Results:
The temperature maps obtained during eight consecutive stellar
rotations show mainly high-latitude or polar spots, with the main
spot concentrations above latitude 45°. The spots concentrate
around phase 0.25 near the beginning of our observations and
around phase 0.75 towards the end. The photometric observations
confirm a small jump in spot phases that occurred in February
2016. The cross-correlation of the temperature maps reveals rather
strong solar-like differential rotation, giving a relative surface
differential rotation coefficient of α = 0.10 ± 0.02. There is a weak
correlation between the locations of starspots and enhanced emission
in the chromosphere at some epochs. <P />Tables 1 and 2, photometry,
and spectra are 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/646/A6">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/646/A6</A>
<P />Based on observations made with the Hertzsprung SONG telescope on
the Spanish Observatorio del Teide on the island of Tenerife and the
Tennessee State University T3 0.4-m Automated Photometric Telescope
at Fairborn Observatory in Arizona.
---------------------------------------------------------
Title: Classical Astronomy as an educational resource in a Faculty
of Education
Authors: Eff-Darwich, Antonio; Stengler, Erik; El-Qady, Gad; Rahona,
Usama; Shaker, Ashraf; Ibrahim, Makram; Núñez, Manuel; Medina,
Victor; Yanes, Adán; Pallé, Pere Ll.; Martínez-Frías, Jesús
2021IAUS..367..411E Altcode:
History, Maths and Astronomy are all mixed up in an innovative
educational project that is being carried out in the Faculty of
Education of the Universidad de La Laguna, in Spain. Students learn
how to teach (to primary school students) about the shape of the Earth,
the distances to the Moon, the Sun and other planets, collecting their
own data with simple instrumentation and, most important, to connect
ideas and different disciplines. The structure and contents of this
project are presented, as well as examples of the activities that are
carried out.
---------------------------------------------------------
Title: VizieR Online Data Catalog: sigma Gem BV photometry (Korhonen+,
2021)
Authors: Korhonen, H.; Roettenbacher, R. M.; Gu, S.; Grundahl, F.;
Andersen, M. F.; Henry, G. W.; Jessen-Hansen, J.; Antoci, V.; Palle,
P. L.
2021yCat..36460006K Altcode:
Photometric and spectroscopic observing logs of sigma Geminorum. <P
/>The photometric observations were obtained between 27 October
2015 and 5 May 2016 with the Tennessee State University T3 0.4m
Automated Photometric Telescope at Fairborn Observatory in Arizona. The
observations consist of Johnson B and V differential magnitudes, which
are defined as the variable star (sigma Gem ) minus the comparison
star (HD 60318). The typical standard deviation of the observations is
0.00935mag in B and 0.00840mag in V. <P />The spectroscopic observations
were obtained with the Hertzsprung SONG telescope between 4 November
2015 and 1 April 2016. We used the spectrograph with slit #5, giving a
resolving power of 77000 and covering wavelengths from 4400Å to 6900Å
in 51 orders, with some small gaps redwards of 5300Å. Each individual
spectrum of sigma Gem had an exposure time of 180 seconds. All
the spectra are freely available in the SONG Data Archive, SODA:
https://soda.phys.au.dk/ <P />(2 data files).
---------------------------------------------------------
Title: VizieR Online Data Catalog: Radial velocity data of epsilon
Cyg (Heeren+, 2021)
Authors: Heeren, P.; Reffert, S.; Trifonov, T.; Wong, K. H.; Lee,
M. H.; Lillo-Box, J.; Quirrenbach, A.; Arentoft, T.; Albrecht, S.;
Grundahl, F.; Andersen, M. F.; Antoci, V.; Palle, P. L.
2021yCat..36470160H Altcode:
Precise radial velocities of the giant star epsilon Cyg are presented. A
total of 109 measurements of this star were taken with the Hamilton
spectrograph at the Lick Observatory, from June 2000 until November
2011. Additionally, we present 228 radial velocities acquired with
the Hertzsprung SONG telescope on Tenerife, from April 2015 until
December 2018. Part of these data are nightly averages from higher
cadence asteroseismic measurements. All observations were acquired
and reduced using the iodine cell approach. <P />(2 data files).
---------------------------------------------------------
Title: Properties of the Hyades, the eclipsing binary HD 27130,
and the oscillating red giant ɛ Tauri
Authors: Brogaard, K.; Pakštienė, E.; Grundahl, F.; Mikolaitis, Š.;
Tautvaišienė, G.; Slumstrup, D.; Talens, G. J. J.; VandenBerg, D. A.;
Miglio, A.; Arentoft, T.; Kjeldsen, H.; Janulis, R.; Drazdauskas,
A.; Marchini, A.; Minkevičiūtė, R.; Stonkutė, E.; Bagdonas, V.;
Fredslund Andersen, M.; Jessen-Hansen, J.; Pallé, P. L.; Dorval,
P.; Snellen, I. A. G.; Otten, G. P. P. L.; White, T. R.
2021A&A...645A..25B Altcode: 2020arXiv201102274B
Context. The derivation of accurate and precise masses and radii is
possible for eclipsing binary stars, allowing for insights into their
evolution. When residing in star clusters, they provide measurements
of even greater precision, along with additional information on their
properties. Asteroseismic investigations of solar-like oscillations
offers similar possibilities for single stars. <BR /> Aims: We wish to
improve the previously established properties of the Hyades eclipsing
binary HD 27130 and re-assess the asteroseismic properties of the
giant star ɛ Tau. The physical properties of these members of the
Hyades can be used to constrain the helium content and age of the
cluster. <BR /> Methods: New multi-colour light curves were combined
with multi-epoch radial velocities to yield masses and radii of HD
27130. Measurements of T<SUB>eff</SUB> were derived from spectroscopy
and photometry, and verified using the Gaia parallax. We estimated
the cluster age from re-evaluated asteroseismic properties of ɛ Tau
while using HD 27130 to constrain the helium content. <BR /> Results:
The masses, radii, and T<SUB>eff</SUB> of HD 27130 were found to be M =
1.0245 ± 0.0024 M<SUB>⊙</SUB>, R = 0.9226 ± 0.015 R<SUB>⊙</SUB>,
T<SUB>eff</SUB> = 5650 ± 50 K for the primary, and M = 0.7426 ± 0.0016
M<SUB>⊙</SUB>, R = 0.7388 ± 0.026 R<SUB>⊙</SUB>, T<SUB>eff</SUB>
= 4300 ± 100 K for the secondary component. Our re-evaluation of ɛ
Tau suggests that the previous literature estimates are trustworthy
and that the HIPPARCOS parallax is more reliable than the Gaia DR2
parallax. <BR /> Conclusions: The helium content of HD 27130 and,
thus, of the Hyades is found to be Y = 0.27 but with a significant
model dependency. Correlations with the adopted metallicity result
in a robust helium enrichment law, with ΔY/ΔZ close to 1.2 We
estimate the age of the Hyades to be 0.9 ± 0.1 (stat) ±0.1 (sys)
Gyr, which is in slight tension with recent age estimates based on the
cluster white dwarfs. The precision of the age estimate can be much
improved via asteroseismic investigations of the other Hyades giants
and by future improvements to the Gaia parallax for bright stars. <P
/>Tables 8-16 are 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/A25">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/645/A25</A>
---------------------------------------------------------
Title: VizieR Online Data Catalog: HD27130 photometric light curves
(Brogaard+, 2021)
Authors: Brogaard, K.; Pakstiene, E.; Grundahl, F.; Mikolaitis, S.;
Tautvaisiene, G.; Slumstrup, D.; Talens, G. J. J.; Vandenberg, D. A.;
Miglio, A.; Arentoft, T.; Kjeldsen, H.; Janulis, R.; Drazdauskas, A.;
Marchini, A.; Minkeviciute, R.; Stonkute, E.; Bagdonas, V.; Fredslund
Andersen, M.; Jessen-Hansen, J.; Palle, P. L.; Dorval, P.; Snellen,
I. A. G.; Otten, G. P. P. L.; White, T. R.
2020yCat..36450025B Altcode:
We obtained photometric light curves (LCs) for HD 27130 in Johnson B,
V, and Cousins I bandpasses at the Moletai Astronomical Observatory of
Vilnius University (MAO, Lithuania) and the Astronomical Observatory
of the University of Siena (AO SU, Italy). We also obtained the
photometric light curve of HD 27130 from the MASCARA survey. These
observed light curves are found in Tables 8-13. <P />For Modelling
purposes, we combined and manipulated the light curves to remove
out-of-eclipse variations, and to only include observations in or very
close to eclipse. These corrected light curves are normalised to 0
mag and available in Tables 14-16. <P />(9 data files).
---------------------------------------------------------
Title: Asteroseismic masses of four evolved planet-hosting stars
using SONG and TESS: resolving the retired A-star mass controversy
Authors: Malla, Sai Prathyusha; Stello, Dennis; Huber, Daniel; Montet,
Benjamin T.; Bedding, Timothy R.; Fredslund Andersen, Mads; Grundahl,
Frank; Jessen-Hansen, Jens; Hey, Daniel R.; Palle, Pere L.; Deng,
Licai; Zhang, Chunguang; Chen, Xiaodian; Lloyd, James; Antoci, Victoria
2020MNRAS.496.5423M Altcode: 2020arXiv200607649P; 2020MNRAS.tmp.1930M
The study of planet occurrence as a function of stellar mass is
important for a better understanding of planet formation. Estimating
stellar mass, especially in the red giant regime, is difficult. In
particular, stellar masses of a sample of evolved planet-hosting stars
based on spectroscopy and grid-based modelling have been put to question
over the past decade with claims they were overestimated. Although
efforts have been made in the past to reconcile this dispute using
asteroseismology, results were inconclusive. In an attempt to resolve
this controversy, we study four more evolved planet-hosting stars in
this paper using asteroseismology, and we revisit previous results
to make an informed study of the whole ensemble in a self-consistent
way. For the four new stars, we measure their masses by locating
their characteristic oscillation frequency, ν<SUB>max</SUB>, from
their radial velocity time series observed by SONG. For two stars,
we are also able to measure the large frequency separation, Δν,
helped by extended SONG single-site and dual-site observations and new
Transiting Exoplanet Survey Satellite observations. We establish the
robustness of the ν<SUB>max</SUB>-only-based results by determining
the stellar mass from Δν, and from both Δν and ν<SUB>max</SUB>. We
then compare the seismic masses of the full ensemble of 16 stars with
the spectroscopic masses from three different literature sources. We
find an offset between the seismic and spectroscopic mass scales that is
mass dependent, suggesting that the previously claimed overestimation
of spectroscopic masses only affects stars more massive than about
1.6 M<SUB>⊙</SUB>.
---------------------------------------------------------
Title: VizieR Online Data Catalog: 4 planet-hosting stars
asteroseismic masses (Malla+, 2020)
Authors: Malla, S. P.; Stello, D.; Huber, D.; Montet, B. T.; Bedding,
T. R.; Andersen, M. F.; Grundahl, F.; Jessen-Hansen, J.; Hey, D. R.;
Palle, P. L.; Deng, L.; Zhang, C.; Chen, X.; Lloyd, J.; Antoci, V.
2020yCat..74965423M Altcode:
We tabulate the observing parameters for the four targets in our
sample, observed using the Stellar Observations Network Group (SONG)
telescope nodes at Tenerife and Delingha. We also tabulate the observed
and derived parameters for each of our targets. The updated results
from Stello et al. (2017MNRAS.472.4110S) are also provided here. We
also provide the approximate frequencies of individual modes extracted
from the echelle diagrams of gamma Cep and 24 Sex. Lastly, we provide
the stellar masses for the evolved planet-hosting stars used for the
ensemble study in this work across various literature sources <P />(5
data files).
---------------------------------------------------------
Title: Doppler Imaging and Differential Rotation of σ<SUP>2</SUP>
Coronae Borealis Using SONG
Authors: Xiang, Yue; Gu, Shenghong; Cameron, A. Collier; Barnes, J. R.;
Christensen-Dalsgaard, J.; Grundahl, F.; Antoci, V.; Andersen, M. F.;
Pallé, P. L.
2020ApJ...893..164X Altcode: 2020arXiv200502592X
We present new Doppler images of both components of the double-lined
binary σ<SUP>2</SUP> CrB, based on the high-resolution spectroscopic
data collected during 11 nights in 2015 March-April. The observed
spectra form two independent data sets with sufficient phase
coverage. We apply the least-squares deconvolution to all observed
spectra to obtain high signal-to-noise mean profiles, from which
we derive the Doppler images of both components of σ<SUP>2</SUP>
CrB simultaneously. The surfaces of both F9 and G0 components are
dominated by pronounced polar spots. The F9 component exhibits a weak
spot at latitude 30° and its mid-to-low latitudes are relatively
featureless. The G0 star shows an extended spot structure at latitude
30°, and its surface spot coverage is larger than that of the F9
star, which suggests a higher level of magnetic activity. With the
cross-correlation method, we derive a solar-like surface differential
rotation on the G0 star of σ<SUP>2</SUP> CrB for the first time, and
the surface shear rate is ΔΩ = 0.180 ± 0.004 rad days<SUP>-1</SUP>
and α = ΔΩ/Ω<SUB>eq</SUB> = 0.032 ± 0.001. We do not obtain a clear
surface shear law for the F9 star due to the lack of mid-to-low latitude
features, but detect a systematic longitude shift of high-latitude
spots, which indicates a slower rotation with respect to the corotating
frame.
---------------------------------------------------------
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: A Comparison of Global Helioseismic-Instrument Performances:
Solar-SONG, GOLF and VIRGO
Authors: Breton, S. N.; García, R. A.; Pallé, P. L.; Mathur, S.;
Hill, F.; Jain, K.; Jiménez, A.; Tripathy, S. C.; Grundahl, F.;
Fredslund-Andersen, M.; Santos, A. R. G.
2020ASSP...57..327B Altcode:
The SONG spectrograph has recently demonstrated its ability to perform
solar radial velocity measurement during the first test run of the
Solar-SONG initiative. A preliminary assessment of its performance
is carried out here by comparing the results of Solar-SONG during
the summer 2018 test run, with GOLF and VIRGO/SPM taken as reference
instruments.
---------------------------------------------------------
Title: The BRITE-SONG of Aldebaran - stellar music in three voices
Authors: Beck, P. G.; Kuschnig, R.; Houdek, G.; Kallinger, T.;
Weiss, W. W.; Palle, P. L.; Grundahl, F.; Hatzes, A.; Parviainen, H.;
Allende Prieto, C.; Deeg, H. J.; Jiménez, A.; Mathur, S.; Garcia,
R. A.; White, T. R.; Bedding, T. R.; Grossmann, D. H.; Janisch, S.;
Zaqarashvili, T.; Hanslmeier, A.; Zwintz, K.
2020svos.conf...75B Altcode: 2020arXiv200104912B
Solar-like oscillations in red-giant stars are now commonly detected
in thousands of stars with space telescopes such as Kepler. Parallel
radial-velocity and photometric measurements would help us understand
better the physics governing the amplitudes of solar-like oscillators,
but most stars targetted for space photometry are too faint for
light-demanding ground-based spectroscopy. The BRITE-Constellation
provides a unique opportunity of monitoring in two colours the flux
variations of bright luminous red giants. Those stars are also bright
enough to be monitored with high-resolution spectrographs on small
telescopes, such as the SONG Network. This contribution provided a
first overview of our comprehensive, multi-year campaign to use both
BRITE and SONG to characterize Aldebaran (one of the brightest red
giants in the sky) seismically. Because luminous red giants can be
seen at large distances, when characterized well they will serve as
valuable benchmark stars for Galactic archeology.
---------------------------------------------------------
Title: Sun-like Oscillations in the Population II giant HD 122563
Authors: Creevey, O.; Thévénin, F.; Grundahl, F.; Corsaro, E.;
Andersen, M. F.; Antoci, V.; Bigot, L.; Collet, R.; Pallé, P. L.;
Pichon, B.; Salabert, D.
2019sf2a.conf..425C Altcode: 2020arXiv200513883C
We have been monitoring the metal-poor Population II giant, HD 122563,
for radial velocity variations since 2016 using the SONG telescope on
Tenerife. We have detected the global seismic quantity \numax\ which
provides information related to the stellar parameters. By combining
these data with complementary data, we derive a new precise surface
gravity, radius and distance to the star. Our results are corroborated
by using the parallax from Gaia DR2. We present these results and some
of their implications.
---------------------------------------------------------
Title: Determining surface rotation periods of solar-like stars
observed by the Kepler mission using machine learning techniques
Authors: Breton, S. N.; Bugnet, L.; Santos, A. R. G.; Le Saux, A.;
Mathur, S.; Pallé, P. L.; García, R. A.
2019sf2a.conf..421B Altcode: 2019arXiv190609609B
For a solar-like star, the surface rotation evolves with time, allowing
in principle to estimate the age of a star from its surface rotation
period. Here we are interested in measuring surface rotation periods
of solar-like stars observed by the NASA mission Kepler. Different
methods have been developed to track rotation signals in Kepler
photometric light curves: time-frequency analysis based on wavelet
techniques, autocorrelation and composite spectrum. We use the learning
abilities of random forest classifiers to take decisions during two
crucial steps of the analysis. First, given some input parameters, we
discriminate the considered Kepler targets between rotating MS stars,
non-rotating MS stars, red giants, binaries and pulsators. We then use
a second classifier only on the MS rotating targets to decide the best
data-analysis treatment.
---------------------------------------------------------
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: Acoustic oscillations and dynamo action in the G8 sub-giant
EK Eridani
Authors: Bonanno, A.; Corsaro, E.; Del Sordo, F.; Pallé, P. L.;
Stello, D.; Hon, M.
2019A&A...628A.106B Altcode: 2019arXiv190701338B
We present further evidence of acoustic oscillations in the slowly
rotating overactive G8 sub-giant EK Eri. This star was observed with
the 1m Hertzsprung SONG telescope at the Observatorio del Teide for two
different runs of 8 and 13 nights, respectively, that were separated
by about a year. We determined a significant excess of power around
ν<SUB>max</SUB> = 253 ± 3 μHz in the first observing run and were
able to determine a large separation, Δν = 16.43 ± 0.22 μHz. No
significant excess of power was instead detected in a subsequent SONG
observing season, as also supported by our analysis of the simultaneous
TESS photometric observations. We propose a new amplitude-luminosity
relation in order to account for the missing power in the power
spectrum. Based on the evolutionary stage of this object, we argue
that a standard α<SUP>2</SUP>Ω dynamo cannot be excluded as the
possible origin for the observed magnetic field. <P />A table of the
radial velocities 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/628/A106">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/628/A106</A>
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: VizieR Online Data Catalog: Radial velocity time series of
EK Eridani (Bonanno+, 2019)
Authors: Bonanno, A.; Corsaro, E.; Del Sordo, F.; Palle, P. L.;
Stello, D.; Hon, M.
2019yCat..36280106B Altcode:
Radial velocity time series of EK Eridani are presented. These data
were obtained using the Hertzsprung telescope, a node of the Stellar
Observations Network Group (SONG) network, located at the Observatorio
del Teide on Tenerife, Spain. <P />(2 data files).
---------------------------------------------------------
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: Looking for the sun within the educational core standards:
the Spanish case
Authors: Eff-Darwich, Antonio; Pallé, Pere Ll.; Rosenberg, Alfred
2019EPJWC.20001005E Altcode:
Although Astronomy is engaging and motivating for both precollege
and college students, it is often difficult to fit it in within
the formal educational core standards. In this work, we present an
analysis of the Spanish educational curricula for primary school to
look for opportunities to adapt the tools and the science behind the
most famous discoveries about the sun. In this way, we attempt to
find opportunities to explain concepts such as: energy, electricity,
magnetism, dynamics, astronomy, data analysis, algebra, arithmetics,
geometry, language and communication skills, music, cooperative working,
computing, the use of new technologies and problem-based learning.
---------------------------------------------------------
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: First detection of oscillations in the Halo giant HD 122563:
Validation of seismic scaling relations and new parameters
Authors: Creevey, O.; Grundahl, F.; Thévenin, F.; Corsaro, E.; Pallé,
P. L.; Salabert, D.; Pichon, B.; Collet, R.; Bigot, L.; Antoci, V.;
Andersen, M. F.
2019A&A...625A..33C Altcode: 2019arXiv190202657C
<BR /> Aims: The nearby metal-poor giant HD 122563 is an important
astrophysical laboratory in which to test stellar atmospheric and
interior physics. It is also a benchmark star for which to calibrate
methods to apply to large scale surveys. Recently it has been remeasured
using various methodologies given the new high precision instruments at
our disposal. However, inconsistencies in the observations and models
have been found. <BR /> Methods: In order to better characterise this
star using complementary techniques we have been measuring its radial
velocities since 2016 using the Hertzsprung telescope (SONG network
node) in order to detect oscillations. <BR /> Results: In this work
we report the first detections of sun-like oscillations in this star,
and to our knowledge, a detection in the most metal-poor giant to
date. We applied the classical seismic scaling relation to derive
a new surface gravity for HD 122563 of log g<SUB>ν</SUB> = 1.39 ±
0.01. Reasonable constraints on the mass imposed by its PopII giant
classification then yields a radius of 30.8 ± 1.0 ℛ<SUB>⊙</SUB>. By
coupling this new radius with recent interferometric measurements
we infer a distance to the star of 306 ± 9 pc. This result places
it further away than was previously thought and is inconsistent
with the HIPPARCOS parallax. Independent data from the Gaia mission
corroborate the distance hypothesis (d<SUB>GDR2</SUB> = 290 ± 5 pc),
and thus the updated fundamental parameters. <BR /> Conclusions: We
confirm the validity of the classical seismic scaling relation for
surface gravity in metal-poor and evolved star regimes. The remaining
discrepancy of 0.04 dex between log g<SUB>GDR2</SUB> (= 1.43 ± 0.03)
reduces to 0.02 dex by applying corrections to the scaling relations
based on the mean molecular weight and adiabatic exponent. The new
constraints on the Hertzsprung-Russell diagram (L<SUB>⋆ν</SUB> =
381 ± 26 ℒ<SUB>⊙</SUB>) significantly reduce the disagreement
between the stellar parameters and evolution models, however, a
discrepancy of the order of 150 K still exists. Fine-tuned stellar
evolution calculations show that this discrepancy can be reconciled by
changing the mixing-length parameter by an amount (-0.35) that is in
agreement with predictions from recent 3D simulations and empirical
results. Asteroseismic measurements are continuing, and analysis of
the full frequency data complemented by a distance estimate promises to
bring important constraints on our understanding of this star and of the
accurate calibration of the seismic scaling relations in this regime. <P
/>SONG radial velocities are 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/625/A33">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/625/A33</A>
---------------------------------------------------------
Title: VizieR Online Data Catalog: Radial velocity time series of
HD 122563 (Creevey+, 2019)
Authors: Creevey, O.; Grundahl, F.; Thevenin, F.; Corsaro, E.; Palle,
P. L.; Salabert, D.; Pichon, B.; Collet, R.; Bigot, L.; Antoci, V.;
Andersen, M. F.
2019yCat..36250033C Altcode:
Radial velocity time series of HD 122563 are presented. These data
were obtained using the Hertzsprung telescope, a node of the Stellar
Observations Network Group (SONG) network, located at the Observatorio
del Teide on Tenerife, Spain. <P />(1 data file).
---------------------------------------------------------
Title: Conducting the SONG: The Robotic Nature and Efficiency of a
Fully Automated Telescope
Authors: Fredslund Andersen, M.; Handberg, R.; Weiss, E.; Frandsen,
S.; Simón-Díaz, S.; Grundahl, F.; Pallé, P.
2019PASP..131d5003F Altcode: 2019arXiv190107560F; 2019PASP..131d5003A
We present a description of “the Conductor,” an automated software
package that handles all observations at the first Stellar Observations
Network Group (SONG) node telescope at the Teide Observatory on the
island of Tenerife. The idea was to provide a complete description
on the automated procedures for target selection and execution of
observations and to demonstrate how the SONG robotic telescope is being
operated. The Conductor is a software package developed in Python and
running on a server in Aarhus that makes use of a large set of database
tables through which it communicates with the SONG nodes. Based on
a number of selection criteria the Conductor is able to identify the
optimum target to be observed at any given moment, taking into account
local weather conditions and technical constraints. The Conductor has
made it possible for the Hertzsprung SONG telescope to become a highly
sophisticated and efficient robotic telescopic facility without human
interaction. It can handle everything from principal investigators
submitting their proposed targets with specific settings, to the data
being available for download after the observations has been carried
out. At present, and thanks to the availability of the Conductor,
the first node of the SONG project can be considered a world leading
robotic telescope with respect to needed human interactions, efficiency,
and flexibility in observing strategy.
---------------------------------------------------------
Title: Oscillations in the Sun with SONG: Setting the scale for
asteroseismic investigations
Authors: Fredslund Andersen, M.; Pallé, P.; Jessen-Hansen, J.; Wang,
K.; Grundahl, F.; Bedding, T. R.; Roca Cortes, T.; Yu, J.; Mathur,
S.; Gacia, R. A.; Arentoft, T.; Régulo, C.; Tronsgaard, R.; Kjeldsen,
H.; Christensen-Dalsgaard, J.
2019A&A...623L...9F Altcode: 2019arXiv190210717F
Context. We present the first high-cadence multiwavelength
radial-velocity observations of the Sun-as-a-star, carried out during
57 consecutive days using the stellar échelle spectrograph at the
Hertzsprung SONG Telescope operating at the Teide Observatory. <BR />
Aims: Our aim was to produce a high-quality data set and reference
values for the global helioseismic parameters ν<SUB>max, ⊙</SUB> and
Δν<SUB>⊙</SUB> of the solar p-modes using the SONG instrument. The
obtained data set or the inferred values should then be used when
the scaling relations are applied to other stars showing solar-like
oscillations observed with SONG or similar instruments. <BR /> Methods:
We used different approaches to analyse the power spectrum of the time
series to determine ν<SUB>max, ⊙</SUB>: simple Gaussian fitting and
heavy smoothing of the power spectrum. We determined Δν<SUB>⊙</SUB>
using the method of autocorrelation of the power spectrum. The amplitude
per radial mode was determined using the method described in Kjeldsen
et al. (2008, ApJ, 682, 1370). <BR /> Results: We found the following
values for the solar oscillations using the SONG spectrograph:
ν<SUB>max, ⊙</SUB> = 3141 ± 12 μHz, Δν<SUB>⊙</SUB> = 134.98
± 0.04 μHz, and an average amplitude of the strongest radial modes of
16.6 ± 0.4 cm s<SUP>-1</SUP>. These values are consistent with previous
measurements with other techniques. <P />Based on observations made at
the Hertzsprung SONG telescope operated at 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: Asteroseismology of the Hyades red giant and planet host
ɛ Tauri
Authors: Arentoft, T.; Grundahl, F.; White, T. R.; Slumstrup, D.;
Handberg, R.; Lund, M. N.; Brogaard, K.; Andersen, M. F.; Silva
Aguirre, V.; Zhang, C.; Chen, X.; Yan, Z.; Pope, B. J. S.; Huber, D.;
Kjeldsen, H.; Christensen-Dalsgaard, J.; Jessen-Hansen, J.; Antoci,
V.; Frandsen, S.; Bedding, T. R.; Pallé, P. L.; Garcia, R. A.; Deng,
L.; Hon, M.; Stello, D.; Jørgensen, U. G.
2019A&A...622A.190A Altcode: 2019arXiv190106187A
Context. Asteroseismic analysis of solar-like stars allows us to
determine physical parameters such as stellar mass, with a higher
precision compared to most other methods. Even in a well-studied cluster
such as the Hyades, the masses of the red giant stars are not well
known, and previous mass estimates are based on model calculations
(isochrones). The four known red giants in the Hyades are assumed
to be clump (core-helium-burning) stars based on their positions
in colour-magnitude diagrams, however asteroseismology offers an
opportunity to test this assumption. <BR /> Aims: Using asteroseismic
techniques combined with other methods, we aim to derive physical
parameters and the evolutionary stage for the planet hosting star ɛ
Tau, which is one of the four red giants located in the Hyades. <BR />
Methods: We analysed time-series data from both ground and space to
perform the asteroseismic analysis. By combining high signal-to-noise
radial-velocity data from the ground-based SONG network with continuous
space-based data from the revised Kepler mission K2, we derive and
characterize 27 individual oscillation modes for ɛ Tau, along with
global oscillation parameters such as the large frequency separation
Δν and the ratio between the amplitude of the oscillations measured
in radial velocity and intensity as a function of frequency. The
latter has been measured previously for only two stars, the Sun and
Procyon. Combining the seismic analysis with interferometric and
spectroscopic measurements, we derive physical parameters for ɛ
Tau, and discuss its evolutionary status. <BR /> Results: Along with
other physical parameters, we derive an asteroseismic mass for ɛ
Tau of M = 2.458 ± 0.073 M<SUB>⊙</SUB>, which is slightly lower
than previous estimates, and which leads to a revised minimum mass
of the planetary companion. Noting that the SONG and K2 data are
non-simultaneous, we estimate the amplitude ratio between intensity
and radial velocity to be 42.2 ± 2.3 ppm m<SUP>-1</SUP> s, which
is higher than expected from scaling relations. <P />Time-series
data are 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/622/A190">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/622/A190</A>Based
on observations made with the SONG telescopes operated on the
Spanish Observatorio del Teide (Tenerife) and at the Chinese Delingha
Observatory (Qinghai) by the Aarhus and Copenhagen Universities, by the
Instituto de Astrofísica de Canarias and by the National Astronomical
Observatories of China, and with NASA's K2 mission.
---------------------------------------------------------
Title: VizieR Online Data Catalog: eps Tau intensity and RV
time-series data (Arentoft+, 2019)
Authors: Arentoft, T.; Grundahl, F.; White, T. R.; Slumstrup, D.;
Handberg, R.; Lund, M. N.; Brogaard, K.; Andersen, M. F.; Silva
Aguirre, V.; Zhang, C.; Chen, X.; Yan, Z.; Pope, B. J. S.; Huber, D.;
Kjeldsen, H.; Christensen-Dalsgaard, J.; Jessen-Hansen, J.; Antoci,
V.; Frandsen, S.; Bedding, T. R.; Palle, P. L.; Garcia, R. A.; Deng,
L.; Hon, M.; Stello, D.; Jorgensen, U. G.
2019yCat..36220190A Altcode:
Time-series data for epsilon Tau; photometric time-series data from
the revised Kepler mission K2 and radial-velocity measurements from
SONG (Stellar Observations Network Group). The time series have been
filtered in order to remove variations and instrumental effects at
low frequencies. <P />(2 data files).
---------------------------------------------------------
Title: The mass and age of the first SONG target: the red giant 46 LMi
Authors: Frandsen, S.; Fredslund Andersen, M.; Brogaard, K.; Jiang,
C.; Arentoft, T.; Grundahl, F.; Kjeldsen, H.; Christensen-Dalsgaard,
J.; Weiss, E.; Pallé, P.; Antoci, V.; Kjærgaard, P.; Sørensen,
A. N.; Skottfelt, J.; Jørgensen, U. G.
2018A&A...613A..53F Altcode: 2018arXiv180602095F
Context. The Stellar Observation Network Group (SONG) is an initiative
to build a worldwide network of 1m telescopes with high-precision
radial-velocity spectrographs. Here we analyse the first radial-velocity
time series of a red-giant star measured by the SONG telescope at
Tenerife. The asteroseismic results demonstrate a major increase
in the achievable precision of the parameters for red-giant stars
obtainable from ground-based observations. Reliable tests of the
validity of these results are needed, however, before the accuracy of
the parameters can be trusted. <BR /> Aims: We analyse the first SONG
time series for the star 46 LMi, which has a precise parallax and an
angular diameter measured from interferometry, and therefore a good
determination of the stellar radius. We use asteroseismic scaling
relations to obtain an accurate mass, and modelling to determine the
age. <BR /> Methods: A 55-day time series of high-resolution, high S/N
spectra were obtained with the first SONG telescope. We derive the
asteroseismic parameters by analysing the power spectrum. To give a
best guess on the large separation of modes in the power spectrum, we
have applied a new method which uses the scaling of Kepler red-giant
stars to 46 LMi. <BR /> Results: Several methods have been applied:
classical estimates, seismic methods using the observed time series,
and model calculations to derive the fundamental parameters of 46
LMi. Parameters determined using the different methods are consistent
within the uncertainties. We find the following values for the mass M
(scaling), radius R (classical), age (modelling), and surface gravity
(combining mass and radius): M = 1.09 ± 0.04M<SUB>⊙</SUB>,
R = 7.95 ± 0.11R<SUB>⊙</SUB> age t = 8.2 ± 1.9 Gy, and logg =
2.674 ± 0.013. <BR /> Conclusions: The exciting possibilities for
ground-based asteroseismology of solar-like oscillations with a fully
robotic network have been illustrated with the results obtained from
just a single site of the SONG network. The window function is still
a severe problem which will be solved when there are more nodes in
the network. <P />Based on observations made with the Hertzsprung
SONG telescope operated at 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: Low-frequency photospheric and wind variability in the early-B
supergiant HD 2905
Authors: Simón-Díaz, S.; Aerts, C.; Urbaneja, M. A.; Camacho, I.;
Antoci, V.; Fredslund Andersen, M.; Grundahl, F.; Pallé, P. L.
2018A&A...612A..40S Altcode: 2017arXiv171108994S
Context. Despite important advances in space asteroseismology during
the last decade, the early phases of evolution of stars with masses
above 15 M<SUB>⊙</SUB> (including the O stars and their evolved
descendants, the B supergiants) have been only vaguely explored
up to now. This is due to the lack of adequate observations for a
proper characterization of the complex spectroscopic and photometric
variability occurring in these stars. Aim. Our goal is to detect,
analyze, and interpret variability in the early-B-type supergiant HD
2905 (κ Cas, B1 Ia) using long-term, ground-based, high-resolution
spectroscopy. <BR /> Methods: We gather a total of 1141 high-resolution
spectra covering some 2900 days with three different high-performance
spectrographs attached to 1-2.6m telescopes at the Canary Islands
observatories. We complement these observations with the hipparcos
light curve, which includes 160 data points obtained during a time
span of 1200 days. We investigate spectroscopic variability of up to
12 diagnostic lines by using the zero and first moments of the line
profiles. We perform a frequency analysis of both the spectroscopic
and photometric dataset using Scargle periodograms. We obtain single
snapshot and time-dependent information about the stellar parameters
and abundances by means of the FASTWIND stellar atmosphere code. <BR
/> Results: HD 2905 is a spectroscopic variable with peak-to-peak
amplitudes in the zero and first moments of the photospheric lines of
up to 15% and 30 km s<SUP>-1</SUP>, respectively. The amplitude of the
line-profile variability is correlated with the line formation depth
in the photosphere and wind. All investigated lines present complex
temporal behavior indicative of multi-periodic variability with
timescales of a few days to several weeks. No short-period (hourly)
variations are detected. The Scargle periodograms of the hipparcos
light curve and the first moment of purely photospheric lines reveal a
low-frequency amplitude excess and a clear dominant frequency at 0.37
d<SUP>-1</SUP>. In the spectroscopy, several additional frequencies are
present in the range 0.1-0.4 d<SUP>-1</SUP>. These may be associated
with heat-driven gravity modes, convectively driven gravity waves, or
sub-surface convective motions. Additional frequencies are detected
below 0.1 d<SUP>-1</SUP>. In the particular case of H<SUB>α</SUB>,
these are produced by rotational modulation of a non-spherically
symmetric stellar wind. <BR /> Conclusions: Combined long-term
uninterrupted space photometry with high-precision spectroscopy is the
best strategy to unravel the complex low-frequency photospheric and
wind variability of B supergiants. Three-dimensional (3D) simulations
of waves and of convective motions in the sub-surface layers can shed
light on a unique interpretation of the variability.
---------------------------------------------------------
Title: Helioseismology: Observations and Space Missions
Authors: Palle, P. L.; Appourchaux, T.; Christensen-Dalsgaard, J.;
Garcia, R. A.
2018arXiv180200674P Altcode:
The great success of Helioseismology resides in the remarkable
progress achieved in the understanding of the structure and dynamics
of the solar interior. This success mainly relies on the ability to
conceive, implement, and operate specific instrumentation with enough
sensitivity to detect and measure small fluctuations (in velocity
and/or intensity) on the solar surface that are well below one meter
per second or a few parts per million. Furthermore the limitation of
the ground observations imposing the day-night cycle (thus a periodic
discontinuity in the observations) was overcome with the deployment of
ground-based networks --properly placed at different longitudes all
over the Earth-- allowing longer and continuous observations of the
Sun and consequently increasing their duty cycles. In this chapter,
we start by a short historical overview of helioseismology. Then we
describe the different techniques used to do helioseismic analyses along
with a description of the main instrumental concepts. We in particular
focus on the instruments that have been operating long enough to study
the solar magnetic activity. Finally, we give a highlight of the main
results obtained with such high-duty cycle observations (>80%)
lasting over the last few decades.
---------------------------------------------------------
Title: Photospheric activity of the Sun with VIRGO and
GOLF. Comparison with standard activity proxies
Authors: Salabert, D.; García, R. A.; Jiménez, A.; Bertello, L.;
Corsaro, E.; Pallé, P. L.
2017A&A...608A..87S Altcode: 2017arXiv170905110S
We study the variability of solar activity using new photospheric
proxies originally developed for the analysis of stellar magnetism
with the CoRoT and Kepler photometric observations. These proxies
were obtained by tracking the temporal modulations in the observations
associated with the spots and magnetic features as the Sun rotates. We
analyzed 21 yr of observations, spanning solar cycles 23 and 24,
collected by the space-based photometric VIRGO and radial velocity
GOLF instruments on board the SoHO satellite. We then calculated
the photospheric activity proxy S<SUB>ph</SUB> is for each of the
three VIRGO photometers and the associated S<SUB>vel</SUB> proxy
from the radial velocity GOLF observations. Comparisons with several
standard solar activity proxies sensitive to different layers of the
Sun demonstrate that these new activity proxies, S<SUB>ph</SUB> and
S<SUB>vel</SUB>, provide a new manner to monitor solar activity. We show
that both the long- and short-term magnetic variabilities respectively
associated with the 11-yr cycle and the quasi-biennial oscillation
are well monitored, and that the magnetic field interaction between
the subsurface, photosphere, and chromosphere of the Sun was modified
between Cycle 24 and Cycle 23. Furthermore, the photometric proxies
show a wavelength dependence of the response function of the solar
photosphere among the three channels of the VIRGO photometers, providing
inputs for the study of the stellar magnetism of Sun-like stars.
---------------------------------------------------------
Title: Asteroseismic masses of retired planet-hosting A-stars
using SONG
Authors: Stello, Dennis; Huber, Daniel; Grundahl, Frank; Lloyd,
James; Ireland, Mike; Casagrande, Luca; Fredslund, Mads; Bedding,
Timothy R.; Palle, Pere L.; Antoci, Victoria; Kjeldsen, Hans;
Christensen-Dalsgaard, Jørgen
2017MNRAS.472.4110S Altcode: 2017arXiv170809613S
To better understand how planets form, it is important to study planet
occurrence rates as a function of stellar mass. However, estimating
masses of field stars is often difficult. Over the past decade, a
controversy has arisen about the inferred occurrence rate of gas-giant
planets around evolved intermediate-mass stars - the so-called 'retired
A-stars'. The high masses of these red-giant planet hosts, derived using
spectroscopic information and stellar evolution models, have been called
into question. Here, we address the controversy by determining the
masses of eight evolved planet-hosting stars using asteroseismology. We
compare the masses with spectroscopic-based masses from the Exoplanet
Orbit Database,which were previously adopted to infer properties of
the exoplanets and their hosts. We find a significant one-sided offset
between the two sets of masses for stars with spectroscopic masses
above roughly 1.6 M<SUB>⊙</SUB>, suggestive of an average 15-20
per cent overestimate of the adopted spectroscopic-based masses. The
only star in our sample well below this mass limit is also the only
one not showing this offset. Finally, we note that the scatter across
literature values of spectroscopic-based masses often exceeds their
formal uncertainties, making it comparable to the offset we report here.
---------------------------------------------------------
Title: Promoting access to and use of seismic data in a large
scientific community. SpaceInn data handling and archiving
Authors: Michel, Eric; Belkacem, Kevin; Samadi, Reza; Assis Peralta,
Raphael de; Renié, Christian; Abed, Mahfoudh; Lin, Guangyuan;
Christensen-Dalsgaard, Jørgen; Houdek, Günter; Handberg, Rasmus;
Gizon, Laurent; Burston, Raymond; Nagashima, Kaori; Pallé, Pere;
Poretti, Ennio; Rainer, Monica; Mistò, Angelo; Panzera, Maria Rosa;
Roth, Markus
2017EPJWC.16001011M Altcode:
The growing amount of seismic data available from space missions
(SOHO, CoRoT, Kepler, SDO,…) but also from ground-based facilities
(GONG, BiSON, ground-based large programmes…), stellar modelling
and numerical simulations, creates new scientific perspectives such as
characterizing stellar populations in our Galaxy or planetary systems
by providing model-independent global properties of stars such as mass,
radius, and surface gravity within several percent accuracy, as well as
constraints on the age. These applications address a broad scientific
community beyond the solar and stellar one and require combining
indices elaborated with data from different databases (e.g. seismic
archives and ground-based spectroscopic surveys). It is thus a basic
requirement to develop a simple and effcient access to these various
data resources and dedicated tools. In the framework of the European
project SpaceInn (FP7), several data sources have been developed or
upgraded. The Seismic Plus Portal has been developed, where synthetic
descriptions of the most relevant existing data sources can be found,
as well as tools allowing to localize existing data for given objects
or period and helping the data query. This project has been developed
within the Virtual Observatory (VO) framework. In this paper, we
give a review of the various facilities and tools developed within
this programme. The SpaceInn project (Exploitation of Space Data for
Innovative Helio- and Asteroseismology) has been initiated by the
European Helio- and Asteroseismology Network (HELAS).
---------------------------------------------------------
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: Kepler sheds new and unprecedented light on the variability
of a blue supergiant: Gravity waves in the O9.5Iab star HD 188209
Authors: Aerts, C.; Símon-Díaz, S.; Bloemen, S.; Debosscher, J.;
Pápics, P. I.; Bryson, S.; Still, M.; Moravveji, E.; Williamson,
M. H.; Grundahl, F.; Fredslund Andersen, M.; Antoci, V.; Pallé,
P. L.; Christensen-Dalsgaard, J.; Rogers, T. M.
2017A&A...602A..32A Altcode: 2017arXiv170301514A
Stellar evolution models are most uncertain for evolved massive
stars. Asteroseismology based on high-precision uninterrupted space
photometry has become a new way to test the outcome of stellar
evolution theory and was recently applied to a multitude of stars,
but not yet to massive evolved supergiants.Our aim is to detect,
analyse and interpret the photospheric and wind variability of the
O9.5 Iab star HD 188209 from Kepler space photometry and long-term
high-resolution spectroscopy. We used Kepler scattered-light photometry
obtained by the nominal mission during 1460 d to deduce the photometric
variability of this O-type supergiant. In addition, we assembled
and analysed high-resolution high signal-to-noise spectroscopy taken
with four spectrographs during some 1800 d to interpret the temporal
spectroscopic variability of the star. The variability of this blue
supergiant derived from the scattered-light space photometry is in full
in agreement with the one found in the ground-based spectroscopy. We
find significant low-frequency variability that is consistently detected
in all spectral lines of HD 188209. The photospheric variability
propagates into the wind, where it has similar frequencies but slightly
higher amplitudes. The morphology of the frequency spectra derived from
the long-term photometry and spectroscopy points towards a spectrum
of travelling waves with frequency values in the range expected for
an evolved O-type star. Convectively-driven internal gravity waves
excited in the stellar interior offer the most plausible explanation
of the detected variability. <P />Based on photometric observations
made with the NASA Kepler satellite and on spectroscopic observations
made with four telescopes: the Nordic Optical Telescope operated by
NOTSA and the Mercator Telescope operated by the Flemish Community,
both at the Observatorio del Roque de los Muchachos (La Palma, Spain)
of the Instituto de Astrofísica de Canarias, the T13 2.0 m Automatic
Spectroscopic Telescope (AST) operated by Tennessee State University at
the Fairborn Observatory, and 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, Spain.
---------------------------------------------------------
Title: Lithium abundance and rotation of seismic solar
analogues. Solar and stellar connection from Kepler and Hermes
observations
Authors: Beck, P. G.; do Nascimento, J. -D., Jr.; Duarte, T.; Salabert,
D.; Tkachenko, A.; Mathis, S.; Mathur, S.; García, R. A.; Castro,
M.; Pallé, P. L.; Egeland, R.; Montes, D.; Creevey, O.; Andersen,
M. F.; Kamath, D.; van Winckel, H.
2017A&A...602A..63B Altcode: 2017arXiv170201152B
Context. Lithium abundance A(Li) and surface rotation are good
diagnostic tools to probe the internal mixing and angular momentum
transfer in stars. <BR /> Aims: We explore the relation between
surface rotation, A(Li), and age in a sample of seismic solar-analogue
stars, and we study their possible binary nature. <BR /> Methods:
We selected a sample of 18 solar-analogue stars observed by the NASA
Kepler satellite for an in-depth analysis. Their seismic properties and
surface rotation rates are well constrained from previous studies. About
53 h of high-resolution spectroscopy were obtained to derive fundamental
parameters from spectroscopy and A(Li). These values were combined and
compared with seismic masses, radii, and ages, as well as with surface
rotation periods measured from Kepler photometry. <BR /> Results:
Based on radial velocities, we identify and confirm a total of six
binary star systems. For each star, a signal-to-noise ratio of 80 ≲
S/N ≲ 210 was typically achieved in the final spectrum around the
lithium line. We report fundamental parameters and A(Li). Using the
surface rotation period derived from Kepler photometry, we obtained a
well-defined relation between A(Li) and rotation. The seismic radius
translates the surface rotation period into surface velocity. With
models constrained by the characterisation of the individual mode
frequencies for single stars, we identify a sequence of three solar
analogues with similar mass ( 1.1 M<SUB>⊙</SUB>) and stellar ages
ranging between 1 to 9 Gyr. Within the realistic estimate of 7% for the
mass uncertainty, we find a good agreement between the measured A(Li)
and the predicted A(Li) evolution from a grid of models calculated with
the Toulouse-Geneva stellar evolution code, which includes rotational
internal mixing, calibrated to reproduce solar chemical properties. We
found a scatter in ages inferred from the global seismic parameters
that is too large when compared with A(Li). <BR /> Conclusions:
We present the Li-abundance for a consistent spectroscopic survey
of solar-analogue stars with a mass of 1.00 ± 0.15 M<SUB>⊙</SUB>
that are characterised through asteroseismology and surface rotation
rates based on Kepler observations. The correlation between A(Li)
and P<SUB>rot</SUB> supports the gyrochronological concept for stars
younger than the Sun and becomes clearer when the confirmed binaries
are excluded. The consensus between measured A(Li) for solar analogues
with model grids, calibrated on the Sun's chemical properties, suggests
that these targets share the same internal physics. In this light,
the solar Li and rotation rate appear to be normal for a star like
the Sun. <P />Based on observations made with the NASA Kepler space
telescope and the Hermes spectrograph mounted on the 1.2 m Mercator
Telescope at the Spanish Observatorio del Roque de los Muchachos of
the Instituto de Astrofísica de Canarias.
---------------------------------------------------------
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: The SONG prototype: Efficiency of a robotic telescope
Authors: Andersen, M. F.; Grundahl, F.; Beck, A. H.; Pallé, P.
2016RMxAC..48...54A Altcode: 2019arXiv190108293A
The Stellar Observations Network Group prototype telescope at the
Teide Observatory has been operating in scientific mode since March
2014. The first year of observations has entirely been carried out
using the high resolution echelle spectrograph. Several asteroseismic
targets were selected for scientific and technical verification. A few
bright subgiants and one red giant were chosen since the oscillations
in these stars have large amplitudes and the periods long enough to
easily be detected. These targets would also be used for evaluation
of the instruments since long term observations of single targets
would reveal potential problems. In this paper the performance of the
first robotic SONG node is described to illustrate the efficiency and
possibilities in having a robotic telescope.
---------------------------------------------------------
Title: Photospheric and chromospheric magnetic activity of seismic
solar analogs. Observational inputs on the solar-stellar connection
from Kepler and Hermes
Authors: Salabert, D.; García, R. A.; Beck, P. G.; Egeland, R.;
Pallé, P. L.; Mathur, S.; Metcalfe, T. S.; do Nascimento, J. -D.,
Jr.; Ceillier, T.; Andersen, M. F.; Triviño Hage, A.
2016A&A...596A..31S Altcode: 2016arXiv160801489S
We identify a set of 18 solar analogs among the seismic sample of
solar-like stars observed by the Kepler satellite rotating between 10
and 40 days. This set is constructed using the asteroseismic stellar
properties derived using either the global oscillation properties
or the individual acoustic frequencies. We measure the magnetic
activity properties of these stars using observations collected by the
photometric Kepler satellite and by the ground-based, high-resolution
Hermes spectrograph mounted on the Mercator telescope. The photospheric
(S<SUB>ph</SUB>) and chromospheric (S index) magnetic activity
levels of these seismic solar analogs are estimated and compared in
relation to the solar activity. We show that the activity of the Sun
is comparable to the activity of the seismic solar analogs, within the
maximum-to-minimum temporal variations of the 11-yr solar activity
cycle 23. In agreement with previous studies, the youngest stars
and fastest rotators in our sample are actually the most active. The
activity of stars older than the Sun seems to not evolve much with
age. Furthermore, the comparison of the photospheric, S<SUB>ph</SUB>,
with the well-established chromospheric, S index, indicates that the
S<SUB>ph</SUB> index can be used to provide a suitable magnetic activity
proxy which can be easily estimated for a large number of stars from
space photometric observations. <P />Based on observations collected
by the NASA Kepler space telescope and the Hermes spectrograph mounted
on the 1.2 m Mercator telescope at the Spanish Observatorio del Roque
de los Muchachos of the Instituto de Astrofísica de Canarias.
---------------------------------------------------------
Title: Probing Seismic Solar Analogues Through Observations With The
NASA Kepler Space Telescope and Hermes High-Resolution Spectrograph
Authors: Beck, P. G.; Salabert, D.; Garcia, R. A.; do Nascimento, J.,
Jr.; Duarte, T. S. S.; Mathis, S.; Regulo, C.; Ballot, J.; Egeland,
R.; Castro, M.; Pérez-Herńandez, F.,; Creevey, O.; Tkachenko, A.;
van Reeth, T.; Bigot, L.; Corsaro, E.; Metcalfe, T.; Mathur, S.; Palle,
P. L.; Allende Prieto, C.; Montes, D.; Johnston, C.; Andersen, M. F.;
van Winckel, H.
2016csss.confE..42B Altcode: 2016arXiv161104329B
Stars similar to the Sun, known as solar analogues, provide an excellent
opportunity to study the preceding and following evolutionary phases of
our host star. The unprecedented quality of photometric data collected
by the Kepler NASA mission allows us to characterise solar-like stars
through asteroseismology and study diagnostics of stellar evolution,
such as variation of magnetic activity, rotation and the surface
lithium abundance. In this project, presented in a series of papers
by Salabert et al (2016ab) and Beck et al. (2016ab), we investigate
the link between stellar activity, rotation, lithium abundance and
oscillations in a group of 18 solar-analogue stars through space
photometry, obtained with the NASA Kepler space telescope and from
currently 50+ hours of ground-based, high-resolution spectroscopy
with the Hermes instrument. In these proceedings, we first discuss the
selection of the stars in the sample, observations and calibrations and
then summarise the main results of the project.<BR /> By investigating
the chromospheric and photospheric activity of the solar analogues in
this sample, it was shown that for a large fraction of these stars the
measured activity levels are compatible to levels of the 11-year solar
activity cycle 23. A clear correlation between the lithium abundance
and surface rotation was found for rotation periods shorter than the
solar value. Comparing the lithium abundance measured in the solar
analogues to evolutionary models with the Toulouse-Geneva Evolutionary
Code (TGEC), we found that the solar models calibrated to the Sun also
correctly describe the set of solar/stellar analogs showing that they
share the same internal mixing physics. Finally, the star KIC3241581
and KIC10644353 are discussed in more detail.
---------------------------------------------------------
Title: The Solar-Stellar Connection: Magnetic Activity Of Seismic
Solar Analogs
Authors: Salabert, David; Garcia, Rafael A.; Beck, Paul G.; Regulo,
C.; Ballot, J.; Creevey, Orlagh L.; Egeland, Ricky; do Nascimento,
Jose-D., Jr.; Perez Hernandez, Fernando; Bigot, Lionel; Mathur,
Savita; Metcalfe, Travis S.; Corsaro, Enrico; Palle, Pere L.
2016csss.confE..30S Altcode: 2016arXiv161000990S
Finding solar-analog stars with fundamental properties as close
as possible to the Sun and studying the characteristics of their
surface magnetic activity is a very promising way to understand
the solar variability and its associated dynamo process. However,
the identification of solar-analog stars depends on the accuracy of
the estimated stellar parameters. Thanks to the photometric CoROT
and Kepler space missions, the addition of asteroseismic data was
proven to provide the most accurate fundamental properties that can
be derived from stellar modeling today. Here, we present our latest
results on the solar-stellar connection by studying 18 solar analogs
that we identified among the Kepler seismic sample (Salabert et al.,
2016a}. We measured their magnetic activity properties using the
observations collected by the Kepler satellite and the ground-based,
high-resolution HERMES spectrograph. The photospheric (Sph) and
chromospheric (S) magnetic activity proxies of these seismic solar
analogs are compared in relation to the solar activity. We show that
the activity of the Sun is comparable to the activity of the seismic
solar analogs, within the maximum-to-minimum temporal variations of the
11-year solar activity cycle. Furthermore, we report on the discovery
of temporal variability in the acoustic frequencies of the young (1
Gyr-old) solar analog KIC10644253 with a modulation of about 1.5 years,
which agrees with the derived photospheric activity Sph (Salabert et
al., 2016b}. It could be the signature of the short-period modulation,
or quasi-biennal oscillation, of its magnetic activity as observed in
the Sun and in the 1-Gyr-old solar analog HD30495. In addition, the
lithium abundance and the chromospheric activity estimated from HERMES
confirms that KIC10644253 is a young and more active star than the Sun.
---------------------------------------------------------
Title: Probing Stellar Dynamics With Space Photometry
Authors: García, Rafael A.; Salabert, D.; Ballot, J.; Beck, P. G.;
Bigot, L.; Corsaro, E.; Creevey, O.; Egeland, R.; Jiménez, A.; Mathur,
S.; Metcalfe, T.; do Nascimento, J.; Pallé, P. L.; Pérez Hernández,
F.; Regulo, C.
2016csss.confE...3G Altcode:
The surface magnetic field has substantial influence on various
stellar properties that can be probed through various techniques. With
the advent of new space-borne facilities such as CoRoT and Kepler,
uninterrupted long high-precision photometry is available for hundred
of thousand of stars. This number will substantially grow through the
forthcoming TESS and PLATO missions. The unique Kepler observations
-covering up to 4 years with a 30-min cadence- allows studying stellar
variability with different origins such as pulsations, convection,
surface rotation, or magnetism at several time scales from hours
to years. We study the photospheric magnetic activity of solar-like
stars by means of the variability induced in the observed signal by
starspots crossing the visible disk. We constructed a solar photometric
magnetic activity proxy, Sph from SPM/VIRGO/SoHO, as if the Sun was a
distant star and we compare it with several solar well-known magnetic
proxies. The results validate this approach. Thus, we compute the
Sph proxy for a set of CoRoT and Kepler solar-like stars for which
pulsations were already detected. After characterizing the rotation and
the magnetic properties of 300 solar-like stars, we use their seismic
properties to characterize 18 solar analogs for which we study their
magnetism. This allows us to put the Sun into context of its siblings.
---------------------------------------------------------
Title: Magnetic variability in the young solar analog KIC
10644253. Observations from the Kepler satellite and the HERMES
spectrograph
Authors: Salabert, D.; Régulo, C.; García, R. A.; Beck, P. G.;
Ballot, J.; Creevey, O. L.; Pérez Hernández, F.; do Nascimento,
J. -D., Jr.; Corsaro, E.; Egeland, R.; Mathur, S.; Metcalfe, T. S.;
Bigot, L.; Ceillier, T.; Pallé, P. L.
2016A&A...589A.118S Altcode: 2016arXiv160300655S
The continuous photometric observations collected by the Kepler
satellite over 4 yr provide a wealth of data with an unequalled
quantity and quality for the study of stellar evolution of more than
200 000 stars. Moreover, the length of the dataset provides a unique
source of information for detecting magnetic activity and associated
temporal variability in the acoustic oscillations. In this regards,
the Kepler mission was awaited with great expectations. The search for
the signature of magnetic activity variability in solar-like pulsations
still remained unfruitful more than 2 yr after the end of the nominal
mission. Here, however, we report the discovery of temporal variability
in the low-degree acoustic frequencies of the young (1 Gyr-old) solar
analog KIC 10644253 with a modulation of about 1.5 yr with significant
temporal variations for the duration of the Kepler observations. The
variations agree with the derived photometric activity. The frequency
shifts extracted for KIC 10644253 are shown to result from the same
physical mechanisms involved in the inner subsurface layers as in the
Sun. In parallel, a detailed spectroscopic analysis of KIC 10644253
is performed based on complementary ground-based, high-resolution
observations collected by the HERMES instrument mounted on the Mercator
telescope. Its lithium abundance and chromospheric activity 𝒮 index
confirm that KIC 10644253 is a young and more active star than the Sun.
---------------------------------------------------------
Title: Long-Term Trends and Gleissberg Cycles in Aurora Borealis
Records (1600 - 2015)
Authors: Vázquez, M.; Vaquero, J. M.; Gallego, M. C.; Roca Cortés,
T.; Pallé, P. L.
2016SoPh..291..613V Altcode: 2016SoPh..tmp...12V
The long-term spatial and temporal variation of aurora borealis events
from 1600 to the present were studied using catalogues and other
records of these phenomena. Geographic and geomagnetic coordinates
were assigned to approximately 45 000 auroral events with more
than 160 000 observations. They were analysed separately for three
large-scale areas: i) Europe and North Africa, ii) North America,
and iii) Asia. Variations in the cumulative numbers of auroral events
with latitude (in both geographic and geomagnetic coordinates) were
used to distinguish between the two main solar sources: coronal mass
ejections and high-speed streams from coronal holes. We find significant
long-term variations in the space-time distribution of auroras. We
mainly identify these with four Gleissberg solar activity cycles whose
overall characteristics we examine. The Asian observations are crucial
in this context, and therefore merit further studies and verifications.
---------------------------------------------------------
Title: Helioseismology: Observations and space missions
Authors: Pallé, P. L.; Appourchaux, T.; Christensen-Dalsgaard, J.;
Garcxía, I. A.
2015exse.book...25P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The two-colour EMCCD instrument for the Danish 1.54 m telescope
and SONG
Authors: Skottfelt, J.; Bramich, D. M.; Hundertmark, M.; Jørgensen,
U. G.; Michaelsen, N.; Kjærgaard, P.; Southworth, J.; Sørensen,
A. N.; Andersen, M. F.; Andersen, M. I.; Christensen-Dalsgaard, J.;
Frandsen, S.; Grundahl, F.; Harpsøe, K. B. W.; Kjeldsen, H.; Pallé,
P. L.
2015A&A...574A..54S Altcode: 2014arXiv1411.7401S
We report on the implemented design of a two-colour instrument based
on electron-multiplying CCD (EMCCD) detectors. This instrument is
currently installed at the Danish 1.54 m telescope at ESO's La Silla
Observatory in Chile, and will be available at the SONG (Stellar
Observations Network Group) 1m telescope node at Tenerife and at other
SONG nodes as well. We present the software system for controlling the
two-colour instrument and calibrating the high frame-rate imaging data
delivered by the EMCCD cameras. An analysis of the performance of the
Two-Colour Instrument at the Danish telescope shows an improvement in
spatial resolution of up to a factor of two when doing shift-and-add
compared with conventional imaging, and the possibility of doing
high-precision photometry of EMCCD data in crowded fields. The Danish
telescope, which was commissioned in 1979, is limited by a triangular
coma at spatial resolutions below 0.5 arcsec, and better results will
thus be achieved at the near diffraction-limited optical system on
the SONG telescopes, where spatial resolutions close to 0.2 arcsec
have been achieved. Regular EMCCD operations have been running at the
Danish telescope for several years and produced a number of scientific
discoveries, including microlensing detected exoplanets, detecting
previously unknown variable stars in dense globular clusters, and
discovering two rings around the small asteroid-like object (10199)
Chariklo. <P />Based on data collected with the Danish 1.54m telescope
at ESO's La Silla Observatory.
---------------------------------------------------------
Title: Hardware and software for a robotic network of telescopes
- SONG
Authors: Andersen, M. F.; Grundahl, F.; Christensen-Dalsgaard, J.;
Frandsen, S.; Jørgensen, U. G.; Kjeldsen, H.; Pallé, P.; Skottfelt,
J.; Sørensen, A. N.; Weiss, E.
2014RMxAC..45...83A Altcode: 2019arXiv190108300A
SONG aims at setting up a network of small 1m telescopes around the
globe to observe stars uninterrupted throughout days, weeks and even
months. This paper describes the fundamental aspects for putting up
such a network and how we will operate each site as part of the full
network. The SONG observatories will be working autonomously and
automatic and can be fully controlled remotely.
---------------------------------------------------------
Title: The Mark-I helioseismic experiment - I. Measurements of the
solar gravitational redshift (1976-2013)
Authors: Roca Cortés, T.; Pallé, P. L.
2014MNRAS.443.1837R Altcode: 2014arXiv1406.5944R
The resonant scattering solar spectrophotometer `Mark-I', designed
and build at the University of Birmingham (UK) and located at the
Observatorio del Teide (Spain), has been continuously in operation
for the past 38 years. During this period of time, it has provided
high-precision measurements of the radial velocity of the Sun as a
star, which has enabled the study of the small velocity fluctuations
produced by the solar oscillations and the characterization of their
spectrum. So far, it has been one of the pioneer experiments in
the field of helioseismology and contributed to the development of
that area. Moreover, because of its high-sensitivity and long-term
instrumental stability, it also provides an accurate determination
(to within a few parts in 10<SUP>3</SUP>) of the absolute daily
velocity offset, which contains the so-called solar gravitational
red-shift. In this paper, results of the analysis of the measurements of
this parameter over the whole period 1976-2013 are presented. The result
of this series of measurements is 600.4 ± 0.8 m s<SUP>-1</SUP> with an
amplitude variation of ±5 m s<SUP>-1</SUP>, which is in anticorrelation
with the phase of the solar activity cycle. The 5 per cent difference
found with respect to the value predicted by the equivalence principle
is probably due to the asymmetry of the solar spectral line used.
---------------------------------------------------------
Title: Impact on asteroseismic analyses of regular gaps in Kepler data
Authors: García, R. A.; Mathur, S.; Pires, S.; Régulo, C.; Bellamy,
B.; Pallé, P. L.; Ballot, J.; Barceló Forteza, S.; Beck, P. G.;
Bedding, T. R.; Ceillier, T.; Roca Cortés, T.; Salabert, D.;
Stello, D.
2014A&A...568A..10G Altcode: 2014arXiv1405.5374G
Context. The NASA Kepler mission has observed more than 190 000
stars in the constellations of Cygnus and Lyra. Around 4 years of
almost continuous ultra high-precision photometry have been obtained
reaching a duty cycle higher than 90% for many of these stars. However,
almost regular gaps due to nominal operations are present in the light
curves on different time scales. <BR /> Aims: In this paper we want to
highlight the impact of those regular gaps in asteroseismic analyses,
and we try to find a method that minimizes their effect on the frequency
domain. <BR /> Methods: To do so, we isolate the two main time scales
of quasi regular gaps in the data. We then interpolate the gaps and
compare the power density spectra of four different stars: two red
giants at different stages of their evolution, a young F-type star,
and a classical pulsator in the instability strip. <BR /> Results:
The spectra obtained after filling the gaps in the selected solar-like
stars show a net reduction in the overall background level, as well
as a change in the background parameters. The inferred convective
properties could change as much as ~200% in the selected example,
introducing a bias in the p-mode frequency of maximum power. When
asteroseismic scaling relations are used, this bias can lead to a
variation in the surface gravity of 0.05 dex. Finally, the oscillation
spectrum in the classical pulsator is cleaner than the original one.
---------------------------------------------------------
Title: Asteroseismology
Authors: Pallé, Pere L.; Esteban, Cesar
2014aste.book.....P Altcode:
Our understanding of stars has grown significantly due to recent
advances in asteroseismology, the stellar analog of helioseismology,
the study of the Sun's acoustic wave oscillations. Using ground-based
and satellite observatories to measure the frequency spectra of
starlight, researchers are able to probe beneath a star's surface and
map its interior structure. This volume provides a wide-ranging and
up-to-date overview of the theoretical, experimental, and analytical
tools for carrying out front-line research in stellar physics using
asteroseismological observations, tools, and inferences. Chapters from
seven eminent scientists in residence at the twenty-second Canary
Islands Winter School of Astrophysics examine the interior of our
Sun relative to data collected from distant stars, how to measure the
fundamental parameters of single field stars, diffusion processes, and
the effects of rotation on stellar structures. The volume also provides
detailed treatments of modeling and computing programs, providing
astronomers and graduate students a practical, methods-based guide.
---------------------------------------------------------
Title: Stellar Observations Network Group: The prototype is nearly
ready
Authors: Grundahl, Frank; Christensen-Dalsgaard, Jørgen; Pallé,
Pere L.; Andersen, Mads F.; Frandsen, Søren; Harpsøe, Kennet;
Jørgensen, Uffe Gråe; Kjeldsen, Hans; Rasmussen, Per K.; Skottfelt,
Jesper; Sørensen, Anton N.; Hage, Andrea Triviño
2014IAUS..301...69G Altcode:
The prototype telescope and instruments for the Stellar Observations
Network Group (SONG) are nearing completion at the Observatorio del
Teide on Tenerife. In this contribution we describe the current status
(autumn 2013) of the telescope and its instrumentation. Preliminary
performance characteristics are presented for the high-resolution
spectrograph based on daytime observations of the Sun and a 4 hour
test series obtained for the sub-giant β Aquilae.
---------------------------------------------------------
Title: The History of the g-mode Quest
Authors: Appourchaux, T.; Pallé, P. L.
2013ASPC..478..125A Altcode: 2013arXiv1309.3835A
The quest for the solar gravity modes (or g modes) is key for the
understanding of the structure and dynamics of the solar core. We
review the history of the solar g-mode searches which is separated in
three nearly distinct eras which correspond to: the theory of g modes,
the search from the ground and the search from space. The prospects
of definitive solar g-mode detection are also discussed.
---------------------------------------------------------
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: Observations of the radial velocity of the Sun as measured
with the novel SONG spectrograph: results from a 1-week campaign
Authors: Pallé, P. L.; Grundahl, F.; Triviño Hage, A.;
Christensen-Dalsgaard, J.; Frandsen, S.; García, R. A.; Uytterhoeven,
K.; Andersen, M. F.; Rasmussen, P. K.; Sørensen, A. N.; Kjeldsen,
H.; Spano, P.; Nilsson, H.; Hartman, H.; Jørgensen, U. G.; Skottfelt,
J.; Harpsøe, K.; Andersen, M. I.
2013JPhCS.440a2051P Altcode:
Deployment of the prototype node of the SONG project took place in April
2012 at Observatorio del Teide (Canary Islands). Its key instrument
(echelle spectrograph) was installed and operational a few weeks later
while its 1 m feeding telescope suffered a considerable delay to meet
the required specifications. Using a fibre-feed, solar light could be
fed to the spectrograph and we carried out a 1-week observing campaign
in June 2012 to evaluate its performance for measuring precision
radial velocities. In this work we present the first results of this
campaign by comparing the sensitivity of the SONG spectrograph with
other helioseismology reference instruments (Mark-I and GOLF) when
simultaneous data are considered.
---------------------------------------------------------
Title: Secular measurements of the solar gravitational redshift
(1976 - 2011)
Authors: Pallé, P. L.; Roca Cortés, T.
2013hsa7.conf..750P Altcode:
The solar spectrophotometer "Mark-I", located at the Observatorio del
Teide and continuously operated for the latest 36, provides a high
precision measurement of the radial velocity of the Sun-as-a-star which
has enabled the study of the small velocity fluctuations produced
by normal modes solar oscillations and the characterization of its
spectrum. Furthermore, because of its high sensitivity and long term
instrumental stability also provides a daily accurate determination
(less than 1 m s^{-1}) of the daily radial velocity offset, the
so-called "solar gravitational red-shift" (GRS). In the present work,
first results of the analysis of this parameter over the whole period
1976-2011 are presented.
---------------------------------------------------------
Title: SONG-OT: The prototype SONG node at Tenerife
Authors: Uytterhoeven, K.; Pallé, P. L.; Grundahl, F.; Frandsen,
S.; Christensen-Dalsgaard, J.; Triviño Hage, A.; SONG Team
2012AN....333.1103U Altcode:
The prototype SONG node, SONG-OT, is currently being installed and
tested at Observatory del Teide on Tenerife. SONG will be a global
network of 1-m robotic telescopes, equipped with a high-resolution
échelle spectrograph and dual-colour lucky imaging cameras. The
network will be devoted to the seismic study of bright stars and
characterisation of low-mass planets. We present the current status
of the network in general and the SONG-OT node in particular.
---------------------------------------------------------
Title: Presentation of the reduction pipeline of the SONG échelle
spectrograph
Authors: Triviño Hage, A.; Uytterhoeven, K.; Grundahl, F.; Pallé,
P. L.; SONG Team
2012AN....333.1107T Altcode:
We give an overview of the spectral reduction pipeline that will be
used to process the data of the échelle spectrograph of the SONG-OT
telescope node of the SONG (Stellar Observations Network Group)
network on Tenerife. In particular, we focus on the iodine absorption
cell technique to derive precise radial velocity measurements. The
telescope and dome of SONG-OT were installed on 23 April 2012, and first
light is foreseen this autumn. The reduction pipeline will be tested,
optimized and improved when real stellar data will become available.
---------------------------------------------------------
Title: Solar Global Oscillations of Low-Degree modes (GOLD): The
Status of the Multi-channel Resonance Spectrometer GOLF-NG
Authors: Turck-Chièze, S.; Carton, P. -H.; Barrière, J. -C.; Pallé,
P. L.; Robillot, J. -M.; Ballot, J.; Chenus, A. -C.; Daniel-Thomas,
P.; Delbart, A.; García, R. A.; Granelli, R.; Lahonde-Hamdoun, C.;
Loiseau, D.; Mathur, S.; Piret, Y.; Salabert, D.; Simoniello, R.;
Davies, G. R.
2012ASPC..462..240T Altcode:
Low-degree pulsation modes are the best way to scrutinize stellar
cores. They also provide, due to their intrinsic nature, a way to
follow varying activity in important subsurface layers. Following
difficulties encountered with the Solar and Heliospheric Observatory
(SoHO) in 1998, we study a new design that improves the detection at
low and high frequencies in comparison with the Global Oscillations at
Low Frequency (GOLF) instrument. It is based on a substantial increase
in the counting rates to get better photon statistics, and a reduction
of the solar turbulent noise in measuring simultaneously the Doppler
velocity at 6-7 heights in the strong sodium spectral line. A prototype,
GOLF-NG (GOLF New Generation), has been built with numerous laboratory
checks of the performance and in situ solar measurements at Tenerife
in 2008 and 2010. All the required specifications are now achieved,
and so GOLD can be prepared for space observations with balloons or
satellites. The substantial improvements allow an improved detection
of weak signals at different frequencies and information on activity
indicators, as the Na D lines are sensitive to the magnetic field
between photosphere and chromosphere.
---------------------------------------------------------
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: The Acoustic Cutoff Frequency of the Sun and the Solar Magnetic
Activity Cycle
Authors: Jiménez, A.; García, R. A.; Pallé, P. L.
2011ApJ...743...99J Altcode: 2011arXiv1109.3326J
The acoustic cutoff frequency—the highest frequency for acoustic
solar eigenmodes—is an important parameter of the solar atmosphere as
it determines the upper boundary of the p-mode resonant cavities. At
frequencies beyond this value, acoustic disturbances are no longer
trapped but are traveling waves. Interference among them gives rise
to higher-frequency peaks—the pseudomodes—in the solar acoustic
spectrum. The pseudomodes are shifted slightly in frequency with
respect to p-modes, making possible the use of pseudomodes to determine
the acoustic cutoff frequency. Using data from the GOLF and VIRGO
instruments on board the Solar and Heliospheric Observatory spacecraft,
we calculate the acoustic cutoff frequency using the coherence function
between both the velocity and intensity sets of data. By using data
gathered by these instruments during the entire lifetime of the mission
(1996 until the present), a variation in the acoustic cutoff frequency
with the solar magnetic activity cycle is found.
---------------------------------------------------------
Title: The SONG project and the prototype node at Tenerife
Authors: Uytterhoeven, K.; Palle, P. L.; Grundahl, F.; Frandsen, S.;
Kjeldsen, H.; Christensen-Dalsgaard, J.; Fredslund Andersen, M.;
Weiss, E.; Joergensen, U. G.; Rasmussen, P. K.; Soerensen, A. N.;
Harpsoee, K.; Skottfelt, J.
2011arXiv1111.1834U Altcode:
SONG (Stellar Observations Network Group) is a global network of 1-m
class robotic telescopes that is under development. The SONG prototype
will shortly be operational at Observatorio del Teide, Tenerife, and
first light is expected by December 2011. The main scientific goals of
the SONG project are asteroseismology of bright stars and follow-up
and characterization of exo-planets by means of precise measurements
of stellar surface motions and brightness variations. We present the
Tenerife SONG node and its instruments.
---------------------------------------------------------
Title: The Observatorio del Teide welcomes SONG:the Stellar
Observations Network Group
Authors: Creevey, O. L.; Grundahl, F.; Pallé, P. L.; Gråe Jørgensen,
U.; Belmonte, J. A.; Christensen-Dalsgaard, J.; Frandsen, S.; Kjeldsen,
H.; Kjærgaard, P.
2011hsa6.conf..686C Altcode: 2011arXiv1112.5539C
The Stellar Observations Network Group (SONG) is an internationalnetwork
project aiming to place eight 1 m robotic telescopes around the
globe,with the primary objectives of studying stellar oscillations
and planetsusing ultra-precision radial velocity measurements.The
prototype of SONG will be installed and running at the Observatoriodel
Teide by Summer 2011. In these proceedings we present the project,
primary scientific objectives, and instrument, and discussthe observing
possibilities for the Spanish community.
---------------------------------------------------------
Title: The acoustic cutoff frequency of the Sun and the solar cycle
Authors: Jiménez, A.; García, R. A.; Pallé, P. L.
2011JPhCS.271a2051J Altcode:
The acoustic cutoff frequency - highest frequency for acoustic solar
eigenmodes-is an important parameter of the solar atmosphere because
it determines the upper boundary of the p mode cavities. At frequencies
beyond this value, acoustic disturbances are no longer trapped waves but
traveling waves. Interferences amongst them, originate higher frequency
peaks -the pseudomodes- in the solar acoustic spectrum. Using data
from GOLF and VIRGO instruments aboard SoHO spacecraft, we determine
the acoustic cutoff frequency using the coherence function between
both sets of data, velocity and intensity. By using data gathered by
these instruments during the whole lifetime of the mission (1996 till
present), it is found a variation of this parameter with the solar
magnetic activity cycle.
---------------------------------------------------------
Title: New insights on the solar core
Authors: García, R. A.; Salabert, D.; Ballot, J.; Eff-Darwich, A.;
Garrido, R.; Jiménez, A.; Mathis, S.; Mathur, S.; Moya, A.; Pallé,
P. L.; Régulo, C.; Sato, K.; Suárez, J. C.; Turck-Chièze, S.
2011JPhCS.271a2046G Altcode: 2010arXiv1012.0506G
Since the detection of the asymptotic properties of the dipole gravity
modes in the Sun, the quest to find individual gravity modes has
continued. An extensive and deeper analysis of 14 years of continuous
GOLF/SoHO observational data, unveils the presence of a pattern of peaks
that could be interpreted as individual dipole gravity modes in the
frequency range between 60 and 140 microHz, with amplitudes compatible
with the latest theoretical predictions. By collapsing the power
spectrum we have obtained a quite constant splitting for these patterns
in comparison to regions where no g modes were expected. Moreover, the
same technique applied to simultaneous VIRGO/SoHO data unveils some
common signals between the power spectra of both instruments. Thus,
we are able to identify and characterize individual g modes with their
central frequencies, amplitudes and splittings allowing to do seismic
inversions of the rotation profile inside the solar core. These results
open a new ligh t on the physics and dynamics of the solar deep core.
---------------------------------------------------------
Title: Global p-mode oscillations throughout the complete solar
cycle 23 and the beginning of cycle 24
Authors: Salabert, D.; García, R. A.; Pallé, P. L.; Jiménez, A.
2011JPhCS.271a2030S Altcode: 2010arXiv1011.4966S
The parameters of the p-mode oscillations vary with solar activity. Such
temporal variations provide insights for the study of the structural and
dynamical changes occurring in the Sun's interior throughout the solar
cycle. We present here a complete picture of the temporal variations
of the global p-mode parameters (excitation, damping, frequency,
peak asymmetry, and rotational splitting) over the entire solar cycle
23 and the beginning of cycle 24 as observed by the space-based,
Sun-as-a-star helioseismic GOLF and VIRGO instruments onboard SoHO.
---------------------------------------------------------
Title: Four years of HELAS
Authors: Roth, M.; Lühe, O. v. d.; Aerts, C.; Christensen-Dalsgaard,
J.; Corbard, T.; Daszyńska-Daszkiewicz, J.; Di Mauro, M. P.; Gizon,
L.; Jiménez-Reyes, S.; Monteiro, M. J. P. F. G.; Pallé, P. L.;
Thompson, M. J.
2010AN....331.1084R Altcode:
The European Coordination Action on HELio- and ASteroseismology
(HELAS) has completed its fourth and final year of initial funding by
the European Commission. Set up as a network which combines solar and
stellar physics communities in the important and vigorously evolving
field of seismology, HELAS has been able to coordinate the efforts of
European astronomers with remarkable success. Four large international
conferences including the HELAS-IV conference on Lanzarote as well as
many workshops were organized with a substantial contribution from
HELAS. About a dozen workshops, addressing specialized questions in
global and local helioseismology and asteroseismology were entirely
organized by HELAS. Data analysis tools to prepare the European
communities for the upcoming influx of data from new missions have
been prepared, tested and demonstrated. Lecture notes and outreach
material have been assembled and prepared for general access. As a
result, HELAS has an important impact on the scientific output of the
astrophysics seismology communities and significantly increased the
visibility of European research in this field. This paper summarizes
the activities and accomplishments of HELAS.
---------------------------------------------------------
Title: Towards a detection of individual g modes in the Sun
Authors: Garcia, R. A.; Ballot, J.; Eff-Darwich, A.; Garrido, R.;
Jimenez, A.; Mathis, S.; Mathur, S.; Moya, A.; Palle, P. L.; Regulo,
C.; Salabert, D.; Suarez, J. C.; Turck-Chieze, S.
2010arXiv1007.4445G Altcode:
Since the detection of the asymptotic properties of the dipole gravity
modes in the Sun, the quest to find the individual gravity modes has
continued. A deeper analysis of the GOLF/SoHO data unveils the presence
of a pattern of peaks that could be interpreted as individual dipole
gravity modes. The computed collapsed spectrum -around these candidate
modes- uncovers the presence of a quasi constant frequency splitting,
in contrast with regions where no g modes are expected in which
the collapsogram gives random results. Besides, the same technique
applied to VIRGO/SoHO unveils some common signals between both power
spectra. Thus, we can identify and characterize the modes, for example,
with their central frequency and splittings. This would open the path
towards new investigations to better constrain the solar core.
---------------------------------------------------------
Title: Frequency Shifts of the Individual Low-Degree P-Modes during
Solar Cycle 23 and its Extended Minimum
Authors: Salabert, D.; García, R. A.; Pallé, P. L.; Jiménez-Reyes,
S. J.
2010ASPC..428...51S Altcode: 2010arXiv1003.4354S
We study the response of the low-degree solar p-mode frequencies
to the unusual extension of the minimum of solar surface activity
since 2007. Helioseismic observations collected by the space-based,
Sun-as-a-star GOLF instrument and by the ground-based, multi-site
network GONG (integrated signal) are analyzed. Temporal variations of
the low-degree (l=0,1,2), p-mode frequencies are obtained. Although the
known correlation of the frequency changes with solar surface activity
is recovered for the period 1996â??2007, since the second half of 2007
and until July 2009 (the latest period analyzed) we notice a peculiar
behavior amongst modes of different angular degrees. In particular,
a clear increase of the l=0 and l=2 p-mode frequencies is obtained
consistently since late 2007, while the l=1 frequencies follow the
general decreasing trend of surface activity. We interpret these
differences in the frequency shifts of individual low-degree modes
as indicative of variations at high latitudes in the magnetic flux
beneath the surface of the Sun related to the onset of solar cycle 24.
---------------------------------------------------------
Title: SONG: an observational new facility at Observatorio del Teide
for stellar observations
Authors: Creevey, O.; Pallé, P. L.; Belmonte, J. A.
2010iac..talk..141C Altcode: 2010iac..talk..161C
No abstract at ADS
---------------------------------------------------------
Title: The extended minimum of solar cycle 23 as seen by radial
velocity (GOLF, GONG) and intensity (VIRGO) helioseismic instruments
Authors: Salabert, D.; Garcia, R. A.; Palle, P. L.; Jimenez-Reyes,
S. J.; Jimenez, A.
2010arXiv1004.2869S Altcode:
We present an analysis of the variability of the solar oscillation
spectrum during solar cycle 23 and its extended minimum. We
use simultaneous observations of the low-degree solar p modes
collected by the space-based, Sun-as-a-star GOLF (radial velocity)
and VIRGO (intensity) instruments, and by the ground-based, multi-site
network GONG. We investigate in particular the response of the p-mode
eigenfrequencies to the observed peculiar deep solar minimum of surface
activity of 2007-2009 as compared with the previous solar cycle 23. We
study the different temporal variations of the p-mode frequencies with
individual angular degrees.
---------------------------------------------------------
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: Interior and Exterior Clues of Solar Activity
Authors: Turck-Chièze, S.; Brun, A. S.; Duez, V.; García, R. A.;
Mathis, S.; Piau, L.; Salabert, D.; Pallé, P. L.; Jiménez-Reyes,
S. J.; Mathur, S.; Simoniello, R.; Robillot, J. M.
2010ASSP...19..368T Altcode: 2010mcia.conf..368T
Two research paths are described to obtain better understanding
of the origin of global solar activity. First, observations with
a multichannel resonant spectrometer may reveal the dynamics of the
solar core, the tachocline, and the temporal evolution of activity
between the photosphere and chromosphere. Such new observations will
deliver constraints for 3D simulations of solar activity. Second, we
examine the ab-initio introduction of a non-force-free field expressed
in spherical harmonics into the solar structure equations and estimate
its impact on the inner and subsurface layers, its time evolution,
and its role in angular momentum transport.
---------------------------------------------------------
Title: First Performance of the GOLF-NG Instrumental Prototype
Observing the Sun in Tenerife
Authors: Salabert, D.; Turck-Chièze, S.; Barrière, J. C.; Carton,
P. H.; Daniel-Thomas, P.; Delbart, A.; García, R. A.; Granelli, R.;
Jiménez-Reyes, S. J.; Lahonde-Hamdoun, C.; Loiseau, D.; Mathur, S.;
Nunio, F.; Pallé, P. L.; Piret, Y.; Robillot, J. M.; Simoniello, R.
2009ASPC..416..341S Altcode: 2008arXiv0810.3393S
The primary challenge of Global Oscillations at Low Frequency New
Generation (GOLF-NG) is the detection of the low-frequency solar
gravity and acoustic modes, as well as the possibility to measure
the high-frequency chromospheric modes. On June 8th 2008, the
first sunlight observations with the multichannel resonant GOLF-NG
prototype spectrometer were obtained at the Observatorio del Teide
(Tenerife). The instrument performs integrated (Sun-as-a-star),
Doppler velocity measurements, simultaneously at eight different
heights in the D1 sodium line profile, corresponding to photospheric
and chromospheric layers of the solar atmosphere. In order to study
its performance, to validate the conceived strategy, and to estimate
the necessary improvements, this prototype has been running on a
daily basis over the whole summer of 2008 at the Observatorio del
Teide. We present here the results of the first GOLF-NG observations,
clearly showing the characteristics of the 5-minute oscillatory signal
at different heights in the solar atmosphere. We compare these signals
with simultaneous observations from Global Oscillations at Low Frequency
(GOLF)/SoHO and from the Mark-I instrument—a node of the Birmingham
Solar Oscillations Network (BiSON) network, operating at the same site.
---------------------------------------------------------
Title: Detecting individual gravity modes in the Sun
Authors: Garcia, R. A.; Ballot, J.; Eff-Darwich, A.; Garrido, R.;
Jimenez, A.; Mathis, S.; Moya, A.; Palle, P. L.; Regulo, C.; Salabert,
D.; Suarez, J. C.; Turck-Chieze, S.
2009arXiv0911.5442G Altcode:
Many questions are still open regarding the structure and the dynamics
of the solar core. By constraining more this region in the solar
evolution models, we can reduce the incertitudes on some physical
processes and on momentum transport mechanisms. A first big step was
made with the detection of the signature of the dipole-gravity modes
in the Sun, giving a hint of a faster rotation rate inside the core. A
deeper analysis of the GOLF/SoHO data unveils the presence of a pattern
of peaks that could be interpreted as dipole gravity modes. In that
case, those modes can be characterized, thus bringing better constraints
on the rotation of the core as well as some structural parameters such
as the density at these very deep layers of the Sun interior.
---------------------------------------------------------
Title: HD 172189: another step in furnishing one of the best
laboratories known for asteroseismic studies
Authors: Creevey, O. L.; Uytterhoeven, K.; Martín-Ruiz, S.; Amado,
P. J.; Niemczura, E.; van Winckel, H.; Suárez, J. C.; Rolland,
A.; Rodler, F.; Rodríguez-López, C.; Rodríguez, E.; Raskin, G.;
Rainer, M.; Poretti, E.; Pallé, P.; Molina, R.; Moya, A.; Mathias,
P.; Le Guillou, L.; Hadrava, P.; Fabbian, D.; Garrido, R.; Decin,
L.; Cutispoto, G.; Casanova, V.; Broeders, E.; Arellano Ferro, A.;
Aceituno, F.
2009A&A...507..901C Altcode: 2009arXiv0909.3435C
HD 172189 is a spectroscopic eclipsing binary system with a
rapidly-rotating pulsating δ Scuti component. It is also a member of
the open cluster IC 4756. These combined characteristics make it an
excellent laboratory for asteroseismic studies. To date, HD 172189 has
been analysed in detail photometrically but not spectroscopically. For
this reason we have compiled a set of spectroscopic data to determine
the absolute and atmospheric parameters of the components. We
determined the radial velocities (RV) of both components using four
different techniques. We disentangled the binary spectra using KOREL,
and performed the first abundance analysis on both disentangled
spectra. By combining the spectroscopic results and the photometric
data, we obtained the component masses, 1.8 and 1.7 M<SUB>⊙</SUB>,
and radii, 4.0 and 2.4 R<SUB>⊙</SUB>, for inclination i = 73.2°,
eccentricity e = 0.28, and orbital period Π = 5.70198 days. Effective
temperatures of 7600 K and 8100 K were also determined. The measured v
sin i are 78 and 74 km s<SUP>-1</SUP>, respectively, giving rotational
periods of 2.50 and 1.55 days for the components. The abundance analysis
shows [Fe/H] = -0.28 for the primary (pulsating) star, consistent with
observations of IC 4756. We also present an assessment of the different
analysis techniques used to obtain the RVs and the global parameters.
---------------------------------------------------------
Title: The onset of solar cycle 24. What global acoustic modes are
telling us
Authors: Salabert, D.; García, R. A.; Pallé, P. L.; Jiménez-Reyes,
S. J.
2009A&A...504L...1S Altcode: 2009arXiv0907.3888S
We study the response of the low-degree, solar p-mode frequencies to
the unusually extended minimum of solar surface activity since 2007. A
total of 4768 days of observations collected by the space-based,
Sun-as-a-star helioseismic GOLF instrument are analyzed. A multi-step
iterative maximum-likelihood fitting method is applied to subseries
of 365 days and 91.25 days to extract the p-mode parameters. Temporal
variations in the l=0, 1, and 2 p-mode frequencies are then obtained
from April 1996 to May 2009. While the p-mode frequency shifts are
closely correlated with solar surface activity proxies during the past
solar cycles, the frequency shifts of the l=0 and l=2 modes increase
from the second half of 2007, when no significant surface activity
is observable. On the other hand, the l=1 modes follow the general
decreasing trend of solar surface activity. The different behaviors
between the l=0 and l=2 modes and the l=1 modes may be interpreted as
different geometrical responses to the spatial distribution of the
solar magnetic field beneath the surface of the Sun. The analysis
of the low-degree, solar p-mode frequency shifts indicates that the
solar activity cycle 24 started in late 2007, despite the absence of
activity on the solar surface.
---------------------------------------------------------
Title: The GOLF-NG prototype and the solar European perspective for
cosmic vision 2015-2025
Authors: Turck-Chièze, Sylvaine; Mathur, Savita; Ballot, Jérome;
García, Rafael A.; Carton, Pierre-Henri; Barrière, Jean-Christophe;
Daniel-Thomas, Philippe; Delbart, Alain; Desforges, Daniel; Granelli,
Rémi; Nunio, Francois; Piret, Yves; Pallé, Pere L.; Jiménez, Antonio
J.; Jiménez-Reyes, Sébastian J.; Simoniello, Rosaria; Dyna MICCS Team
2008JPhCS.118a2044T Altcode:
The progress on the dynamics of the radiative zone by global Doppler
velocity measurements aboard SoHO (GOLF+ MDI) and with ground networks
(BiSON and GONG) opens a new perspective for solar and stellar
physics. It is why we prepare a new generation of solar resonant
spectrometer. The objectives of the GOLF-NG instrument and its present
status are described. We have demonstrated this year that most of the
technical challenges have been successfully faced and the next steps
are mentioned. We then recall the scientific questions that might
be solved with the next generation of instruments in construction
in different european laboratories to reach a complete 3D vision of
our star from the core to the corona. Two formation flying missions
DynaMICCS and HIRISE have been proposed to ESA in the framework of
the 2015-2025 Cosmic Vision perspective to contribute to solve these
questions. A strategy of measurements must be found for the next decade.
---------------------------------------------------------
Title: Preliminary results on the contribution of the convection
motions to the Doppler velocity signal
Authors: Simoniello, R.; Ruiz-Cobo, B.; Jiménez-Reyes, S. J.; García,
R. A.; Pallé, P. L.
2008JPhCS.118a2089S Altcode:
This investigation aims to study the correlation of the solar
background with atmosphere. We used high resolution observations of
the NaDl spectral line. In fact the large span in formation heights
of this spectral line allowed us to infer the signal from photosphere
to chromosphere. We analyzed the data by applying the SIR code (Stokes
Inversion based on response functions). It is an inversion method of the
RTE (Radiative transfer equation) that provides physical information
on the region where the spectral lines are sensitive to changes in
thermal and dynamical parameters of the atmosphere. The survey has
been divided in two different steps: <SUP>1)</SUP> identification of a
model of the atmosphere that reproduce our observations; <SUP>2)</SUP>
determination of the degree of correlation of convective motions with
the solar atmosphere. Here we present the results of the first step:
we identified in the model presented by Vernazza the best model that
matches our observations.
---------------------------------------------------------
Title: Update on g-mode research
Authors: García, R. A.; Jiménez, A.; Mathur, S.; Ballot, J.;
Eff-Darwich, A.; Jiménez-Reyes, S. J.; Pallé, P. L.; Provost, J.;
Turck-Chièze, S.
2008AN....329..476G Altcode: 2008arXiv0802.4296G
Since the beginning of this century we have attended a blooming
of the gravity-mode research thanks to the unprecedented quality
of the data available, either from space with SoHO, or from the
ground-based networks as BiSON or GONG. From the first upper limit
of the gravity-mode amplitudes fixed at 10 mm/s at 200 μHz given
by Appourchaux et al. (2000), on one hand, a peak was supposed
to be a component of the ℓ = 1, n = 1 mixed mode (García et
al. 2001a, 2001b; Gabriel et al. 2002) and, on the other hand, a
couple of patterns - multiplets - were attributed to gravity modes
(Turck-Chièze et al. 2004; Mathur et al. 2007). One of these patterns,
found around 220 μHz, could be labeled as the ℓ = 2, n =-3 g mode,
which is expected to be the one with the highest surface amplitude
(Cox & Guzik 2004). Finally, in 2007, García et al. were able to
measure the fingertips of the dipole gravity modes looking for their
asymptotic properties. In the present paper we present an update of the
recent developments on this subject with special attention to the 220
μHz region, the dipole asymptotic properties and the impact of the
incoming g-mode observations on the knowledge of the solar structure
and rotation profile.
---------------------------------------------------------
Title: p-mode power variation with solar atmosphere as observed in
the Na D1 and K spectral lines
Authors: Simoniello, R.; Jiménez-Reyes, S. J.; García, R. A.;
Pallé, P. L.
2008AN....329..494S Altcode:
In this work we investigate p-mode power variation with solar
atmosphere. To this aim, we use THÉMIS observations of the Na D1
(λ5896 Å) and K (λ7699 Å) spectral lines. While the formation
heights of the K spectral line are essentially located in the
photospheric layer, the formation heights of the Na D1 line span a much
wider region: from photosphere up to chromosphere. Hence, we had the
opportunity to infer p-mode power variation up to the chromospheric
layer. By analyzing power spectra obtained by temporal series at
different points of the Na D1 and K spectral lines, we confirm and
quantify the increase in p-mode power towards higher atmospheric
layers. Furthermore, the large span in formation heights of the Na D1
line induces a larger enhancement of p-mode power with solar atmosphere
compared to the K spectral line.
---------------------------------------------------------
Title: HELAS IT-platform: A new tool for the European Helio- and
Asteroseismology community.
Authors: Jiménez-Reyes, S. J.; Quintero Nerkhorn, J.; Pallé, P. L.;
Helas Board
2008CoAst.153..108J Altcode:
HELAS is a Coordination Action funded under the European Commission's
Sixth Framework Programme (FP6) since April 1st, 2006 till March
31st, 2010. The HELAS Consortium includes 10 partner institutions
that host researchers active in helio- and asteroseismology. This
initiative offers a unique chance to advance the field further by
coordinating the activities of researchers, enhancing the quality
and quantity of science performed in Europe. The HELAS Forum is one
of its Networking Activities. Its main goal is to encourage, provide,
and support the tools, activities, and initiatives emanating from the
European helio- and asterosesimology scientific communities. Thus,
the HELAS Forum should ensure European competence and competitiveness
in these areas by better coordinating the groups. It also enhances
the synergies between the helio- and astero communities and between
those and other non-European related activities. Here, we present the
Helas Forum IT-platform (www.helas-eu.org), developed to facilitate
the coordinated activities such as data and software package exchange,
information about workshops and meetings, knowledge of the community,
etc., as well as to allow tracking the development of HELAS activities.
---------------------------------------------------------
Title: Tracking Solar Gravity Modes: The Dynamics of the Solar Core
Authors: García, Rafael A.; Turck-Chièze, Sylvaine; Jiménez-Reyes,
Sebastian J.; Ballot, Jérôme; Pallé, Pere L.; Eff-Darwich, Antonio;
Mathur, Savita; Provost, Janine
2007Sci...316.1591G Altcode:
Solar gravity modes have been actively sought because they directly
probe the solar core (below 0.2 solar radius), but they have not
been conclusively detected in the Sun because of their small surface
amplitudes. Using data from the Global Oscillation at Low Frequency
instrument, we detected a periodic structure in agreement with the
period separation predicted by the theory for gravity dipole modes. When
studied in relation to simulations including the best physics of the
Sun determined through the acoustic modes, such a structure favors a
faster rotation rate in the core than in the rest of the radiative zone.
---------------------------------------------------------
Title: The DynaMICS perspective
Authors: Turck-Chièze, S.; Schmutz, W.; Thuillier, G.; Jefferies,
S.; Pallé; Dewitt, S.; Ballot, J.; Berthomieu, G.; Bonanno, A.;
Brun, A. S.; Christensen-Dalsgaard, J.; Corbard, T.; Couvidat, S.;
Darwich, A. M.; Dintrans, B.; Domingo, V.; Finsterle, W.; Fossat,
E.; Garcia, R. A.; Gelly, B.; Gough, D.; Guzik, J.; Jiménez, A. J.;
Jiménez-Reyes, S.; Kosovichev, A.; Lambert, P.; Lefebvre, S.; Lopes,
I.; Martic, M.; Mathis, S.; Mathur, S.; Nghiem, P. A. P.; Piau, L.;
Provost, J.; Rieutord, M.; Robillot, J. M.; Rogers, T.; Roudier, T.;
Roxburgh, I.; Rozelot, J. P.; Straka, C.; Talon, S.; Théado, S.;
Thompson, M.; Vauclair, S.; Zahn, J. P.
2006ESASP.624E..24T Altcode: 2006soho...18E..24T
No abstract at ADS
---------------------------------------------------------
Title: European helio- and asteroseismology network HELAS
Authors: Roth, M.; Luhe, O. v. d.; Palle, P.; Thompson, M. J.;
Christensen-Dalsgaard, J.; Monteiro, M. J. P. F. G.; Gizon, L.;
Di Mauro, M. P.; Aerts, C.; Daszynska-Daszkiewicz, J.; Corbard, T.
2006ESASP.624E.130R Altcode: 2006soho...18E.130R
The Helio- and Asteroseismology Network (HELAS) is a Coordinated
Action funded by the FP6-Infrastructure-Programme of the European
Commission. Currently, HELAS consists of ten members. The objective
of HELAS is to co-ordinate European activities in helio- and
asteroseismology. HELAS will transfer knowledge and data analysis
techniques, and will prepare the European research community for
important missions in the immediate future.
---------------------------------------------------------
Title: Detection of periodic signatures in the solar power spectrum
On the track of l=1 gravity modes
Authors: García, R. A.; Turck-Chièze, S.; Jiménez-Reyes, S. J.;
Ballot, J.; Pallé, P. L.; Eff-Darwich, A.; Mathur, S.; Provost, J.
2006ESASP.624E..23G Altcode: 2006astro.ph.11806G; 2006soho...18E..23G
In the present work we show robust indications of the existence
of g modes in the Sun using 10 years of GOLF data. The present
analysis is based on the exploitation of the collective properties
of the predicted low-frequency (25 to 140 microHz) g modes: their
asymptotic nature, which implies a quasi equidistant separation of
their periods for a given angular degree (l). The Power Spectrum (PS)
of the Power Spectrum Density (PSD), reveals a significant structure
indicating the presence of features (peaks) in the PSD with near
equidistant periods corresponding to l=1 modes in the range n=-4 to
n=-26. The study of its statistical significance of this feature was
fully undertaken and complemented with Monte Carlo simulations. This
structure has a confidence level better than 99.86% not to be due to
pure noise. Furthermore, a detailed study of this structure suggests
that the gravity modes have a much more complex structure than the one
initially expected (line-widths, magnetic splittings...). Compared to
the latest solar models, the obtained results tend to favor a solar
core rotating significantly faster than the rest of the radiative
zone. In the framework of the Phoebus group, we have also applied the
same methodology to other helioseismology instruments on board SoHO
and ground based networks.
---------------------------------------------------------
Title: Knowledge of the solar core dynamics through g modes
Authors: Garcia, R. A.; Turck-Chièze, S.; Jimenez-Reyes, S. J.;
Ballot, J.; Pallé, P. L.; Eff-Darwich, A.; Mathur, S.; Provost, J.
2006IAUJD..17E...8G Altcode:
Helioseismology is able to study the solar interior through the
observation of the solar oscillation modes propagating inside the
Sun. Pressure-driven modes (p modes) provide a very detailed picture
of the external convective zone above 0.7 R[⊙]and the radiative zone
down to ~0.2 R[⊙] where only a few of such modes penetrate so far. To
study deeper layers, still containing more than 40% of the totals mass,
another type of oscillations are needed: the gravity-driven modes
(g modes). Since the early 19 80s, this type of mode has been looked
for. Only very recently have we have found some structures that are
compatible with some global properties of these modes in the GOLF/ SOHO
data. In this contribution we will show these signals. By explaining
them as the signature of the asymptotic properties of the ℓ = 1 g
modes, we could start constraining the solar core dynamics.
---------------------------------------------------------
Title: Scientific Objectives of the Novel Formation Flying Mission
Aspiics
Authors: Turck-Chièze, S.; Schmutz, W.; Thuillier, G.; Jefferies,
S.; Pallé; Dewitt, S.; Ballot, J.; Berthomieu, G.; Bonanno, A.;
Brun, A. S.; Christensen-Dalsgaard, J.; Corbard, T.; Couvidat, S.;
Darwich, A. M.; Dintrans, B.; Domingo, V.; Finsterle, W.; Fossat,
E.; Garcia, R. A.; Gelly, B.; Gough, D.; Guzik, J.; Jiménez, A. J.;
Jiménez-Reyes, S.; Kosovichev, A.; Lambert, P.; Lefebvre, S.; Lopes,
I.; Martic, M.; Mathis, S.; Mathur, S.; Nghiem, P. A. P.; Piau, L.;
Provost, J.; Rieutord, M.; Robillot, J. M.; Rogers, T.; Roudier, T.;
Roxburgh, I.; Rozelot, J. P.; Straka, C.; Talon, S.; Théado, S.;
Thompson, M.; Vauclair, S.; Zahn, J. P.
2006ESASP.617E.164L Altcode: 2006soho...17E.164L
No abstract at ADS
---------------------------------------------------------
Title: The EUV Variability Experiment (EVE) on the Solar Dynamics
Observatory (SDO): Science Plan and Instrument Overview
Authors: Turck-Chièze, S.; Schmutz, W.; Thuillier, G.; Jefferies,
S.; Pallé; Dewitt, S.; Ballot, J.; Berthomieu, G.; Bonanno, A.;
Brun, A. S.; Christensen-Dalsgaard, J.; Corbard, T.; Couvidat, S.;
Darwich, A. M.; Dintrans, B.; Domingo, V.; Finsterle, W.; Fossat,
E.; Garcia, R. A.; Gelly, B.; Gough, D.; Guzik, J.; Jiménez, A. J.;
Jiménez-Reyes, S.; Kosovichev, A.; Lambert, P.; Lefebvre, S.; Lopes,
I.; Martic, M.; Mathis, S.; Mathur, S.; Nghiem, P. A. P.; Piau, L.;
Provost, J.; Rieutord, M.; Robillot, J. M.; Rogers, T.; Roudier, T.;
Roxburgh, I.; Rozelot, J. P.; Straka, C.; Talon, S.; Théado, S.;
Thompson, M.; Vauclair, S.; Zahn, J. P.
2006ESASP.617E.165W Altcode: 2006soho...17E.165W
No abstract at ADS
---------------------------------------------------------
Title: Detection of the Periodic Signatures of l=1 Solar g Modes
with 10 Years of GOLF/SOHO Data
Authors: Garcia, Rafael A.; Turck-Chiéze, Sylvaine; Jiménez-Reyes,
Sebastián J.; Ballot, Jerome; Palle, Pere L.; Eff-Darwich, Antonio;
Mathur, Savita; Provost, Janine
2006ESASP.617E...3G Altcode: 2006soho...17E...3G
No abstract at ADS
---------------------------------------------------------
Title: Helas-European Helio- and Asteroseismology Network
Authors: Roth, M.; Lühe, O. v. d.; Pallé, P.; Thompson, M.;
Christensen-Dalsgaard, J.; Monteiro, M. J. P. F. G; Gizon, L.; Di
Mauro, M. P.; Aerts, C.; Daszynska-Daszkiewicz, J.; Corbard, T.
2006ESASP.617E.157R Altcode: 2006soho...17E.157R
No abstract at ADS
---------------------------------------------------------
Title: The Dynamics Project
Authors: Turck-Chièze, S.; Schmutz, W.; Thuillier, G.; Jefferies,
S.; Pallé; Dewitt, S.; Ballot, J.; Berthomieu, G.; Bonanno, A.;
Brun, A. S.; Christensen-Dalsgaard, J.; Corbard, T.; Couvidat, S.;
Darwich, A. M.; Dintrans, B.; Domingo, V.; Finsterle, W.; Fossat,
E.; Garcia, R. A.; Gelly, B.; Gough, D.; Guzik, J.; Jiménez, A. J.;
Jiménez-Reyes, S.; Kosovichev, A.; Lambert, P.; Lefebvre, S.; Lopes,
I.; Martic, M.; Mathis, S.; Mathur, S.; Nghiem, P. A. P.; Piau, L.;
Provost, J.; Rieutord, M.; Robillot, J. M.; Rogers, T.; Roudier, T.;
Roxburgh, I.; Rozelot, J. P.; Straka, C.; Talon, S.; Théado, S.;
Thompson, M.; Vauclair, S.; Zahn, J. P.
2006ESASP.617E.162T Altcode: 2006soho...17E.162T
No abstract at ADS
---------------------------------------------------------
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: Jovian seismology: preliminary results of the SYMPA instrument
Authors: Gaulme, P.; Schmider, F. X.; Gay, J.; Jacob, C.; Jeanneaux,
F.; Alvarez, M.; Reyes, M.; Valtier, J. C.; Fossat, E.; Palle, P. L.;
Belmonte, J. C.; Gelly, B.
2006sf2a.conf..403G Altcode:
Jupiter's internal structure is poorly known (Guillot et
al. 2004). Seismology is a powerful tool to investigate the internal
structure of planets and stars, by analyzing how acoustic waves
propagate. Mosser (1997) and Gudkova & Zarkhov (1999) showed
that the detection and the identification of non-radial modes up to
degree ℓ=25 can constrain strongly the internal structure. SYMPA is
a ground-based network project dedicated to the Jovian oscillations
(Schmider et al. 2002). The instrument is composed of a Mach-Zehnder
interferometer producing four interferograms of the planetary
spectrum. The combination of the four images in phase quadrature allows
the reconstruction of the incident light phase, which is related to
the Doppler shift generated by the oscillations. Two SYMPA instruments
were built at the Nice university and were used simultaneously during
two observation campaigns, in 2004 and 2005, at the San Pedro Martir
observatory (Mexico) and the Teide observatory (Las Canarias). We will
present for the first time the data processing and the preliminary
results of the experiment.
---------------------------------------------------------
Title: GOLF-NG spectrometer, a space prototype for studying the
dynamics of the deep solar interior
Authors: Turck-Chièze, Sylvaine; Carton, Pierre-Henri; Ballot,
Jérome; Barrière, Jean-Christophe; Daniel-Thomas, Philippe; Delbart,
Alain; Desforges, Daniel; Garcia, Rafaël A.; Granelli, Rémi; Mathur,
Savita; Nunio, François; Piret, Yves; Pallé, Pere L.; Jiménez,
Antonio J.; Jiménez-Reyes, Sebastian J.; Robillot, Jean Maurice;
Fossat, Eric; Eff-Darwich, Antonio. M.; Gelly, Bernard
2006AdSpR..38.1812T Altcode: 2005astro.ph.10753T
The GOLF-NG (Global Oscillations at Low Frequency New Generation)
instrument is devoted to the search for solar gravity and acoustic
modes, and also chromospheric modes from space. This instrument which
is a successor to GOLF/SOHO will contribute to improve our knowledge
of the dynamics of the solar radiative zone. It is a 15 points resonant
scattering spectrometer, working on the D1 sodium line. A ground-based
prototype is under construction to validate the difficult issues. It
will be installed at the Teide Observatory, on Tenerife in 2006 to
analyse the separation of the effects of the magnetic turbulence of
the line from the solar oscillations. We are prepared to put a space
version of this instrument including a capability of identification of
the modes, in orbit during the next decade. This instrument should be
included in the ILWS program as it offers a key to the improvement of
our knowledge of the solar core in combination with observations from
SDO and PICARD. We hope to determine the core rotation and magnetic
field, through precise measurements of oscillation mode frequency
splittings. Understanding the magnetic field of the radiative zone
is important for progress in the study of solar activity sources,
an important player for the long-term Sun-Earth relationship.
---------------------------------------------------------
Title: The origin of the solar cyclic activities: the DynaMICS project
Authors: Turck-Chieze, S.; Brun, A. S.; Garcia, R. A.; Jiménez-Reyes,
S. J.; Palle, P.; Dynamics Team
2006cosp...36.2001T Altcode: 2006cosp.meet.2001T
In order to better estimate the earth climatic variations at scales
corresponding to decennia or centuries it appears more and more
important to understand the internal origin of the solar magnetic
cyclic activities together with the evolution of the internal solar
rotation profile It is the only way to be able to predict how they
will evolve in the future The seismic techniques are totally adapted
to this knowledge and an enriched information will allow to interpret
the solar global variations as irradiance luminosity at different
wavelengths and will measure temporal global mode characteristics which
must be linked to the total magnetic fluxes ldots Our main objectives
are to predict the characteristics of the coming solar cycles and to
determine if there is different origins for the longer solar cycles or
if it is only a temporal evolution of the eleven cycle 22 years which
produces grand minima or maxima SDO is well adapted to progress on the
convective zone with increased resolution in comparison with the SoHO
mission it will allow to improve the 11 year solar cycle predictions In
complementarity we consider very important to get a general description
of the dynamics of the solar radiative zone which contains the main
part of the solar mass and to understand the interconnection between
magnetic fields of the radiative zone and of the convective zones Such
information stays today poorly known even SoHO results on the solar
radiative zone through acoustic and gravity modes are very promising
to pursue this investigation In this
---------------------------------------------------------
Title: Jis - the Joint Information System
Authors: Kienreich, I.; Hanslmeier, A.; Palle, P.; Sosa, A.
2005ESASP.600E.159K Altcode: 2005dysu.confE.159K; 2005ESPM...11..159K
No abstract at ADS
---------------------------------------------------------
Title: GOLF New Generation: a spectrophotometer for the quest of
solar gravity modes
Authors: Turck-Chièze, S.; Mathur, S.; Carton, P. H.; García, R. A.;
Palle, P.; Ballot, J.
2005sf2a.conf..167T Altcode:
The Global Oscillations at Low Frequency: New Generation instrument
(GOLF-NG), the successor of GOLF aboard SoHO, is devoted to the study
the dynamics of the solar radiative zone thanks to the detection of
solar gravity modes and low-frequency acoustic modes. This instrument
built under a French-Spanish collaboration, is based on the Doppler
velocity method using a 15 points resonant scattering spectrometer
working on the D1 sodium line and will be placed in Tenerife. The
observations of the space version called DynaMICS (for Dynamics and
Magnetism of the Innner Core of the Sun) will enable us to improve
our knowledge of the radiative zone, especially the solar core and the
influence of the Sun on our planet by the determination of the origin
of the magnetic activities. The investigation of the sodium line will
also provide interesting information on the atmosphere of the Sun,
between the photosphere and the chromosphere.
---------------------------------------------------------
Title: Global solar Doppler velocity determination with the GOLF/SoHO
instrument
Authors: García, R. A.; Turck-Chièze, S.; Boumier, P.; Robillot,
J. M.; Bertello, L.; Charra, J.; Dzitko, H.; Gabriel, A. H.;
Jiménez-Reyes, S. J.; Pallé, P. L.; Renaud, C.; Roca Cortés, T.;
Ulrich, R. K.
2005A&A...442..385G Altcode:
The Global Oscillation at Low Frequencies (GOLF) experiment is
a resonant scattering spectrophotometer on board the Solar and
Heliospheric Observatory (SoHO) mission, originally designed to measure
the disk-integrated solar oscillations of the Sun. This instrument was
designed in a relative photometric mode involving both wings of the
neutral sodium doublet (D<SUB>1</SUB> at λ 5896 and D<SUB>2</SUB> at
λ 5890 Å). However, a "one-wing" photometric mode has been selected
to ensure 100% continuity in the measurements after a problem in the
polarization mechanisms. Thus the velocity is obtained from only two
points on the same wing of the lines. This operating configuration
imposes tighter constraints on the stability of the instrument with a
higher sensitivity to instrumental variations. In this paper we discuss
the evolution of the instrument during the last 8 years in space and
the corrections applied to the measured counting rates due to known
instrumental effects. We also describe a scaling procedure to obtain
the variation of the Doppler velocity based on our knowledge of the
sodium profile slope and we compare it to previous velocity estimations.
---------------------------------------------------------
Title: JIS - the Joint Information System
Authors: Hanslmeier, A.; Kienreich, I.; Palle, P.; Sosa, A.
2005HvaOB..29..329H Altcode:
The main aim of JIS (Joint Information System) is to overcome the
present lack of detailed knowledge amongst the European Solar Physics
community. This lack of knowledge occurs at several levels: groups of
researchers, institutions, scientific activities, running programs,
resources, new opportunities, observational campaigns etc. <P />JIS
will not be data archives -- this is the aim of EGSO, but will provide
all information mentioned above collecting all possible data about the
institutes and scientists working in the field of solar physics. All
European solar physicists will be provided with this information
by means of an easy accessible webpage including different inquiry
modes (query by country, university, institute, scientist and area
of research). Until now such a system did not exist in Europe, but in
foreseeable future a user-friendly and logical structured webpage will
take on this task.
---------------------------------------------------------
Title: The solar radiative interior: gravity modes and future
instrumentation
Authors: Garcia, R. A.; Turck-Chieze, S.; Ballot, J.; Couvidat, S.;
Eff-Darwich, A.; Jiménez-Reyes, S. J.; Mathur, S.; Pallé, P. L.;
GOLF-Ng Team
2004sf2a.conf...99G Altcode: 2004sf2a.confE.281G
Today, the knowledge of the solar radiative interior is obtained by the
solar acoustic modes. Thanks to the latest modes detected by SoHO the
sound speed has been determined down to 0.06 Ro with a resolution of
3%. This profile is used to improve the solar model and its deviations
from a static vision. The rotation profile is now clearly established
down to the limit of the core (Garcia et al. 2004). In order to progress
toward the core and reduce the uncertainties in the radiative region,
gravity modes should be measured. Recently, Turck-Chieze et al. (2004)
have identified some patterns using GOLF data during the last solar
minimum, that can be interpreted in terms of gravity modes. These
candidates, with an amplitude of ~2 mm/s, are at the limit of the
signal-to-noise ratio and are difficult to follow when the activity
increases. Their research will continue until the end of the SoHO
lifetime in 2008 during the next solar minimum. In the best case,
only a few mixed and gravity modes will be detected with SoHO. This
is the reason why a French-Spanish collaboration is now building a
prototype of a new spatial instrument, GOLF-NG, that will be tested
during the Summer 2005 in the Observatorio del Teide. GOLF-NG will
directly address the problem of the solar convective background noise
to improve the g-mode detection.
---------------------------------------------------------
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: Gravity Modes with a Resonant Scattering Spectrophotometer
Authors: Turck-Chièze, S.; Garcia, R. A.; Couvidat, S.; Ballot, J.;
Jiménez-Reyes, S. J.; Fossat, E.; Gelly, B.; Mathur, S.; Nghiem,
P. A. P.; Pallé, P.; Robillot, Jm.; GOLF-Ng Technical Team
2004ESASP.559...85T Altcode: 2004soho...14...85T
No abstract at ADS
---------------------------------------------------------
Title: Erratum: “Looking for Gravity-Mode Multiplets with the GOLF
Experiment aboard SOHO” (<A href="/abs/2004ApJ...604..455T">ApJ,
604, 455 [2004]</A>)
Authors: Turck-Chièze, S.; García, R. A.; Couvidat, S.; Ulrich,
R. K.; Bertello, L.; Varadi, F.; Kosovichev, A. G.; Gabriel, A. H.;
Berthomieu, G.; Brun, A. S.; Lopes, I.; Pallé, P.; Provost, J.;
Robillot, J. M.; Roca Cortés, T.
2004ApJ...608..610T Altcode:
As a result of an error at the Press, the second panel of Figure 9
was repeated twice in the top row of the printed, black-and-white
version of this figure, and the first panel was omitted. This error
appears in the print edition and the PDF and postscript (PS) versions
available with the electronic edition of the journal, although the
panels of the color figure displayed in the electronic article itself
are correct. Please see below for the corrected print version of Figure
9. The Press sincerely regrets the error.
---------------------------------------------------------
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: Looking for Gravity-Mode Multiplets with the GOLF Experiment
aboard SOHO
Authors: Turck-Chièze, S.; García, R. A.; Couvidat, S.; Ulrich,
R. K.; Bertello, L.; Varadi, F.; Kosovichev, A. G.; Gabriel, A. H.;
Berthomieu, G.; Brun, A. S.; Lopes, I.; Pallé, P.; Provost, J.;
Robillot, J. M.; Roca Cortés, T.
2004ApJ...604..455T Altcode:
This paper is focused on the search for low-amplitude solar gravity
modes between 150 and 400 μHz, corresponding to low-degree, low-order
modes. It presents results based on an original strategy that looks
for multiplets instead of single peaks, taking into consideration
our knowledge of the solar interior from acoustic modes. Five years
of quasi-continuous measurements collected with the helioseismic GOLF
experiment aboard the SOHO spacecraft are analyzed. We use different
power spectrum estimators and calculate confidence levels for the
most significant peaks. This approach allows us to look for signals
with velocities down to 2 mm s<SUP>-1</SUP>, not far from the limit
of existing instruments aboard SOHO, amplitudes that have never been
investigated up to now. We apply the method to series of 1290 days,
beginning in 1996 April, near the solar cycle minimum. An automatic
detection algorithm lists those peaks and multiplets that have a
probability of more than 90% of not being pure noise. The detected
patterns are then followed in time, considering also series of 1768 and
2034 days, partly covering the solar cycle maximum. In the analyzed
frequency range, the probability of detection of the multiplets
does not increase with time as for very long lifetime modes. This is
partly due to the observational conditions after 1998 October and the
degradation of these observational conditions near the solar maximum,
since these modes have a “mixed” character and probably behave as
acoustic modes. Several structures retain our attention because of
the presence of persistent peaks along the whole time span. These
features may support the idea of an increase of the rotation in the
inner core. There are good arguments for thinking that complementary
observations up to the solar activity minimum in 2007 will be decisive
for drawing conclusions on the presence or absence of gravity modes
detected aboard the SOHO satellite.
---------------------------------------------------------
Title: Solar gravity modes: the present and future
Authors: Turck-Chièze, S.; Garcià, R.; Fossat, E.; Gelly, B.; Palle,
P.; Robillot, Jm; Golf-Ng
2004cosp...35.3949T Altcode: 2004cosp.meet.3949T
Gravity modes are the best probes to study the solar radiative zone,
in particular the nuclear core and to follow its potential variability
with time and latitude. Nevertheless, their amplitude is small and
the solar noise particularly high in the range of frequency where
they stand (below 500 μ Hz). It is why they are looked for more than
20 years and actively serached with GOLF and MDI instruments aboard
SoHO which offers the best conditions of observation. Some candidates
(Turck-Chièze et al. 2004) have been identified in the GOLF instrument,
during the period of low solar activity thanks to an original research
of multiplets corresponding to surface amplitudes of about 2mm/s. The
examination of the interesting frequency range (100 to 400 μ Hz) will
be pursued up to the end of the SoHO mission scheduled for 2007. Today
our knowledge of the radiative zone is due to acoustic modes. Recent
clear progress is due to the detection of modes less influenced by
the sun activity, in the range 400-1600 μ Hz. The sound speed is
determined down to 0.06 Ro with a resolution of 3%. This profile
is used to improve the solar model and its deviations from a static
vision. The rotation profile is now clearly established down to the
limit of the core and its rigidity can only be explained by invoking
a magnetic field effect. We present here GOLF-NG (Turck-Chièze et
al., 2000) built by a French Spanish collaboration to improve g-mode
detection. Based on the Doppler velocity method using a resonant
spectrometer with a 16 channels on the sodium line, the main objective
of GOLF-NG is to contribute to get an MHD picture of the Sun to better
understand the influence of the Sun on earth climate, in improving
the detection by a factor 10 in decreasing the solar noise thanks
to a variable magnet. Consequently, the physical information will be
extracted at different heights in the atmosphere. A prototype will be
installed in 2005 in Tenerife. Then a spatial version will be available
for taking place in one project of the ILWS mission. Turck-Chièze,
S., Robillot, J.M., Dzitko, H ., Boumier, P., Decaudin, M., Gabriel,
A.H., Garcia, R.A., Grec, G., Pallé, P.L., Renaud, C., Schmidt, D.,
2000, ESA SP-464, 331; Turck-Chieze, S., Garcia, R.A., Couvidat, S.,
et al., 2004, ApJ, vol 604,
---------------------------------------------------------
Title: Helioseismology: probing the solar interior
Authors: Palle, P. L.
2004cosp...35.4454P Altcode: 2004cosp.meet.4454P
The direct access to the interior of the Sun has been possible,
over the past 25 years, by successfully applying seismic techniques
to detect and to characterize the whole spectrum of its oscillation
eigenmodes. The unique and huge amount of observational data provided
by earth-based networks and space-borne instruments, has allowed a high
degree of refinement on present Solar Models as well as the development
of robust inversion techniques. In addition, the sensitivity and
correlation of acoustic solar eigenmodes characteristics (frequencies,
power, linewidths, etc.) to solar activity (as measured by any of the
many indicators) is providing further and additional insights on the
so-called "Solar Activity Cycle". In this talk, a comprehensive review
on the actual knowledge of the interior of the Sun and its relation
with solar variability will be presented.
---------------------------------------------------------
Title: Solar gravity modes: the present and future
Authors: Turck-Chièze, S.; Garcià, R.; Fossat, E.; Gelly, B.; Palle,
P.; Robillot, Jm
2004cosp...35.3946T Altcode: 2004cosp.meet.3946T
Gravity modes are the best probes to study the solar radiative zone,
in particular the nuclear core and to follow its potential variability
with time and latitude. Nevertheless, their amplitude is small and
the solar noise particularly high in the range of frequency where
they stand (below 500 μ Hz). It is why they are looked for more than
20 years and actively serached with GOLF and MDI instruments aboard
SoHO which offers the best conditions of observation. Some candidates
(Turck-Chièze et al. 2004) have been identified in the GOLF instrument,
during the period of low solar activity thanks to an original research
of multiplets corresponding to surface amplitudes of about 2mm/s. The
examination of the interesting frequency range (100 to 400 μ Hz) will
be pursued up to the end of the SoHO mission scheduled for 2007. Today
our knowledge of the radiative zone is due to acoustic modes. Recent
clear progress is due to the detection of modes less influenced by the
sun activity, in the range 400-1600 μ Hz. The sound speed is determined
down to 0.06 Ro with a resolution of 3%. This profile is used to improve
the solar model and its deviations from a static vision. The rotation
profile is now clearly established down to the limit of the core and its
rigidity can only be explained by invoking a magnetic field effect. We
present here GOLF-NG (Turck-Chièze et al., 2000) built by a French
Spanish collaboration to improve g-mode detection. Based on the Doppler
velocity method using a resonant spectrometer with a 16 channels on
the sodium line, the main objective of GOLF-NG is to contribute to
get an MHD picture of the Sun to better understand the influence of
the Sun on earth climate, in improving the detection by a factor 10 in
decreasing the solar noise thanks to a variable magnet. Consequently,
the physical information will be extracted at different heights in the
atmosphere. A prototype will be installed in 2005 in Tenerife. Then a
spatial version will be available for taking place in one project of the
ILWS mission. Turck-Chièze, S., Robillot, J.M., Dzitko, H ., Boumier,
P., Decaudin, M., Gabriel, A.H., Garcia, R.A., Grec, G., Pallé, P.L.,
Renaud, C., Schmidt, D., 2000, ESA SP-464, 331; Turck-Chièze, S.,
Garcia, R.A., Couvidat, S., et al., 2004, ApJ, vol 604,
---------------------------------------------------------
Title: Eleven years of IRIS frequencies and splittings
Authors: Fossat, E.; Salabert, David; Cacciani, A.; Ehgamberdiev,
S.; Gelly, B.; Grec, G.; Hoeksema, J. T.; Kholikov, S.; Lazrek, M.;
Palle, P.; Schmider, F. X.; Tomczyk, S.
2003ESASP.517..139F Altcode: 2003soho...12..139F
Having acquired since July, 1989, a complete 11-year solar cycle of
full disk data, the IRIS++ network has now made available to anyone the
longest helioseismic data base to-date. A few results obtained from this
very long time series are briefly presented here, with some emphasis
on the low degree p-mode frequencies themselves, and their rotational
splittings that have been estimated with unprecedented accuracy.
---------------------------------------------------------
Title: A search for solar g modes in the GOLF data
Authors: Gabriel, A. H.; Baudin, F.; Boumier, P.; García, R. A.;
Turck-Chièze, S.; Appourchaux, T.; Bertello, L.; Berthomieu, G.;
Charra, J.; Gough, D. O.; Pallé, P. L.; Provost, J.; Renaud, C.;
Robillot, J. -M.; Roca Cortés, T.; Thiery, S.; Ulrich, R. K.
2002A&A...390.1119G Altcode:
With over 5 years of GOLF data having some 90% continuity, a new
attempt has been made to search for possible solar g modes. Statistical
methods are used, based on the minimum of assumptions regarding the
solar physics; namely that mode line-widths are small compared with
the inverse of the observing time, and that modes are sought in the
frequency interval 150 to 400 mu Hz. A number of simulations are carried
out in order to understand the expected behaviour of a system consisting
principally of a solar noise continuum overlaid with some weak sharp
resonances. The method adopted is based on the FFT analysis of a time
series with zero-padding by a factor of 5. One prominent resonance at
284.666 mu Hz coincides with a previous tentative assignment as one
member of an n=1, l=1, p-mode multiplet. Components of two multiplets,
previously tentatively identified as possible g-mode candidates from
the GOLF data in 1998, continue to be found, although their statistical
significance is shown to be insufficient, within the present assumption
regarding the nature of the signal. An upper limit to the amplitude
of any g mode present is calculated using two different statistical
approaches, according to either the assumed absence (H0 hypothesis)
or the assumed presence (H1 hypothesis) of a signal. The former yields
a slightly lower limit of around 6 mm/s.
---------------------------------------------------------
Title: IRIS<SUP>++</SUP> database: Merging of IRIS + Mark-1 + LOWL
Authors: Salabert, D.; Fossat, E.; Gelly, B.; Tomczyk, S.; Pallé, P.;
Jiménez-Reyes, S. J.; Cacciani, A.; Corbard, T.; Ehgamberdiev, S.;
Grec, G.; Hoeksema, J. T.; Kholikov, S.; Lazrek, M.; Schmider, F. X.
2002A&A...390..717S Altcode:
The IRIS network has been operated continuously since July 1st
1989. To date, it has acquired more than a complete solar cycle
of full-disk helioseismic data which has been used to constrain
the structure and rotation of the deep solar interior. However,
the duty cycle of the network data has never reached initial
expectations. To improve this situation, several cooperations have
been developed with teams collecting observations with similar
instruments. This paper demonstrates that we are able to merge data
from these different instruments in a consistent manner resulting
in a very significant improvement in network duty cycle over more
than one solar cycle initiating what we call the IRIS<SUP>++</SUP>
network. The integrated radial velocities from the IRIS<SUP>++</SUP>
database (1989 to 1999) are available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/390/717
---------------------------------------------------------
Title: Analysis of variability of p-mode parameters in 11 years of
IRIS data
Authors: Salabert, D.; Jiménez-Reyes, S. J.; Fossat, E.; Cacciani,
A.; Ehgamberdiev, S.; Gelly, B.; Grec, G.; Hoeksema, J. T.; Khalikov,
S.; Lazrek, M.; Pallé, P.; Schmider, F. X.; Tomczyk, S.
2002ESASP.477..253S Altcode: 2002scsw.conf..253S
11 years of IRIS (the low degree helioseismology network) have been
analysed for the study of p-modes parameters variability. The duty
cycle of the network data has been improved by the partial gap filling
method named "repetitive music". This paper discusses the variations
of all p-modes parameters along these 11 years.
---------------------------------------------------------
Title: δ Scuti stars with STARE: a project on planetary transits
and stellar variability
Authors: Alonso, R.; Brown, T. M.; Belmonte, J. A.; Charbonneau, D.;
Fox Machado, L.; Pallé, P. L.
2002ESASP.485..245A Altcode: 2002sshp.conf..245A
In this contribution, we show the capability of STARE to obtain
frequencies and amplitudes from high temporal resolution δ Scuti
spectra. Lightcurves of 13 new field δ Scuti stars are analyzed and a
total of 21 oscillation modes are found in a single field. Noise level
in the spectra falls bellow 3 mmag for stars fainter than magnitude
9. Subsequent analysis of the other observed fields, a new location
for STARE, as well as the sharing of data with similar projects will
provide higher-quality results and a valuable δ Scuti database,
which would be useful for follow-up observations.
---------------------------------------------------------
Title: The STELLA project: two 1.2m robotic telescopes for
simultaneous high-resolution Echelle spectroscopy and imaging
photometry
Authors: Strassmeier, K. G.; Granzer, T.; Weber, M.; Woche, M.;
Hildebrandt, G.; Bauer, S. -M.; Paschke, J.; Roth, M. M.; Washuettl,
A.; Arlt, K.; Stolz, P. A.; Schmitt, J. H. M. M.; Hempelmann, A.;
Hagen, H. -J.; Ruder, H.; Palle, P. L.; Arnay, R.
2001AN....322..287S Altcode:
We present an overview and a brief report on the status of the STELLA
project (abbreviation for STELLar Activity). The STELLA-I telescope
will be the first robotic telescope that feeds a bench-mounted
high-resolution Echelle spectrograph with a set of 50 and 100 μm
fibres and provides spectral resolutions of up to 47,000 with a
1 arcsec slit. The spectrograph is a white-pupil design located
in a separated temperature-controlled room to guarantee long-term
stability. The building will have a roll-off roof and is capable to
host two telescopes. First light for STELLA-I is planned for summer
2002. STELLA-II is foreseen to be a photometric imaging telescope for
the optical and near-infrared wavelengths and will follow in 2003.
---------------------------------------------------------
Title: Analysis of the solar cycle and core rotation using 15 years
of Mark-I observations: 1984-1999 . I. The solar cycle
Authors: Jiménez-Reyes, S. J.; Corbard, T.; Pallé, P. L.; Roca
Cortés, T.; Tomczyk, S.
2001A&A...379..622J Altcode: 2001astro.ph.10364J
High quality observations of the low-degree acoustic modes
(p-modes) exist for almost two complete solar cycles using the solar
spectrophotometer Mark-I, located at the Observatorio del Teide
(Tenerife, Spain) and operating now as part of the Birmingham Solar
Oscillations Network (BiSON). We have performed a Fourier analysis of
30 calibrated time-series of one year duration covering a total period
of 15 years between 1984 and 1999. Applying different techniques to the
resulting power spectra, we study the signature of the solar activity
changes on the low-degree p-modes. We show that the variation of the
central frequencies and the total velocity power (TVP) changes. A
new method of simultaneous fit is developed and a special effort
has been made to study the frequency-dependence of the frequency
shift. The results confirm a variation of the central frequencies of
acoustic modes of about 0.45 mu Hz, peak-to-peak, on average for low
degree modes between 2.5 and 3.7 mHz. The TVP is anti-correlated with
the common activity indices with a decrease of about 20% between the
minimum and the maximum of solar cycle 22. The results are compared
with those obtained for intermediate degrees, using the LOWL data. The
frequency shift is found to increase with the degree with a weak
l-dependence similar to that of the inverse mode mass. This verifies
earlier suggestions that near surface effects are predominant.
---------------------------------------------------------
Title: An estimation of global solar p-mode frequencies from IRIS
network data: 1989-1996
Authors: Serebryanskiy, A.; Ehgamberdiev, Sh.; Kholikov, Sh.; Fossat,
E.; Gelly, B.; Schmider, F. X.; Grec, G.; Cacciani, A.; Palle, P. L.;
Lazrek, M.; Hoeksema, J. T.
2001NewA....6..189S Altcode:
The IRIS network has accumulated full disk helioseismological data
since July 1989, i.e. a complete 11-year solar cycle. Since the
last paper publishing a frequency list [A&A 317 (1997) L71],
not only has the network acquired new data, but has also developed
new co-operative programs with compatible instruments [Abstr. SOHO
6/GONG 98 Workshop (1998) 51], so that merging IRIS files with these
co-operative program data sets has made possible the improvement
of the overall duty cycle. This paper presents new estimations of
low degree p-mode frequencies obtained from this IRIS<SUP>++</SUP>
data bank covering the period 1989-1996, as well as the variation of
their main parameters along the total range of magnetic activity, from
before the last maximum to the very minimum. A preliminary estimation
of the peak profile asymmetries is also included.
---------------------------------------------------------
Title: Foreword
Authors: Pallé, Pere L.
2001ESASP.464....3P Altcode: 2001soho...10....3P
No abstract at ADS
---------------------------------------------------------
Title: g-mode: a new generation of helioseismic instrument
Authors: Turck-Chièze, S.; Robillot, J. M.; Dzitko, H.; Boumier, P.;
Decaudin, M.; Gabriel, A.; Garcia, R. A.; Gree, G.; Pallé, P. L.;
Renaud, C.; Schmitt, D.
2001ESASP.464..331T Altcode: 2001soho...10..331T
The GOLF team pushes a new concept of instrument devoted to the search
of gravity modes and low order low frequency p modes in order to improve
our knowledge of the deep solar interior. The instrumental concept
is to measure the Doppler shift together with the time evolution of
the D1 sodium line using a 15 point resonance spectrometer. A sodium
vapor resonance cell placed in a static magnetic field varying along
the longitudinal axis is used to sample simultaneously 8 points on
each wing of the line. New Active Pixel Sensor detectors will be
specifically designed for this instrument. A low spatial resolution
of the Sun is also under study in this concept. First ground-based
observations with this instrument are scheduled for 2001/2002 at
Tenerife. The space concept of this instrument is under study in France
as an R&T (Research and Technology) study sponsored by CNES, the
French Space Agency. After some determining validation tests, this
kind of instrument might be placed onboard either a micro satellite
or a satellite dedicated to the study of the Sun.
---------------------------------------------------------
Title: LOWL p-mode frequencies and their variation with solar activity
Authors: Jiménez-Reyes, Sebastián J.; Corbard, Thierry; Pallé,
Pere L.; Tomczyk, Steve
2001ESASP.464..107J Altcode: 2001soho...10..107J; 2000astro.ph.11410J
We present an analysis of the frequency shift and the even terms of the
frequency splitting coefficients carried out using six years of LOWL
data, starting in 1994. The temporal Variations and their Dependences
with the frequency and degree are addressed. The results are consistent
with previous analysis.
---------------------------------------------------------
Title: Helio- and asteroseismology at the dawn of the millennium
Authors: Wilson, A.; Pallé, Pere L.
2001ESASP.464.....W Altcode: 2001soho...10.....W
No abstract at ADS
---------------------------------------------------------
Title: Signature of the solar cycle in the low degree p-modes
using Mark-I
Authors: Jiménez-Reyes, Sebastián J.; Corbard, Thierry; Pallé,
Pere L.
2001ESASP.464..103J Altcode: 2001soho...10..103J; 2000astro.ph.11411J
High quality observations of the low degree p-modes exist for almost two
complete solar cycles using the solar spectrophotometer Mark-I, located
and operating at the Observatorio del Teide (Tenerife, Spain). In this
work, the observations available have been re-analyzed over a much
wider time interval than before. We analyze the time variation of the
yearly frequency shift and its frequency dependence. This information
will be used in order to average annual power spectra by removing
the effect of the solar cycle. Using this average power spectrum,
a new estimate of the rotational splittings is attempted.
---------------------------------------------------------
Title: A self-consistent procedure to detect low-l low-n solar p-modes
Authors: Eff-Darwich, A.; Régulo, C.; Roca Cortés, T.; Pallé,
P. L.; Korzennik, S. G.
2001ESASP.464..511E Altcode: 2001soho...10..511E
Recent data colleted by the helioseismic experiments aboard SOHO have
allowed the detection of low degree p-modes with lower and lower order,
n. In particular, the GOLF experiment is currently able to identify
unambiguously modes as low as n = 8 for l = 0, and l = 1 (e.g., ≍1.3
mHz). To detect p-modes with lower n (hence lower frequeny), where the
signal-to-noise ratio gets small, one needs some guidance. Several
groups use theoretical predictions from a standard solar model as a
guide. But using theoretical predictions has the potential to bias
the mode identification and in turn produce modes that confirm the
features of the model rather than the properties of the actual sun. To
alleviate this, we propose an alternative methodology based on peak
fitting techniques and helioseismic data inversion procedures. This
method allow us to reject many peaks from the spectrum by using the
prediction capability of the inversion. We describe the method and
show resuls from its application to current GOLF spectra.
---------------------------------------------------------
Title: Solar cycle variations of oscillation mode parameters from
LOWL and MARK-I instruments
Authors: Jimeńez Reyes, S. J.; Corbard, T.; Tomczyk, S.; Pallé, P. L.
2000SPD....31.0112J Altcode: 2000BAAS...32.1289J
The signature of the Solar-Cycle appears clearly in the p-mode
parameters (Jiménez-Reyes et al. 1998, Libbrecht & Woodard 1990,
and Anguera et al. 1992). At present, the study of the p-mode parameter
variation is a very active topic in helioseismology where, thanks to
projects like BISON, IRIS, GONG, LOWL and MDI, we are able for the first
time to analyse, using heliosismology, how the Sun internal structure
and dynamic change over the magnetic cycle. High-quality observations
for low degree p-modes have been accumulated for more than twenty years
using the solar spectro photometer MARK-I, located and operating at the
Observatorio del Teide (Tenerife, Spain). The data-base available have
been re-analyzed over a much wider time interval than before. Moreover,
the LOWL instrument, a Potassium Magneto-Optical Filter, located at the
Manua Loa Observatory, has been measuring for more than six years solar
oscillations of intermadiate p-mode degree. The data-base represents
one of the best available to analyze the influence of the Solar-Cycle
on the mode parameters, mainly because these data, concerning both low
and intermadiate degree modes, give us information over an extensive
range of the solar depths which may allow us to locate characteristics
of the solar dynamo process. Using different data sets and different
techniques, we analyse the behaviour of the solar p-modes in an attempt
to better understand the origin of the Solar-Cycle.
---------------------------------------------------------
Title: The ECHO (Experiment for Coordinated Helioseismic Observations)
Network
Authors: Tomczyk, S.; Jiménez Reyes, S. J.; Jiménez, A.; Pallé,
P. L.
2000SPD....31.0117T Altcode: 2000BAAS...32..804T
The High Altitude Observatory of the National Center for Atmospheric
Research (HAO/NCAR) in collaboration with the Instituto de Astrofísica
de Canarias (IAC) have recently completed a two-station helioseismic
network with sites at Mauna Loa, Hawaii and Izana, Tenerife. The
instruments are Doppler imagers employing Magneto-Optical filters and
are based on the existing LOWL instrument. We expect the network to
provide a duty cycle of 50%, compared to 22% for the LOWL. In addition,
the ECHO incorporates several improvements over the LOWL including:
1) a CCD detector with square pixels and a factor of two increase
in spatial resolution; 2) better guiding; 3) exchange of red and blue
images every 15 seconds to better facilitate detector flat fielding; and
4) improved thermal control of the instrument enclosure. We will present
initial data from the network and demonstrate network performance.
---------------------------------------------------------
Title: p-mode Frequency Shift as Solar Activity Index
Authors: Jiménez-Reyes, S. J.; Corbard, Thierry; Palle, Pere L.;
Tomczyk
2000ESASP.463..341J Altcode: 2000sctc.proc..341J
No abstract at ADS
---------------------------------------------------------
Title: Frequencies of Solar p-Modes from GOLF and VIRGO-SPM (SOHO)
Authors: Roca Cortés, T.; Jiménez, A.; Pallé, P. L.; GOLF Team;
Virgo Team
1999ESASP.448..135R Altcode: 1999ESPM....9..135R; 1999mfsp.conf..135R
No abstract at ADS
---------------------------------------------------------
Title: A new observational strategy in search for solar g-modes
Authors: Mateos, I. Martí; n.; Pallé, P. L.
1999SoPh..189..241M Altcode:
The aim of the present work is the detection of solar g-modes, by
means of a new observational strategy based on the exploitation of
their spatial and temporal properties. The basic data, obtained at
the Observatorio del Teide in 1993, consists of daily solar velocity
measurements taken continuously and sequentially at six different
and symmetric positions on the solar disk. By correlating the time
series resulting from the reduction process, from different solar disk
positions and considering the geometrical properties of different
modes (l,m) on the Sun's surface, some of these can be selectively
eliminated or enhanced. Moreover, the main spectral features present
in the resulting power spectra must have precise phase relations
if they correspond to global solar g-modes. The severe constraints
established by the above properties have been applied to the best
observed series (summer 1993). As a result, a discrete series of peaks
have been selected that fulfill all the imposed conditions and which
can therefore be interpreted as being of solar origin.
---------------------------------------------------------
Title: Power spectra comparison between GOLF and MDI velocity
observations
Authors: Henney, C. J.; Ulrich, R. K.; Bertello, L.; Bogart,
R. S.; Bush, R. I.; Scherrer, P. H.; Palle, P. L.; Roca Cortes, T.;
Turck-Chieze, S.
1999AAS...194.5617H Altcode: 1999BAAS...31..914H
We present a comparison of the velocity power spectra between the GOLF
and MDI instruments. In addition, this poster outlines work towards
creating a GOLF-simulated signal utilizing MDI velocity images. The
simulation of the GOLF signal is achieved by integrating spatially
weighted masks with MDI LOI-proxy velocity images. The GOLF-simulated
signal and a selection of additional spatially masked MDI velocity
signals are compared with the observed GOLF signal for a 759 day period
from May 25, 1996 through June 22, 1998. Ultimately, a cross-analysis
process between GOLF and MDI signals could lead to an enhancement
of our ability to detect low frequency solar oscillations. The
signal-to-background ratio (S/B) for the GOLF and the spatially masked
MDI velocity data is presented for low degree (l <= 3) and low
frequency p-modes. We find that signals from both MDI and GOLF are
beneficial for detecting low degree (l <= 3) and low frequency
(< 2000 mu Hz) p-modes. For the frequency range and the signals
compared in this poster, the GOLF signal has the highest S/B for l=0
p-modes. The S/B of the GOLF and MDI central region masked signals
is good for detecting l=1 p-modes. For l >= 2 p-modes, the central
region masked signals have the highest S/B of the power spectra compared
here. In addition, the S/B of the preliminary GOLF-simulated signal
is found to be more similar to the GOLF signal than the MDI LOI-proxy
signal without spatial masking for the modes investigated here.
---------------------------------------------------------
Title: Improving the signal-to-noise ratio in solar oscillation
spectra
Authors: García, R. A.; Jefferies, S. M.; Toner, C. G.; Pallé, P. L.
1999A&A...346L..61G Altcode:
We describe a data analysis technique for helioseismology that
provides a reduction in the contamination of the solar oscillation
spectrum from incoherent noise. We show that the technique allows:
(i) a significant improvement in the signal-to-noise ratio for the
modes in the oscillation power spectrum, and (ii) the solar velocity
background spectrum to be observed at low frequencies using ground-based
observations.
---------------------------------------------------------
Title: Full disk helioseismology: repetitive music and the question
of gap filling
Authors: Fossat, E.; Kholikov, Sh.; Gelly, B.; Schmider, F. X.;
Fierry-Fraillon, D.; Grec, G.; Palle, P.; Cacciani, A.; Ehgamberdiev,
S.; Hoeksema, J. T.; Lazrek, M.
1999A&A...343..608F Altcode:
Helioseismology requires continuous measurements of very long
duration, months to years. This paper addresses the specific and
limited case of full disk measurements of p-mode oscillations,
although it can be generalized, to some extent, to the case of imaged
helioseismology. First, a method of mode by mode (or rather pair of
modes by pair of modes) interpolation of the signal in gaps is tested,
and shown to be efficient for gaps as long as two days, but limited to
the frequency range where the signal to noise ratio is good. It is then
noted that the autocorrelation function of the full disk signal, after
dropping quickly to zero in 20 or 30 minutes, shows secondary quasi
periodic bumps, due to the quasi-periodicity of the peak distribution
in the Fourier spectrum. The first of these bumps, at 4 hours or so,
is higher than 70 percent and climbs to nearly 90 percent in limited
frequency ranges. This suggests that an easy gap filling method can
be developed, with a confidence of nearly 90 percent across all the
frequency range, as long as the gap does not exceed 8 hours, with
at least 4 hours of data at both ends. Even a short gap of one or
two periods is better filled by the data taken 4 hours earlier or
later than by local interpolation. This relaxes quite considerably
the requirement of continuity of the observations for the case the
full disk p-mode helioseismology. Applied to 7 years of IRIS data,
this method permits the detection of all low frequency p-modes already
seen by 2 years of the GOLF instrument data, and makes possible the
measurement of their frequencies with an accuracy consistent with the
partially filled 7 years of statistics.
---------------------------------------------------------
Title: Results from the GOLF instrument on SOHO
Authors: Gabriel, A. H.; Turck-Chièze, S.; García, R. A.; Pallé,
P. L.; Boumier, P.; Thiery, S.; Baudin, F.; Grec, G.; Ulrich, R. K.;
Bertello, L.; Roca Cortés, T.; Robillot, J. -M.
1999AdSpR..24..147G Altcode:
An 800 day series of GOLF velocity data, with uniquely high continuity
and stability, offers the best ever signal to noise ratio obtained
in global Sun observations. Following meticulous efforts to provide
reliable calibration, these data have been used for measurements of
frequencies, line-widths and power in the p-modes, which are used
for inversion to give the internal sound speed, for comparison with
theoretical models. A search for g-modes is at present inconclusive, but
has yielded two possible candidate frequencies. The analysis available
today is regarded as preliminary and more complete methods are currently
in hand. With the resumption of routine observations following the
SOHO recovery, it is hoped that the data can be considerably extended,
enabling changes with the solar cycle to be explored, as well as an
extended g-mode search.
---------------------------------------------------------
Title: On the nature of the current GOLF p-mode signal
Authors: Pallé, P. L.; Régulo, C.; Roca Cortés, T.; García, R. A.;
Jiménez, A.; Boumier, P.; Gabriel, A.; Grec, G.; Robillot, J. M.;
Turck-Chièze, S.; Ulrich, R. K.; SOI Team
1999A&A...341..625P Altcode:
The GOLF experiment on board SOHO is designed to measure global
oscillations of the disk-integrated sunlight with high sensitivity and
with long term stability. The GOLF data is thus ideally suited for
both the study of the p-mode spectrum and to address the search for
gravity modes. Due to their occasional malfunction the project decided
to stop the rotating polarizing elements at an optimum place in order to
maintain a precise sequence of measurements with the highest possible
duty cycle. This action means that subsequently GOLF only measures two
monochromatic intensities {I}_b(+) and {I}_b(-) on the blue wing of
the sodium doublet. In this work we investigate the nature of these
signals separately and in combinations. Our method is to study the
temporal relative phase relations between the low degree (l <=
3) p-mode signals derived from data sets obtained from simultaneous
observations, both from other SOHO instruments (GOLF and SOI) and from
Mark- I, the Tenerife station of the ground-based BiSON network. It
is found that these signals are “almost” pure velocity signals. A
simple model indicates that a contamination of a pure intensity-like
signal of 14% amplitude would fully explain the true nature of the
current GOLF signal. Moreover, it is found that the ratios, defined
for other instruments (Mark-I, SOI and, by extension BiSON and IRIS),
also have exactly the same nature as the GOLF ratio.
---------------------------------------------------------
Title: The Sun as a Star: Background, Intensity and Velocity, Power
Spectra and Convection
Authors: Pallé, P. L.; Roca Cortés, T.; Jiménez, A.; GOLF Team;
Virgo Team
1999ASPC..173..297P Altcode: 1999sstt.conf..297P
No abstract at ADS
---------------------------------------------------------
Title: Low L Solar p-Mode Oscillations Parameters and Convection
Authors: Roca Cortés, T.; Montañés, P.; Pallé, P. L.; Pérez
Hernández, F.; Jiménez, A.; Régulo, C.; GOLF Team
1999ASPC..173..305R Altcode: 1999sstt.conf..305R
No abstract at ADS
---------------------------------------------------------
Title: Power spectra comparison between GOLF and MDI velocity
observations.
Authors: Henney, C. J.; Ulrich, R. K.; Bertello, L.; Bogart, R. S.;
Bush, R. I.; Scherrer, P. H.; Pallé, P. L.; Roca Cortés, T.;
Turck-Chièze, S.
1999BAAS...31Q1237H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Measurements of the solar aureole at the Teide Observatory
Authors: González Jorge, H.; Martínez Pillet, V.; Vázquez, M.;
Pallé, P.; McGovern, F.; Raes, F.
1998NewAR..42..515G Altcode:
Daily measurements of the solar aureole were made at the Vacuum Newton
Telescope ( D=40 cm) at the Teide Observatory (Tenerife) for various
airmasses. We use these measurements to understand how the aureole
is produced and to extrapolate visible measurements to the infrared
range (1.6 μm). This information will be used to correct sunspot
photometric measurements. This programme is included in the second
Aerosol Characterization Experiment (ACE-2) held on Tenerife from
mid June to July 1997. During this period a large variety of aerosol
measurements were made at different altitudes on the island and by
aircraft flying over this area of the North Atlantic Ocean. This
information will be used to constrain the physical parameters of the
aerosols needed for our extrapolation.
---------------------------------------------------------
Title: High-Frequency Peaks in the Power Spectrum of Solar Velocity
Observations from the GOLF Experiment
Authors: García, R. A.; Pallé, P. L.; Turck-Chièze, S.; Osaki,
Y.; Shibahashi, H.; Jefferies, S. M.; Boumier, P.; Gabriel, A. H.;
Grec, G.; Robillot, J. M.; Roca Cortés, T.; Ulrich, R. K.
1998ApJ...504L..51G Altcode:
The power spectrum of more than 630 days of full-disk solar velocity
data, provided by the GOLF spectrophotometer aboard the Solar and
Heliospheric Observatory, has revealed the presence of modelike
structure well beyond the acoustic cutoff frequency for the solar
atmosphere (ν<SUB>ac</SUB>~5.4 mHz). Similar data produced by
full-disk instruments deployed in Earth-based networks (BiSON and
IRIS) had not shown any peak structure above ν<SUB>ac</SUB>: this
is probably due to the higher levels of noise that are inherent in
Earth-based experiments. We show that the observed peak structure
(ν<SUB>ac</SUB><=ν<=7.5 mHz) can be explained by a simple
two-wave interference model if the high-frequency waves are partially
reflected at the back side of the Sun.
---------------------------------------------------------
Title: Probing the Solar Subphotospheric Layers Using Ring Analysis
Authors: González Hernández, I.; Patrón, J.; Roca-Cortés, T.;
Pérez Hernández, F.; Jiménez, A.; Jiménez-Reyes, S. J.; Martín,
I.; Pallé, P. L.; Régulo, C.
1998Ap&SS.263..335G Altcode: 1999Ap&SS.263..335G; 1998Ap&SS.263..335H
No abstract at ADS
---------------------------------------------------------
Title: 3-D Helioseismology: Rings and Horizontal Flows
Authors: Patrón, J.; González Hernández, I.; Jiménez, A.;
Jiménez-Reyes, S. J.; Martín, I.; Pallé, P. L.; Pérez Hernández,
F.; Régulo, C.; Roca-Cortés, T.
1998Ap&SS.263..327P Altcode: 1999Ap&SS.263..327P
No abstract at ADS
---------------------------------------------------------
Title: A New Observational Strategy to Search for Solar g-Modes
Authors: Martín Mateos, I.; González Hernández, I.; Jiménez, A.;
Jiménez-Reyes, S. J.; Patrón, J.; Pallé, P. L.; Pérez Hernández,
F.; Régulo, C.; Roca-Cortés, T.
1998Ap&SS.263..339M Altcode: 1999Ap&SS.263..339M
No abstract at ADS
---------------------------------------------------------
Title: The Solar Rotation Rate Ω(R, θ)
Authors: Eff-Darwich, A.; Korzennik, S. G.; Roca Cortés, T.; Pérez
Hernández, F.; Pallé, P.
1998Ap&SS.263..347E Altcode: 1999Ap&SS.263..347E
In recent years, the capability to detect and analyse solar oscillation
acoustic modes has greatly improved. The development of ground based
networks like GONG or BiSON and the use of space platforms like SOHO
has allowed us to study the structure and dynamics of the Sun with
unprecedented precision.
---------------------------------------------------------
Title: Progress Toward an IRIS<SUP>++</SUP> Database Open to the
Helioseismological Community
Authors: Gelly, B.; Khalikov, S.; Pallé, P. L.; IRIS Team
1998ESASP.418..199G Altcode: 1998soho....6..199G
The IRIS network is now fourteen years old, and has continuously
been taking data since 1989. The data analysis, which produced some
noticeable scientifical results, like the measurement of the ell =
1 rotationnal splitting or the measurement of the solar acoustic
cut-off frequency, was mainly performed with the summer campaigns
data of 1989 to 1992. P-mode frequency and width tables were recently
published using the same subset of the IRIS data . We are now finishing
the calibration and the timing of the whole set of IRIS data from 89
to 97, which will increase by a factor of 4 the amount of available
data. The duty cycle of the IRIS network ranges from about 65% over 3
months of the summer campaigns to some 23% over one year in the worst
case. To improve our duty cycle we developed several collaborations with
other teams running similar instruments: (1) the Mark I instrument,
ran at the IAC for many years, a potassium resonance single pixel
device, also part of the BiSON network (Elsworth et al., 1988). (2)
Alexandro Cacciani's MOF, ran at the JPL in Pasadena. Although this
is a sodium resonance imaging instrument, it has been used in “one
pixel” format for several summer seasons since 1989 (Cacciani et
al., 1984). (3) the LOWL instrument is a Doppler imager also based
on a Magneto-Optical Filter (MOF), operated at the Mauna Loa solar
observatory since 1994 (Tomczyk et al., 1995). The merging of those
'alien' data has been carefully adressed at the calibration ands timing
stages, and we can now present the advantages of such a-posteriori
collaborations. We endeavour to set-up the corresponding database of
'one-pixel seismological data from ground-based intruments' in Nice
and to open it to the scientific community of this meeting by the
end of 1998. This database will soon have the potential to trace the
spectral features of the solar signal over one 11-years cycle.
---------------------------------------------------------
Title: Solar activity cycle frequency shifts of low-degree p-modes
Authors: Jimenez-Reyes, S. J.; Regulo, C.; Palle, P. L.; Roca
Cortes, T.
1998A&A...329.1119J Altcode:
We report on an extensive analysis of the low-degree p-mode frequency
shifts over Solar Cycle n(b {o}) 22 (1984--1995) based on continuous
data taken at the Observatorio del Teide (Tenerife). Aside from the
known good correlation between frequency shifts and solar activity
indices, we have also investigated on short and long time-scales
correlations (from 2 months to 1.5 years and from 1.5 to 11 years)
showing different behavior. In addition, by using smoothed data for
both, frequency shifts and solar activity indices, a “hysteresis”
phenomenon is observed. This implies different behavior of both
quantities in the ascending and descending parts of the cycle,
while saturation effects exists at extreme phases. Finally, a degree
dependence of this behavior is also noticed when analyzing separately
the shifts for the even (0, 2) and odd (1, 3) mode groups. These results
show that the p-mode frequency shifts are very sensitive to structural
changes taking place in the Sun as the solar activity cycle proceeds;
either in their upper layers, as activity migrates towards the equator,
or, in its interior with a phenomenon that slowly progresses outwards,
or both. A much more complete picture should emerge when data obtained
from the new operational helioseismic projects over more than one
solar cycle come into existence.
---------------------------------------------------------
Title: Frequency Stability in GOLF Data, 1996-97
Authors: Fierry Fraillon, D.; Pallé, P. L.; Golf Team
1998ESASP.418..911F Altcode: 1998soho....6..911F
The solar activity, following an eleven years cycle, modifies the
physical properties of the resonant cavity where the oscillation
acoustic modes are trapped. Its effect on p-modes frequencies is
a positive shift as the solar activity grows from a minimum to
a maximum (Fossat et al. 1987, Pallé et al. 1989, Elsworth et
al. 1990). A continuous set of observation like the Golf data set,
fron the 11 April 1996 to the 3 January 1998, allows a study of the
p-modes frequency shift during a minimal solar activity. We selected
3 power spectra with differents MPSI magnetic index and with a 36 days
duration of observation according to the evolution time of the magnetic
index. Then, we used a mode to mode cross-correlation technique in
order to estimate an individual shift of the mean frequency of n =
13 to 24, l = 0 to 3 modes by fitting a Lorentzian profile on the
cross-correlation. We also investigate for a global frequency shift
using the same cross-correlation technique. The results show the
evidence of the frequency stability of p-modes in the 19-months GOLF
data set even with the light increase of the solar activity since
September 1998.
---------------------------------------------------------
Title: High Frequency signal in GOLF Data
Authors: Garcia, R. A.; Palle, P. L.; GOLF Team
1998IAUS..185..447G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Cycle Changes of the p-Mode Spectrum and Mean Irradiance
Authors: Jiménez-Reyes, Sebastián J.; Pallé, Pere L.
1998sers.conf..419J Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Presence of the Solar 160-min Signal in GOLF Data
Authors: Pallé, P. L.; Roca Cortés, T.; Gelly, B.; GOLF Team
1998ESASP.418..291P Altcode: 1998soho....6..291P
GOLF data continuously obtained over the last two years, provides a
unique and ideal set for studying the low frequency (ν <= 500 muHz)
range of the solar spectrum oscillations. In this work we have focused
our attention to the spectral region around 160 minute (~104.2 muHz),
where a controversial “solar g-mode” is claimed to be (Kotov et al.,
1997). Various spectral techniques have been used in order to reveal
its possible presence and stability as well as to set an upper limit
to its amplitude. In this poster, the results obtained at the time of
the meeting will be presented and discussed.
---------------------------------------------------------
Title: On the Nature of the Current GOLF Signal
Authors: Pallé, P. L.; Regulo, C.; Roca Cortés, T.; Garcia, R. A.;
Jiménez, A.; GOLF Team
1998ESASP.418..285P Altcode: 1998soho....6..285P
Although the occasional malfunction of rotating polarizing elements
at the beginning of the SOHO mission, which led to its stop, GOLF
instrument has been performing precise and continuous measurements
over the last two years. In this work, the nature of the actual GOLF
measurement, two monochromatic intensities I<SUB>b</SUB><SUP>+</SUP>
and I<SUB>b</SUB><SUP>-</SUP> on the blue wing of the sodium doublet,
is investigated by comparing the temporal phase of the low degree (ell
<= 3) p-modes obtained from simultaneous data sets, either from SOHO
(GOLF in different operating modes) and from a well known ground-based
instrument (MARK-I). It is found that the signals are “almost”
pure velocity signals whose behaviour can be explained, amongst other
possible mechanisms, by a contamination of an intensity-like signal of
14% amplitude. Furthermore is it proved that the ratio (instrumental
velocity) as defined in MARK-I instrument (and by extension in IRIS one)
do have the same nature as the GOLF blue wing signal X<SUB>b</SUB>.
---------------------------------------------------------
Title: High-Frequency Signals in the Power Spectrum of Integrated
Solar Velocity Observations from the GOLF Experiment
Authors: Garcia, R. A.; Pallé, P. L.; Turck-Chièze, S.; Osaki, Y.;
Shibahashi, H.; Jefferies, S.; GOLF Team
1998ESASP.418..177G Altcode: 1998soho....6..177G
The power spectrum of ~630 days of full-disk solar velocity data,
provided by the GOLF spectrophotometer aboard SOHO, has revealed
the presence of mode-like structure well beyond the acoustic cut-off
frequency for the solar atmosphere (nu<SUB>ac</SUB> ~5.4 mHz). This
kind of structure has already been observed in intermediate and high
spatial resolution oscillation data (Duvall et al. 1991), but never
before in integrated data like BiSON or IRIS. This is probably due
to the higher level of noise that are inherent to the earth-based
experiments. In this contribution, we analyse the observed peak
structure (nu<SUB>ac</SUB> < ν < 7.5 mHz) and we describe the
theoretical analysis of such signal.
---------------------------------------------------------
Title: A Parametric Model of the Solar Full-Disk Seismological Signal
Authors: Mouret, D.; Gelly, B.; Ferrari, A.; Pallé, P. L.; GOLF Team
1998ESASP.418..271M Altcode: 1998soho....6..271M
Solar eigenmodes frequencies are most often determined using some
kind of modelisation of the Fourier spectrum of the data in one or
two dimensions. Many statistical refinements have lead to significant
improvements in the determination of the frequencies and widths of the
spectral lines. Nevertheless, this technique relies strongly on several
asumptions on the nature of the signal (damped oscillators) and of
the resulting spectrum (Lorentz profiles). We present here a different
method based on the parametric modeling of the solar signal, seen as
an autoregressive (AR) process of 2nd order. A parametric modeling with
model orders between 20 to 35 is performed on the filtered GOLF signal,
on a per-mode basis. Preliminary tests show that for ell = 0 modes the
frequencies and widths from the parametric model are in good agreement
(within the error-bars) of the 'classical' published results. A more
complete evaluation is now ongoing and we will be presenting a first
evaluation of the potential of this new signal analysis.
---------------------------------------------------------
Title: The Exact Fractions Technique Applied to the Search of Solar
Gravity Modes
Authors: Pallé, P. L.; Roca Cortés, T.; Gelly, B.; Pérez-Hernández,
F.; GOLF Team
1998ESASP.418..279P Altcode: 1998soho....6..279P
Amongst the different techniques applied up to now to the search
for solar g--modes (peaks identification, study of the phase/power
coherence, the P<SUB>0</SUB> - nu<SUB>r</SUB> diagrams, etc ldots),
some ones are primarily based on the use of their asymptotic behaviour:
the constant separation in period between consecutive modes of the
same degree ell. The exact fractions technique is one of those and has
already been applied to ground based helioseismology data (H.B. van
der Raay, 1998). In the present work, the technique is fully tested
in order to see of its adequacy when the asymptotic property is not
fully accomplished, either because of the rotational splitting of the
modes or because of the range of radial order values considered. The
encouraging results obtained, led us to apply it to a temporal series
of 690 consecutive days obtained with GOLF instrument on board SOHO. The
results are shown by Gabriel et al. in this Workshop.
---------------------------------------------------------
Title: Application of a new observational strategy to the study of
gravitational solar modes
Authors: Martin Mateos, I.; Palle, P. L.
1998IAUS..185...51M Altcode:
The aim of the present work is the detection of solar g-modes, making
use of their spatial and temporal properties, by means of a new
observational strategy. The basic data, gathered at the Observatorio
del Teide in 1993, consists on daily solar velocity measurements
taken continuous and sequentially at six different and symmetric
positions on the solar disk. By correlating the time series resulting
of the reduction process, from different positions and considering the
geometrical properties of different modes (l,m) on the Sun's surface,
some of them can selectively be eliminated of enhanced. Moreover the
main spectral features present in the resulting power spectra must have
precise phase relations if they correspond to global solar g-modes. The
severe constraints that the above properties established, have been
applied to the best observational obtained series (summer 1993). As
a result, a discrete series of peaks have been selected that fulfill
all the imposed conditions, and therefore they can be interpreted as
being of solar origin.
---------------------------------------------------------
Title: First Results on it P Modes from GOLF Experiment
Authors: Lazrek, M.; Baudin, F.; Bertello, L.; Boumier, P.; Charra,
J.; Fierry-Fraillon, D.; Fossat, E.; Gabriel, A. H.; García, R. A.;
Gelly, B.; Gouiffes, C.; Grec, G.; Pallé, P. L.; Pérez Hernández,
F.; Régulo, C.; Renaud, C.; Robillot, J. -M.; Roca Cortés, T.;
Turck-Chièze, S.; Ulrich, R. K.
1997SoPh..175..227L Altcode:
The GOLF experiment on the SOHO mission aims to study the internal
structure of the Sun by measuring the spectrum of global oscillations
in the frequency range 10<SUP>-7</SUP> to 10<SUP>-2</SUP> Hz. Here
we present the results of the analysis of the first 8 months of
data. Special emphasis is put into the frequency determination of the p
modes, as well as the splitting in the multiplets due to rotation. For
both, we show that the improvement in S/N level with respect to the
ground-based networks and other experiments is essential in achieving
a very low-degree frequency table with small errors ∼ 2 parts in
10<SUP>-5</SUP>). On the other hand, the splitting found seems to favour
a solar core which does not rotate slower than its surface. The line
widths do agree with theoretical expectations and other observations.
---------------------------------------------------------
Title: Performance and Early Results from the GOLF Instrument Flown
on the SOHO Mission
Authors: Gabriel, A. H.; Charra, J.; Grec, G.; Robillot, J. -M.;
Roca Cortés, T.; Turck-Chièze, S.; Ulrich, R.; Basu, S.; Baudin,
F.; Bertello, L.; Boumier, P.; Charra, M.; Christensen-Dalsgaard, J.;
Decaudin, M.; Dzitko, H.; Foglizzo, T.; Fossat, E.; García, R. A.;
Herreros, J. M.; Lazrek, M.; Pallé, P. L.; Pétrou, N.; Renaud, C.;
Régulo, C.
1997SoPh..175..207G Altcode:
GOLF in-flight commissioning and calibration was carried out during the
first four months, most of which represented the cruise phase of SOHO
towards its final L1 orbit. The initial performance of GOLF is shown
to be within the design specification, for the entire instrument as
well as for the separate sub-systems. Malfunctioning of the polarising
mechanisms after 3 to 4 months operation has led to the adoption of an
unplanned operating sequence in which these mechanisms are no longer
used. This mode, which measures only the blue wing of the solar sodium
lines, detracts little from the detection and frequency measurements of
global oscillations, but does make more difficult the absolute velocity
calibration, which is currently of the order of 20%. Data continuity
in the new mode is extremely high and the instrument is producing
exceptionally noise-free p-mode spectra. The data set is particularly
well suited to the study of effects due to the excitation mechanism
of the modes, leading to temporal variations in their amplitudes. The
g modes have not yet been detected in this limited data set. In the
present mode of operation, there are no indications of any degradation
which would limit the use of GOLF for up to 6 years or more.
---------------------------------------------------------
Title: Solar P-mode frequencies from the IRIS network.
Authors: Gelly, B.; Fierry-Fraillon, D.; Fossat, E.; Palle, P.;
Cacciani, A.; Ehgamberdiev, S.; Grec, G.; Hoeksema, J. T.; Khalikov,
S.; Lazrek, M.; Loudagh, S.; Pantel, A.; Regulo, C.; Schmider, F. X.
1997A&A...323..235G Altcode:
The Iris network for helioseismology has operated since 1989. We present
tables of solar p-mode frequencies for observations taken during the
four summer seasons from 1989 to 1992. This analysis uses the technique
of maximum likelihood fitting and a χ_2_^2^ model for the probability
density function of the spectrum. The simultaneous fitting of odd and
even pairs of peaks strengthens the identification of the l=3 eigenmodes
and improves the error bars on the 0-2 group. The frequencies are in
good agreement with other observational results and with theoretical
values for the D_0_ and the {DELTA}ν parameters of the asymptotic
approximation. A decrease of 0.25+/-0.12μHz is seen between the 1989
and the 1992 data sets. The change is associated with the decrease of
solar activity and is comparable with results of previous studies.
---------------------------------------------------------
Title: The state of art in helioseismic ground-based experiments
Authors: Palle, P.
1997IAUS..181...15P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: New IRIS constraints on the solar core rotation.
Authors: Gizon, L.; Fossat, E.; Lazrek, M.; Cacciani, A.; Ehgamberdiev,
S.; Gelly, B.; Grec, G.; Hoeksema, J. T.; Khalikov, S.; Palle, P. L.;
Pantel, A.; Regulo, C.; Schmider, F. -X.; Wilson, P. R.
1997A&A...317L..71G Altcode:
Four time series of IRIS data (4 to 6 months) have been used to obtain
improved measurements of the low degree (l=1,2,3) rotational splitting
frequencies. Assuming that the rotation law is known in the outer
layers of the Sun, we investigate the implications of IRIS splittings
for the central regions. Both a one-shell and a two-shell rotation
model have been considered in the solar core. A core rotating slightly
faster than the outer radiative envelope provides the best fit to the
data. Some evidence for the reliability of the observations is shown
by the visibility of differential rotation in the l=3 multiplets.
---------------------------------------------------------
Title: Performance and first results from the GOLF instrument on SoHO
Authors: Gabriel, A. H.; Charra, J.; Grec, G.; Robillot, J. -M.; Roca
Cortés, T.; Turck-Chièze, S.; Ulrich, R.; Baudin, F.; Bertello,
L.; Boumier, P.; Decaudin, M.; Dzitko, H.; Foglizzo, T.; Fossat, E.;
García, R. A.; Herreros, J. M.; Lazrek, M.; Pallé, P. L.; Pétrou,
N.; Renaud, C.; Régulo, C.
1997IAUS..181...53G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Actual Status and Early Results from GOLF Experiment on-board
SOHO
Authors: Roca Cortes, T.; Gabriel, A. H.; Charra, J.; Grec, G.; Ulrich,
R. K.; Turck-Chieze, S.; Robillot, J. M.; Boumier, P.; Regulo, C.;
Baudin, F.; Lazrek, M.; Garcia, R. A.; Palle, P. L.; GOLF Team
1997ASPC..118..249R Altcode: 1997fasp.conf..249R
GOLF is a resonant scattering spectrophotomer which is flying onboard
SOHO. The first four months were dedicated to the commissioning
and calibration of the instrument which led to the conclusion of
a performance within design specification at system and subsystem
levels. However, mal-functioning of the polarising mechanisms at the end
of this period led to the adoption of an unplanned operating sequence in
which the mechanisms are no longer used. This photometric mode, which
measures at two points on the blue wing of the solar sodium lines, has
very little effect on the possibility of reaching the first objective
of the mission: measuring the solar spectrum of normal modes. However,
the precise calibration procedure to transform the actual measurements
into velocity is not trivial. The actual operating mode allows the
obtention of continuous data without interruptions which is producing
exceptionally noise-free p-mode spectra. Although this spectrum is
being studied, the data accumulated do not allow a positive detection
of the g-mode spectrum yet. On the other hand, the present mode of
operation do not show any indication of degradation which could limit
its use for up to 6 years or more of operation.
---------------------------------------------------------
Title: Temporal characteristics of solar p-modes.
Authors: Baudin, F.; Gabriel, A.; Gibert, D.; Palle, P. L.; Regulo, C.
1996A&A...311.1024B Altcode:
A method for “time/frequency” analysis is shortly described, with
a discussion of its limitations in time and frequency resolution,
and in sensitivity to noise in the signal. This is then applied to
observational data. The data used are the luminosity measurements of
the IPHIR experiment, and the velocity measurements performed at the
Observatorio del Teide. The application to these two contemporary data
sets confirms the reliability of the method and provides additional
proof that the observed variation with time is not an effect of
noise. The long and continuous data set allows to extract information
on the temporal behaviour of low degree solar p-modes. The power
of the modes is shown to vary strongly over a time-scale of a few
days. These estimates are direct measurements from power variations,
unlike those deduced from width measured in Fourier spectra. The
temporal behaviour of several modes are compared, mainly showing
independent behaviour, but also giving some indications of weak
correlations between neighbouring modes.
---------------------------------------------------------
Title: Is the Solar Core Rotating Faster of Slower Than the Envelope?
Authors: Lazrek, M.; Pantel, A.; Fossat, E.; Gelly, B.; Schmider,
F. X.; Fierry-Fraillon, D.; Grec, G.; Loudagh, S.; Ehgamberdiev, S.;
Khamitov, I.; Hoeksema, J. T.; Pallé, P. L.; Régulo, C.
1996SoPh..166....1L Altcode:
The Sun is not a rigid body and it is well known that its surface
rotation is differential, the polar regions rotating substantially
slower than the equator. This differential rotation has been
demonstrated by helioseismology to continue down to the base of
the convective zone, below which it becomes closer to a rigid body
rotation. Far deeper, inside the energy generating core, the rotation
has generally been assumed to be much faster, keeping memory of the
presumably high speed of the young Sun. However, several recent results
of helioseismology have decreased this likelihood more and more,
so that the core rotation could be suspected to be only marginally,
or even not at all faster than the envelope. Certain results would
even imply a core rotation slower than the envelope, an interesting
but unlikely possibility. We present here a complete analysis of
the rotational splitting of the low degree modes measured in three
different time series obtained in 1990, 1991, and 1992 by the IRIS
full-disk network. With a time of integration slightly longer than 4
months, the splitting has been measured by 4 different global methods
on 42 doublets of l= 1, 35 triplets of l = 2, and 30 quadruplets of l =
3. With a high level of confidence, our result is consistent with a
rigid solar core rotation.
---------------------------------------------------------
Title: Global Oscillations at Low Frequency from the SOHO Mission
(GOLF)
Authors: Gabriel, A. H.; Grec, G.; Charra, J.; Robillot, J. -M.; Roca
Cortés, T.; Turck-Chièze, S.; Bocchia, R.; Boumier, P.; Cantin, M.;
Cespédes, E.; Cougrand, B.; Crétolle, J.; Damé, L.; Decaudin, M.;
Delache, P.; Denis, N.; Duc, R.; Dzitko, H.; Fossat, E.; Fourmond,
J. -J.; García, R. A.; Gough, D.; Grivel, C.; Herreros, J. M.;
Lagardère, H.; Moalic, J. -P.; Pallé, P. L.; Pétrou, N.; Sanchez,
M.; Ulrich, R.; van der Raay, H. B.
1995SoPh..162...61G Altcode:
The GOLF experiment on the SOHO mission aims to study the internal
structure of the sun by measuring the spectrum of global oscillations in
the frequency range 10<SUP>−7</SUP> to 10<SUP>−2</SUP> Hz. Bothp
andg mode oscillations will be investigated, with the emphasis on
the low order long period waves which penetrate the solar core. The
instrument employs an extension to space of the proven ground-based
technique for measuring the mean line-of-sight velocity of the viewed
solar surface. By avoiding the atmospheric disturbances experienced
from the ground, and choosing a non-eclipsing orbit, GOLF aims to
improve the instrumental sensitivity limit by an order of magnitude
to 1 mm s<SUP>−1</SUP> over 20 days for frequencies higher than
2.10<SUP>−4</SUP> Hz. A sodium vapour resonance cell is used in
a longitudinal magnetic field to sample the two wings of the solar
absorption line. The addition of a small modulating field component
enables the slope of the wings to be measured. This provides not only
an internal calibration of the instrument sensitivity, but also offers a
further possibility to recognise, and correct for, the solar background
signal produced by the effects of solar magnetically active regions. The
use of an additional rotating polariser enables measurement of the
mean solar line-of-sight magnetic field, as a secondary objective.
---------------------------------------------------------
Title: Comportement temporel des oscillations solaires.
Authors: Baudin, F.; Gabriel, F.; Gibert, D.; Palle, P. L.; Regulo, C.
1995JAF....49R..52B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Variation of the P-Mode Power Spectrum at Solar Activity
Cycle Scales and Shorter
Authors: Roca Cortés, T.; Pallé, P. L.; Régulo, C.
1995ESASP.376b.103R Altcode: 1995soho....2..103R; 1995help.confP.103R
Disk integrated sunlight, radial velocity observations performed
using a resonant scattering spectrophotometer from 1980 to 1994 at the
Observatorio del Teide, have been used to calculate the monthly power
spectra. Cross-correlations of each spectra with one at the minimum of
the cycle are used to measure the frequency shifts. These shifts, with
a peak to peak variation of 0.52±0.02 μHz, show a clear variation with
the solar activity cycle that correlate very well with several activity
indices. However, at shorter time scales the correlation fails. On the
other hand, the amplitudes of the low-l p-modes studied at maximum
and minimum of the solar cycle are anticorrelated with the activity
cycle, being 30% higher at solar maximum. Using a cumulative power
spectrum and a definition for the frequency cut-off of the spectrum,
it is found that a significantly different result is obtained for
maximum and for minimum of the solar activity cycle.
---------------------------------------------------------
Title: Temporal Behaviour of Solar P-Modes of Low Degree L
Authors: Baudin, F.; Gabriel, A.; Gibert, D.; Pallé, P.; Régulo, C.
1995ESASP.376b.323B Altcode: 1995help.confP.323B; 1995soho....2..323B
No abstract at ADS
---------------------------------------------------------
Title: Solar Core Rotation: Latest IRIS Results
Authors: Fossat, E.; Lazrek, M.; Loudagh, S.; Pantel, A.; Gelly, B.;
Grec, G.; Schmider, F. X.; Pallé, P. L.; Régulo, C.; Ehgamberdiev,
S.; Khalikov, S.; Hoeksema, T.
1995ESASP.376b.261F Altcode: 1995help.confP.261F; 1995soho....2..261F
No abstract at ADS
---------------------------------------------------------
Title: A Search for G-Modes
Authors: Martín, I.; Pallé, P. L.; Pérez-Hernández, F.; van der
Raay, H. R.
1995ESASP.376b.423M Altcode: 1995help.confP.423M; 1995soho....2..423M
No abstract at ADS
---------------------------------------------------------
Title: Calibration and Analysis of Simulated GOLF Data
Authors: Garcia, R. A.; Roca Cortés, T.; Régulo, C.; Pallé, P. L.
1995ESASP.376b.369G Altcode: 1995help.confP.369G; 1995soho....2..369G
No abstract at ADS
---------------------------------------------------------
Title: Solar P-Mode Frequencies from the IRIS Network
Authors: Gelly, B.; Fossat, E.; Palle, P.; Appourchaux, T.;
Eghamberdiev, S.; Fierry-Fraillon, D.; Grec, G.; Hoeksema, J. T.;
Khalikov, S.; Lazrek, M.; Loudagh, S.; Pantel, A.; Regulo, C.; Sanchez,
L.; Schmider, F. X.
1995ESASP.376b.373G Altcode: 1995help.confP.373G; 1995soho....2..373G
No abstract at ADS
---------------------------------------------------------
Title: A Measurement of the Background Solar Velocity Spectrum
Authors: Palle, P. L.; Jimenez, A.; Perez Hernandez, F.; Regulo, C.;
Roca Cortes, T.; Sanchez, L.
1995ApJ...441..952P Altcode:
Ten years of continuous measurements of the radial velocity of the
Sun have been used to estimate the contribution of various solar
surface phenomena to the observed background solar velocity spectrum
(BSVS). The characteristics of this spectrum are of great importance,
as they represent the ultimate limit on the sensitivity of measurements
of solar oscillations. A precise determination of this spectrum from
the ground is invariably contaminated by the discontiniuity in the
observations, the unavoidable effect of the Earth's atmosphere and,
possibly, by the instrumentation itself. The present analysis uses
observations made with a very stable instrument to allow comparison
of several sets of data, collected along different phases of the solar
activity cycle. The results show a high stability of the BSVS throughout
the frequency ranges of interest for helioseismology and, moreover,
its profile cannot be modeled using a single exponential function, as
the exponent changes with frequency. The roughness of the spectrum is
calculated, allowing an estimate of the required signal-to-noise ratio
in order to detect an oscillation with a given amplitude. Finally,
following the modeling of the expected background spectrum proposed
by Harvey, the rms full disk velocity of the main solar atmospheric
phenomena (granulation, mesogranulation, supergranulation, and active
regions) are calculated. Despite the limitations of the procedure
employed in this analysis, the main conclusion is the overall good
agreement with the model, although mesogranulation seems to have been
underestimated. Comparison with the different phases of the solar
activity cycle reveals a different behavior of the mesogranulation,
while granulation appears to be stable.
---------------------------------------------------------
Title: Solar Cycle Frequency Shifts at Low L
Authors: Palle, P. L.
1995ASPC...76..239P Altcode: 1995gong.conf..239P
No abstract at ADS
---------------------------------------------------------
Title: Results from Mark-II Spectrophotometer. Measuring Odd (l+m)
Low Degree p-Modes
Authors: Eff-Darwich, A.; Perez Hernandez, F.; Palle, P.; Jimenez,
A.; Roca Cortes, T.; van der Raay, H. B.
1995ASPC...76...47E Altcode: 1995gong.conf...47E
No abstract at ADS
---------------------------------------------------------
Title: Does the Solar Core Rotation Change with the Activity Cycle?
Authors: Jimenez, A.; Perez Hernandez, F.; Claret, A.; Palle, P. L.;
Regulo, C.; Roca Cortes, T.
1995ASPC...76..284J Altcode: 1995gong.conf..284J
No abstract at ADS
---------------------------------------------------------
Title: On the Solar Core Rotation - IRIS Results
Authors: Fossat, E.; Loudagh, S.; Gelly, B.; Grec, G.; Pantel, A.;
Provost, J.; Berthomieu, G.; Ehgamberdiev, S.; Khalikov, S.; Lazrek,
M.; Palle, P. L.; Regulo, C.
1995ASPC...76...24F Altcode: 1995gong.conf...24F
No abstract at ADS
---------------------------------------------------------
Title: The Observed Background Solar Velocity Spectrum over the
Solar Activity Cycle
Authors: Palle, P. L.; Jimenez, A.; Martin, I.; Perez Hernandez, F.;
Regulo, C.; Roca Cortes, T.; Sanchez, L.
1995ASPC...76..288P Altcode: 1995gong.conf..288P
No abstract at ADS
---------------------------------------------------------
Title: On the Solar Core Rotation - IRIS Results
Authors: Fossat, E.; Loudagh, S.; Gelly, B.; Grec, G.; Panel, A.;
Provost, J.; Berthomieu, G.; Ehgamberdiev, S.; Khalikov, S.; Lazrek,
M.; Palle, P. L.; Regulo, C.
1995ASPC...76....4F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Rotation of the Solar Core
Authors: Jimenez, Antonio; Perez Hernandez, Fernando; Claret, Antonio;
Palle, Pere Lluis; Regulo, Clara; Roca Cortes, Teodoro
1994ApJ...435..874J Altcode:
The solar p-mode spectrum of very low l has already been measured
with high accuracy for a sufficiently long period of time to permit
the search for solar cycle variations. The longest one-site velocity
observations for low l solar p-modes (Tenerife) has been used to measure
the l = 1 mode splitting at the two extremes of the solar activity
cycle. The results found exclude the rigid body rotation for the
Sun. When taking the extreme values measured for the splitting, a solar
core rotation between 2 and 4 times larger than that at the surface is
obtained. Also, the observational results indicate an increase (1.3-2
times) of the rotation rate at the maximum of the solar activity cycle.
---------------------------------------------------------
Title: Variation of the Frequencies of Very Low L p-Modes
Authors: Regulo, C.; Jimenez, A.; Palle, P. L.; Perez Hernandez, F.;
Roca Cortes, T.
1994ApJ...434..384R Altcode:
Radial velocity observations performed using a resonant scattering
instrument from 1980 to 1993 at the Observatorio del Teide have been
used to calculate the monthly power spectra of very low degree solar
oscillations. Cross-correlations among the spectra allow to determine
the p-mode frequency shifts along the observed period. These shifts
show a clear correlation with several indices of solar activity along
the 11 years cycle but, on shorter timescales, the correlation is not
clear. As the size of the effect is approximately 30% higher than the
one found found using high degree modes, other phenomena (probably
related to magnetic fields) possibly occurring in the interior of the
Sun may be involved in these solar cycle-related frequency shifts.
---------------------------------------------------------
Title: The Global Oscillation Network Group Site Survey - Part Two
Authors: Hill, Frank; Fischer, George; Forgach, Suzanne; Grier,
Jennifer; Leibacher, John W.; Jones, Harrison P.; Jones, Patricia
B.; Kupke, Renate; Stebbins, Robin T.; Clay, Donald W.; Ingram,
Robert E. L.; Libbrecht, Kenneth G.; Zirin, Harold; Ulrichi, Roger
K.; Websteri, Lawrence; Hieda, Lester S.; Labonte, Barry J.; Lu,
Wayne M. T.; Sousa, Edwin M.; Garcia, Charles J.; Yasukawa, Eric
A.; Kennewell, John A.; Cole, David G.; Zhen, Huang; Su-Min, Xiao;
Bhatnagar, Arvind; Ambastha, Aashok; Al-Khashlan, Abdulrahman Sa'ad;
Abdul-Samad, Muhammad-Saleh; Benkhaldoun, Zouhair; Kadiri, Samir;
Sánchez, Francisco; Pallé, Pere L.; Duhalde, Oscar; Solis, Hernan;
Saá, Oscar; González, Ricardo
1994SoPh..152..351H Altcode:
The Global Oscillation Network Group (GONG) Project will place a
network of instruments around the world to observe solar oscillations as
continuously as possible for three years. The Project has now chosen the
six network sites based on analysis of survey data from fifteen sites
around the world. The chosen sites are: Big Bear Solar Observatory,
California; Mauna Loa Solar Observatory, Hawaii; Learmonth Solar
Observatory, Australia; Udaipur Solar Observatory, India; Observatorio
del Teide, Tenerife; and Cerro Tololo Interamerican Observatory, Chile.
---------------------------------------------------------
Title: Secular Variations in the Spectrum of Solar P-Modes
Authors: Jimenez, A.; Palle, P. L.; Regulo, C.; Roca Cortes, T.
1994SoPh..152..253J Altcode: 1994svs..coll..253J; 1994IAUCo.143..253J
The solar p-mode spectrum of very low I is measured with high
accuracy for a long enough period of time so as to allow the search
for solar cycle variations. In this paper solar cycle variations
of the frequency and energy of the modes are confirmed. Moreover,
a slight variation,within errors, of its rotational splitting with
the solar cycle, is suggested.
---------------------------------------------------------
Title: Full-disk helioseismic IRIS raw data calibration.
Authors: Palle, P. L.; Fossat, E.; Regulo, C.; Loudagh, S.; Schmider,
F. X.; Ehgamberdiev, S.; Gelly, B.; Grec, G.; Khalikov, S.; Lazrek,
M.; Sanchez, L.
1993A&A...280..324P Altcode:
The International Research on the Interior of the Sun (IRIS)
helioseismometer measures the full disk line of sight velocity of the
Sun. In fact, it makes a photometric mesurement using two monochromatic
spectral windows located on the wings of the D1 solar line. This is
a non-linear measurement. Before a scientific exploitation of the
IRIS data, the instrumental signal must be converted from non-linear
photometric data into calibrated line of sight velocity. In this
process, it is necessary to extract the small component due to the
solar surface motions from the much larger contributions of the
Earth spin, the Earth orbit, the gravitational redshift, the D1
line distortions produced by solar activity and even some telluric
atmospheric effects. This paper describes the calibration method
which is now used for pre-processing the IRIS data. It is the result
of several iterations, and the use of one and a half years of IRIS
data from one instrument, at Teide Observatory. It is certainly the
best possible method to date, given the quality of the current data,
and it can be regarded as valid over all the entire p-mode frequency
range, and down to 100 microHz or so in the g-mode range. At lower
frequencies, calibration, solar noise and merging techniques cannot
be completely separated, and possible further improvements are still
under investigation.
---------------------------------------------------------
Title: Modeling of integrated sunlight velocity measurements: The
effect of surface darkening by magnetic fields
Authors: Ulrich, R. K.; Henney, C. J.; Schimpf, S.; Fossat, E.; Gelly,
B.; Grec, G.; Loudagh, S.; Schmider, F. -X.; Palle, P.; Regulo, C.
1993A&A...280..268U Altcode:
It has been known since the work by Claverie et al. (1982) that
integrated-sunlight velocities measured with the resonance scattering
technique show variations with time scales of weeks to months. The
cause can be understood in terms of the effects of solar activity
as was pointed out by Edmunds & Gough (1983) and Andersen &
Maltby (1983). The latter authors included a model calculation based on
sunspot areas which showed good promise of being able to quantitatively
reproduce the observed velocity shifts. We discuss in this paper a
new modeling effort based on daily magnetograms obtained at the 150-ft
tower on Mt. Wilson. This type of database is more quantitative than
sunspot area. Similar maps of magnetically sensitive quantities will
be measured on a continuous time base as part of several planned
helioseismology experiments (from space with the Solar Oscillations
Imagery/Michelson Doppler Imager (SOI/MDI) experiment on the Solar and
Heliospheric Observatory (SOHO), see Scherrer et al. (1991) or with
ground-based networks, see Hill & Leibacher (1991)). We discuss
the correlations between various magnetically sensitive quantities and
develop a new model for the effects of magnetic field on line profiles
and surface brightness. From these correlations we integrate the
line profile changes over the solar surface using observed magnetic
field strengths measured at lambda 5250.2. The final output is a
new model for the effects of magnetic fields on integrated sunlight
velocities which we compare with daily offset velocities derived
from the International Research on the Interior of the Sun (IRIS)-T
instrument at the Observatorio del Teide.
---------------------------------------------------------
Title: A measurement of the I = I solar rotational splitting
Authors: Loudagh, S.; Provost, J.; Berthomieu, G.; Ehgamberdiev, S.;
Fossat, E.; Gelly, B.; Grec, G.; Khalikov, S.; Lazrek, M.; Palle,
P.; Regulo, C.; Sanchez, L.; Schmider, F. -X.
1993A&A...275L..25L Altcode:
A precise measurement of the l = 1 rotational splitting has been
derived from the 1991 IRIS data and it leads to a moderate rotation
rate in the solar core.
---------------------------------------------------------
Title: Observations of Low Degree P-Modes with Odd L+M
Authors: Palle, P. L.; Perez-Hernandez, F.; Regulo, C.; Roca-Cortes, T.
1993ASPC...42..189P Altcode: 1993gong.conf..189P
No abstract at ADS
---------------------------------------------------------
Title: On Full Disk Helioseismology Power Spectra around the Cut-Off
Frequency
Authors: Regulo, C.; Fossat, E.; Roca-Cortes, T.; Ehgamberdiev, S.;
Gelly, B.; Grec, G.; Khalikov, S.; Lazrek, I. Khamitov M.; Palle,
P. L.; Sanchez-Duarte, L.
1993ASPC...42..103R Altcode: 1993gong.conf..103R
No abstract at ADS
---------------------------------------------------------
Title: On the acoustic cut-off frequency of the sun
Authors: Fossat, E.; Regulo, C.; Roca Cortes, T.; Ekhgamberdiev, S.;
Gelly, B.; Grec, G.; Khalikov, S.; Khamitov, I.; Lazrek, M.; Palle,
P. I.
1992A&A...266..532F Altcode:
Full solar disk observations of radial velocity, obtained with the IRIS
network of resonant scattering spectrometers, are used to analyze the
acoustic p-mode spectrum around the acoustic cut-off frequency. Three
different methods are used to determine it; two use the power spectrum,
while the third uses the phase spectrum. The three values measured
converge to a common value of 5.55 +/- 0.1 mHz, which is higher than any
theoretical prediction. Beyond this frequency, the power spectra still
decreases down to 10 mHz at which point it becomes flat, showing the
presence of some power due to the so-called pseudomodes which we show
are the result of interference between traveling waves. The acoustic
power density measured beyond the cut-off frequency makes it possible
to estimate the energy deposited into the chromosphere about 10 exp 7
erg/sq cm per sec, which is high enough to compensate the losses that
take place in this layer.
---------------------------------------------------------
Title: The low L solar p-mode spectrum at maximum and minimum solar
activity
Authors: Anguera Gubau, M.; Palle, P. L.; Perez Hernandez, F.; Regulo,
C.; Roca Cortes, T.
1992A&A...255..363A Altcode:
Velocity measurements of disc integrated sunlight obtained at the
Observatorio del Teide (Izana) from 1980 throughout 1989 are used to
find the frequencies and amplitudes of each p-mode with l less than
4 and n between 5 and 33. The 32 best monthly spectra obtained are
averaged in two separate groups corresponding to periods with solar
activity maximum and minimum. The observational p-mode frequencies
differ from those predicted by standard solar models by more than
their errors; however the frequency separations are in reasonable
agreement. Such parameters, which give information about the core of
the sun, can be determined for the maximum and the minimum of solar
activity cycle. Significant differences between maximum and minimum
on these parameters have not been found and they agree well with the
predictions of standard models although the small observational errors
achieved allow distinguishing among them. It is also found that the
energy of the modes is smaller at the maximum than during the minimum
of solar activity, telling us a bit more about the structure and
efficiency of the sunlayers in exciting these modes.
---------------------------------------------------------
Title: Solar Radial Velocity and Oscillations as Measured by Sodium
and Potassium Resonant Scattering Spectrometers
Authors: Palle, P. L.; Regulo, C.; Roca-Cortes, T.; Sanchez-Duarte,
L.; Schmider, F. X.
1992A&A...254..348P Altcode:
Since the beginning of 1990, a sodium based resonance scattering
spectrometer belonging to the IRIS Network has operated at Observatorio
del Teide side by side with the MkI instrument (a resonance scattering
spectrometer based on potassium) from the University of Birmingham
and operated since 1975. A 3 month series of simultaneous data
obtained in summer 1990 is the basis for this study that compares the
performance of both instruments in measuring the solar radial velocity
and oscillations. Interesting features of the p-modes as seen at two
different levels of the solar atmosphere such as the ratio of energies
per unit mass and the difference of phases are obtained. These results
demonstrate that the p-modes are truly standing waves. Crosscorrelation
of the spectra of the series obtained with both instruments shows
the existence of signals well above the cutoff frequency of the
solar atmosphere, being interpreted as travelling waves, also called
pseudomodes. An estimation of the cutoff frequency gives a value of
5.6 ± 0.1 mHz, higher than theoretically predicted.
---------------------------------------------------------
Title: The Teide Observatory
Authors: Palle, P. L.
1991SoPh..133...65P Altcode:
The Teide Observatory in the Canary Islands is, at present, a
well-known nucleus for solar physics research. In this contribution,
the facilities at the Observatory, which now houses one of the IRIS
network instruments, are presented.
---------------------------------------------------------
Title: Preliminary performance of a 4-point resonance scattering
experiment to access long-period global oscillations from space
Authors: Boumier, P.; Bocchia, R.; Damé, L.; Martic, M.; Pallé,
P.; van der Raay, H. B.; Robillot, J. M.; Roca Cortés, T.
1991AdSpR..11d.199B Altcode: 1991AdSpR..11..199B
The first data of a SOHO-GOLF type instrument are presented
hereafter. The slopes of the solar sodium lines profiles D1 and
D2, and their variations with the excursion of the working point
are shown. Two methods of determining the oscillation velocity are
compared, one usually used with 2-point spectrometers and one using
the 4-point information. We show that the second method gives spectra
which are significantly less noisy in the very low frequency range
(up to 300 μHz). For higher frequencies, terrestrial atmospheric
fluctuations alter the measurement, and as far as ground based
instruments are concerned, the 4-point method loses its efficiency
if the magnetic modulation commutation time (in our case 20 seconds)
is not significantly reduced.
---------------------------------------------------------
Title: Solar p-mode frequencies.
Authors: Palle, Pere L.
1991sia..book.1249P Altcode:
The author presents some mathematical formulae which have been derived
from observed frequencies and which allow the reader, not only to
reproduce the observed frequencies accurately, but also to extrapolate
them to limits beyond present observations.
---------------------------------------------------------
Title: The search for solar gravity modes
Authors: Palle, Pere L.
1991AdSpR..11d..29P Altcode: 1991AdSpR..11...29P
Well after the discovery of the global acoustic oscillations of the Sun,
(p-modes), it was realized that another type of mode should exist in
such a stratified medium: the internal gravity modes. It was also
noticed that this type of mode was only providing information on
the inner 40% of the Sun; precisely the region where p-modes are less
sensitive to the physical conditions. This fact turned the g-modes into
the most powerful tool for the investigation of the solar core. <P
/>Excepting the 160<SUP>m</SUP> oscillation/artifact /16/, the first
observational claim of internal g-mode detection took place in 1983
/14/, and, since then, a lot of effort has been devoted to this subject
both, observationally and in data analysis, and in the theoretical
field. In the last seven years, three different principal data sets
have been extensively analized in a search for g-modes (Tenerife,
ACRIM and Stanford). Their characteristics and the results claimed
from the analysis will be reviewed and discussed. However the present
situation is that the discrepancies between observers suggest that
the solar g-modes though probably detected, are not yet measured nor
classified. What is of general agreement is the existence of signals,
embedded in noise, in the low frequency range where g-modes are
expected to lie. As we will emphasize in this review, we are dealing
with a far different situation than for the p-modes: lower frequencies,
poorer signal-to-noise ratio, etc... <P />Taking into account these
difficulties, there is a real hope of success in the near future: with
the space experiments devoted to Helioseismology on board of SOHO and
the earth-based networks of helioseismic instruments.
---------------------------------------------------------
Title: Global Acoustic Oscillations on alpha Bootis
Authors: Belmonte, Juan A.; Jones, Andrew R.; Palle, Pere L.; Roca
Cortes, Teodoro
1990ApJ...358..595B Altcode:
A two-week time series of precise radial velocity measurements of
Alpha Bootis (Arcturus) covering 7-8 hr per night is reported. The
radial barycentric velocity of the star is found to be -5021 +
or - 5 m/s. When data from the whole run are jointly analyzed,
several equispaced peaks in the frequency appear in the range of
a few microhertz, the highest amplitude being some 60 m/s at 4.3
microhertz. The most probable frequency spacing seems to be 50
microhertz, while the frequency cutoff is around 80 microhertz.
---------------------------------------------------------
Title: An Attempt to Identify Low-L / Low-N Solar Acoustic Modes
Authors: Anguera Gubau, M.; Palle, P. L.; Perez Hernandez, F.; Roca
Cortes, T.
1990SoPh..128...79A Altcode: 1990IAUCo.121P..79A
The low l solar acoustic spectrum has been measured with great accuracy
(Δv/v ∼ 10<SUP>−4</SUP>), for intermediate radial order modes, 11
≤ n ≤ 34 (Jiménez et al., 1986; Grec, Fossat, and Pomerantz, 1983;
Pallé et al., 1986). The measurement of the frequencies of modes of
lower n, up to the fundamental one, are very important as they depart
from asymptotic behaviour and, therefore, put more severe constraints
on solar models. However, their amplitudes are very low (under 2 cm
s<SUP>−1</SUP>) and when compared to the solar velocity background
noise (Jiménez et al., 1986), a S/N ∼ 1 is obtained. Taking advantage
of the fact that lifetimes seem to be higher at lower frequencies
(lower n values) (Jefferies et al., 1988; Elsworth et al., 1990), very
long Doppler velocity measurements, obtained at Teide Observatory,
have been used to increase S/N, therefore, providing the possibility
to detect such modes. The frequencies observed are compared to
those predicted by a solar model (Christensen-Dalsgaard, Däppen,
and Lebreton, 1988), using the best equation of state yet computed
(Mihalas, Däppen, and Hummer, 1988).
---------------------------------------------------------
Title: Acoustic Oscillations in the K2111-STAR Arcturus
Authors: Belmonte, J. A.; Jones, A. R.; Palle, P. L.; Roca Cortes, T.
1990Ap&SS.169...77B Altcode:
Simultaneous spectrometric and photometric observations have been
performed, on the red giant star Arcturus (α Boo), in a search
for radial velocity or luminosity variations related to global
oscillations of the stellar structure. From a preliminary analysis
of the spectrometric data, several frequencies have been discovered
in the range from 1 to 50 μHz, the highest amplitude being of ∼60
ms<SUP>-1</SUP> at 4.3 μHz. From the analysis of the photometric data,
slight evidence of this variation has been found, yielding a value of
ΔV/Δm=48 km s<SUP>-1</SUP> mag<SUP>-1</SUP>.
---------------------------------------------------------
Title: Phase Differences Between Luminosity and Velocity Measurements
of the Acoustic Modes
Authors: Jiménez, A.; Álvarez, M.; Andersen, N. B.; Domingo, V.;
Jones, A.; Pallé, P. L.; Roca Cortés, T.
1990SoPh..126....1J Altcode:
With two photometric stations (Tenerife and Baja California)
the luminosity p-mode spectrum at different wavelengths has been
identified. After a coherence analysis between data from both stations
to verify the solar origin of the peaks identified in luminosity, a
comparative study with simultaneous velocity measurements (obtained at
Tenerife only) has also been made. As a result the frequency dependence
of the phase difference between luminosity and velocity p-modes has been
obtained that is interpreted in terms of a nonadiabatic behaviour of the
solar atmosphere. The amplitude ratios between luminosity and velocity
p-modes have also been obtained. All these results are compared with
theoretical expectations.
---------------------------------------------------------
Title: Frequencies, Linewidths, and Splittings of Low-Degree Solar
p-Modes
Authors: Pallé, P. L.; Régulo, C.; Roca Cortés, T.
1990LNP...367..189P Altcode: 1990psss.conf..189P
The measurement of frequencies, linewidths, and splittings of low
degree solar p-modes is a difficult task due, firstly, to time scales
involved and, secondly, to the spurious presence of side lobes when
data is not collected continuously. However, a long set of observations
have been obtained at Observatorio del Teide: a total of 52 months of
data, spread over 12 years (1977 to 1989), from which the best ones
have been selected. These data allows averaging of power spectra,
therefore giving statistical significant profiles for the p-modes,
which can be fitted to appropriate functions (i.e. Lorentzian). Such
analysis is applied to the data mentioned before and preliminary
results of the aforementioned parameters are obtained.
---------------------------------------------------------
Title: Variations of the Low / Solar Acoustic Spectrum Correlated
with the Activity Cycle
Authors: Pallé, Pere L.; Régulo, C.; Roca Cortés, T.
1990ASSL..159..349P Altcode: 1990insu.conf..349P; 1990IAUCo.121..349P
No abstract at ADS
---------------------------------------------------------
Title: The Spectrum of Solar p-Modes and the Solar Activity Cycle
Authors: Pallé, P. L.; Régulo, C.; Roca Cortés, T.
1990LNP...367..129P Altcode: 1990psss.conf..129P
Solar cycle variations on the power and frequencies of the low l p-mode
solar acoustic oscillations are investigated using an extensive set of
observations obtained at Observatorio del Teide (Izaña, Tenerife). The
radial velocity of integrated sunlight has been monitored, by means of
a resonant scattering spectrophotometer, at several epochs (basically
each year) from 1977 to 1989. The latest data (1988 and 1989) confirm
previously found results (Pallé et al., 1988, 1989a,b): a) A variation
of nearly 40% peak to peak in the power of the low l solar p-modes,
being higher when the solar activity is at its minimum. b) A null
variation in frequency for l = 0 and a decrease of ≈ 0.5 µ.Hz for l
= 1 when solar activity goes from maximum to minimum (similar results
for l = 2 and l = 3) by using a cross-correlation technique.
---------------------------------------------------------
Title: Solar cycle induced variations of the low L solar acoustic
spectrum.
Authors: Palle, P. L.; Regulo, C.; Roca Cortes, T.
1989A&A...224..253P Altcode:
Doppler velocity data are used to study solar cycle variation of the
frequencies of solar acoustic oscillations from 1977 to 1988. The
results show a clear shift in frequency of the cross-correlation peaks
of -0.37 + or - 0.04 microHz peak to peak as the solar activity cycle
progresses from maximum to minimum. This effect is dependent on the l
value of the modes. The results suggest that, as low l modes penetrate
deeply into the sun's interior, there are structural changes correlated
with the solar activity cycle.
---------------------------------------------------------
Title: Search for radial velocity variations in rapidly oscillating
AP star using the Fabry-Perot interferometric stellar oscillation
spectrometer.
Authors: Belmonte, J. A.; Bell, C. R.; Leeper, M.; Palle, P. L.;
Pietraszewski, K. A. R. B.; Renton, R. E.; Roca Cortes, T.
1989A&A...221...41B Altcode:
Radial velocity measurements of a group of Ap stars were obtained
in May and December 1987 using a Fabry-Perot interferometric stellar
oscillation spectrometer that has been improved to enable the instrument
to be referenced to the Cd blue line. Observations of the rapidly
oscillating Ap stars 33 Lib and HR 1217 were analyzed in order to search
for radial velocity variations corresponding to the photometric periods
found in these stars. The radial velocity and photometric data sets have
been reduced with the aid of a weighted sine wave fitting routine. For
HR 1217, a peak at 2.72 mHz and an amplitude of about 240 m/s are found.
---------------------------------------------------------
Title: Observations of solar p-modes with L of not greater than 5
Authors: Palle, P. L.; Perez Hernandez, F.; Roca Cortes, T.; Isaak,
G. R.
1989A&A...216..253P Altcode:
Results are presented for the sun's radial velocity in integrated
sunlight. A resonant scattering spectrometer has been used to determine
the frequencies and amplitudes of p-modes with spherical harmonics
of degree (l) of less than 3, and a second spectrophotometer, which
observes part of the sun by means of a spatial filter, has been used
to measure the frequencies and amplitudes of p-modes with l of not
greater than 5. The frequencies at both ends of the p-mode 5-minute
oscillations with l of between 3 and 5, inclusively, are obtained with
greater precision than previous determinations.
---------------------------------------------------------
Title: The 160 Minute Solar Oscillation: an Artifact?
Authors: Elsworth, Y. P.; Jefferies, S. M.; McLeod, C. P.; New, R.;
Palle, P. L.; van der Raay, H. B.; Regulo, C.; Roca Cortes, T.
1989ApJ...338..557E Altcode:
Analysis of data obtained over the years 1980-1985 are analyzed to show
that the period of the 160-minute signal is indeed 160.00 minutes. It is
demonstrated that this signal may be simulated by a slightly distorted
diurnal sine wave such as that occasioned by differential atmospheric
extinction.
---------------------------------------------------------
Title: Solar oscillations as seen in the Na I and K I absorption
lines.
Authors: Isaak, G. R.; McLeod, C. P.; Palle, P. L.; van der Raay,
H. B.; Roca Cortes, T.
1989A&A...208..297I Altcode:
Data on the solar p modes observed simultaneously in the solar NaI and
KI absorption lines were obtained in 1985 by operating two independent
resonant scattering spectrometers at the same site (Observatorio del
Teide, Tenerife). Since the abundances of the ground state atoms of
these two elements are not the same, different depths of the solar
photosphere are sampled. A comparison of the data obtained is given.
---------------------------------------------------------
Title: Frequency shift of solar p-modes as seen by cross-correlation
analysis.
Authors: Palle, Pere L.; Regulo, C.; Roca Cortés, Teodoro
1988ESASP.286..285P Altcode: 1988ssls.rept..285P
Data obtained at the Observatorio del Teide (Izaña, Tenerife) during
the years 1978 to 1988 using a resonant scattering spectrophotometer,
is analyzed to look for variations of the low degree p-mode frequencies
along the solar cycle. The analysis based on the cross-correlation of
power spectra leads to the conclusion that the variation of its maximum
correlation correlates well with the solar cycle. An overall variation,
from minimum to maximum solar activity, of 0.5±0.1 μHz is found,
when low l modes are considered. Moreover, this effect depends on
the l values of the modes being absent for l = 0 and of 0.7±0.1 μHz
for l = 1. Therefore, other interpretations than a simple frequency
shift are plausible, such as different amplitudes between modes in
the same multiplet of an asymmetric change of the splitting along the
solar cycle.
---------------------------------------------------------
Title: Solar Luminosity Oscillation Telescope (SLOT).
Authors: Andersen, Bo Nyborg; Domingo, V.; Jones, A. R.; Korzennik,
Sylvain G.; Jimenez, A.; Palle, Pere L.; Regulo, C.; Roca Cortés,
Teodoro
1988ESASP.286..175A Altcode: 1988ssls.rept..175A
Low degree l = 0-2 solar p-modes have been detected with the
SLOT instruments at Izaña and Baja California. The main source
of noise for these ground based observations is in the terrestrial
atmosphere. However, the data acquisition system still has to have very
slow intrinsic noise. The authors describe how this is achieved in the
SLOT instruments. They also give a general description of the design
and operating principles of the photometers and data acquisition system.
---------------------------------------------------------
Title: High precision velocity observations of Arcturus using the
7699 Å line of potassium.
Authors: Innis, J. L.; Isaak, G. R.; Brazier, R. I.; Belmonte, Juan
A.; Palle, Pere L.; Roca Cortés, Teodoro; Jones, A. R.
1988ESASP.286..569I Altcode: 1988ssls.rept..569I
The K giant Arcturus (α Boo) was observed with the Birmingham
double magneto-optical filter spectrometer using the GHRIL facility
at the Nasmyth focus of the 4.2 m William Herschel Telescope
of the Observatorio del Roque de los Muchachos in 1988 April -
May. Approximately 80 hours of data were obtained over a 2 week
interval. The authors' preliminary analysis of the data shows the
presence of the large (≡200 m s<SUP>-1</SUP>) amplitude velocity
variation reported earlier by other observers. However, this more
extensive data set strongly suggests that this variation is not
singly periodic, as was previously indicated. The authors present
some speculative comments as to the nature of this variation, and the
implications for stellar seismology.
---------------------------------------------------------
Title: Can solar g-modes be identified from ground-based velocity
measurements?
Authors: Garcia, C.; Palle, Pere L.; Roca Cortés, Teodoro
1988ESASP.286..353G Altcode: 1988ssls.rept..353G
After ten years of helioseismology research the question of whether
or not solar g modes can be detected and identified from ground
observations is still unclear. The limitation imposed by the earth's
atmosphere, the background solar noise spectrum at low frequencies,
and a poor theoretical knowledge of these modes are some of the
reasons. Using the best uninterrupted full disk velocity measurements
obtained over the period 1984 - 1987, signals with amplitudes less than
5 cm/s are found in the g modes spectral region. Cross-correlation and
other techniques used to detect stable signals (g modes) show negative
results which allow to put an upper limit to their amplitudes and/or
lifetimes.
---------------------------------------------------------
Title: Linewidth of low degree acoustic modes of the Sun.
Authors: Elsworth, Y. P.; Isaak, G. R.; Jefferies, S. M.; McLeod,
C. P.; New, R.; Palle, Pere L.; Regulo, C.; Roca Cortés, Teodoro
1988ESASP.286...27E Altcode: 1988ssls.rept...27E
Estimates of the spectral linewidths of low degree (l = 0 and l = 1),
"5 minute" p-modes obtained from Doppler shift observations in 1984,
1986 and 1987 are reported. The observed linewidths increase from 0.5
μHz at 2000 μHz to 3.8 μHz at 4300 μHz for l = 0. Comparison with
other data suggest that for a given frequency the linewidth increases
with increasing l value. On the assumption that the linewidth is
substantially due to damping processes the linewidths are consistent
with e-folding times between 3.7 and 0.5 days.
---------------------------------------------------------
Title: The GONG site survey.
Authors: Hill, F.; Ambastha, A.; Ball, W.; Duhalde, O.; Farris,
D.; Fischer, G.; Hieda, L.; Zhen, Huang; Ingram, B.; Jackson, P.;
Jones, H.; Jones, W.; Kennewell, J.; Kunkel, W.; Kupke, R.; Labonte,
B.; Leibacher, J.; Libbrecht, K.; Lu, W.; Morrison, L.; Odell, C.;
Pallé, P.; Saá, O.; Sousa, E.; Stebbins, T.; Xiao, Suming; GONG
Site Survey Team
1988ESASP.286..209H Altcode:
The Global Oscillation Network Group (GONG) project is planning to
place six observing stations around the world to observe the solar
oscillations as continuously as possible. This paper describes the
procedures that are being used to select the six sites. The latest
results of measurements of cloud cover obtained by networks of 6
(out of 10) radiometers show a duty cycle of over 93%, with the first
diurnal sidelobe in the window power spectrum suppressed by a factor
of 400. The results are in good agreement with the predictions of a
computer model of the expected cloud cover at individual sites.
---------------------------------------------------------
Title: Effect of atmospheric extinction on solar radial velocity
measurements.
Authors: Belmonte, Juan A.; Elsworth, Y. P.; Isaak, G. R.; New, R.;
Palle, Pere L.; Roca Cortés, Teodoro
1988ESASP.286..177B Altcode: 1988ssls.rept..177B
Differential extinction across the Earth's atmosphere affects
astronomical photometry in a well known way. Under the same
circumstances when a rotating extended object is observed
spectrometrically, a residual radial velocity is obtained which varies
during the day. In the case of integral sunlight observations, this
effect has been calculated along the day in all possible observing
situations during the year. Applications to real observations are
shown and discussed leading to some conclusions specially relevant to
ground-based networks.
---------------------------------------------------------
Title: Rotational splitting of low l solar p-mode.
Authors: Palle, Pere L.; Pérez Hernández, F.; Regulo, C.; Roca
Cortés, Teodoro
1988ESASP.286..125P Altcode: 1988ssls.rept..125P
Rotational splitting measurements of l < 5 p-modes are calculated
using different sources of data. For l = 1, data obtained from years
1981 to 1985 is used to find out the stretches where each particular
mode remains excited, then its splitting is measured and the mean
found. Cross-correlation of power spectra confirms these finding,
and this method is used to look for the l = 2 splitting. For 2 <
l < 5 only one month of data is available and superposition of peak
structures gives an upper limit for their splitting.
---------------------------------------------------------
Title: Solar luminosity oscillations from two stations and correlation
with velocity measurements.
Authors: Jimenez, A.; Palle, Pere L.; Roca Cortés, Teodoro; Andersen,
N. B.; Domingo, V.; Jones, A. R.; Alvarez, M.; Ledezma, E.
1988ESASP.286..163J Altcode: 1988ssls.rept..163J
Since 1984 the measurements of a quadrupole photometer sites at the
Observatorio del Teide (Izaña, Tenerife) have made it possible to
identify the p-mode luminosity spectrum with simultaneous velocity
observations. Comparing this data, the adiabatic behaviour of solar
atmosphere and theoretical expectations from solar models have been
tested. Now, in order to increase the signal-to-noise ratio and reduce
the sidebands due to the night-time data gaps, a second identical
photometer was set-up in December 1987, at the Observatorio de San
Pedro Mártir (Baja California Norte, Mexico). The first results of
the observations of these two stations are analyzed and compared with
simultaneous velocity measurements.
---------------------------------------------------------
Title: The search for radial velocity variations in rapidly
oscillating Ap stars using the Fabry-Perot interferometric stellar
oscillation spectrometer (FP-ISOS).
Authors: Leeper, M.; Bell, C. R.; Pietraszewski, K. A. R. B.; Renton,
R. E.; Belmonte, J. A.; Pallé, P. L.; Roca Cortés, T.
1988ESASP.286..587L Altcode: 1988ssls.rept..587L
Radial velocity measurements were taken of a group of Ap stars using
a newly improved FP-ISOS. Observations were made using the 1.5 m TCS
on Tenerife in May 1987 and December 1987. The already known rapidly
oscillating Ap stars 33 Lib and HR 1217 were observed in order to search
for radial velocity variations corresponding to the photometric periods
found in these stars. Simultaneous photometric measurements were made on
HR 1217 on the last two nights using the nearby 0.5 m telescope. The
radial velocity and photometric data sets have been reduced using
a weighted sine wave fitting routine. Promising results have been
obtained for HR 1217, while results obtained for the other Ap stars
observed do not allow to any conclusion. Data taken several years ago
on α Cir was re-examined and the results obtained are also discussed.
---------------------------------------------------------
Title: Further implications of solar p-modes as measured in Na and
K resonance lines.
Authors: Palle, Pere L.; Pérez Hernández, F.; Roca Cortés, Teodoro
1988ESASP.286..513P Altcode: 1988ssls.rept..513P
The ratios between the amplitudes of p-modes measured simultaneously
in the Na and K resonance lines are compared with the expected ratios
for adiabatic waves at two different levels in the atmosphere. The
results agree within errors with the energy decaying solution for the
waves at the photosphere.
---------------------------------------------------------
Title: Search for rapid oscillations in the northern Ap stars HD
62140, HD 81009 and HD 22374.
Authors: Belmonte, Juan A.; Palle, Pere L.; Roca Cortés, Teodoro;
Shoch, Fritz
1988ESASP.286..609B Altcode: 1988ssls.rept..609B
High-speed photometric observations have been performed of the Ap stars
HD 62140 (49 Cam), HD 81009 and HD 22374 for more than 60 hours in
October and December 1986 using the 1 m-JKT at the Observatorio del
Roque de los Muchachos (ORM) and the 1.5 m-TCS of the Observatorio
del Teide (OT), Canary Islands (Spain). Photometric measurements in
the B band were reduced and the residuals obtained were subjected to
a harmonic analysis searching for periodicities in the range of a few
minutes to 2 hours. There is some evidence that the star 49 Cam is
oscillating. HD 81009 and HD 22374 were observed in order to confirm
some traces of oscillation present in earlier observations however,
these possible oscillations did not repeat in the new data.
---------------------------------------------------------
Title: Luminosity Oscillations Imager (LOI).
Authors: Andersen, Bo Nyborg; Domingo, V.; Jones, A. R.; Jimenez,
A.; Palle, Pere L.; Regulo, C.; Roca Cortés, Teodoro
1988ESASP.286..385A Altcode: 1988ssls.rept..385A
The VIRGO (Variability in Irradiance and Gravity Oscillations)
investigation has been selected to fly on ESA's SOHO mission. One of
the components of the VIRGO is a small imaging solar photometer. This
instrument, the Luminosity Oscillations Imager (LOI), will observe
the solar radiance with 12 pixels resolution. A prototype of the LOI
has been developed at ESTEC. This prototype was built mainly to test
possible detector configurations, the data acquisition system and the
internal guider. The prototype has been operating at Izaña, Tenerife
since April this year.
---------------------------------------------------------
Title: Diurnal photometric conditions at Teide observatory and
long-term solar irradiance variations
Authors: Andersen, B.; Domingo, V.; Jiménez, A.; Jones, A.; Korzennik,
S.; Pallé, P. L.; Pérez Hernández, F.; Régulo, C.; Roca Cortés,
T.; Tomás, L. L.
1988SoPh..116..391A Altcode:
Monochromatic extinction coefficients at four wavelengths have been
obtained over a period of more than two years at the Observatorio del
Teide (Izaña Tenerife) using a full disc, direct sunlight, quadruple
photometer devoted to the detection of integral luminosity oscillations
of the Sun. The mean extinction coefficients (0.13 at 500 nm) show
a seasonal variation of about 15%, the best atmospheric conditions
being in winter and autumn. Moreover, in anyone day the extinction
coefficient in the afternoon is always lower than the one in the
morning by ∼ 7%. A one-year period fluctuation, with an amplitude
of ∼ 0.035 mag, has been identified in the instrumental magnitudes
outside the atmosphere, and is interpreted as the variation produced
by the different Sun-Earth distance from winter to summer. Finally,
the study made to detect periodic time fluctuations in both, Sun's
magnitude and extinction coefficients, has given null results at levels
of ∼ 0.04 and ∼ 1.8%, respectively.
---------------------------------------------------------
Title: Frequency stability of solar oscillations
Authors: Jefferies, S. M.; Pallé, P. L.; van der Raay, H. B.; Régulo,
C.; Roca Cortés, T.
1988Natur.333..646J Altcode:
Changes in the internal structure of the Sun over the 11-year
magnetic activity cycle could be reflected in the eigenfrequencies
of the acoustic p-modes. The first tentative experimental evidence
was presented in 1984<SUP>1</SUP> and subsequently an analysis
of ACRIM solar intensity data<SUP>2</SUP> suggested a decrease of
frequencies of the 5-min solar p-modes between 1980 and 1984 of ~0.4
μHz. Recently<SUP>3-6</SUP> further experimental data have provided
conflicting results; frequency increases, decreases and stability have
all been reported.
---------------------------------------------------------
Title: The observed background solar velocity noise
Authors: Jimenez, A.; Palle, P. L.; Perez Hernandez, F.; Regulo, C.;
Roca Cortes, T.
1988A&A...192L...7J Altcode:
Using accurate radial velocity observations of integral sunlight,
the background solar velocity noise has been measured at different
frequencies of interest for solar oscillations within a frequency
interval between 10<SUP>-7</SUP> and 10<SUP>-2</SUP>Hz. Comparison
with a numerical model, simulating the most important solar processes:
granulation, mesogranulation, supergranulation and active regions,
with associated velocity fields shows good agreement at the amplitudes
and their, already known, characteristic time scales.
---------------------------------------------------------
Title: Correlation between velocity and luminosity measurements of
solar oscillations
Authors: Jimenez, A.; Palle, P. L.; Roca Cortes, T.; Domingo, V.
1988A&A...193..298J Altcode:
Following the work started in 1984 to detect the solar intensity
oscillations from ground (Jimenez et al., 1986), simultaneous
velocity and intensity observations of 16 contiguous days of very high
atmospheric quality obtained at Izana (Tenerife) have been analyzed. The
frequencies of the p-mode intensity spectrum at three channels
(500, 680 and 870 nm) and those of the velocity spectrum have been
obtained. Amplitude ratios in the intensity measurements give results
of 1.6 and 2.2 when comparing the last two channels with the first one,
and their relative phases give a null result at any frequency in the
5 minute range. The relative phases between luminosity and intensity
measurements give a mean result of -120 degrees. Finally, the ratio
of the amplitudes of the intensity oscillations to the velocity ones
correlates very well with theoretical expectations and it yields a
fractional variation of the effective temperature of 2 x 10 to the -6th.
---------------------------------------------------------
Title: Search for Oscillations in Some Ap-Stars
Authors: Belmonte, J. A.; Palle, P. L.; Roca-Cortes, T.
1988IAUS..123..265B Altcode:
Photometric observations of some Ap stars with a 50 cm telescope have
been carried out at Izaña (Tenerife) in February 1986. The stars
observed were, generally, magnetic-cool Ap stars. A search for global
oscillations in the range 3 to 15 minutes has been undertaken and they
seem to be present in some of the stars observed.
---------------------------------------------------------
Title: Search for Solar G-Modes from 1981-1985
Authors: Palle, P. L.; Roca-Cortes, T.
1988IAUS..123...79P Altcode:
Analysis of solar velocity data obtained at Izaña (Tenerife) over the
years 1981 - 1985, has shown the existence of significant signals in
the frequency range 25 - 125 μHz. Several ways of analyzing the data
have been used in order to interpret these as solar internal gravity
modes of degree l ≤ 3.
---------------------------------------------------------
Title: Splitting of the Low L Solar P-Modes
Authors: Jefferies, S. M.; McLeod, C. P.; van der Raay, H. B.; Palle,
P. L.; Roca-Cortes, T.
1988IAUS..123...25J Altcode:
An analysis of full disc line of sight velocity data yield line
splitting values of the low l-value non-radial modes. Possible
variations of the line splitting with the solar cycle are investigated.
---------------------------------------------------------
Title: Solar Cycle Dependence of Solar P-Modes
Authors: Isaak, G. R.; Jefferies, S. M.; McLeod, C. P.; New, R.;
van der Raay, H. B.; Palle, P. L.; Regulo, C.; Roca-Cortes, T.
1988IAUS..123..201I Altcode:
Data obtained at Izaña (Tenerife) and Haleakala (Maui), using optical
resonant scattering with a potassium vapour cell over the years 1980 -
84, are used to determine the frequencies of the low l p modes. Possible
variation in these frequencies with the solar cycle are investigated.
---------------------------------------------------------
Title: Variations in the Mean Line-Of Velocity of the Sun - 1976-1985
Authors: Jimenez, A.; Palle, P. L.; Regulo, C.; Roca-Cortes, T.;
Elsworth, Y. P.; Isaak, G. R.; Jefferies, S. M.; McLeod, C. P.; New,
R.; van der Raay, H. B.
1988IAUS..123..215J Altcode:
Measurements of the line of sight velocity of the sun with respect to
earth have been obtained at Izaña (Tenerife) during the years 1976 to
1985. The mean values found for each year show a trend of ≡30 m/s from
minimum to maximum. Their mean value is of 583.1±0.2 m/s which is 92%
of the gravitational redshift predicted by theory and their variation
seems to be related to the solar cycle with the clear exception of 1985.
---------------------------------------------------------
Title: Earthbased Observations of Solar Luminosity Oscillations
Authors: Jimenez, A.; Palle, P. L.; Perez-Hernandez, F.; Regulo, C.;
Roca-Cortes, T.; Domingo, V.; Korzennik, S.
1988IAUS..123...71J Altcode:
Earth based multichannel photometry of integral sunlight has been
obtained at Izaña (Tenerife) during 1984 - 1986. Power spectra of the
solar luminosity variations of individual days show power in the 5
minute interval above noise at a level comparable to SMM data. When
combining contigous days of data the signature of p mode solar
oscillations spectrum appears, although individual peak identification
is difficult.
---------------------------------------------------------
Title: Experience in Operating a Limited Global Network of Stations
Measuring Full-Disc Oscillations of the Sun
Authors: Elsworth, Y. P.; Isaak, G. R.; Jefferies, S. M.; McLeod,
C. P.; New, R.; van der Raay, H. B.; Palle, P. L.; Regulo, C.;
Roca-Cortes, T.
1988IAUS..123..535E Altcode:
Details are given about the operation of a two station network and of
a new semi-automatic station which has recently been added. Comparison
is made with predicted duty cycles. A possible way of quantifying the
sky quality is also given.
---------------------------------------------------------
Title: Comparison of Solar Oscillation Data Obtained from a Study
of the NA and K Fraunhoffer Absorption Lines
Authors: Isaak, G. R.; McLeod, C. P.; van der Raay, H. B.; Palle,
P. L.; Roca-Cortes, T.
1988IAUS..123...53I Altcode:
Two independent resonant scattering spectrometers, one using a sodium
and the other a potassium vapour cell, were operated simultaneously at
the same site. Due to the differing abundances of ground state atoms of
these two elements different depths of the photosphere are sampled. An
inter-comparison of solar p modes obtained with these spectrometers
is given.
---------------------------------------------------------
Title: The Solar Oscillations Spectrum and the Solar Cycle
Authors: Jimenez, A.; Palle, P. L.; Perez, J. C.; Regulo, C.;
Roca-Cortes, T.; Isaak, G. R.; McLeod, C. P.; van der Raay, H. B.
1988IAUS..123..205J Altcode:
During the summer seasons of the years 1977 to 1985 daily velocity
measurements of solar global oscillations have been obtained using a
resonant scattering spectrometer. After calculating the power spectra
of the daily residuals, the mean for each season is found. Several
discrete frequency intervals are defined in the spectrum. The mean
power in these intervals and the cut-off frequency of the p-mode
spectrum, determined for each year, are correlated with the solar
activity cycle. Furthermore, several series of 13 contiguous days for
each year are analyzed.
---------------------------------------------------------
Title: The 13-DAY Period Oscillation and the Solar Cycle
Authors: Jimenez, A.; Palle, P. L.; Regulo, C.; Roca-Cortes, T.;
Isaak, G. R.; McLeod, C. P.; van der Raay, H. B.
1988IAUS..123..211J Altcode:
From the analysis of radial velocity measurements of the Sun, obtained
at Izaña from 1976 to 1985, stable periods longer than 1 day, have
been found in the observed signal. The appearance of an oscillation
with a 13 day period has been confirmed. The comparison, for 1981 -
84, of the observations with a calibrated numerical model of the
passage of inhomogeneities (spots and plages) on the solar surface,
shows that the signal is not only due to this effect. It is believed
that a velocity field, probably related to the surface inhomogeneities,
contributes to the observed signal.
---------------------------------------------------------
Title: On the 160-MINUTE Oscillation
Authors: Palle, P. L.; Roca-Cortes, T.
1988IAUS..123...75P Altcode:
Solar velocity data collected at Izaña (Tenerife) over the years 1980
- 1985 have been used to search for the 160 minute oscillation. The
peculiar behaviour of the ninth harmonic of a day, in amplitude and
phase, suggests the existence of a solar signal with a 160.02±0.01
minute period, which can be interpreted as a g-mode.
---------------------------------------------------------
Title: Search for solar g modes.
Authors: Palle, P. L.; Roca Cortes, T.; Isaak, G. R.; van der Raay,
H. B.
1987PAICz..66..177P Altcode: 1987eram....1..177P
Using a resonant scattering spectrophotometer the authors measured
the radial velocity of the Sun at the K I 769.9 nm line with very
high resolution and temporal stability. The observations carried out
at Izaña (Tenerife) continuously for the last three years, have been
used to search for solar g modes. Individual peaks, well above noise
level, are identified and their frequencies are likely to correspond
with g modes.
---------------------------------------------------------
Title: The Limb Shift Effect and its Variation with the Solar Cycle
Authors: Anguera, M.; Pallé, P. L.; Régulo, C.; Roca Cortés, T.;
Isaak, G. R.; McLeod, C. P.; van der Raay, H. B.
1987rfsm.conf...24A Altcode:
The radial velocity limb shift effect has been measured for the K
I 7699 Å line using a resonant scattering spectrophotometer in the
summer of 1982. On the other hand, using integral sunlight, the line of
sight velocity has been measured during the years 1976 to 1986 and the
gravitational redshift determined. This value shows a variation over
those years and, when compared with the phase of the solar activity
cycle, the most probable interpretation is a change of the limb shift
effect with the cycle.
---------------------------------------------------------
Title: Ground-based measurements of solar intensity oscillations
Authors: Jimenez, A.; Palle, P. L.; Roca Cortes, T.; Domingo, V.;
Korzennik, S.
1987A&A...172..323J Altcode:
Ground-based multichannel photometry of integral sunlight has been
obtained at Izaña (Tenerife) during three months in 1984 with a
photometer built at ESTEC. Power spectra of solar irradiance variations
of individual days show power in the 5 min band just above noise at
a level comparable to the one found from the SMM data (Woodard and
Hudson, 1983). Previous similar ground work had never achieved the
signal level required at the 5 min interval. When combining the best
7 contiguous days of data, the signature of p mode solar oscillations
spectra appears, but individual identification is difficult due to a
low signal-to-noise ratio.
---------------------------------------------------------
Title: The global oscillation spectrum of the sun. II - The observed
low L high N solar p-mode spectrum
Authors: Palle, P. L.; Perez, J. C.; Regulo, C.; Roca Cortes, T.;
Issak, G. R.
1986A&A...170..114P Altcode:
Using data from observing seasons 1977 through 1984, an analysis
of the low l, high n p-mode solar spectra is made with a 0.9 μHz
resolution. Frequencies and amplitudes of modes of l < 3 and 11 <
n < 33 are determined for each observing season. No clear variation
of the frequencies at the 1 μHz level is found and the amplitudes
remain constant to ∼ 20%. The frequency spacings between different
modes are compared over the solar cycle, as are the constants in
Tassoul's asymptotic formula evaluated for each season: no conclusive
variations are found.
---------------------------------------------------------
Title: The global oscillation spectrum of the sun. I - Analysis of
daily power spectra of velocity measurements
Authors: Palle, P. L.; Perez, J. C.; Regulo, C.; Roca Cortes, T.;
Isaak, G. R.
1986A&A...169..313P Altcode:
Daily observations of solar global oscillations using a resonant
scattering spectrometer have been obtained by observing integral
sunlight during the summer seasons of the years 1977 to 1984. The power
spectra of the daily residuals are calculated and the mean for each
observing season is found. Several discrete frequency intervals are
defined in the spectrum which yield information on the characteristics
of the p-mode and noise levels. The power in these intervals and the
cut-off frequency of the p-mode spectrum determined for each year,
show no correlation with the solar activity cycle.
---------------------------------------------------------
Title: A liquid crystal modulator
Authors: Eccles, D. G.; Elsworth, Y.; van der Raay, H. B.; Palle,
P. L.; Roca Cortes, T.
1986ASIC..169..343E Altcode: 1986ssds.proc..343E
The use of a liquid crystal as an optical modulator for use with a
resonant scattering spectrometer has been investigated. Preliminary data
indicate that using this simple device velocity signals corresponding
to 5 minute oscillations have been detected.
---------------------------------------------------------
Title: The radial velocity of the sun as a star and the solar cycle
Authors: Jiménez, A.; Pallé, P. L.; Régulo, C.; Roca Cortés, T.;
Isaak, G. R.; McLeod, C. P.; van der Raay, H. B.
1986AdSpR...6h..89J Altcode: 1986AdSpR...6...89J
Radial velocity measurements of the sun as a star using a resonant
scattering spectrometer have been obtained at Izan~a (Tenerife) during
long observing seasons from 1976 to 1985. Its analysis shows that except
for the global oscillations with periods shorter than one day there are
stable signals with longer periods: at ~13 days with mean amplitude of
~ 3 m/s (it changes with the solar cycle) and another one of ~ 15 m/s
amplitude which shows a temporal variation of various years related
to the solar cycle. The first signal has a partial explanation as an
effect produced by the passage of active regions through the visible
surface of the sun but it does not completely explain the observed
signal. The second one, related to the limb shift, is probably due to
changes in the convection zone in connection with the solar cycle.
