explanation blue bibcodes open ADS page with paths to full text
Author name code: hawley
ADS astronomy entries on 2022-09-14
author:"Hawley, Suzanne L."
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Title: Llamaradas Estelares: Modeling the Morphology of White-light
Flares
Authors: Mendoza, Guadalupe Tovar; Davenport, James R. A.; Agol,
Eric; Jackman, James A. G.; Hawley, Suzanne L.
2022AJ....164...17M Altcode:
Stellar variability is a limiting factor for planet detection and
characterization, particularly around active M-type stars. Here we
revisit one of the most active stars from the Kepler mission, the M4
star GJ 1243, and use a sample of 414 flare events from 11 months
of 1-minute cadence light curves to study the empirical morphology
of white-light stellar flares. We use a Gaussian process detrending
technique to account for the underlying starspots. We present an
improved analytic, continuous flare template that is generated by
stacking the flares onto a scaled time and amplitude and uses a Markov
Chain Monte Carlo analysis to fit the model. Our model is defined
using classical flare events but can also be used to model complex,
multipeaked flare events. We demonstrate the utility of our model using
TESS data at the 10-minute, 2-minute, and 20 s cadence modes. Our new
flare model code is made publicly available on GitHub. <SUP>5</SUP>
<SUP>5</SUP> https://github.com/lupitatovar/Llamaradas-Estelares
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Title: Blue asymmetries in Balmer lines and possible mass ejections
during mid M dwarf flares
Authors: Notsu, Yuta; Shibata, Kazunari; Enoto, Teruaki; Hamaguchi,
Kenji; Honda, Satoshi; Maehara, Hiroyuki; Nogami, Daisaku; Ikuta,
Kai; Kowalski, Adam; Hawley, Suzanne; Davenport, James; Tristan,
Isaiah; Namekata, Kosuke
2022cosp...44.1382N Altcode:
Flares are releases of magnetic energy in the solar/stellar atmosphere,
and they have strong emissions from radio to X-rays. During some M
dwarf flares, chromospheric line profiles show blue asymmetries (Honda
et al. 2018), although red asymmetries are more commonly observed in
solar flares. Similar enhancements of the blue wings of Balmer lines
may provide clues for investigating the early phases of stellar coronal
mass ejections (CMEs) during flares (cf. Vida et al. 2016&2019), but
this is still controversial. Thus, we need simultaneous spectroscopic
and photometric observations of flares with high time resolution
to understand the relationship between mass ejections and flaring
events. We have conducted simultaneous spectroscopic and photometric
observations of mid M dwarf flare stars (YZCMi, EVLac, ADLeo) using
APO 3.5m/ARCES, SMARTS 1.5m/CHIRON, Nayuta 2m/MALLS (high-dispersion
spectroscopy), TESS (space high-precision single-color photometry),
ground-based 0.4-1m telescopes (ground-based photometry), and NICER
(X-ray spectroscopy). During 34 nights of observations, we detected more
than 46 flares in Balmer lines (e.g. H$\alpha$). Among them, at least
8 flare event showed clear blue asymmetries with velocities 100-200
km s$ ^{-1}$(Maehara et al. 2021 PASJ, Notsu et al. in prep). We
found various correspondences in the durations of blue asymmetries
and intensities of white light emissions. In most cases, while the
blue asymmetries were not significant in the higher-order Balmer lines
and other chromospheric lines such as the Ca II K/8542A line. As for
one event, we succeeded in the simultaneous observation of the blue
asymmetry and X-ray flare for the first time. These results might
be a clue to investigate the formation processes of the blue-shifted
components, and discuss how blue asymmteries are helpful for dicussing
CME properties. By assuming that the blue asymmetries were caused by
prominence eruptions, we estimate the mass and kinetic energy of the
upward-moving material to be 10$ ^{15}$ — 10$ ^{18}$ g and 10$ ^{29}$
—10$ ^{32}$ erg, respectively. The estimated masses are comparable
to expectations from the empirical relation between the flare X-ray
energy and mass of upward-moving material for stellar flares and
solar CMEs. In contrast, the estimated kinetic energies for these
non-white-light flares are roughly 2-3 orders of magnitude smaller than
that expected from the relation between flare X-ray energy and kinetic
energy for solar CMEs. This could be understood by the difference in
the velocity between CMEs and prominence eruptions.
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Title: Modeling Stellar Surface Features on a Subgiant Star with an
M-dwarf Companion
Authors: Schutte, Maria C.; Hebb, Leslie; Lowry, Simon; Wisniewski,
John; Hawley, Suzanne L.; Mahadevan, Suvrath; Morris, Brett M.;
Robertson, Paul; Rohn, Graeme; Stefansson, Gudmundur
2022AJ....164...14S Altcode: 2022arXiv220508620S
Understanding magnetic activity on the surface of stars other than the
Sun is important for exoplanet analyses to properly characterize an
exoplanet's atmosphere and to further characterize stellar activity on
a wide range of stars. Modeling stellar surface features of a variety
of spectral types and rotation rates is key to understanding the
magnetic activity of these stars. Using data from Kepler, we use the
starspot modeling program STarSPot (STSP) to measure the position and
size of spots for KOI-340, which is an eclipsing binary consisting of a
subgiant star (T <SUB>eff</SUB> = 5593 ± 27 K, R <SUB>⋆</SUB> = 1.98
± 0.05 R <SUB>⊙</SUB>) with an M-dwarf companion (M <SUB>⋆</SUB>
= 0.214 ± 0.006 M <SUB>⊙</SUB>). STSP uses a novel technique to
measure the spot positions and radii by using the transiting secondary
to study and model individual active regions on the stellar surface
using high-precision photometry. We find that the average size of spot
features on KOI-340's primary is ~10% the radius of the star, i.e.,
two times larger than the mean size of solar-maximum sunspots. The
spots on KOI-340 are present at every longitude and show possible
signs of differential rotation. The minimum fractional spotted area of
KOI-340's primary is ${2}_{-2}^{+12}{\rm{ \% }}$ , while the spotted
area of the Sun is at most 0.2%. One transit of KOI-340 shows a signal
in the transit consistent with a plage; this plage occurs right before
a dark spot, indicating that the plage and spot might be colocated on
the surface of the star.
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Title: Llamaradas Estelares: Modeling the Morphology of White-Light
Flares
Authors: Tovar Mendoza, Guadalupe; Davenport, James R. A.; Agol,
Eric; Jackman, James A. G.; Hawley, Suzanne L.
2022arXiv220505706T Altcode:
Stellar variability is a limiting factor for planet detection and
characterization, particularly around active M-type stars. Here we
revisit one of the most active stars from the Kepler mission, the M4
star GJ 1243, and use a sample of 414 flare events from 11 months
of 1-minute cadence light curves to study the empirical morphology
of white-light stellar flares. We use a Gaussian process detrending
technique to account for the underlying starspots. We present an
improved analytic, continuous flare template that is generated by
stacking the flares onto a scaled time and amplitude and uses a Markov
Chain Monte Carlo analysis to fit the model. Our model is defined
using classical flare events, but can also be used to model complex,
multi-peaked flare events. We demonstrate the utility of our model using
TESS data at the 10-minute, 2-minute and 20-second cadence modes. Our
new flare model code is made publicly available on GitHub.
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Title: Recent observations of stellar flares on G-, K-, and M-dwarf
stars and possible mass ejections
Authors: Notsu, Yuta; Kowalski, Adam; Maehara, Hiroyuki; Namekata,
Kosuke; Tristan, Isaiah; Okamoto, Soshi; Ikuta, Kai; Hawley, Suzanne;
Davenport, James; Enoto, Teruaki; Hamaguchi, Kenji; Nogami, Daisaku;
Shibata, Kazunari
2021AGUFM.U43B..01N Altcode:
Flares are frequent energetic explosions in the stellar atmosphere,
and are thought to occur by impulsive releases of magnetic energy
stored around starspots. Large flares (so called superflares) generate
strong high energy emissions and coronal mass ejections (CMEs), which
can greatly affect the planetary environment and habitability. Recent
Kepler/TESS photometric data have revealed the statistical properties
of superflares on G, K, M-type stars. Superflare stars are well
characterized by the existence of large starspots on the surface,
and their magnetic fluxes can explain well superflare energies. Flare
frequency/energy depends on stellar rotation period and stellar
temperature. Young rapidly-rotating stars and cooler stars tend to
have frequent flares, which can be more hazardous for the habitable
planets. However, we still do not know the emission mechanisms of
superflares, and how large CMEs are associated with superflares on these
active stars. Then recently, these active superflare stars have been
investigated in more detail thorugh recent multi-wavelength surveys. For
example, Hydrogen chromospheric lines during flares show blue-shifted
profiles, which can give us some hints on dynamics or mass ejections
during superflares. In the early part of this invited overview talk,
I briefly overview the recent statistical results of superflares from
Kepler/TESS data. Then in the latter part, I also briefly discuss the
results of recent multi-wavelength campaign observations of superflares,
and discuss possible detections of mass ejections (stellar CMEs).
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Title: VizieR Online Data Catalog: IRD and HPF spectra of
TRAPPIST-1b,e and f (Krishnamurthy+, 2021)
Authors: Krishnamurthy, V.; Hirano, T.; Stefansson, G.; Ninan, J. P.;
Mahadevan, S.; Gaidos, E.; Kopparapu, R.; Sato, B.; Hori, Y.; Bender,
C. F.; Canas, C. I.; Diddams, S. A.; Halverson, S.; Harakawa, H.;
Hawley, S.; Hearty, F.; Hebb, L.; Hodapp, K.; Jacobson, S.; Kanodia,
S.; Konishi, M.; Kotani, T.; Kowalski, A.; Kudo, T.; Kurokawa,
T.; Kuzuhara, M.; Lin, A.; Maney, M.; Metcalf, A. J.; Morris, B.;
Nishikawa, J.; Omiya, M.; Robertson, P.; Roy, A.; Schwab, C.; Serizawa,
T.; Tamura, M.; Ueda, A.; Vievard, S.; Wisniewski, J.
2021yCat..51620082K Altcode:
We observed a photometric transit of TRAPPIST-1b on the night of UT
2020 September 5 using the Astrophysical Research Consortium Telescope
Imaging Camera (ARCTIC) on the 3.5m Astrophysical Research Consortium
Telescope at Apache Point Observatory. We adopted the SDSS filter using
an exposure time of 18s in the 4x4 binning fast-readout mode. <P />We
observed the transit of TRAPPIST-1b on the night of UT 2020 September
17 using Infrared Doppler (IRD), which has a spectral resolution of
~70000 in the operating wavelength range of 0.95-1.75μm, mounted on the
8.2m Subaru Telescope on Maunakea, Hawaii. <P />Habitable Planet Finder
(HPF) is a fiber-fed high-resolution (R=55000) spectrograph on the 10m
Hobby-Eberly Telescope (HET) at McDonald Observatory in Texas. Using
HPF, we obtained three transits on the nights of UT 2018 October 2,
2019 July 31, and 2020 September 5. <P />(3 data files).
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Title: A Search for Planetary Metastable Helium Absorption in the
V1298 Tau System
Authors: Vissapragada, Shreyas; Stefánsson, Gudmundur; Greklek-McKeon,
Michael; Oklopčić, Antonija; Knutson, Heather A.; Ninan, Joe P.;
Mahadevan, Suvrath; Cañas, Caleb I.; Chachan, Yayaati; Cochran,
William D.; Collins, Karen A.; Dai, Fei; David, Trevor J.; Halverson,
Samuel; Hawley, Suzanne L.; Hebb, Leslie; Kanodia, Shubham; Kowalski,
Adam F.; Livingston, John H.; Maney, Marissa; Metcalf, Andrew J.;
Morley, Caroline; Ramsey, Lawrence W.; Robertson, Paul; Roy, Arpita;
Spake, Jessica; Schwab, Christian; Terrien, Ryan C.; Tinyanont,
Samaporn; Vasisht, Gautam; Wisniewski, John
2021AJ....162..222V Altcode: 2021arXiv210805358V
Early in their lives, planets endure extreme amounts of ionizing
radiation from their host stars. For planets with primordial
hydrogen and helium-rich envelopes, this can lead to substantial
mass loss. Direct observations of atmospheric escape in young
planetary systems can help elucidate this critical stage of planetary
evolution. In this work, we search for metastable helium absorption-a
tracer of tenuous gas in escaping atmospheres-during transits of three
planets orbiting the young solar analog V1298 Tau. We characterize
the stellar helium line using HET/HPF, and find that it evolves
substantially on timescales of days to months. The line is stable
on hour-long timescales except for one set of spectra taken during
the decay phase of a stellar flare, where absoprtion increased with
time. Utilizing a beam-shaping diffuser and a narrowband filter
centered on the helium feature, we observe four transits with
Palomar/WIRC: two partial transits of planet d (P = 12.4 days), one
partial transit of planet b (P = 24.1 days), and one full transit of
planet c (P = 8.2 days). We do not detect the transit of planet c,
and we find no evidence of excess absorption for planet b, with ΔR
<SUB>b</SUB>/R <SUB>⋆</SUB> < 0.019 in our bandpass. We find
a tentative absorption signal for planet d with ΔR <SUB>d</SUB>/R
<SUB>⋆</SUB> = 0.0205 ± 0.054, but the best-fit model requires a
substantial (-100 ± 14 minutes) transit-timing offset on a two-month
timescale. Nevertheless, our data suggest that V1298 Tau d may have
a high present-day mass-loss rate, making it a priority target for
follow-up observations.
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Title: TOI-532b: The Habitable-zone Planet Finder confirms a Large
Super Neptune in the Neptune Desert orbiting a metal-rich M-dwarf host
Authors: Kanodia, Shubham; Stefansson, Gudmundur; Cañas, Caleb I.;
Maney, Marissa; Lin, Andrea S. J.; Ninan, Joe P.; Jones, Sinclaire;
Monson, Andrew; Parker, Brock A.; Kobulnicky, Henry A.; Rothenberg,
Jason; Beard, Corey; Lubin, Jack; Robertson, Paul; Gupta, Arvind F.;
Mahadevan, Suvrath; Cochran, William D.; Bender, Chad F.; Diddams,
Scott A.; Fredrick, Connor; Halverson, Samuel; Hawley, Suzanne;
Hearty, Fred; Hebb, Leslie; Kopparapu, Ravi; Metcalf, Andrew J.;
Ramsey, Lawrence W.; Roy, Arpita; Schwab, Christian; Schutte, Maria;
Terrien, Ryan C.; Wisniewski, John; Wright, Jason T.
2021AJ....162..135K Altcode: 2021arXiv210713670K
We confirm the planetary nature of TOI-532b, using a combination of
precise near-infrared radial velocities with the Habitable-zone Planet
Finder, Transiting Exoplanet Survey Satellite (TESS) light curves,
ground-based photometric follow up, and high-contrast imaging. TOI-532
is a faint (J ~ 11.5) metal-rich M dwarf with T<SUB>eff</SUB> = 3957 ±
69 K and [Fe/H] = 0.38 ± 0.04; it hosts a transiting gaseous planet
with a period of ~2.3 days. Joint fitting of the radial velocities
with the TESS and ground-based transits reveal a planet with radius
of 5.82 ± 0.19 R<SUB>⊕</SUB>, and a mass of ${61.5}_{-9.3}^{+9.7}$
M<SUB>⊕</SUB>. TOI-532b is the largest and most massive super Neptune
detected around an M dwarf with both mass and radius measurements,
and it bridges the gap between the Neptune-sized planets and the
heavier Jovian planets known to orbit M dwarfs. It also follows the
previously noted trend between gas giants and host-star metallicity for
M-dwarf planets. In addition, it is situated at the edge of the Neptune
desert in the Radius-Insolation plane, helping place constraints on
the mechanisms responsible for sculpting this region of planetary
parameter space.
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Title: Nondetection of Helium in the Upper Atmospheres of TRAPPIST-1b,
e, and f
Authors: Krishnamurthy, Vigneshwaran; Hirano, Teruyuki; Stefánsson,
Gumundur; Ninan, Joe P.; Mahadevan, Suvrath; Gaidos, Eric; Kopparapu,
Ravi; Sato, Bunei; Hori, Yasunori; Bender, Chad F.; Cañas, Caleb
I.; Diddams, Scott A.; Halverson, Samuel; Harakawa, Hiroki; Hawley,
Suzanne; Hearty, Fred; Hebb, Leslie; Hodapp, Klaus; Jacobson, Shane;
Kanodia, Shubham; Konishi, Mihoko; Kotani, Takayuki; Kowalski, Adam;
Kudo, Tomoyuki; Kurokawa, Takashi; Kuzuhara, Masayuki; Lin, Andrea;
Maney, Marissa; Metcalf, Andrew J.; Morris, Brett; Nishikawa, Jun;
Omiya, Masashi; Robertson, Paul; Roy, Arpita; Schwab, Christian;
Serizawa, Takuma; Tamura, Motohide; Ueda, Akitoshi; Vievard,
Sébastien; Wisniewski, John
2021AJ....162...82K Altcode: 2021arXiv210611444K
We obtained high-resolution spectra of the ultracool M-dwarf TRAPPIST-1
during the transit of its planet "b" using two high-dispersion
near-infrared spectrographs, the Infrared Doppler (IRD) instrument on
the Subaru 8.2m telescope, and the Habitable Zone Planet Finder (HPF)
instrument on the 10 m Hobby-Eberly Telescope. These spectroscopic
observations are complemented by a photometric transit observation
for planet "b" using the APO/ARCTIC, which assisted us in capturing
the correct transit times for our transit spectroscopy. Using the
data obtained by the new IRD and HPF observations, as well as the
prior transit observations of planets "b," "e" and "f" from IRD,
we attempt to constrain the atmospheric escape of the planet using
the He I triplet 10830 Å absorption line. We do not detect evidence
for any primordial extended H-He atmospheres in all three planets. To
limit any planet-related absorption, we place an upper limit on the
equivalent widths of <7.754 mÅ for planet "b," <10.458 mÅ for
planet "e," <4.143 mÅ for planet "f" at 95% confidence from the
IRD data, and <3.467 mÅ for planet "b" at 95% confidence from HPF
data. Using these limits along with a solar-like composition isothermal
Parker wind model, we attempt to constrain the mass-loss rates for the
three planets. For TRAPPIST-1b, our models exclude the highest possible
energy-limited rate for a wind temperature <5000 K. This nondetection
of extended atmospheres with low mean-molecular weights in all three
planets aids in further constraining their atmospheric composition by
steering the focus toward the search of high-molecular-weight species
in their atmospheres. <SUP>*</SUP>Based on data collected at Subaru
Telescope, operated by the National Astronomical Observatory of Japan,
Hobby-Eberly Telescope operated by The University of Texas McDonald
Observatory, and ARC 3.5m Telescope at Apache Point Observatory.
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Title: Blue asymmetries in Balmer lines during mid M dwarf flares
Authors: Notsu, Yuta; Kowalski, Adam F.; Maehara, Hiroyuki; Namekata,
Kosuke; Honda, Satoshi; Enoto, Teruaki; Hamaguchi, Kenji; Tristan,
Isaiah; Hawley, Suzanne L.; Davenport, James R. A.; Okamoto, Soshi;
Ikuta, Kai; Nogami, Daisaku; Shibata, Kazunari
2021tsc2.confE.118N Altcode:
Flares are releases of magnetic energy in the stellar atmosphere, and
they have strong emissions from radio to X-rays. During some M dwarf
flares, chromospheric line profiles show blue asymmetries, although
red asymmetries are more commonly observed in solar flares. Similar
enhancements of the blue wings of Balmer lines may provide clues for
investigating the early phases of stellar coronal mass ejections (CMEs),
but this is still controversial. Thus, we need more observations to
understand the relationship between mass ejections and flares. We have
conducted simultaneous spectroscopic and photometric observations of
mid M dwarf flare stars using APO 3.5m/ARCES, SMARTS1.5m/CHIRON, TESS,
and etc. During 34 night observations, we detected 48 flares in Balmer
lines (e.g. Hα). At least 7 flares show clear blue asymmetries. Blue
asymmetry durations are different among the 7 events (20min ~
2hr). These results suggest upward flows of chromospheric plasma during
flare events. By assuming that the blue asymmetries were caused by
prominence eruptions, we estimated the mass and kinetic energy. The
estimated masses are comparable to expectations from the empirical
relation between the flare X-ray energy and mass of solar CMEs.
---------------------------------------------------------
Title: Modeling the Morphology of White-Light Flares
Authors: Tovar Mendoza, Guadalupe; Davenport, James R. A.; Hawley,
Suzanne L.
2021tsc2.confE.149T Altcode:
Stellar variability is a limiting factor for planet detection and
characterization, particularly around active stars. By understanding
the light curve profile of flares on active M-dwarfs we can help
improve exoplanet detection and characterization. Here we revisit
one of the most active stars from the Kepler mission, the M4 dwarf
GJ 1243, and use a sample of 303 stellar flares from 11 months of
1-minute cadence light curves to study the empirical morphology of
stellar flares. We use a Gaussian process detrending technique to
account for the underlying starspots. We present an improved analytic,
continuous flare template that is generated by stacking the flares in
a scaled time and amplitude and using Markov Chain Monte Carlo to fit
the model. Our model is defined using classical flare events, but can
also be used to model complex, multi-peaked flare events. We test our
model using TESS data at both the 2-minute and 20-second cadence modes,
showing the general utility of our empirical flare template.
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Title: The Mega-MUSCLES Spectral Energy Distribution of TRAPPIST-1
Authors: Wilson, David J.; Froning, Cynthia S.; Duvvuri, Girish
M.; France, Kevin; Youngblood, Allison; Schneider, P. Christian;
Berta-Thompson, Zachory; Brown, Alexander; Buccino, Andrea P.; Hawley,
Suzanne; Irwin, Jonathan; Kaltenegger, Lisa; Kowalski, Adam; Linsky,
Jeffrey; Parke Loyd, R. O.; Miguel, Yamila; Pineda, J. Sebastian;
Redfield, Seth; Roberge, Aki; Rugheimer, Sarah; Tian, Feng; Vieytes,
Mariela
2021ApJ...911...18W Altcode: 2021arXiv210211415W
We present a 5 Å-100 μm spectral energy distribution (SED)
of the ultracool dwarf star TRAPPIST-1, obtained as part of
the Mega-MUSCLES Treasury Survey. The SED combines ultraviolet
and blue-optical spectroscopy obtained with the Hubble Space
Telescope, X-ray spectroscopy obtained with XMM-Newton, and models
of the stellar photosphere, chromosphere, transition region, and
corona. A new differential emission measure model of the unobserved
extreme-ultraviolet spectrum is provided, improving on the Lyα-EUV
relations often used to estimate the 100-911 Å flux from low-mass
stars. We describe the observations and models used, as well as the
recipe for combining them into an SED. We also provide a semiempirical,
noise-free model of the stellar ultraviolet spectrum based on our
observations for use in atmospheric modeling of the TRAPPIST-1 planets.
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Title: From Kepler to TESS: 10 Years of Flare Activity from Space
Authors: Davenport, James; Tovar Mendoza, Guadalupe; Hawley, Suzanne
2021csss.confE..27D Altcode:
We have carried out the first flare and starspot analysis of GJ 1243
from over 50 days of data from TESS Sectors 14 and 15. Using 133 flare
events detected in the 2 minute cadence TESS data, we compare the
cumulative flare frequency distributions, and find the flare activity
for GJ 1243 is unchanged between the Kepler and TESS epochs. Two
distinct starspot groups are found in the TESS data, with the primary
spot having the same rotational period and phase as in Kepler. As
expected for this highly active M4, the constant spot and flare activity
reveal no sign of solar-like activity cycles over 10 yr. However, we
highlight the unique ability for Kepler and TESS to use flare rates to
detect activity cycles for many years to come. New 20-second cadence
data from TESS will also allow us to test the widely used empirical
flare profile created for GJ 1243 using Kepler 1-minute data.
---------------------------------------------------------
Title: Blue asymmetries in Balmer lines during mid M dwarf flares
Authors: Notsu, Yuta; Kowalski, Adam F.; Maehara, Hiroyuki; Namekata,
Kosuke; Honda, Satoshi; Enoto, Teruaki; Hamaguchi, Kenji; Tristan,
Isaiah; Hawley, Suzanne L.; Davenport, James R. A.; Okamoto, Soshi;
Ikuta, Kai; Nogami, Daisaku; Shibata, Kazunari
2021csss.confE.103N Altcode:
Flares are releases of magnetic energy in the solar/stellar atmosphere,
and they have strong emissions from radio to X-rays. During some
M dwarf flares, chromospheric line profiles show blue asymmetries
(Eason et al. 1992; Honda et al. 2018), although red asymmetries are
more commonly observed in solar flares. Similar enhancements of the
blue wings of Balmer lines may provide clues for investigating the
early phases of stellar coronal mass ejections (CMEs) during flares
(cf. Vida et al. 2016&2019), but this is still controversial. Thus,
we need more flare spectroscopic observations with high time resolution
to understand the relationship between mass ejections and flaring
events. The latter is helpful for estimating the impact on planets
from flares.We have conducted several simultaneous spectroscopic
and photometric observations of mid M dwarf flare stars using
APO 3.5m/ARCES, SMARTS 1.5m/CHIRON, TESS, and ground- based 0.4-1m
photometric telescopes. During 34 nights of observations, we detected
48 flares in Balmer lines (e.g. H-alpha). Among them, at least 7
flare events show clear blue asymmetries. Blue asymmetry durations
are different among the 7 events (20min ~ 2hr).These results suggest
upward flows of chromospheric plasma during flare events. By assuming
that the blue asymmetries were caused by prominence eruptions, we
estimate the mass and kinetic energy of the upward-moving material
to be 10<SUP>15</SUP> - 10<SUP>18</SUP> g and 10<SUP>29 </SUP>-
10<SUP>32</SUP> erg, respectively. The estimated masses are comparable
to expectations from the empirical relation between the flare X-ray
energy and mass of upward-moving material for stellar flares and
solar CMEs. In contrast, the estimated kinetic energies for these
non-white-light flares are roughly 2-3 orders of magnitude smaller than
that expected from the relation between flare X-ray energy and kinetic
energy for solar CMEs. This could be understood by the difference in
the velocity between CMEs and prominence eruptions.
---------------------------------------------------------
Title: Blue asymmetries in Balmer lines during mid M dwarf flares
Authors: Notsu, Y.; Kowalski, A.; Maehara, H.; Namekata, K.; Honda,
S.; Enoto, T.; Hamaguchi, K.; Tristan, I.; Hawley, S.; Davenport,
J.; Okamoto, S.; Ikuta, K.; Nogami, D.; Shibata, K.
2021AAS...23751501N Altcode:
Flares are releases of magnetic energy in the solar/stellar atmosphere,
and they have strong emissions from radio to X-rays. During some
M dwarf flares, chromospheric line profiles show blue asymmetries
(Honda et al. 2018), although red asymmetries are more commonly
observed in solar flares. Similar enhancements of the blue wings of
Balmer lines may provide clues for investigating the early phases
of stellar coronal mass ejections (CMEs) during flares (cf. Vida et
al. 2016&2019), but this is still controversial. Thus, we need
more flare spectroscopic observations with high time resolution
to understand the relationship between mass ejections and flaring
events. The latter is helpful for estimating the impact on planets
from flares. We have conducted several simultaneous spectroscopic
and photometric observations of mid M dwarf flare stars using APO
3.5m/ARCES, SMARTS 1.5m/CHIRON, Nayuta 2m/MALLS (high-dispersion
spectroscopy), TESS (space high-precision single-color photometry),
and ground-based 0.4-1m telescopes (ground-based photometry). During
~20 nights of observations, we detected more than 30 flares in Balmer
lines (e.g. Hα). Among them, at least 6 flare events (including one
already reported in Maehara et al. 2020) show clear blue asymmetries,
but none show brightening in the continuum. Blue asymmetry durations are
different among the 6 events (20min ~ 2hr). These results suggest upward
flows of chromospheric plasma during "non-white light" flare events. By
assuming that the blue asymmetries were caused by prominence eruptions,
we estimate the mass and kinetic energy of the upward-moving material to
be 10<SUP>15</SUP>-10<SUP>18</SUP> g and 10<SUP>29</SUP>-10<SUP>32</SUP>
erg, respectively. The estimated masses are comparable to expectations
from the empirical relation between the flare X-ray energy and mass of
upward-moving material for stellar flares and solar CMEs. In contrast,
the estimated kinetic energies for these non-white-light flares are
roughly 2 orders of magnitude smaller than that expected from the
relation between flare X-ray energy and kinetic energy for solar
CMEs. This could be understood by the difference in the velocity
between CMEs and prominence eruptions.
---------------------------------------------------------
Title: Superflares investigated with Kepler&TESS photometric
data and recent multi-wavelength campaign observations
Authors: Notsu, Yuta; Shibata, Kazunari; Enoto, Teruaki; Hamaguchi,
Kenji; Honda, Satoshi; Maehara, Hiroyuki; Nogami, Daisaku; Namekata,
Kosuke; Ikuta, Kai; Kowalski, Adam; Hawley, Suzanne; Davenport, James;
Okamoto, Soshi; Notsu, Shota
2021cosp...43E1750N Altcode:
Solar flares are frequent energetic explosions in the solar atmosphere,
and are thought to occur by impulsive releases of magnetic energy
stored around sunspots. Large solar flares sometimes can have large
impacts on our Earth and society (e.g., magnetic storms). Stars other
than the Sun also show flares. Many young stars, active M-dwarfs known
as flare stars, and close binary stars have “superflares”, which are
flares that have a total energy 10--10$^{6}$ times larger than that of
the largest solar flares on the Sun ($\sim$10$^{32}$ erg). These stars
generally rotate very fast (Period $\sim$ 2--3 days). In contrast, the
Sun slowly rotates (Period $\sim$25 days). Then it had been thought that
superflares cannot occur on slowly-rotating G-type main-sequence stars
like the Sun. Recently, more than 1000 superflares on solar-type stars
(G-type main sequence stars) have been found using the photometric
data of Kepler spece telescope (and also TESS satellite). Using these
large number of data, it is now possible to do statistical studies
of superflares on solar-type stars. First, superflare stars are well
characterized by the existence of large starspots on the surface,
and their magnetic fluxes can explain well superflare energies. Then,
maximum superflare energy continuously decreases as the rotation period
increases. Superflares with their energy $\le \sim$ 5$\times$10$^{34}$
erg (a few hundred times larger than the largest solar flares) would
occur on old slowly-rotating Sun-like stars (Rotation Period $\sim$25
days) once every 2000-3000 years, while young rapidly-rotating
stars with Rotation Period $\sim$ a few days have superflares up
to 10$^{36}$ erg. These results presented in this work support that
even slowly-rotating stars similar to the Sun can have superflares,
considering long-term activity level changes. In addition to these
photometric observation results of solar-type superflare stars, cool
M-dwarf superflare stars have been investigated in more detail by
recent multi-wavelength surveys. For example, Hydrogen chromospheric
lines during flares show a lot of blue-shifted profiles, which can give
us some hints on dynamics or mass ejections during superflares. In
the main part of this review talk, I review the recent statistical
results of superflares from Kepler\&TESS data. Then in the latter
part, I also briefly discuss the results of recent multi-wavelength
campaign observations of M-dwarf superflares, and finally show the
future prospects of superflare studies, which are closely related with
solar physics and studies of effects on planets.
---------------------------------------------------------
Title: 10 Years of Stellar Activity for GJ 1243
Authors: Davenport, James. R. A.; Mendoza, Guadalupe Tovar; Hawley,
Suzanne L.
2020AJ....160...36D Altcode: 2020arXiv200510281D
The flaring M4 dwarf GJ 1243 has become a benchmark for studying stellar
flare and starspot activity thanks to the exceptional photometric
monitoring archive from the Kepler mission. New light curves from
the Transiting Exoplanet Survey Satellite (TESS) mission for this
star allow precise stellar activity characterization over more than
a decade timescale. We have carried out the first flare and starspot
analysis of GJ 1243 from over 50 days of data from TESS Sectors 14 and
15. Using 133 flare events detected in the 2 minute cadence TESS data,
we compare the cumulative flare frequency distributions, and find
the flare activity for GJ 1243 is unchanged between the Kepler and
TESS epochs. Two distinct starspot groups are found in the TESS data,
with the primary spot having the same rotational period and phase as
seen in Kepler. The phase of the secondary spot feature is consistent
with the predicted location of the secondary starspot and measurement
of weak differential rotation, suggesting this secondary spot may be
long-lived and stable in both latitude and longitude. As expected for
this highly active star, the constant spot and flare activity reveal no
sign of solar-like activity cycles over 10 yr. However, we highlight
the unique ability for Kepler and TESS to use flare rates to detect
activity cycles.
---------------------------------------------------------
Title: The stellar variability noise floor for transiting exoplanet
photometry with PLATO
Authors: Morris, Brett M.; Bobra, Monica G.; Agol, Eric; Lee, Yu Jin;
Hawley, Suzanne L.
2020MNRAS.493.5489M Altcode: 2020arXiv200208072M; 2020MNRAS.tmp..581M
One of the main science motivations for the ESA PLAnetary Transit and
Oscillations (PLATO) mission is to measure exoplanet transit radii
with 3 per cent precision. In addition to flares and starspots, stellar
oscillations and granulation will enforce fundamental noise floors for
transiting exoplanet radius measurements. We simulate light curves of
Earth-sized exoplanets transiting continuum intensity images of the Sun
taken by the Helioseismic and Magnetic Imager (HMI) instrument aboard
the Solar Dynamics Observatory (SDO) to investigate the uncertainties
introduced on the exoplanet radius measurements by stellar granulation
and oscillations. After modelling the solar variability with a
Gaussian process, we find that the amplitude of solar oscillations
and granulation is of order 100 ppm - similar to the depth of an
Earth transit - and introduces a fractional uncertainty on the depth
of transit of 0.73 per cent assuming four transits are observed over
the mission duration. However, when we translate the depth measurement
into a radius measurement of the planet, we find a much larger radius
uncertainty of 3.6 per cent. This is due to a degeneracy between the
transit radius ratio, the limb darkening, and the impact parameter
caused by the inability to constrain the transit impact parameter in
the presence of stellar variability. We find that surface brightness
inhomogeneity due to photospheric granulation contributes a lower limit
of only 2 ppm to the photometry in-transit. The radius uncertainty due
to granulation and oscillations, combined with the degeneracy with the
transit impact parameter, accounts for a significant fraction of the
error budget of the PLATO mission, before detector or observational
noise is introduced to the light curve. If it is possible to constrain
the impact parameter or to obtain follow-up observations at longer
wavelengths where limb darkening is less significant, this may enable
higher precision radius measurements.
---------------------------------------------------------
Title: Temporal Evolution of Spatially Resolved Individual Star
Spots on a Planet-hosting Solar-type Star: Kepler-17
Authors: Namekata, Kosuke; Davenport, James R. A.; Morris, Brett M.;
Hawley, Suzanne L.; Maehara, Hiroyuki; Notsu, Yuta; Toriumi, Shin;
Ikuta, Kai; Notsu, Shota; Honda, Satoshi; Nogami, Daisaku; Shibata,
Kazunari
2020ApJ...891..103N Altcode: 2020arXiv200201086N
Star spot evolution is visible evidence of the emergence/decay of the
magnetic field on a stellar surface, and it is therefore important for
the understanding of the underlying stellar dynamo and consequential
stellar flares. In this paper, we report the temporal evolution
of individual star spot areas on the hot-Jupiter-hosting, active
solar-type star Kepler-17, whose transits occur every 1.5 days. The
spot longitude and area evolution are estimated (1) from the stellar
rotational modulations of Kepler data and (2) from the brightness
enhancements during the exoplanet transits caused by existence of
large star spots. As a result of the comparison, the number of spots,
spot locations, and the temporal evolution derived from the rotational
modulations are largely different from those of in-transit spots. We
confirm that, although only two light-curve minima appear per rotation,
there are clearly many spots present on the star. We find that the
observed differential intensity changes are sometimes consistent with
the spot pattern detected by transits, but at other times they do not
match with each other. Although the temporal evolution derived from
the rotational modulation differs from those of in-transit spots to
a certain degree, the emergence/decay rates of in-transit spots are
within an order of magnitude of those derived for sunspots as well
as our previous research based only on rotational modulations. This
supports the hypothesis that the emergence/decay of sunspots and
extremely large star spots on solar-type stars occur through the same
underlying processes.
---------------------------------------------------------
Title: Lifetimes and emergence/decay rates of star spots on solar-type
stars estimated by Kepler data in comparison with those of sunspots
Authors: Namekata, K.; Shibata, K.; Maehara, H.; Notsu, Y.; Nogami,
D.; Toriumi, S.; Davenport, J.; Hawley, S.; Morris, B.
2020AAS...23514805N Altcode:
Active solar-type stars show large quasi-periodic brightness variations
caused by stellar rotations with large star spots, and the amplitude
changes as the spots emerge and decay. Temporal evolution of star spots
has been hardly measured because of its difficulty in measurement,
especially on solar-type stars. The Kepler's long-term data are suitable
for investigations on the emergence and decay processes of star spots,
which are important to understand underlying stellar dynamo. In this
talk, we report the measurements of temporal evolution of individual
star-spot area on solar-type stars by using Kepler data. We estimated
it (i) by tracing local minima of the Kepler light curves (Namekata et
al. 2019) and (ii) by modeling the small brightness variation during
exoplanet transit (c.f. Morris et al. 2017, Namekata et al. submitted
to ApJ). We successfully obtained temporal evolution of individual star
spots showing clear emergence and decay, and derived the statistical
values of the lifetimes and emergence/decay rates of star spots. As
a result, we found that lifetimes (T) of star spots are ranging
from 10 to 350 days when spot areas (A) are 0.1-2.3% of a solar
hemisphere (SH). The lifetimes of star spots are much shorter than
those extrapolated from an empirical relation of sunspots, while being
consistent with other researches on star spot lifetimes. The emerging
and decay rates of star spots are typically 5×10<SUP>20</SUP> Mx/h
(8 MSH/h) with the area of 0.1-2.3% of SH and are mostly consistent
with those expected from sunspots observations (Petrovay et al. 1997,
Norton et al. 2017). This strongly supports a possibility that the
emergence/decay mechanism of extremely large star spots (0.1-2.3%
of SH) is same as that of smaller sunspots (< 0.5% of SH), which
can constrain the stellar dynamo theory.
---------------------------------------------------------
Title: Blue asymmetries of Balmer lines during M-dwarf flares
investigated with multi-wavelength observations
Authors: Notsu, Y.; Kowalski, A.; Maehara, H.; Namekata, K.; Hawley,
S.; Davenport, J.; Enoto, T.; Hamaguchi, K.; Honda, S.; Notsu, S.;
Ikuta, K.; Nogami, D.; Shibata, K.
2020AAS...23528805N Altcode:
Flares are magnetic energy release in the solar/stellar atmosphere,
and they have strong emissions from radio to X-rays. During some
M-dwarf superflares, chromospheric line profiles show blue asymmetries
(Honda et al. 2018), though red asymmetries have been seen during many
ordinary solar flares. it is also thought that similar enhancements of
the blue wing of Balmer lines can provide clues for investigating mass
ejections from flares (stellar CMEs) (cf. Vida et al. 2016&2019),
but this is still very controversial. Thus, we need more flare
spectroscopic observations with high time resolution for understanding
how superflares occur and how large mass ejections occur during
superflares occur. The latter is helpful for estimating the impacts
on planets from superflares. We have conducted several simultaneous
spectroscopic and photometric observations of M-dwarf flare stars. In
2019 January, we observed a M-dwarf flare star YZCMi using APO3.5m/ARCES
(high-dispersion spectroscopy), APO/ARCSAT0.5m (multi-color photometry),
TESS (space high-precision single-color photometry), and NICER (soft
X-ray telescope on ISS). During the observation, we detected large
enhancements of chromospheric lines lasting for longer than 3 hours
(e.g., H- alpha and H-beta). H-alpha line profiles during this event
show some blue asymmetries. In this event, we also detected soft
X-ray intensity increases, but a bit strangely and a bit different
from previous expectations, the photometric data (optical continuum
white light data) show no clear flare-like brightness increases. This
might suggest that these intensity increases of chromospheric lines
(with possible blue asymmetries) and soft X-rays occurred as a
"non white-light" flare events, which are often seen in the case of
solar flares (e.g., Watanabe et al. 2017). We also observed another
M-dwarf flare star AU Mic using CTIO/SMART1.5m/CHIRON (high-dispersion
spectroscopy), LCO (U&V-band photometry), and XMM-Newton (soft
X-ray), and detected several flares in Oct 2018. In contrast to the
above "non-white light" events, these flares show enhancements in
Balmer lines (e.g., H-alpha), optical continuum white light, and soft
X-ray. Then this event is a so-called "white-light" flare. Moreover,
this "white-light" event does not show clear blue asymmetries, which are
different from the above YZCMi "non-white light" event. In this poster,
we introduce ongoing results on the analyses of these two events.
---------------------------------------------------------
Title: Stellar Properties of Active G and K Stars: Exploring the
Connection between Starspots and Chromospheric Activity
Authors: Morris, Brett M.; Curtis, Jason L.; Sakari, Charli; Hawley,
Suzanne L.; Agol, Eric
2019AJ....158..101M Altcode: 2019arXiv190700423M
We gathered high resolution spectra for an ensemble of 55 bright active
and inactive stars using the ARC 3.5 m Telescope Echelle Spectrograph
at Apache Point Observatory (R ≈ 31,500). We measured spectroscopic
effective temperatures, surface gravities, and metallicities for
most stars in the sample with SME and MOOG. Our stellar property
results are consistent with the photometric effective temperatures
from the Gaia DR2 pipeline. We also measured their chromospheric S and
{log}{R}<SUB>HK</SUB>}<SUP>{\prime</SUP> } indices to classify the stars
as active or inactive and study the connection between chromospheric
activity and starspots. We then inferred the starspot covering
fractions on the active stars by modeling their spectra as a linear
combination of hot and cool inactive stellar spectral templates. We
find that it is critical to use precise colors of the stars to place
stringent priors on the plausible spot covering fractions. The inferred
spot covering fractions generally increase with the chromospheric
activity indicator {log}{R}<SUB>HK</SUB>}<SUP>{\prime</SUP> },
though we are largely insensitive to spot coverages smaller than
f <SUB> S </SUB> ≲ 20%. We find a dearth of stars with small
{log}{R}<SUB>HK</SUB>}<SUP>{\prime</SUP> } and significant spot
coverages.
---------------------------------------------------------
Title: Measurements of the Ultraviolet Spectral Characteristics of
Low-mass Exoplanetary Systems (Mega-MUSCLES)
Authors: Wilson, David John; Froning, Cynthia; France, Kevin;
Youngblood, Allison; Duvvuri, Girish M.; Brown, Alexander; Schneider,
P. Christian; Kowalski, Adam; Loyd, R. O. Parke; Berta-Thompson,
Zachory Berta-; Pineda, J. Sebastian; Linsky, Jeffrey; Rugheimer,
Sarah; Newton, Elizabeth; Miguel, Yamila; Roberge, Aki; Buccino,
Andrea P.; Irwin, Jonathan; Kaltenegger, Lisa; Vieytes, Mariela;
Mauas, Pablo; Redfield, Seth; Hawley, Suzanne; Tian, Feng
2019ESS.....431906W Altcode:
M dwarf stars have emerged as ideal targets for exoplanet
observations. Their small radii aids planetary discovery, their
close-in habitable zones allow short observing campaigns, and their
red spectra provide opportunities for transit spectroscopy with
JWST. The potential of M dwarfs has been underlined by the discovery
of remarkable systems such as the seven Earth-sized planets orbiting
TRAPPIST-1 and the habitable-zone planet around the closest star to
the Sun. <P />However, to accurately assess the conditions in these
systems requires a firm understanding of how M dwarfs differ from the
Sun, beyond just their smaller size and mass. Of particular importance
are the time-variable, high-energy ultraviolet and x-ray regions of
the M dwarf spectral energy distribution (SED), which can influence
the chemistry and lifetime of exoplanet atmospheres, as well as their
surface radiation environments. <P />The Measurements of the Ultraviolet
Spectral Characteristics of Low-mass Exoplanetary Systems (Mega-MUSCLES)
Treasury project, together with the precursor MUSCLES project, aims to
produce full SEDs of a representative sample of M dwarfs, covering a
wide range of stellar mass, age, and planetary system architecture. We
have obtained x-ray and ultraviolet data for 13 stars using the Hubble,
Chandra and XMM space telescopes, along with ground-based data in the
optical and state-of-the-art DEM modelling to fill in the unobservable
extreme ultraviolet regions. Our completed SEDs will be available as a
community resource, with the aim that a close MUSCLES analogue should
exist for most M dwarfs of interest. <P />In this presentation I will
overview the Mega-MUSCLES project, describing our choice of targets,
observation strategy and SED production methodology. I will also
discuss notable targets such as the TRAPPIST-1 host star, comparing
our observations with previous data and model predictions. Finally,
I will present an exciting by-product of the Mega-MUSCLES project:
time-resolved ultraviolet spectroscopy of stellar flares at multiple
targets, spanning a range of stellar types, ages and flare energies.
---------------------------------------------------------
Title: The Mysterious Activity of TRAPPIST-1
Authors: Morris, Brett; Agol, Eric; Davenport, James; Hawley, Suzanne
2019ESS.....433311M Altcode:
TRAPPIST-1 is one of the most tantalizing exoplanet systems discovered
to date, with seven Earth-sized transiting exoplanets in a resonant
chain orbiting an ultra-cool dwarf star. To make robust inferences
about the properties of the exoplanets orbiting TRAPPIST-1, we must
first identify any stellar surface inhomogeneities which will confound
exoplanet transmission spectroscopy (Morris et al. 2018, Rackham
et al. 2018, Ducrot et al. 2018). TRAPPIST-1 is the first M8V star
to be scrutinized with long-term 1% precision photometry in multiple
wavebands, and preliminary analyses of the surface features of the host
star are full of surprises. There is no definitive evidence for coverage
of the stellar surface by dark starspots, but there is photometric
and spectroscopic evidence for bright, hot regions on the surface of
the star. Furthermore, the occurence of flares seems to be correlated
with the optical flux of the star, perhaps suggesting that the apparent
rotational modulation of the star could instead be evolution of bright
active regions. We will discuss the available evidence for activity
and rotation of the host star, and conclude with a discussion of the
implications for transmission spectroscopy of the exoplanets.
---------------------------------------------------------
Title: Do Kepler superflare stars really include slowly-rotating
Sun-like stars ? - Results using APO 3.5m telescope spectroscopic
observations and Gaia-DR2 data -
Authors: Notsu, Yuta; Maehara, Hiroyuki; Honda, Satoshi; Hawley,
Suzanne L.; Davenport, James R. A.; Namekata, Kosuke; Notsu, Shota;
Ikuta, Kai; Nogami, Daisaku; Shibata, Kazunari
2019AAS...23412202N Altcode:
Solar and stellar flares are the energetic explosions in the solar and
stellar atmosphere, and superflares are very large flares that release
total energy 10∼10<SUP>4</SUP> times greater than that of the biggest
solar flares (∼10<SUP>32</SUP> erg). Recent Kepler-space-telescope
observations found more than 1000 superflares on a few hundred
solar-type stars. We report the latest view of Kepler solar-type
(G-type main-sequence) superflare stars, including recent updates
with Apache Point Observatory (APO) 3.5m telescope spectroscopic
observations and Gaia-DR2 data. First, more than half (43 stars) are
confirmed to be "single" stars, among 64 superflare stars in total
that have been spectroscopically investigated so far in this APO3.5m
and our previous Subaru/HDS observations. The measurements of v sin i
(projected rotational velocity) and chromospheric lines (Ca II H&K
and Ca II 8542 A) support the brightness variation of superflare stars
is caused by the rotation of a star with large starspots. Then, we
investigated again the statistical properties of Kepler solar- type
superflare stars by incorporating Gaia-DR2 stellar radius values. As
a result, the maximum superflare energy continuously decreases as the
rotation period Prot increases. Superflares with their energy <
5×10<SUP>34</SUP> erg would occur on old slowly-rotating Sun-like
stars (P<SUB>rot</SUB> ∼25 days) once every 2000-3000 years, while
young rapidly- rotating stars with P<SUB>rot</SUB> ∼ a few days
have superflares up to 10<SUP>36</SUP> erg. The maximum starspot area
does not depend on the rotation period when the star is young rapidly-
rotating, but as the rotation slows down, it starts to steeply decrease
at P<SUB>rot</SUB> 12 days for Sun-like stars. These two decreasing
trends can be consistent since the magnetic energy stored around
starspots explains the flare energy, but other factors like spot
magnetic structure should be also considered. These results presented
in this work support that even slowly-rotating stars similar to the
Sun can have large starspots necessary for superflares, considering
long-term (1,000-10,000 years) activity level changes.
---------------------------------------------------------
Title: Lifetimes and emergence/decay rates of star spots on solar-type
stars estimated by Kepler data in comparison with those of sunspots
Authors: Namekata, Kosuke; Maehara, H.; Davenport, J.; Morris, B.;
Hawley, S.; Notsu, Y.; Toriumi, S.; Hayakawa, H.; Honda, S.; Notsu,
S.; Ikuta, K.; Nogami, D.; Shibata, K.
2019shin.confE..42N Altcode:
Active solar-type stars show large quasi-periodic brightness variations
caused by stellar rotations with large star spots, and the amplitude
change as the spots emerge and decay. Temporal evolution of star spots
has been hardly measured because of its difficulty in measurement,
especially on solar-type stars. The Kepler’s long-term data is
suitable for investigations on the emergence and decay processes
of star spots, which are important to understand underlying stellar
dynamo. In this talk, we report the measurements of temporal evolution
of individual star-spot area on solar-type stars by using Kepler
data. We estimated it (i) by tracing local minima of the Kepler
light curves (Namekata et al. 2019) and (ii) by modeling the small
brightness variation during exoplanet transit (c.f. Morris et al. 2017,
Namekata et al. in prep). We successfully obtained temporal evolution
of individual star spots showing clear emergence and decay, and derived
the statistical values of the lifetimes and emergence/decay rates of
star spots. As a result, we found that lifetimes (T) of star spots
are ranging from 10 to 350 days when spot areas (A) are 0.1-2.3% of
a solar hemisphere (SH). The lifetimes of star spots are much shorter
than those extrapolated from an empirical relation of sunspots, while
being consistent with other researches on star spot lifetimes. The
emerging and decay rates of star spots are typically 5×10^20 Mx/h
(8 MSH/h) with the area of 0.1-2.3% of SH and are mostly consistent
with those expected from sunspots observations (Petrovay et al. 1997,
Norton et al. 2017). This strongly supports a possibility that the
emergence/decay mechanism of extremely large star spots (0.1-2.3%
of SH) is same as that of smaller sunspots (<0.5% of SH), which
can constrain the stellar dynamo theory.
---------------------------------------------------------
Title: Do Kepler Superflare Stars Really Include Slowly Rotating
Sun-like Stars?—Results Using APO 3.5 m Telescope Spectroscopic
Observations and Gaia-DR2 Data
Authors: Notsu, Yuta; Maehara, Hiroyuki; Honda, Satoshi; Hawley,
Suzanne L.; Davenport, James R. A.; Namekata, Kosuke; Notsu, Shota;
Ikuta, Kai; Nogami, Daisaku; Shibata, Kazunari
2019ApJ...876...58N Altcode: 2019arXiv190400142N
We report the latest view of Kepler solar-type (G-type main-sequence)
superflare stars, including recent updates with Apache Point
Observatory (APO) 3.5 m telescope spectroscopic observations and
Gaia-DR2 data. First, we newly conducted APO 3.5 m spectroscopic
observations of 18 superflare stars found from Kepler 1-minute
time-cadence data. More than half (43 stars) are confirmed to be
“single” stars, among 64 superflare stars in total that have
been spectroscopically investigated so far in this APO 3.5 m and
our previous Subaru/HDS observations. The measurements of v sin i
(projected rotational velocity) and chromospheric lines (Ca II H and K
and Ca II λ8542) support that the brightness variation of superflare
stars is caused by the rotation of a star with large starspots. We then
investigated the statistical properties of Kepler solar-type superflare
stars by incorporating Gaia-DR2 stellar radius estimates. As a result,
the maximum superflare energy continuously decreases as the rotation
period P <SUB>rot</SUB> increases. Superflares with energies ≲5
× 10<SUP>34</SUP> erg occur on old, slowly rotating Sun-like stars
(P <SUB>rot</SUB> ∼ 25 days) approximately once every 2000-3000 yr,
while young, rapidly rotating stars with P <SUB>rot</SUB> ∼ a few
days have superflares up to 10<SUP>36</SUP> erg. The maximum starspot
area does not depend on the rotation period when the star is young,
but as the rotation slows down, it starts to steeply decrease at P
<SUB>rot</SUB> ≳ 12 days for Sun-like stars. These two decreasing
trends are consistent since the magnetic energy stored around starspots
explains the flare energy, but other factors like spot magnetic
structure should also be considered.
---------------------------------------------------------
Title: Do superflares really occur on slowly-rotating Sun-like stars
in the long-term activity changes? -- Latest statistical results
using Kepler and Gaia-DR2 data -
Authors: Notsu, Yuta; Maehara, Hiroyuki; Honda, Satoshi; Hawley,
Suzanne L.; Davenport, James R. A.; Namekata, Kosuke; Notsu, Shota;
Ikuta, Kai; Nogami, Daisaku; Shibata, Kazunari
2019shin.confE..17N Altcode:
Superflares are very large flares that release total energy 10-10^4
times greater than that of the biggest solar flares (?10^32 erg). Recent
Kepler space telescope observations found more than 1000 superflares
on a few hundred solar-type stars. Our previous statistical studies
of these data suggested that superflares with energy up to 10^35 erg
could occur on Sun-like slowly-rotating stars (Rotation period Prot
? 25 days) once in a few thousand years. <P />On the other hand, the
recent Gaia-DR2 stellar radius data have suggested the possibility of
severe contaminations of subgiant stars in the classification of Kepler
solar-type (G-type main-sequence) stars used for the above previous
studies. <P />Then in this new study (Notsu+2019, ApJ, 876, 58), we
investigated again the statistical properties of Kepler solar-type
superflare stars by incorporating Gaia-DR2 stellar radius values. More
than 40% of the original solar-type superflare stars in our previous
studies are now classified as subgiant stars and are rejected from the
following statistical results. As a result, the maximum superflare
energy continuously decreases as the Prot increases. Superflares
with their energy 5 × 10^34 erg would occur on old slowly-rotating
Sun-like stars (Prot ?25 days) once every 2000-3000 years. In contrast,
superflares up to ?10^36 erg can occur on young rapidly-rotating
stars (Prot ? a few days), and the flare frequency of such young
rapidly-rotating stars is at least 100 times higher compared with the
old slowly-rotating Sun-like stars. The maximum starspot area does not
depend on the rotation period when the star is young rapidly-rotating,
but as the rotation slows down, it starts to steeply decrease at Prot
12 days for Sun-like stars. These two decrease trends can be consistent
since the magnetic energy stored around the starspots explains the
flare energy, but other factors like spot magnetic structure should
be also considered.
---------------------------------------------------------
Title: The solar benchmark: rotational modulation of the Sun
reconstructed from archival sunspot records
Authors: Morris, Brett M.; Davenport, James R. A.; Giles, Helen A. C.;
Hebb, Leslie; Hawley, Suzanne L.; Angus, Ruth; Gilman, Peter A.;
Agol, Eric
2019MNRAS.484.3244M Altcode: 2019arXiv190104557M; 2019MNRAS.tmp..205M
We use archival daily spot coverage measurements from Howard et
al. to study the rotational modulation of the Sun as though it
were a distant star. A quasi-periodic Gaussian process measures the
solar rotation period P<SUB>rot</SUB> = 26.3 ± 0.1 d, and activity
cycle period P<SUB>cyc</SUB> = 10.7 ± 0.3 yr. We attempt to search
for evidence of differential rotation in variations of the apparent
rotation period throughout the activity cycle and do not detect a clear
signal of differential rotation, consistent with the null results of
the hare-and-hounds exercise of Aigrain et al. The full reconstructed
solar light curve is available online.
---------------------------------------------------------
Title: The Evolution of Flare Activity with Stellar Age
Authors: Davenport, James R. A.; Covey, Kevin R.; Clarke, Riley W.;
Boeck, Austin C.; Cornet, Jonathan; Hawley, Suzanne L.
2019ApJ...871..241D Altcode: 2019arXiv190100890D
Using a recent census of flare stars from the Kepler survey, we have
explored how flare activity evolves across stellar main-sequence
lifetimes. We utilize a sample of 347 stars with robust flare activity
detections and which have rotation periods measured via starspot
modulations in their Kepler light curves. We consider three separate
methods for quantifying flare activity from optical light curves and
compare their utility for comparing flare activity between stars of
differing ages and luminosities. These metrics include the fractional
luminosity emitted in flares, the specific rate of flares emitted at a
given energy, and a model for the entire flare frequency distribution
(FFD). With all three approaches, we find that flare activity
decreases for all low-mass stars as they spin down, and thus with
age. Most striking is the evolution of the flare occurrence frequency
distributions, which show no significant change in the power-law slope
with age. Since our sample is preferentially constructed of younger,
more active stars, our model overpredicts the superflare rate previously
estimated for the Sun. Finally, we parameterize our best-fit model of
the FFD for ease in predicting the rates of flares and their associated
impacts on planet habitability and detection.
---------------------------------------------------------
Title: The Near-ultraviolet Continuum Radiation in the Impulsive
Phase of HF/GF-type dMe Flares. I. Data
Authors: Kowalski, Adam F.; Wisniewski, John P.; Hawley, Suzanne L.;
Osten, Rachel A.; Brown, Alexander; Fariña, Cecilia; Valenti, Jeff
A.; Brown, Stephen; Xilouris, Manolis; Schmidt, Sarah J.; Johns-Krull,
Christopher
2019ApJ...871..167K Altcode: 2018arXiv181104021K
We present near-UV (NUV) flare spectra from the Hubble Space Telescope
(HST)/Cosmic Origins Spectrograph during two moderate-amplitude
U-band flares on the dM4e star GJ 1243. These spectra are some of
the first accurately flux-calibrated, NUV flare spectra obtained
over the impulsive phase in M dwarf flares. We observed these flares
with a fleet of nine ground-based telescopes simultaneously, which
provided broadband photometry and low-resolution spectra at the
Balmer jump. An increase in the broadband continuum occurred with a
signal-to-noise ratio >20 in the HST spectra, while numerous Fe
II lines and the Mg II lines also increased but with smaller flux
enhancements than the continuum radiation. These two events produced
the most prominent Balmer line radiation and the largest Balmer jumps
that have been observed to date in dMe flare spectra. A T = 9000 K
blackbody underestimates the NUV continuum flare flux by a factor of
two and is a poor approximation to the white light in these types of
flare events. Instead, our data suggest that the peak of the specific
continuum flux density is constrained to U-band wavelengths near the
Balmer series limit. A radiative-hydrodynamic simulation of a very
high energy deposition rate averaged over times of impulsive heating
and cooling better explains the properties of the λ > 2500 Å
flare continuum. These two events sample only one end of the empirical
color-color distribution for dMe flares, and more time-resolved flare
spectra in the NUV, U band, and optical from 2000 to 4200 Å are needed
during more impulsive and/or more energetic flares.
---------------------------------------------------------
Title: Towards space-quality photometry from the ground with
beam-shaping diffusers for K2, TESS and Beyond.
Authors: Stefansson, Gudmundur K.; Mahadevan, Suvrath; Wisniewski,
John; Morris, Brett M.; Hebb, Leslie; Maney, Marissa; Li, Yiting;
Monson, Andrew; Robertson, Paul; Huehnerhoff, Joseph; Hawley, Suzanne
2019AAS...23321512S Altcode:
Precision ground-based photometry plays a key role in discovering and
characterizing transiting exoplanet candidates. Using custom-fabricated
beam-shaping diffusers, we demonstrate a path to achieving some of
the highest differential photometric precisions from the ground. These
diffusers are micro-structured optical components capable of molding
the image of a star into a broad and stable top-hat shape, minimizing
photometric errors due to non-uniform pixel response, atmospheric
seeing effects, and telescope-induced variable aberrations seen in
defocusing. I discuss our efforts in commissioning an optical diffuser
on the ARC 3.5m Telescope at Apache Point Observatory demonstrating
62ppm precision in 30 minute bins—some of the highest photometric
precisions from the ground. I will present our current results
from our ongoing ground-based follow-up program to follow up K2 and
soon-to-come TESS candidates. Being inexpensive and easily adaptable,
I will highlight some of our ongoing efforts to install beam-shaping
diffusers on other telescopes large and small.
---------------------------------------------------------
Title: Modeling Repeated M Dwarf Flaring at an Earth-like Planet in
the Habitable Zone: Atmospheric Effects for an Unmagnetized Planet
Authors: Tilley, Matt A.; Segura, Antígona; Meadows, Victoria;
Hawley, Suzanne; Davenport, James
2019AsBio..19...64T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Diffuser-assisted Photometric Follow-up Observations of the
Neptune-sized Planets K2-28b and K2-100b
Authors: Stefansson, Gudmundur; Li, Yiting; Mahadevan, Suvrath;
Wisniewski, John; Hebb, Leslie; Morris, Brett; Huehnerhoff, Joseph;
Hawley, Suzanne
2018AJ....156..266S Altcode: 2018arXiv180704420S
We present precision transit observations of the Neptune-sized planets
K2-28b and K2-100b using the Engineered Diffuser on the Astrophysical
Research Council Telescope Imaging Camera (ARCTIC) imager on the ARC
3.5 m Telescope at Apache Point Observatory. K2-28b is a R <SUB> p
</SUB> = 2.56 R <SUB>⊕</SUB> mini-Neptune transiting a bright (J =
11.7) metal-rich M4 dwarf offering compelling prospects for future
atmospheric characterization. K2-100b is an R <SUB> p </SUB> = 3.45
R <SUB>⊕</SUB> Neptune in the Praesepe Cluster and is one of few
planets known in a cluster transiting a host star bright enough (V =
10.5) for precision radial velocity observations. Using the precision
photometric capabilities of the diffuser/ARCTIC system allows us to
achieve a precision of 365 ppm and 70 ppm in 30-minute bins for K2-28b
and K2-100b, respectively. Our joint-fits to the K2 and ground-based
light curves give an order-of-magnitude improvement in the orbital
ephemeris for both planets, yielding a timing precision of 2 minutes
in the James Webb Space Telescope (JWST) era. Although we show that
the currently available broad-band measurements of K2-28b’s radius
are currently too imprecise to place useful constraints on K2-28b’s
atmosphere, we demonstrate that JWST/NIRISS will be able to discern
between a cloudy/clear atmosphere in a modest number of transit
observations. Our light curve of K2-100b marks the first transit
follow-up observation of this challenging-to-observe transit, where
we obtain a transit depth of 822 ± 50 ppm in the SDSS i‧ band. We
conclude that diffuser-assisted photometry can play an important role in
the Transiting Exoplanet Survey Satellite (TESS) era to perform timely
and precise follow-up of the expected bounty of TESS planet candidates.
---------------------------------------------------------
Title: Are Starspots and Plages Co-located on Active G and K Stars?
Authors: Morris, Brett M.; Curtis, Jason L.; Douglas, Stephanie T.;
Hawley, Suzanne L.; Agüeros, Marcel A.; Bobra, Monica G.; Agol, Eric
2018AJ....156..203M Altcode: 2018arXiv180904522M
We explore the connection between starspots and plages of three
main-sequence stars by studying the chromospheric and photospheric
activity over several rotation periods. We present simultaneous
photometry and high-resolution (R ∼ 31500) spectroscopy of KIC
9652680, a young, super-flare-producing G1 star with a rotation period
of 1.4 days. Its Kepler light curve shows rotational modulation
consistent with a bright hemisphere followed by a relatively dark
hemisphere, generating photometric variability with a semi-amplitude
of 4%. We find that KIC 9652680 is darkest when its S-index of Ca II H
& K emission is at its maximum. We interpret this anti-correlation
between flux and S to indicate that dark starspots in the photosphere
are co-located with the bright plages in the chromosphere, as they are
on the Sun. Moving to lower masses and slower rotators, we present K2
observations with simultaneous spectroscopy of EPIC 211928486 (K5V)
and EPIC 211966629 (K4V), two active stars in the 650 Myr old open
cluster Praesepe. The K2 photometry reveals that both stars have
rotation periods of 11.7 days; while their flux varies by 1 and 2%
respectively, their Ca II H & K S-indices seem to hold relatively
constant as a function of rotational phase. This suggests that extended
chromospheric networks of plages are not concentrated into regions of
emission centered on the starspots that drive rotational modulation,
unlike KIC 9652680. We also note that the Ca II emission of EPIC
211928486 dipped and recovered suddenly over the duration of one
rotation, suggesting that the evolution timescale of plages may be of
order the rotation period.
---------------------------------------------------------
Title: Robust Transiting Exoplanet Radii in the Presence of Starspots
from Ingress and Egress Durations
Authors: Morris, Brett M.; Agol, Eric; Hebb, Leslie; Hawley, Suzanne L.
2018AJ....156...91M Altcode: 2018arXiv180704886M
We typically measure the radii of transiting exoplanets from the
transit depth, which are given by the ratio of cross-sectional
areas of the planet and star. However, if a star has dark starspots
(or bright regions) distributed throughout the transit chord, the
transit depth will be biased toward smaller (larger) values, and
thus the inferred planet radius will be smaller (larger) if these
are unaccounted for. We reparameterize the transit light curve to
account for “self-contamination” by photospheric inhomogeneities
by splitting the parameter R <SUB> p </SUB>/R <SUB>⋆</SUB> into two
parameters: one for the radius ratio, which controls the duration of
ingress and egress, and another which measures the possibly contaminated
transit depth. We show that this is equivalent to the formulation
for contamination by a second star (with positive or negative flux),
and that it is sensitive to time-steady inhomogeneity of the stellar
photosphere. We use synthetic light curves of spotted stars at high
signal-to-noise to show that the radius recovered from measurement
of the ingress/egress duration can recover the true radii of planets
transiting spotted stars with axisymmetric spot distributions if the
limb-darkening parameters are precisely known. We fit time-averaged
high signal-to-noise transit light curves from Kepler and Spitzer
of 10 planets to measure the planet radii and search for evidence of
spot distributions. We find that this sample has a range of measured
depths and ingress durations that are self-consistent, providing
no strong evidence for contamination by spots. However, there is
suggestive evidence for occultation of starspots on Kepler-17, and that
relatively bright regions are occulted by the planets of Kepler-412
and HD 80606. Future observations with the James Webb Space Telescope
may enable this technique to yield accurate planetary radii in the
presence of stellar inhomogeneities.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Kepler EB classifications and
rotation periods (Lurie+, 2017)
Authors: Lurie, J. C.; Vyhmeister, K.; Hawley, S. L.; Adilia, J.; Chen,
A.; Davenport, J. R. A.; Juric, M.; Puig-Holzman, M.; Weisenburger,
K. L.
2018yCat..51540250L Altcode:
We began with the 2863 targets in the Kepler Eclipsing Binary Catalog
(KEBC, http://keplerebs.villanova.edu, Prsa et al. 2011, J/AJ/141/83;
Slawson et al. 2011, J/AJ/142/160; Kirk et al. 2016, J/AJ/151/68),
downloaded on 2017 March 24. The KEBC includes orbital periods,
ephemerides, and primary and secondary (when detected) eclipse depths,
widths, and phase separations. After exclusions, there were 2278 EBs
remaining that we analyzed. Our analysis involved two steps. First,
we visually inspected the light curves to classify EBs with starspot
modulations, as well as other types of EBs. Next, we measured rotation
periods for the 816 EBs with starspot modulations using the following
procedure. First, we linearly interpolated over eclipses, and then
measured initial rotation periods using the autocorrelation function
(ACF, see McQuillan et al. 2013, J/MNRAS/432/1203). <P />(1 data file).
---------------------------------------------------------
Title: Non-detection of Contamination by Stellar Activity in the
Spitzer Transit Light Curves of TRAPPIST-1
Authors: Morris, Brett M.; Agol, Eric; Hebb, Leslie; Hawley, Suzanne
L.; Gillon, Michaël; Ducrot, Elsa; Delrez, Laetitia; Ingalls, James;
Demory, Brice-Olivier
2018ApJ...863L..32M Altcode: 2018arXiv180802808M
We apply the transit light curve self-contamination technique of Morris
et al. to search for the effect of stellar activity on the transits
of the ultracool dwarf TRAPPIST-1 with 2018 Spitzer photometry. The
self-contamination method fits the transit light curves of planets
orbiting spotted stars, allowing the host star to be a source of
contaminating positive or negative flux that influences the transit
depths but not the ingress/egress durations. We find that none of the
planets show statistically significant evidence for self-contamination
by bright or dark regions of the stellar photosphere. However, we show
that small-scale magnetic activity, analogous in size to the smallest
sunspots, could still be lurking undetected in the transit photometry.
---------------------------------------------------------
Title: Spectroscopic observations of Kepler/TESS solar-type supeflare
stars
Authors: Notsu, Yuta; Maehara, Hiroyuki; Honda, Satoshi; Hawley,
Suzanne; Davenport, James; Notsu, Shota; Namekata, Kosuke; Ikuta,
Kai; Nogami, Daisaku; Shibata, Kazunari
2018csss.confE..14N Altcode:
Recent Kepler-space-telescope observations found more than 1000
superflares on 300 solar-type stars (e.g., Maeahra+2012 Nature;
Shibayama+2013 ApJS). Many of the superflare stars show quasi-periodic
brightness variations with the typical period of 1-30 days and the
typical amplitude of 0.1-10 percent. We conducted spectroscopic
observations of these superflare stars using Subaru/HDS and APO 3.5m
telescope (Notsu+2015a&b, 2018 in prep). The projected rotation
velocity (v sin i) values are consistent with brightness variation
period, and there is a good correlation between Kepler brightness
variation amplitude and the intensity of Ca II lines (Ca II H&K, Ca
II 8542Å). These results support that the above brightness variations
are caused by stellar rotation with large starspots, and existence of
large starspots should be a key to understand superflares.More detailed
spectroscopic studies (e.g., activity cycle) of superflare stars are
important, but Kepler target stars are faint and not appropriate for
such detailed studies. TESS satellite, launched in April 2018, brings us
a large sample of brighter (e.g., V < 12 mag) superflare stars. We
have started spectroscopic monitoring observations of nearby active
solar-type stars (superflare candidate stars) in the TESS field. These
results can have good collaborations with multi-wavelength project
observations (e.g., X-ray, UV, polarimetry) of young solar-type stars.
---------------------------------------------------------
Title: The Evolution of T = 10,000 K Blackbody-Like Continuum
Radiation in the Impulsive Phase of dMe Flares
Authors: Kowalski, Adam F.; Mathioudakis, Mihalis; Hawley, Suzanne L.
2018csss.confE..42K Altcode: 2018arXiv181007226K
The near-ultraviolet and optical (white-light) continuum radiation
in M dwarf flares exhibits a range of observed characteristics,
suggesting that the amount of heating at large optical depth varies
among impulsive-type and gradual-type flares. Specific flux ratios
from high-time cadence spectra and narrowband continuum photometry
have also shown that these characteristics vary from the peak to the
gradual decay phases of flares. In these proceedings, we present the
highest-time cadence ( 1 s), highest signal-to-noise ( 100) constraints
on the optical color temperature evolution during the rise phase of a
large, impulsive-type dMe flare event. The flare exhibits compelling
evidence of a hot, color temperature (T 10,000 K), but the Balmer jump
ratios show that the flare cannot be explained by isothermal slabs or
blackbody surfaces at any time in the evolution. The new data analysis
establish these properties as critical challenges for any flare model,
and we discuss 1D radiative-hydrodynamic modeling that will be compared
to the evolution of the flare colors in this intriguing event.
---------------------------------------------------------
Title: Structure in the Disk of epsilon Aurigae -- Analysis of ARCES
and TripleSpec data from the 2010 eclipse
Authors: Gibson, Justus; Stencel, Robert E.; ARCES Team; Ketzeback, W.;
Barentine, J.; Bradley, A.; Coughlin, J.; Dembicky, J.; Hawley, S.;
Huehnerhoff, J.; Leadbeater, R.; McMillan, R.; Saurage, G.; Schmidt,
S.; Ule, N.; Wallerstein, G.; York, D.
2018AAS...23231501G Altcode:
Worldwide interest in the recent eclipse of epsilon Aurigae resulted
in the generation of several extensive data sets, including high
resolution spectroscopic monitoring. This lead to the discovery, among
other things, of the existence of a mass transfer stream, seen notably
during third contact. We explored spectroscopic facets of the mass
transfer stream during third contact, using high resolution spectra
obtained with the ARCES and TripleSpec instruments at Apache Point
Observatory. One hundred and sixteen epochs of data were obtained
between 2009 and 2012, and equivalent widths and line velocities
measured for high versus low eccentricity accretion disk lines. These
datasets also enable greater detail to be measured of the mid-eclipse
enhancement of the He I 10830A line, and the discovery of the P Cygni
shape of the Pa-beta line at third contact. We found evidence of higher
speed material, associated with the mass transfer stream, persisting
between third and fourth eclipse contacts. We visualized the disk and
stream interaction using SHAPE software, and used CLOUDY software
to estimate that the source of the enhanced He I 10830A absorption
arises from a region with log nH = 11 cm<SUP>-3</SUP> and temperature
of 20,000 K, consistent with a mid-B type central star. We thank the
following for their contributions to this paper: William Ketzeback,
John Barentine, Jeffrey Coughlin, Robin Leadbeater, Gabrelle Saurage,
and others. This paper has been submitted to Monthly Notices.
---------------------------------------------------------
Title: Spotting stellar activity cycles in Gaia astrometry
Authors: Morris, Brett M.; Agol, Eric; Davenport, James R. A.; Hawley,
Suzanne L.
2018MNRAS.476.5408M Altcode: 2018MNRAS.tmp..549M; 2018arXiv180209943M
Astrometry from Gaia will measure the positions of stellar photometric
centroids to unprecedented precision. We show that the precision of
Gaia astrometry is sufficient to detect starspot-induced centroid
jitter for nearby stars in the Tycho-Gaia Astrometric Solution (TGAS)
sample with magnetic activity similar to the young G-star KIC 7174505
or the active M4 dwarf GJ 1243, but is insufficient to measure centroid
jitter for stars with Sun-like spot distributions. We simulate Gaia
observations of stars with 10 year activity cycles to search for
evidence of activity cycles, and find that Gaia astrometry alone
likely cannot detect activity cycles for stars in the TGAS sample,
even if they have spot distributions like KIC 7174505. We review the
activity of the nearby low-mass stars in the TGAS sample for which we
anticipate significant detections of spot-induced jitter.
---------------------------------------------------------
Title: Possible Bright Starspots on TRAPPIST-1
Authors: Morris, Brett M.; Agol, Eric; Davenport, James R. A.; Hawley,
Suzanne L.
2018ApJ...857...39M Altcode: 2018arXiv180304543M
The M8V star TRAPPIST-1 hosts seven roughly Earth-sized planets and is a
promising target for exoplanet characterization. Kepler/K2 Campaign 12
observations of TRAPPIST-1 in the optical show an apparent rotational
modulation with a 3.3-day period, though that rotational signal is
not readily detected in the Spitzer light curve at 4.5 μm. If the
rotational modulation is due to starspots, persistent dark spots can be
excluded from the lack of photometric variability in the Spitzer light
curve. We construct a photometric model for rotational modulation due
to photospheric bright spots on TRAPPIST-1 that is consistent with both
the Kepler and Spitzer light curves. The maximum-likelihood model with
three spots has typical spot sizes of R <SUB>spot</SUB>/R <SUB>⋆</SUB>
≈ 0.004 at temperature T <SUB>spot</SUB> ≳ 5300 ± 200 K. We also
find that large flares are observed more often when the brightest spot
is facing the observer, suggesting a correlation between the position
of the bright spots and flare events. In addition, these flares may
occur preferentially when the spots are increasing in brightness,
which suggests that the 3.3-day periodicity may not be a rotational
signal, but rather a characteristic timescale of active regions.
---------------------------------------------------------
Title: The Fourteenth Data Release of the Sloan Digital Sky Survey:
First Spectroscopic Data from the Extended Baryon Oscillation
Spectroscopic Survey and from the Second Phase of the Apache Point
Observatory Galactic Evolution Experiment
Authors: Abolfathi, Bela; Aguado, D. S.; Aguilar, Gabriela; Allende
Prieto, Carlos; Almeida, Andres; Ananna, Tonima Tasnim; Anders,
Friedrich; Anderson, Scott F.; Andrews, Brett H.; Anguiano, Borja;
Aragón-Salamanca, Alfonso; Argudo-Fernández, Maria; Armengaud,
Eric; Ata, Metin; Aubourg, Eric; Avila-Reese, Vladimir; Badenes,
Carles; Bailey, Stephen; Balland, Christophe; Barger, Kathleen A.;
Barrera-Ballesteros, Jorge; Bartosz, Curtis; Bastien, Fabienne;
Bates, Dominic; Baumgarten, Falk; Bautista, Julian; Beaton, Rachael;
Beers, Timothy C.; Belfiore, Francesco; Bender, Chad F.; Bernardi,
Mariangela; Bershady, Matthew A.; Beutler, Florian; Bird, Jonathan C.;
Bizyaev, Dmitry; Blanc, Guillermo A.; Blanton, Michael R.; Blomqvist,
Michael; Bolton, Adam S.; Boquien, Médéric; Borissova, Jura;
Bovy, Jo; Bradna Diaz, Christian Andres; Brandt, William Nielsen;
Brinkmann, Jonathan; Brownstein, Joel R.; Bundy, Kevin; Burgasser,
Adam J.; Burtin, Etienne; Busca, Nicolás G.; Cañas, Caleb I.;
Cano-Díaz, Mariana; Cappellari, Michele; Carrera, Ricardo; Casey,
Andrew R.; Cervantes Sodi, Bernardo; Chen, Yanping; Cherinka, Brian;
Chiappini, Cristina; Choi, Peter Doohyun; Chojnowski, Drew; Chuang,
Chia-Hsun; Chung, Haeun; Clerc, Nicolas; Cohen, Roger E.; Comerford,
Julia M.; Comparat, Johan; Correa do Nascimento, Janaina; da Costa,
Luiz; Cousinou, Marie-Claude; Covey, Kevin; Crane, Jeffrey D.;
Cruz-Gonzalez, Irene; Cunha, Katia; da Silva Ilha, Gabriele; Damke,
Guillermo J.; Darling, Jeremy; Davidson, James W., Jr.; Dawson, Kyle;
de Icaza Lizaola, Miguel Angel C.; de la Macorra, Axel; de la Torre,
Sylvain; De Lee, Nathan; de Sainte Agathe, Victoria; Deconto Machado,
Alice; Dell'Agli, Flavia; Delubac, Timothée; Diamond-Stanic,
Aleksandar M.; Donor, John; Downes, Juan José; Drory, Niv; du
Mas des Bourboux, Hélion; Duckworth, Christopher J.; Dwelly, Tom;
Dyer, Jamie; Ebelke, Garrett; Davis Eigenbrot, Arthur; Eisenstein,
Daniel J.; Elsworth, Yvonne P.; Emsellem, Eric; Eracleous, Michael;
Erfanianfar, Ghazaleh; Escoffier, Stephanie; Fan, Xiaohui; Fernández
Alvar, Emma; Fernandez-Trincado, J. G.; Fernando Cirolini, Rafael;
Feuillet, Diane; Finoguenov, Alexis; Fleming, Scott W.; Font-Ribera,
Andreu; Freischlad, Gordon; Frinchaboy, Peter; Fu, Hai; Gómez Maqueo
Chew, Yilen; Galbany, Lluís; García Pérez, Ana E.; Garcia-Dias,
R.; García-Hernández, D. A.; Garma Oehmichen, Luis Alberto; Gaulme,
Patrick; Gelfand, Joseph; Gil-Marín, Héctor; Gillespie, Bruce A.;
Goddard, Daniel; González Hernández, Jonay I.; Gonzalez-Perez,
Violeta; Grabowski, Kathleen; Green, Paul J.; Grier, Catherine J.;
Gueguen, Alain; Guo, Hong; Guy, Julien; Hagen, Alex; Hall, Patrick;
Harding, Paul; Hasselquist, Sten; Hawley, Suzanne; Hayes, Christian
R.; Hearty, Fred; Hekker, Saskia; Hernandez, Jesus; Hernandez Toledo,
Hector; Hogg, David W.; Holley-Bockelmann, Kelly; Holtzman, Jon A.;
Hou, Jiamin; Hsieh, Bau-Ching; Hunt, Jason A. S.; Hutchinson, Timothy
A.; Hwang, Ho Seong; Jimenez Angel, Camilo Eduardo; Johnson, Jennifer
A.; Jones, Amy; Jönsson, Henrik; Jullo, Eric; Khan, Fahim Sakil;
Kinemuchi, Karen; Kirkby, David; Kirkpatrick, Charles C., IV; Kitaura,
Francisco-Shu; Knapp, Gillian R.; Kneib, Jean-Paul; Kollmeier, Juna A.;
Lacerna, Ivan; Lane, Richard R.; Lang, Dustin; Law, David R.; Le Goff,
Jean-Marc; Lee, Young-Bae; Li, Hongyu; Li, Cheng; Lian, Jianhui;
Liang, Yu; Lima, Marcos; Lin, Lihwai; Long, Dan; Lucatello, Sara;
Lundgren, Britt; Mackereth, J. Ted; MacLeod, Chelsea L.; Mahadevan,
Suvrath; Maia, Marcio Antonio Geimba; Majewski, Steven; Manchado,
Arturo; Maraston, Claudia; Mariappan, Vivek; Marques-Chaves, Rui;
Masseron, Thomas; Masters, Karen L.; McDermid, Richard M.; McGreer,
Ian D.; Melendez, Matthew; Meneses-Goytia, Sofia; Merloni, Andrea;
Merrifield, Michael R.; Meszaros, Szabolcs; Meza, Andres; Minchev,
Ivan; Minniti, Dante; Mueller, Eva-Maria; Muller-Sanchez, Francisco;
Muna, Demitri; Muñoz, Ricardo R.; Myers, Adam D.; Nair, Preethi;
Nandra, Kirpal; Ness, Melissa; Newman, Jeffrey A.; Nichol, Robert
C.; Nidever, David L.; Nitschelm, Christian; Noterdaeme, Pasquier;
O'Connell, Julia; Oelkers, Ryan James; Oravetz, Audrey; Oravetz,
Daniel; Ortíz, Erik Aquino; Osorio, Yeisson; Pace, Zach; Padilla,
Nelson; Palanque-Delabrouille, Nathalie; Palicio, Pedro Alonso; Pan,
Hsi-An; Pan, Kaike; Parikh, Taniya; Pâris, Isabelle; Park, Changbom;
Peirani, Sebastien; Pellejero-Ibanez, Marcos; Penny, Samantha;
Percival, Will J.; Perez-Fournon, Ismael; Petitjean, Patrick; Pieri,
Matthew M.; Pinsonneault, Marc; Pisani, Alice; Prada, Francisco;
Prakash, Abhishek; Queiroz, Anna Bárbara de Andrade; Raddick,
M. Jordan; Raichoor, Anand; Barboza Rembold, Sandro; Richstein,
Hannah; Riffel, Rogemar A.; Riffel, Rogério; Rix, Hans-Walter; Robin,
Annie C.; Rodríguez Torres, Sergio; Román-Zúñiga, Carlos; Ross,
Ashley J.; Rossi, Graziano; Ruan, John; Ruggeri, Rossana; Ruiz, Jose;
Salvato, Mara; Sánchez, Ariel G.; Sánchez, Sebastián F.; Sanchez
Almeida, Jorge; Sánchez-Gallego, José R.; Santana Rojas, Felipe
Antonio; Santiago, Basílio Xavier; Schiavon, Ricardo P.; Schimoia,
Jaderson S.; Schlafly, Edward; Schlegel, David; Schneider, Donald P.;
Schuster, William J.; Schwope, Axel; Seo, Hee-Jong; Serenelli, Aldo;
Shen, Shiyin; Shen, Yue; Shetrone, Matthew; Shull, Michael; Silva
Aguirre, Víctor; Simon, Joshua D.; Skrutskie, Mike; Slosar, Anže;
Smethurst, Rebecca; Smith, Verne; Sobeck, Jennifer; Somers, Garrett;
Souter, Barbara J.; Souto, Diogo; Spindler, Ashley; Stark, David V.;
Stassun, Keivan; Steinmetz, Matthias; Stello, Dennis; Storchi-Bergmann,
Thaisa; Streblyanska, Alina; Stringfellow, Guy S.; Suárez, Genaro;
Sun, Jing; Szigeti, Laszlo; Taghizadeh-Popp, Manuchehr; Talbot,
Michael S.; Tang, Baitian; Tao, Charling; Tayar, Jamie; Tembe,
Mita; Teske, Johanna; Thakar, Aniruddha R.; Thomas, Daniel; Tissera,
Patricia; Tojeiro, Rita; Tremonti, Christy; Troup, Nicholas W.; Urry,
Meg; Valenzuela, O.; van den Bosch, Remco; Vargas-González, Jaime;
Vargas-Magaña, Mariana; Vazquez, Jose Alberto; Villanova, Sandro;
Vogt, Nicole; Wake, David; Wang, Yuting; Weaver, Benjamin Alan;
Weijmans, Anne-Marie; Weinberg, David H.; Westfall, Kyle B.; Whelan,
David G.; Wilcots, Eric; Wild, Vivienne; Williams, Rob A.; Wilson,
John; Wood-Vasey, W. M.; Wylezalek, Dominika; Xiao, Ting; Yan, Renbin;
Yang, Meng; Ybarra, Jason E.; Yèche, Christophe; Zakamska, Nadia;
Zamora, Olga; Zarrouk, Pauline; Zasowski, Gail; Zhang, Kai; Zhao,
Cheng; Zhao, Gong-Bo; Zheng, Zheng; Zheng, Zheng; Zhou, Zhi-Min; Zhu,
Guangtun; Zinn, Joel C.; Zou, Hu
2018ApJS..235...42A Altcode: 2017arXiv170709322A
The fourth generation of the Sloan Digital Sky Survey (SDSS-IV)
has been in operation since 2014 July. This paper describes the
second data release from this phase, and the 14th from SDSS overall
(making this Data Release Fourteen or DR14). This release makes the
data taken by SDSS-IV in its first two years of operation (2014-2016
July) public. Like all previous SDSS releases, DR14 is cumulative,
including the most recent reductions and calibrations of all data
taken by SDSS since the first phase began operations in 2000. New
in DR14 is the first public release of data from the extended Baryon
Oscillation Spectroscopic Survey; the first data from the second phase
of the Apache Point Observatory (APO) Galactic Evolution Experiment
(APOGEE-2), including stellar parameter estimates from an innovative
data-driven machine-learning algorithm known as “The Cannon”
and almost twice as many data cubes from the Mapping Nearby Galaxies
at APO (MaNGA) survey as were in the previous release (N = 2812 in
total). This paper describes the location and format of the publicly
available data from the SDSS-IV surveys. We provide references to the
important technical papers describing how these data have been taken
(both targeting and observation details) and processed for scientific
use. The SDSS web site (<A href="http://www.sdss.org">www.sdss.org</A>)
has been updated for this release and provides links to data downloads,
as well as tutorials and examples of data use. SDSS-IV is planning to
continue to collect astronomical data until 2020 and will be followed
by SDSS-V.
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Title: VizieR Online Data Catalog: MUSCLES Treasury Survey. IV. M
dwarf UV fluxes (Youngblood+, 2017)
Authors: Youngblood, A.; France, K.; Loyd, R. O. P.; Brown, A.;
Mason, J. P.; Schneider, P. C.; Tilley, M. A.; Berta-Thompson, Z. K.;
Buccino, A.; Froning, C. S.; Hawley, S. L.; Linsky, J.; Mauas,
P. J. D.; Redfield, S.; Kowalski, A.; Miguel, Y.; Newton, E. R.;
Rugheimer, S.; Segura, A.; Roberge, A.; Vieytes, M.
2018yCat..18430031Y Altcode:
We selected stars with HST UV spectra and ground-based optical spectra
either obtained directly by us or available in the VLT/XSHOOTER or
Keck/HIRES public archives. <P />Several targets have spectroscopic
data obtained with the Dual Imaging Spectrograph (DIS) on the
ARC 3.5m telescope at Apache Point Observatory (APO), R~2500, or
the REOSC echelle spectrograph on the 2.15m telescope at Complejo
Astronomico El Leoncito (CASLEO), R~12000, within a day or two of
the HST observations. We also gathered spectra of GJ1132, GJ1214,
and Proxima Cen on the nights of 2016 March 7-9 using the MIKE echelle
spectrograph on the Magellan Clay telescope. <P />(2 data files).
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Title: Large Starspot Groups on HAT-P-11 in Activity Cycle 1
Authors: Morris, Brett M.; Hawley, Suzanne L.; Hebb, Leslie
2018RNAAS...2...26M Altcode: 2018RNAAS...2a..26M; 2018arXiv180110076M
HAT-P-11 is a planet-hosting K4V star in the Kepler field,
with an activity cycle that bear similarities to the Sun's. The
chromospheric activity of HAT-P-11 indicates that a new activity cycle
is beginning. We report ground-based observations with holographic
diffuser photometry to measure the starspots of HAT-P-11 in its second
observed magnetic activity cycle (Cycle 1). We find the area coverage
of starspots within the transit chord for UTC 2017-10-30 is 14% ---
which makes this transit the most spotted HAT-P-11 transit observed
to date. We suggest that we are likely observing occultations of large
spot groups appearing at the beginning of Cycle 1.
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Title: Photometric Analysis and Transit Times of TRAPPIST-1 B and C
Authors: Morris, Brett M.; Agol, Eric; Hawley, Suzanne L.
2018RNAAS...2...10M Altcode: 2018RNAAS...2a..10M; 2018arXiv180104460M
TRAPPIST-1 hosts seven Earth-sized planets transiting an M8
star. We observed mid-transit times of each of the inner two
planets with the Astrophysical Research Consortium (ARC)
3.5 m Telescope at Apache Point Observatory (APO) to help
constrain the planet masses with transit timing variations,
and we outline a procedure for analyzing transit observations of
late-M stars with APO. The transit times of TRAPPIST-1 b and c are
$\mathrm{BJD}_{\mathrm{TDB}} = 2457580.87634^{+0.00034}_{-0.00034}$
and $2457558.89477^{+0.00080}_{-0.00085}$, respectively, which will
help constrain the planet masses.
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Title: The Time-domain Spectroscopic Survey: Target Selection for
Repeat Spectroscopy
Authors: MacLeod, Chelsea L.; Green, Paul J.; Anderson, Scott F.;
Eracleous, Michael; Ruan, John J.; Runnoe, Jessie; Brandt, William
Nielsen; Badenes, Carles; Greene, Jenny; Morganson, Eric; Schmidt,
Sarah J.; Schwope, Axel; Shen, Yue; Amaro, Rachael; Lebleu, Amy; Filiz
Ak, Nurten; Grier, Catherine J.; Hoover, Daniel; McGraw, Sean M.;
Dawson, Kyle; Hall, Patrick B.; Hawley, Suzanne L.; Mariappan, Vivek;
Myers, Adam D.; Pâris, Isabelle; Schneider, Donald P.; Stassun, Keivan
G.; Bershady, Matthew A.; Blanton, Michael R.; Seo, Hee-Jong; Tinker,
Jeremy; Fernández-Trincado, J. G.; Chambers, Kenneth; Kaiser, Nick;
Kudritzki, R. -P.; Magnier, Eugene; Metcalfe, Nigel; Waters, Chris Z.
2018AJ....155....6M Altcode: 2017arXiv170604240M
As astronomers increasingly exploit the information available in the
time domain, spectroscopic variability in particular opens broad new
channels of investigation. Here we describe the selection algorithms
for all targets intended for repeat spectroscopy in the Time Domain
Spectroscopic Survey (TDSS), part of the extended Baryon Oscillation
Spectroscopic Survey within the Sloan Digital Sky Survey (SDSS)-IV. Also
discussed are the scientific rationale and technical constraints leading
to these target selections. The TDSS includes a large “repeat quasar
spectroscopy” (RQS) program delivering ∼13,000 repeat spectra of
confirmed SDSS quasars, and several smaller “few-epoch spectroscopy”
(FES) programs targeting specific classes of quasars as well as
stars. The RQS program aims to provide a large and diverse quasar data
set for studying variations in quasar spectra on timescales of years,
a comparison sample for the FES quasar programs, and an opportunity
for discovering rare, serendipitous events. The FES programs cover
a wide variety of phenomena in both quasars and stars. Quasar FES
programs target broad absorption line quasars, high signal-to-noise
ratio normal broad line quasars, quasars with double-peaked or very
asymmetric broad emission line profiles, binary supermassive black hole
candidates, and the most photometrically variable quasars. Strongly
variable stars are also targeted for repeat spectroscopy, encompassing
many types of eclipsing binary systems, and classical pulsators like
RR Lyrae. Other stellar FES programs allow spectroscopic variability
studies of active ultracool dwarf stars, dwarf carbon stars, and white
dwarf/M dwarf spectroscopic binaries. We present example TDSS spectra
and describe anticipated sample sizes and results.
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Title: FBEYE: Analyzing Kepler light curves and validating flares
Authors: Johnson, Emily; Davenport, James R. A.; Hawley, Suzanne L.
2017ascl.soft12011J Altcode:
FBEYE, the "Flares By-Eye" detection suite, is written in IDL and
analyzes Kepler light curves and validates flares. It works on any
3-column light curve that contains time, flux, and error. The success
of flare identification is highly dependent on the smoothing routine,
which may not be suitable for all sources.
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Title: Tidal Synchronization and Differential Rotation of Kepler
Eclipsing Binaries
Authors: Lurie, John C.; Vyhmeister, Karl; Hawley, Suzanne L.;
Adilia, Jamel; Chen, Andrea; Davenport, James R. A.; Jurić, Mario;
Puig-Holzman, Michael; Weisenburger, Kolby L.
2017AJ....154..250L Altcode: 2017arXiv171007339L
Few observational constraints exist for the tidal synchronization rate
of late-type stars, despite its fundamental role in binary evolution. We
visually inspected the light curves of 2278 eclipsing binaries (EBs)
from the Kepler Eclipsing Binary Catalog to identify those with starspot
modulations, as well as other types of out-of-eclipse variability. We
report rotation periods for 816 EBs with starspot modulations,
and find that 79% of EBs with orbital periods of less than 10 days
are synchronized. However, a population of short-period EBs exists,
with rotation periods typically 13% slower than synchronous, which we
attribute to the differential rotation of high-latitude starspots. At
10 days, there is a transition from predominantly circular,
synchronized EBs to predominantly eccentric, pseudosynchronized
EBs. This transition period is in good agreement with the predicted and
observed circularization period for Milky Way field binaries. At orbital
periods greater than about 30 days, the amount of tidal synchronization
decreases. We also report 12 previously unidentified candidate δ Scuti
and γ Doradus pulsators, as well as a candidate RS CVn system with an
evolved primary that exhibits starspot occultations. For short-period
contact binaries, we observe a period-color relation and compare it
to previous studies. As a whole, these results represent the largest
homogeneous study of tidal synchronization of late-type stars.
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Title: The 13th Data Release of the Sloan Digital Sky Survey: First
Spectroscopic Data from the SDSS-IV Survey Mapping Nearby Galaxies
at Apache Point Observatory
Authors: Albareti, Franco D.; Allende Prieto, Carlos; Almeida,
Andres; Anders, Friedrich; Anderson, Scott; Andrews, Brett H.;
Aragón-Salamanca, Alfonso; Argudo-Fernández, Maria; Armengaud,
Eric; Aubourg, Eric; Avila-Reese, Vladimir; Badenes, Carles; Bailey,
Stephen; Barbuy, Beatriz; Barger, Kat; Barrera-Ballesteros, Jorge;
Bartosz, Curtis; Basu, Sarbani; Bates, Dominic; Battaglia, Giuseppina;
Baumgarten, Falk; Baur, Julien; Bautista, Julian; Beers, Timothy
C.; Belfiore, Francesco; Bershady, Matthew; Bertran de Lis, Sara;
Bird, Jonathan C.; Bizyaev, Dmitry; Blanc, Guillermo A.; Blanton,
Michael; Blomqvist, Michael; Bolton, Adam S.; Borissova, J.; Bovy,
Jo; Brandt, William Nielsen; Brinkmann, Jonathan; Brownstein,
Joel R.; Bundy, Kevin; Burtin, Etienne; Busca, Nicolás G.;
Camacho Chavez, Hugo Orlando; Cano Díaz, M.; Cappellari, Michele;
Carrera, Ricardo; Chen, Yanping; Cherinka, Brian; Cheung, Edmond;
Chiappini, Cristina; Chojnowski, Drew; Chuang, Chia-Hsun; Chung,
Haeun; Cirolini, Rafael Fernando; Clerc, Nicolas; Cohen, Roger E.;
Comerford, Julia M.; Comparat, Johan; Correa do Nascimento, Janaina;
Cousinou, Marie-Claude; Covey, Kevin; Crane, Jeffrey D.; Croft, Rupert;
Cunha, Katia; Darling, Jeremy; Davidson, James W., Jr.; Dawson, Kyle;
Da Costa, Luiz; Da Silva Ilha, Gabriele; Deconto Machado, Alice;
Delubac, Timothée; De Lee, Nathan; De la Macorra, Axel; De la Torre,
Sylvain; Diamond-Stanic, Aleksandar M.; Donor, John; Downes, Juan
Jose; Drory, Niv; Du, Cheng; Du Mas des Bourboux, Hélion; Dwelly,
Tom; Ebelke, Garrett; Eigenbrot, Arthur; Eisenstein, Daniel J.;
Elsworth, Yvonne P.; Emsellem, Eric; Eracleous, Michael; Escoffier,
Stephanie; Evans, Michael L.; Falcón-Barroso, Jesús; Fan, Xiaohui;
Favole, Ginevra; Fernandez-Alvar, Emma; Fernandez-Trincado, J. G.;
Feuillet, Diane; Fleming, Scott W.; Font-Ribera, Andreu; Freischlad,
Gordon; Frinchaboy, Peter; Fu, Hai; Gao, Yang; Garcia, Rafael A.;
Garcia-Dias, R.; Garcia-Hernández, D. A.; Garcia Pérez, Ana E.;
Gaulme, Patrick; Ge, Junqiang; Geisler, Douglas; Gillespie, Bruce;
Gil Marin, Hector; Girardi, Léo; Goddard, Daniel; Gomez Maqueo
Chew, Yilen; Gonzalez-Perez, Violeta; Grabowski, Kathleen; Green,
Paul; Grier, Catherine J.; Grier, Thomas; Guo, Hong; Guy, Julien;
Hagen, Alex; Hall, Matt; Harding, Paul; Harley, R. E.; Hasselquist,
Sten; Hawley, Suzanne; Hayes, Christian R.; Hearty, Fred; Hekker,
Saskia; Hernandez Toledo, Hector; Ho, Shirley; Hogg, David W.;
Holley-Bockelmann, Kelly; Holtzman, Jon A.; Holzer, Parker H.; Hu,
Jian; Huber, Daniel; Hutchinson, Timothy Alan; Hwang, Ho Seong;
Ibarra-Medel, Héctor J.; Ivans, Inese I.; Ivory, KeShawn; Jaehnig,
Kurt; Jensen, Trey W.; Johnson, Jennifer A.; Jones, Amy; Jullo, Eric;
Kallinger, T.; Kinemuchi, Karen; Kirkby, David; Klaene, Mark; Kneib,
Jean-Paul; Kollmeier, Juna A.; Lacerna, Ivan; Lane, Richard R.; Lang,
Dustin; Laurent, Pierre; Law, David R.; Leauthaud, Alexie; Le Goff,
Jean-Marc; Li, Chen; Li, Cheng; Li, Niu; Li, Ran; Liang, Fu-Heng;
Liang, Yu; Lima, Marcos; Lin, Lihwai; Lin, Lin; Lin, Yen-Ting; Liu,
Chao; Long, Dan; Lucatello, Sara; MacDonald, Nicholas; MacLeod,
Chelsea L.; Mackereth, J. Ted; Mahadevan, Suvrath; Maia, Marcio
Antonio Geimba; Maiolino, Roberto; Majewski, Steven R.; Malanushenko,
Olena; Malanushenko, Viktor; Mallmann, Nícolas Dullius; Manchado,
Arturo; Maraston, Claudia; Marques-Chaves, Rui; Martinez Valpuesta,
Inma; Masters, Karen L.; Mathur, Savita; McGreer, Ian D.; Merloni,
Andrea; Merrifield, Michael R.; Mészáros, Szabolcs; Meza, Andres;
Miglio, Andrea; Minchev, Ivan; Molaverdikhani, Karan; Montero-Dorta,
Antonio D.; Mosser, Benoit; Muna, Demitri; Myers, Adam; Nair,
Preethi; Nandra, Kirpal; Ness, Melissa; Newman, Jeffrey A.; Nichol,
Robert C.; Nidever, David L.; Nitschelm, Christian; O'Connell, Julia;
Oravetz, Audrey; Oravetz, Daniel J.; Pace, Zachary; Padilla, Nelson;
Palanque-Delabrouille, Nathalie; Pan, Kaike; Parejko, John; Paris,
Isabelle; Park, Changbom; Peacock, John A.; Peirani, Sebastien;
Pellejero-Ibanez, Marcos; Penny, Samantha; Percival, Will J.;
Percival, Jeffrey W.; Perez-Fournon, Ismael; Petitjean, Patrick;
Pieri, Matthew; Pinsonneault, Marc H.; Pisani, Alice; Prada, Francisco;
Prakash, Abhishek; Price-Jones, Natalie; Raddick, M. Jordan; Rahman,
Mubdi; Raichoor, Anand; Barboza Rembold, Sandro; Reyna, A. M.; Rich,
James; Richstein, Hannah; Ridl, Jethro; Riffel, Rogemar A.; Riffel,
Rogério; Rix, Hans-Walter; Robin, Annie C.; Rockosi, Constance M.;
Rodríguez-Torres, Sergio; Rodrigues, Thaíse S.; Roe, Natalie; Roman
Lopes, A.; Román-Zúñiga, Carlos; Ross, Ashley J.; Rossi, Graziano;
Ruan, John; Ruggeri, Rossana; Runnoe, Jessie C.; Salazar-Albornoz,
Salvador; Salvato, Mara; Sanchez, Sebastian F.; Sanchez, Ariel G.;
Sanchez-Gallego, José R.; Santiago, Basílio Xavier; Schiavon,
Ricardo; Schimoia, Jaderson S.; Schlafly, Eddie; Schlegel, David J.;
Schneider, Donald P.; Schönrich, Ralph; Schultheis, Mathias; Schwope,
Axel; Seo, Hee-Jong; Serenelli, Aldo; Sesar, Branimir; Shao, Zhengyi;
Shetrone, Matthew; Shull, Michael; Silva Aguirre, Victor; Skrutskie,
M. F.; Slosar, Anže; Smith, Michael; Smith, Verne V.; Sobeck,
Jennifer; Somers, Garrett; Souto, Diogo; Stark, David V.; Stassun,
Keivan G.; Steinmetz, Matthias; Stello, Dennis; Storchi Bergmann,
Thaisa; Strauss, Michael A.; Streblyanska, Alina; Stringfellow, Guy S.;
Suarez, Genaro; Sun, Jing; Taghizadeh-Popp, Manuchehr; Tang, Baitian;
Tao, Charling; Tayar, Jamie; Tembe, Mita; Thomas, Daniel; Tinker,
Jeremy; Tojeiro, Rita; Tremonti, Christy; Troup, Nicholas; Trump,
Jonathan R.; Unda-Sanzana, Eduardo; Valenzuela, O.; Van den Bosch,
Remco; Vargas-Magaña, Mariana; Vazquez, Jose Alberto; Villanova,
Sandro; Vivek, M.; Vogt, Nicole; Wake, David; Walterbos, Rene; Wang,
Yuting; Wang, Enci; Weaver, Benjamin Alan; Weijmans, Anne-Marie;
Weinberg, David H.; Westfall, Kyle B.; Whelan, David G.; Wilcots,
Eric; Wild, Vivienne; Williams, Rob A.; Wilson, John; Wood-Vasey,
W. M.; Wylezalek, Dominika; Xiao, Ting; Yan, Renbin; Yang, Meng;
Ybarra, Jason E.; Yeche, Christophe; Yuan, Fang-Ting; Zakamska,
Nadia; Zamora, Olga; Zasowski, Gail; Zhang, Kai; Zhao, Cheng; Zhao,
Gong-Bo; Zheng, Zheng; Zheng, Zheng; Zhou, Zhi-Min; Zhu, Guangtun;
Zinn, Joel C.; Zou, Hu
2017ApJS..233...25A Altcode: 2016arXiv160802013S
The fourth generation of the Sloan Digital Sky Survey (SDSS-IV)
began observations in 2014 July. It pursues three core programs: the
Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2),
Mapping Nearby Galaxies at APO (MaNGA), and the Extended Baryon
Oscillation Spectroscopic Survey (eBOSS). As well as its core program,
eBOSS contains two major subprograms: the Time Domain Spectroscopic
Survey (TDSS) and the SPectroscopic IDentification of ERosita Sources
(SPIDERS). This paper describes the first data release from SDSS-IV,
Data Release 13 (DR13). DR13 makes publicly available the first 1390
spatially resolved integral field unit observations of nearby galaxies
from MaNGA. It includes new observations from eBOSS, completing the
Sloan Extended QUasar, Emission-line galaxy, Luminous red galaxy
Survey (SEQUELS), which also targeted variability-selected objects
and X-ray-selected objects. DR13 includes new reductions of the
SDSS-III BOSS data, improving the spectrophotometric calibration
and redshift classification, and new reductions of the SDSS-III
APOGEE-1 data, improving stellar parameters for dwarf stars and
cooler stars. DR13 provides more robust and precise photometric
calibrations. Value-added target catalogs relevant for eBOSS, TDSS,
and SPIDERS and an updated red-clump catalog for APOGEE are also
available. This paper describes the location and format of the data
and provides references to important technical papers. The SDSS web
site, <A href="http://www.sdss.org">http://www.sdss.org</A>, provides
links to the data, tutorials, examples of data access, and extensive
documentation of the reduction and analysis procedures. DR13 is the
first of a scheduled set that will contain new data and analyses from
the planned ∼6 yr operations of SDSS-IV.
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Title: The Recurrent Nova Candidate M31N 1966-08a = 1968-10c is a
Galactic Flare Star
Authors: Shafter, A. W.; Henze, M.; Darnley, M. J.; Ciardullo, R.;
Davis, B. D.; Hawley, S. L.
2017RNAAS...1...44S Altcode: 2017arXiv171205023S; 2017RNAAS...1a..44S
A spectrum of the quiescent counterpart of the Recurrent Nova candidate
M31N 1966-08a (= M31N 1968-10c) obtained with LRS2 on the Hobby-Eberly
Telescope reveals the object to be a foreground Galactic dMe flare star,
and not a nova in M31.
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Title: Modeling Repeated M-dwarf Flaring at an Earth-like Planet in
the Habitable Zone: I. Atmospheric Effects for an Unmagnetized Planet
Authors: Tilley, Matt A.; Segura, Antigona; Meadows, Victoria S.;
Hawley, Suzanne; Davenport, James
2017arXiv171108484T Altcode:
Understanding the impact of active M-dwarf stars on the atmospheric
equilibrium and surface conditions of a habitable zone Earth-like
planet is key to assessing M dwarf planet habitability. Previous
modeling of the impact of electromagnetic (EM) radiation and protons
from a single large flare on an Earth-like atmosphere indicated
that significant and long-term reductions in ozone were possible,
but the atmosphere recovered. These stars more realistically exhibit
frequent flaring with a power-law distribution of energies. Here
we use a coupled 1D photochemical and radiative-convective model to
investigate the effects of repeated flaring on the photochemistry and
surface UV of an Earth-like planet unprotected by an intrinsic magnetic
field. We use time-resolved flare spectra obtained for the dM3 star
AD Leo, combined with flare occurrence frequencies and total energies
(typically 10$^{30.5}$ to 10$^{34}$ erg) from the 4-year Kepler light
curve for the dM4 flare star GJ1243. Our model results show repeated
EM-only flares have little effect on the ozone column depth, but that
multiple proton events can rapidly destroy the ozone column. Combining
the realistic flare and proton event frequencies with nominal CME &
SEP geometries, we find the ozone column for an Earth-like planet can be
depleted by 94% in 10 years, with a downward trend that makes recovery
unlikely and suggests further destruction. For more extreme stellar
inputs O3 depletion allows a constant 0.1-1 W m$^{-2}$ of UV-C at the
planet's surface, which is likely detrimental to organic complexity. Our
results suggest that active M dwarf hosts may comprehensively destroy
ozone shields and subject the surface of magnetically-unprotected
Earth-like planets to long-term radiation that can damage complex
organic structures. However, this does not preclude habitability,
as a safe haven for life could still exist below an ocean surface.
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Title: Toward Space-like Photometric Precision from the Ground with
Beam-shaping Diffusers
Authors: Stefansson, Gudmundur; Mahadevan, Suvrath; Hebb, Leslie;
Wisniewski, John; Huehnerhoff, Joseph; Morris, Brett; Halverson, Sam;
Zhao, Ming; Wright, Jason; O'rourke, Joseph; Knutson, Heather; Hawley,
Suzanne; Kanodia, Shubham; Li, Yiting; Hagen, Lea M. Z.; Liu, Leo J.;
Beatty, Thomas; Bender, Chad; Robertson, Paul; Dembicky, Jack; Gray,
Candace; Ketzeback, William; McMillan, Russet; Rudyk, Theodore
2017ApJ...848....9S Altcode: 2017arXiv171001790S
We demonstrate a path to hitherto unachievable differential photometric
precisions from the ground, both in the optical and near-infrared
(NIR), using custom-fabricated beam-shaping diffusers produced using
specialized nanofabrication techniques. Such diffusers mold the focal
plane image of a star into a broad and stable top-hat shape, minimizing
photometric errors due to non-uniform pixel response, atmospheric seeing
effects, imperfect guiding, and telescope-induced variable aberrations
seen in defocusing. This PSF reshaping significantly increases the
achievable dynamic range of our observations, increasing our observing
efficiency and thus better averages over scintillation. Diffusers work
in both collimated and converging beams. We present diffuser-assisted
optical observations demonstrating {62}<SUB>-16</SUB><SUP>+26</SUP>
ppm precision in 30 minute bins on a nearby bright star 16 Cygni A
(V = 5.95) using the ARC 3.5 m telescope—within a factor of ∼2 of
Kepler's photometric precision on the same star. We also show a transit
of WASP-85-Ab (V = 11.2) and TRES-3b (V = 12.4), where the residuals
bin down to {180}<SUB>-41</SUB><SUP>+66</SUP> ppm in 30 minute bins
for WASP-85-Ab—a factor of ∼4 of the precision achieved by the
K2 mission on this target—and to 101 ppm for TRES-3b. In the NIR,
where diffusers may provide even more significant improvements over
the current state of the art, our preliminary tests demonstrated
{137}<SUB>-36</SUB><SUP>+64</SUP> ppm precision for a K <SUB> S </SUB> =
10.8 star on the 200 inch Hale Telescope. These photometric precisions
match or surpass the expected photometric precisions of TESS for
the same magnitude range. This technology is inexpensive, scalable,
easily adaptable, and can have an important and immediate impact on
the observations of transits and secondary eclipses of exoplanets.
---------------------------------------------------------
Title: Chromospheric Activity of HAT-P-11: An Unusually Active
Planet-hosting K Star
Authors: Morris, Brett M.; Hawley, Suzanne L.; Hebb, Leslie; Sakari,
Charli; Davenport, James. R. A.; Isaacson, Howard; Howard, Andrew W.;
Montet, Benjamin T.; Agol, Eric
2017ApJ...848...58M Altcode: 2017arXiv170903913M
Kepler photometry of the hot Neptune host star HAT-P-11 suggests
that its spot latitude distribution is comparable to the Sun’s
near solar maximum. We search for evidence of an activity cycle in
the Ca II H & K chromospheric emission S-index with archival
Keck/HIRES spectra and observations from the echelle spectrograph on
the Astrophysical Research Consortium 3.5 m Telescope at Apache Point
Observatory. The chromospheric emission of HAT-P-11 is consistent with
an ≳ 10 year activity cycle, which plateaued near maximum during
the Kepler mission. In the cycle that we observed, the star seemed
to spend more time near active maximum than minimum. We compare the
{log}{R}<SUB>{HK</SUB>}<SUP>{\prime</SUP> } normalized chromospheric
emission index of HAT-P-11 with other stars. HAT-P-11 has unusually
strong chromospheric emission compared to planet-hosting stars of
similar effective temperature and rotation period, perhaps due to
tides raised by its planet.
---------------------------------------------------------
Title: The Starspots of HAT-P-11: Evidence for a Solar-like Dynamo
Authors: Morris, Brett M.; Hebb, Leslie; Davenport, James R. A.;
Rohn, Graeme; Hawley, Suzanne L.
2017ApJ...846...99M Altcode: 2017arXiv170802583M
We measure the starspot radii and latitude distribution on the
K4 dwarf HAT-P-11 from Kepler short-cadence photometry. We take
advantage of starspot occultations by HAT-P-11’s highly misaligned
planet to compare the spot size and latitude distributions to those of
sunspots. We find that HAT-P-11’s spots are distributed in latitude
much like sunspots near the solar activity maximum, with a mean spot
latitude of ≈16° ± 1°. The majority of HAT-P-11’s starspots
have physical sizes that closely resemble the sizes of sunspots at
solar maximum. We estimate the mean spotted area coverage on HAT-P-11
to be {3}<SUB>-1</SUB><SUP>+6</SUP> % , roughly two orders of magnitude
greater than the typical solar spotted area.
---------------------------------------------------------
Title: First Detection of a Strong Magnetic Field on a Bursty Brown
Dwarf: Puzzle Solved
Authors: Berdyugina, S. V.; Harrington, D. M.; Kuzmychov, O.; Kuhn,
J. R.; Hallinan, G.; Kowalski, A. F.; Hawley, S. L.
2017ApJ...847...61B Altcode: 2017arXiv170902861B
We report the first direct detection of a strong, 5 kG magnetic field on
the surface of an active brown dwarf. LSR J1835+3259 is an M8.5 dwarf
exhibiting transient radio and optical emission bursts modulated by
fast rotation. We have detected the surface magnetic field as circularly
polarized signatures in the 819 nm sodium lines when an active emission
region faced the Earth. Modeling Stokes profiles of these lines reveals
the effective temperature of 2800 K and log gravity acceleration of
4.5. These parameters place LSR J1835+3259 on evolutionary tracks as
a young brown dwarf with the mass of 55+/- 4{M}<SUB>{{J</SUB>}} and
age of 22 ± 4 Myr. Its magnetic field is at least 5.1 kG and covers
at least 11% of the visible hemisphere. The active region topology
recovered using line profile inversions comprises hot plasma loops with
a vertical stratification of optical and radio emission sources. These
loops rotate with the dwarf in and out of view causing periodic emission
bursts. The magnetic field is detected at the base of the loops. This
is the first time that we can quantitatively associate brown dwarf
non-thermal bursts with a strong, 5 kG surface magnetic field and
solve the puzzle of their driving mechanism. This is also the coolest
known dwarf with such a strong surface magnetic field. The young age
of LSR J1835+3259 implies that it may still maintain a disk, which may
facilitate bursts via magnetospheric accretion, like in higher-mass
T Tau-type stars. Our results pave a path toward magnetic studies of
brown dwarfs and hot Jupiters.
---------------------------------------------------------
Title: Science-Driven Optimization of the LSST Observing Strategy
Authors: LSST Science Collaboration; Marshall, Phil; Anguita, Timo;
Bianco, Federica B.; Bellm, Eric C.; Brandt, Niel; Clarkson, Will;
Connolly, Andy; Gawiser, Eric; Ivezic, Zeljko; Jones, Lynne; Lochner,
Michelle; Lund, Michael B.; Mahabal, Ashish; Nidever, David; Olsen,
Knut; Ridgway, Stephen; Rhodes, Jason; Shemmer, Ohad; Trilling, David;
Vivas, Kathy; Walkowicz, Lucianne; Willman, Beth; Yoachim, Peter;
Anderson, Scott; Antilogus, Pierre; Angus, Ruth; Arcavi, Iair; Awan,
Humna; Biswas, Rahul; Bell, Keaton J.; Bennett, David; Britt, Chris;
Buzasi, Derek; Casetti-Dinescu, Dana I.; Chomiuk, Laura; Claver, Chuck;
Cook, Kem; Davenport, James; Debattista, Victor; Digel, Seth; Doctor,
Zoheyr; Firth, R. E.; Foley, Ryan; Fong, Wen-fai; Galbany, Lluis;
Giampapa, Mark; Gizis, John E.; Graham, Melissa L.; Grillmair, Carl;
Gris, Phillipe; Haiman, Zoltan; Hartigan, Patrick; Hawley, Suzanne;
Hlozek, Renee; Jha, Saurabh W.; Johns-Krull, C.; Kanbur, Shashi;
Kalogera, Vassiliki; Kashyap, Vinay; Kasliwal, Vishal; Kessler,
Richard; Kim, Alex; Kurczynski, Peter; Lahav, Ofer; Liu, Michael C.;
Malz, Alex; Margutti, Raffaella; Matheson, Tom; McEwen, Jason D.;
McGehee, Peregrine; Meibom, Soren; Meyers, Josh; Monet, Dave; Neilsen,
Eric; Newman, Jeffrey; O'Dowd, Matt; Peiris, Hiranya V.; Penny, Matthew
T.; Peters, Christina; Poleski, Radoslaw; Ponder, Kara; Richards,
Gordon; Rho, Jeonghee; Rubin, David; Schmidt, Samuel; Schuhmann,
Robert L.; Shporer, Avi; Slater, Colin; Smith, Nathan; Soares-Santos,
Marcelles; Stassun, Keivan; Strader, Jay; Strauss, Michael; Street,
Rachel; Stubbs, Christopher; Sullivan, Mark; Szkody, Paula; Trimble,
Virginia; Tyson, Tony; de Val-Borro, Miguel; Valenti, Stefano; Wagoner,
Robert; Wood-Vasey, W. Michael; Zauderer, Bevin Ashley
2017arXiv170804058L Altcode:
The Large Synoptic Survey Telescope is designed to provide an
unprecedented optical imaging dataset that will support investigations
of our Solar System, Galaxy and Universe, across half the sky and
over ten years of repeated observation. However, exactly how the LSST
observations will be taken (the observing strategy or "cadence")
is not yet finalized. In this dynamically-evolving community white
paper, we explore how the detailed performance of the anticipated
science investigations is expected to depend on small changes to
the LSST observing strategy. Using realistic simulations of the LSST
schedule and observation properties, we design and compute diagnostic
metrics and Figures of Merit that provide quantitative evaluations of
different observing strategies, analyzing their impact on a wide range
of proposed science projects. This is work in progress: we are using
this white paper to communicate to each other the relative merits
of the observing strategy choices that could be made, in an effort
to maximize the scientific value of the survey. The investigation of
some science cases leads to suggestions for new strategies that could
be simulated and potentially adopted. Notably, we find motivation for
exploring departures from a spatially uniform annual tiling of the sky:
focusing instead on different parts of the survey area in different
years in a "rolling cadence" is likely to have significant benefits
for a number of time domain and moving object astronomy projects. The
communal assembly of a suite of quantified and homogeneously coded
metrics is the vital first step towards an automated, systematic,
science-based assessment of any given cadence simulation, that will
enable the scheduling of the LSST to be as well-informed as possible.
---------------------------------------------------------
Title: The MUSCLES Treasury Survey. IV. Scaling Relations for
Ultraviolet, Ca II K, and Energetic Particle Fluxes from M Dwarfs
Authors: Youngblood, Allison; France, Kevin; Loyd, R. O. Parke; Brown,
Alexander; Mason, James P.; Schneider, P. Christian; Tilley, Matt A.;
Berta-Thompson, Zachory K.; Buccino, Andrea; Froning, Cynthia S.;
Hawley, Suzanne L.; Linsky, Jeffrey; Mauas, Pablo J. D.; Redfield,
Seth; Kowalski, Adam; Miguel, Yamila; Newton, Elisabeth R.; Rugheimer,
Sarah; Segura, Antígona; Roberge, Aki; Vieytes, Mariela
2017ApJ...843...31Y Altcode: 2017arXiv170504361Y
Characterizing the UV spectral energy distribution (SED) of
an exoplanet host star is critically important for assessing its
planet’s potential habitability, particularly for M dwarfs, as they
are prime targets for current and near-term exoplanet characterization
efforts and atmospheric models predict that their UV radiation can
produce photochemistry on habitable zone planets different from that
on Earth. To derive ground-based proxies for UV emission for use when
Hubble Space Telescope (HST) observations are unavailable, we have
assembled a sample of 15 early to mid-M dwarfs observed by HST and
compared their nonsimultaneous UV and optical spectra. We find that
the equivalent width of the chromospheric Ca II K line at 3933 Å, when
corrected for spectral type, can be used to estimate the stellar surface
flux in ultraviolet emission lines, including H I Lyα. In addition,
we address another potential driver of habitability: energetic particle
fluxes associated with flares. We present a new technique for estimating
soft X-ray and >10 MeV proton flux during far-UV emission line flares
(Si IV and He II) by assuming solar-like energy partitions. We analyze
several flares from the M4 dwarf GJ 876 observed with HST and Chandra as
part of the MUSCLES Treasury Survey and find that habitable zone planets
orbiting GJ 876 are impacted by large Carrington-like flares with peak
soft X-ray fluxes ≥10<SUP>-3</SUP> W m<SUP>-2</SUP> and possible
proton fluxes ∼10<SUP>2</SUP>-10<SUP>3</SUP> pfu, approximately four
orders of magnitude more frequently than modern-day Earth.
---------------------------------------------------------
Title: Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby
Galaxies, and the Distant Universe
Authors: Blanton, Michael R.; Bershady, Matthew A.; Abolfathi,
Bela; Albareti, Franco D.; Allende Prieto, Carlos; Almeida,
Andres; Alonso-García, Javier; Anders, Friedrich; Anderson,
Scott F.; Andrews, Brett; Aquino-Ortíz, Erik; Aragón-Salamanca,
Alfonso; Argudo-Fernández, Maria; Armengaud, Eric; Aubourg, Eric;
Avila-Reese, Vladimir; Badenes, Carles; Bailey, Stephen; Barger,
Kathleen A.; Barrera-Ballesteros, Jorge; Bartosz, Curtis; Bates,
Dominic; Baumgarten, Falk; Bautista, Julian; Beaton, Rachael; Beers,
Timothy C.; Belfiore, Francesco; Bender, Chad F.; Berlind, Andreas A.;
Bernardi, Mariangela; Beutler, Florian; Bird, Jonathan C.; Bizyaev,
Dmitry; Blanc, Guillermo A.; Blomqvist, Michael; Bolton, Adam S.;
Boquien, Médéric; Borissova, Jura; van den Bosch, Remco; Bovy,
Jo; Brandt, William N.; Brinkmann, Jonathan; Brownstein, Joel R.;
Bundy, Kevin; Burgasser, Adam J.; Burtin, Etienne; Busca, Nicolás G.;
Cappellari, Michele; Delgado Carigi, Maria Leticia; Carlberg, Joleen
K.; Carnero Rosell, Aurelio; Carrera, Ricardo; Chanover, Nancy J.;
Cherinka, Brian; Cheung, Edmond; Gómez Maqueo Chew, Yilen; Chiappini,
Cristina; Choi, Peter Doohyun; Chojnowski, Drew; Chuang, Chia-Hsun;
Chung, Haeun; Cirolini, Rafael Fernando; Clerc, Nicolas; Cohen, Roger
E.; Comparat, Johan; da Costa, Luiz; Cousinou, Marie-Claude; Covey,
Kevin; Crane, Jeffrey D.; Croft, Rupert A. C.; Cruz-Gonzalez, Irene;
Garrido Cuadra, Daniel; Cunha, Katia; Damke, Guillermo J.; Darling,
Jeremy; Davies, Roger; Dawson, Kyle; de la Macorra, Axel; Dell'Agli,
Flavia; De Lee, Nathan; Delubac, Timothée; Di Mille, Francesco;
Diamond-Stanic, Aleks; Cano-Díaz, Mariana; Donor, John; Downes, Juan
José; Drory, Niv; du Mas des Bourboux, Hélion; Duckworth, Christopher
J.; Dwelly, Tom; Dyer, Jamie; Ebelke, Garrett; Eigenbrot, Arthur D.;
Eisenstein, Daniel J.; Emsellem, Eric; Eracleous, Mike; Escoffier,
Stephanie; Evans, Michael L.; Fan, Xiaohui; Fernández-Alvar, Emma;
Fernandez-Trincado, J. G.; Feuillet, Diane K.; Finoguenov, Alexis;
Fleming, Scott W.; Font-Ribera, Andreu; Fredrickson, Alexander;
Freischlad, Gordon; Frinchaboy, Peter M.; Fuentes, Carla E.;
Galbany, Lluís; Garcia-Dias, R.; García-Hernández, D. A.; Gaulme,
Patrick; Geisler, Doug; Gelfand, Joseph D.; Gil-Marín, Héctor;
Gillespie, Bruce A.; Goddard, Daniel; Gonzalez-Perez, Violeta;
Grabowski, Kathleen; Green, Paul J.; Grier, Catherine J.; Gunn,
James E.; Guo, Hong; Guy, Julien; Hagen, Alex; Hahn, ChangHoon;
Hall, Matthew; Harding, Paul; Hasselquist, Sten; Hawley, Suzanne
L.; Hearty, Fred; Gonzalez Hernández, Jonay I.; Ho, Shirley; Hogg,
David W.; Holley-Bockelmann, Kelly; Holtzman, Jon A.; Holzer, Parker
H.; Huehnerhoff, Joseph; Hutchinson, Timothy A.; Hwang, Ho Seong;
Ibarra-Medel, Héctor J.; da Silva Ilha, Gabriele; Ivans, Inese I.;
Ivory, KeShawn; Jackson, Kelly; Jensen, Trey W.; Johnson, Jennifer A.;
Jones, Amy; Jönsson, Henrik; Jullo, Eric; Kamble, Vikrant; Kinemuchi,
Karen; Kirkby, David; Kitaura, Francisco-Shu; Klaene, Mark; Knapp,
Gillian R.; Kneib, Jean-Paul; Kollmeier, Juna A.; Lacerna, Ivan;
Lane, Richard R.; Lang, Dustin; Law, David R.; Lazarz, Daniel; Lee,
Youngbae; Le Goff, Jean-Marc; Liang, Fu-Heng; Li, Cheng; Li, Hongyu;
Lian, Jianhui; Lima, Marcos; Lin, Lihwai; Lin, Yen-Ting; Bertran de
Lis, Sara; Liu, Chao; de Icaza Lizaola, Miguel Angel C.; Long, Dan;
Lucatello, Sara; Lundgren, Britt; MacDonald, Nicholas K.; Deconto
Machado, Alice; MacLeod, Chelsea L.; Mahadevan, Suvrath; Geimba Maia,
Marcio Antonio; Maiolino, Roberto; Majewski, Steven R.; Malanushenko,
Elena; Malanushenko, Viktor; Manchado, Arturo; Mao, Shude; Maraston,
Claudia; Marques-Chaves, Rui; Masseron, Thomas; Masters, Karen L.;
McBride, Cameron K.; McDermid, Richard M.; McGrath, Brianne; McGreer,
Ian D.; Medina Peña, Nicolás; Melendez, Matthew; Merloni, Andrea;
Merrifield, Michael R.; Meszaros, Szabolcs; Meza, Andres; Minchev,
Ivan; Minniti, Dante; Miyaji, Takamitsu; More, Surhud; Mulchaey, John;
Müller-Sánchez, Francisco; Muna, Demitri; Munoz, Ricardo R.; Myers,
Adam D.; Nair, Preethi; Nandra, Kirpal; Correa do Nascimento, Janaina;
Negrete, Alenka; Ness, Melissa; Newman, Jeffrey A.; Nichol, Robert C.;
Nidever, David L.; Nitschelm, Christian; Ntelis, Pierros; O'Connell,
Julia E.; Oelkers, Ryan J.; Oravetz, Audrey; Oravetz, Daniel; Pace,
Zach; Padilla, Nelson; Palanque-Delabrouille, Nathalie; Alonso Palicio,
Pedro; Pan, Kaike; Parejko, John K.; Parikh, Taniya; Pâris, Isabelle;
Park, Changbom; Patten, Alim Y.; Peirani, Sebastien; Pellejero-Ibanez,
Marcos; Penny, Samantha; Percival, Will J.; Perez-Fournon, Ismael;
Petitjean, Patrick; Pieri, Matthew M.; Pinsonneault, Marc; Pisani,
Alice; Poleski, Radosław; Prada, Francisco; Prakash, Abhishek;
Queiroz, Anna Bárbara de Andrade; Raddick, M. Jordan; Raichoor,
Anand; Barboza Rembold, Sandro; Richstein, Hannah; Riffel, Rogemar A.;
Riffel, Rogério; Rix, Hans-Walter; Robin, Annie C.; Rockosi, Constance
M.; Rodríguez-Torres, Sergio; Roman-Lopes, A.; Román-Zúñiga,
Carlos; Rosado, Margarita; Ross, Ashley J.; Rossi, Graziano; Ruan,
John; Ruggeri, Rossana; Rykoff, Eli S.; Salazar-Albornoz, Salvador;
Salvato, Mara; Sánchez, Ariel G.; Aguado, D. S.; Sánchez-Gallego,
José R.; Santana, Felipe A.; Santiago, Basílio Xavier; Sayres, Conor;
Schiavon, Ricardo P.; da Silva Schimoia, Jaderson; Schlafly, Edward
F.; Schlegel, David J.; Schneider, Donald P.; Schultheis, Mathias;
Schuster, William J.; Schwope, Axel; Seo, Hee-Jong; Shao, Zhengyi;
Shen, Shiyin; Shetrone, Matthew; Shull, Michael; Simon, Joshua D.;
Skinner, Danielle; Skrutskie, M. F.; Slosar, Anže; Smith, Verne V.;
Sobeck, Jennifer S.; Sobreira, Flavia; Somers, Garrett; Souto, Diogo;
Stark, David V.; Stassun, Keivan; Stauffer, Fritz; Steinmetz,
Matthias; Storchi-Bergmann, Thaisa; Streblyanska, Alina; Stringfellow,
Guy S.; Suárez, Genaro; Sun, Jing; Suzuki, Nao; Szigeti, Laszlo;
Taghizadeh-Popp, Manuchehr; Tang, Baitian; Tao, Charling; Tayar,
Jamie; Tembe, Mita; Teske, Johanna; Thakar, Aniruddha R.; Thomas,
Daniel; Thompson, Benjamin A.; Tinker, Jeremy L.; Tissera, Patricia;
Tojeiro, Rita; Hernandez Toledo, Hector; de la Torre, Sylvain;
Tremonti, Christy; Troup, Nicholas W.; Valenzuela, Octavio; Martinez
Valpuesta, Inma; Vargas-González, Jaime; Vargas-Magaña, Mariana;
Vazquez, Jose Alberto; Villanova, Sandro; Vivek, M.; Vogt, Nicole;
Wake, David; Walterbos, Rene; Wang, Yuting; Weaver, Benjamin Alan;
Weijmans, Anne-Marie; Weinberg, David H.; Westfall, Kyle B.; Whelan,
David G.; Wild, Vivienne; Wilson, John; Wood-Vasey, W. M.; Wylezalek,
Dominika; Xiao, Ting; Yan, Renbin; Yang, Meng; Ybarra, Jason E.;
Yèche, Christophe; Zakamska, Nadia; Zamora, Olga; Zarrouk, Pauline;
Zasowski, Gail; Zhang, Kai; Zhao, Gong-Bo; Zheng, Zheng; Zheng, Zheng;
Zhou, Xu; Zhou, Zhi-Min; Zhu, Guangtun B.; Zoccali, Manuela; Zou, Hu
2017AJ....154...28B Altcode: 2017arXiv170300052B
We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project
encompassing three major spectroscopic programs. The Apache Point
Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing
hundreds of thousands of Milky Way stars at high resolution and high
signal-to-noise ratios in the near-infrared. The Mapping Nearby Galaxies
at Apache Point Observatory (MaNGA) survey is obtaining spatially
resolved spectroscopy for thousands of nearby galaxies (median z∼
0.03). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is
mapping the galaxy, quasar, and neutral gas distributions between z∼
0.6 and 3.5 to constrain cosmology using baryon acoustic oscillations,
redshift space distortions, and the shape of the power spectrum. Within
eBOSS, we are conducting two major subprograms: the SPectroscopic
IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGNs
and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey
(TDSS), obtaining spectra of variable sources. All programs use the
2.5 m Sloan Foundation Telescope at the Apache Point Observatory;
observations there began in Summer 2014. APOGEE-2 also operates a
second near-infrared spectrograph at the 2.5 m du Pont Telescope
at Las Campanas Observatory, with observations beginning in early
2017. Observations at both facilities are scheduled to continue through
2020. In keeping with previous SDSS policy, SDSS-IV provides regularly
scheduled public data releases; the first one, Data Release 13, was
made available in 2016 July.
---------------------------------------------------------
Title: Hydrogen Balmer Line Broadening in Solar and Stellar Flares
Authors: Kowalski, Adam F.; Allred, Joel C.; Uitenbroek, Han; Tremblay,
Pier-Emmanuel; Brown, Stephen; Carlsson, Mats; Osten, Rachel A.;
Wisniewski, John P.; Hawley, Suzanne L.
2017ApJ...837..125K Altcode: 2017arXiv170203321K
The broadening of the hydrogen lines during flares is thought to
result from increased charge (electron, proton) density in the flare
chromosphere. However, disagreements between theory and modeling
prescriptions have precluded an accurate diagnostic of the degree
of ionization and compression resulting from flare heating in the
chromosphere. To resolve this issue, we have incorporated the unified
theory of electric pressure broadening of the hydrogen lines into
the non-LTE radiative-transfer code RH. This broadening prescription
produces a much more realistic spectrum of the quiescent, A0 star Vega
compared to the analytic approximations used as a damping parameter
in the Voigt profiles. We test recent radiative-hydrodynamic (RHD)
simulations of the atmospheric response to high nonthermal electron
beam fluxes with the new broadening prescription and find that
the Balmer lines are overbroadened at the densest times in the
simulations. Adding many simultaneously heated and cooling model
loops as a “multithread” model improves the agreement with the
observations. We revisit the three-component phenomenological flare
model of the YZ CMi Megaflare using recent and new RHD models. The
evolution of the broadening, line flux ratios, and continuum flux
ratios are well-reproduced by a multithread model with high-flux
nonthermal electron beam heating, an extended decay phase model, and a
“hot spot” atmosphere heated by an ultrarelativistic electron beam
with reasonable filling factors: ∼0.1%, 1%, and 0.1% of the visible
stellar hemisphere, respectively. The new modeling motivates future
work to understand the origin of the extended gradual phase emission.
---------------------------------------------------------
Title: The Active Latitudes of HAT-P-11
Authors: Morris, Brett; Hebb, Leslie; Davenport, James R. A.; Hawley,
Suzanne L.
2017AAS...22923005M Altcode:
Transiting planets map the brightness of their host stars, as the flux
lost during exoplanet transits is proportional to the integrated flux
occulted by the planet. We analyze four years of Kepler short-cadence
photometry of HAT-P-11 - an active K4 dwarf with a 29 day rotation
period, orbited by a hot-Neptune. Due to its highly-misaligned orbit,
the planet occults most stellar latitudes during each transit,
and the latitude distribution of spots is encoded in the transit
light curves. We model each spot occultation in transit to create a
spot map of HAT-P-11, which reveals two active latitudes near ±17
degrees. We investigate whether the spot distribution changes in time,
and we compare the spot latitude distributions of HAT-P-11 and the
Sun throughout the solar activity cycle.
---------------------------------------------------------
Title: VizieR Online Data Catalog: SDSS WD-M binary parameters
(Raymond+, 2003)
Authors: Raymond, S. N.; Szkody, P.; Hawley, S. L.; Anderson, S. F.;
Brinkmann, J.; Covey, K. R.; McGehee, P. M.; Schneider, D. P.; West,
A. A.; York, D. G.
2016yCat..51252621R Altcode:
We have compiled a sample of 109 WD-M binaries from the first year of
the Sloan Digital Sky Survey. <P />(1 data file).
---------------------------------------------------------
Title: Kepler Flares. IV. A Comprehensive Analysis of the Activity
of the dM4e Star GJ 1243
Authors: Silverberg, Steven M.; Kowalski, Adam F.; Davenport, James
R. A.; Wisniewski, John P.; Hawley, Suzanne L.; Hilton, Eric J.
2016ApJ...829..129S Altcode: 2016arXiv160703886S
We present a comprehensive study of the active dM4e star GJ 1243. We
use previous observations and ground-based echelle spectroscopy
to determine that GJ 1243 is a member of the Argus association of
field stars, suggesting it is ∼ 30{--}50 {{Myr}} old. We analyze 11
months of 1 minute cadence data from Kepler, presenting Kepler flare
frequency distributions, as well as determining correlations between
flare energy, amplitude, duration, and decay time. We find that the
exponent α of the power-law flare energy distribution varies in
time, primarily due to completeness of sample and the low frequency
of high-energy flares. We also find a deviation from a single power
law at high energy. We use ground-based spectroscopic observations
that were simultaneous with the Kepler data to provide simultaneous
photometric and spectroscopic analysis of three low-energy flares,
the lowest-energy dMe flares with detailed spectral analysis to date on
any star. The spectroscopic data from these flares extend constraints
for radiative hydrodynamic flare models to a lower energy regime than
has previously been studied. We use this simultaneous spectroscopy and
Kepler photometry to develop approximate conversions from the Kepler
bandpass to the traditional U and B bands. This conversion will be a
critical factor in comparing any Kepler flare analyses to the canon
of previous ground-based flare studies.
---------------------------------------------------------
Title: Maximizing Science in the Era of LSST: A Community-Based
Study of Needed US Capabilities
Authors: Najita, Joan; Willman, Beth; Finkbeiner, Douglas P.; Foley,
Ryan J.; Hawley, Suzanne; Newman, Jeffrey A.; Rudnick, Gregory; Simon,
Joshua D.; Trilling, David; Street, Rachel; Bolton, Adam; Angus, Ruth;
Bell, Eric F.; Buzasi, Derek; Ciardi, David; Davenport, James R. A.;
Dawson, Will; Dickinson, Mark; Drlica-Wagner, Alex; Elias, Jay; Erb,
Dawn; Feaga, Lori; Fong, Wen-fai; Gawiser, Eric; Giampapa, Mark;
Guhathakurta, Puragra; Hoffman, Jennifer L.; Hsieh, Henry; Jennings,
Elise; Johnston, Kathryn V.; Kashyap, Vinay; Li, Ting S.; Linder,
Eric; Mandelbaum, Rachel; Marshall, Phil; Matheson, Thomas; Meibom,
Soren; Miller, Bryan W.; O'Meara, John; Reddy, Vishnu; Ridgway, Steve;
Rockosi, Constance M.; Sand, David J.; Schafer, Chad; Schmidt, Sam;
Sesar, Branimir; Sheppard, Scott S.; Thomas, Cristina A.; Tollerud,
Erik J.; Trump, Jon; von der Linden, Anja
2016arXiv161001661N Altcode:
The Large Synoptic Survey Telescope (LSST) will be a discovery machine
for the astronomy and physics communities, revealing astrophysical
phenomena from the Solar System to the outer reaches of the observable
Universe. While many discoveries will be made using LSST data alone,
taking full scientific advantage of LSST will require ground-based
optical-infrared (OIR) supporting capabilities, e.g., observing
time on telescopes, instrumentation, computing resources, and
other infrastructure. This community-based study identifies, from a
science-driven perspective, capabilities that are needed to maximize
LSST science. Expanding on the initial steps taken in the 2015 OIR
System Report, the study takes a detailed, quantitative look at the
capabilities needed to accomplish six representative LSST-enabled
science programs that connect closely with scientific priorities from
the 2010 decadal surveys. The study prioritizes the resources needed
to accomplish the science programs and highlights ways that existing,
planned, and future resources could be positioned to accomplish the
science goals.
---------------------------------------------------------
Title: Astrophysical Research Consortium Telescope Imaging Camera
(ARCTIC) facility optical imager for the Apache Point Observatory
3.5m telescope
Authors: Huehnerhoff, Joseph; Ketzeback, William; Bradley, Alaina;
Dembicky, Jack; Doughty, Caitlin; Hawley, Suzanne; Johnson, Courtney;
Klaene, Mark; Leon, Ed; McMillan, Russet; Owen, Russell; Sayres,
Conor; Sheen, Tyler; Shugart, Alysha
2016SPIE.9908E..5HH Altcode:
The Astrophysical Research Consortium Telescope Imaging Camera, ARCTIC,
is a new optical imaging camera now in use at the Astrophysical Research
Consortium (ARC) 3.5m telescope at Apache Point Observatory (APO). As
a facility instrument, the design criteria broadly encompassed many
current and future science opportunities, and the components were
built for quick repair or replacement, to minimize down-time. Examples
include a quick change shutter, filter drive components accessible from
the exterior and redundant amplifiers on the detector. The detector
is a Semiconductor Technology Associates (STA) device with several
key properties (e.g. high quantum efficiency, low read-noise, quick
readout, minimal fringing, operational bandpass 350-950nm). Focal
reducing optics (f/10.3 to f/8.0) were built to control aberrations
over a 7.8'x7.8' field, with a plate scale of 0.11" per 0.15 micron
pixel. The instrument body and dewar were designed to be simple and
robust with only two components to the structure forward of the dewar,
which in turn has minimal feedthroughs and permeation areas and holds
a vacuum <10<SUP>-8</SUP> Torr. A custom shutter was also designed,
using pneumatics as the driving force. This device provides exceptional
performance and reduces heat near the optical path. Measured performance
is repeatable at the 2ms level and offers field uniformity to the same
level of precision. The ARCTIC facility imager will provide excellent
science capability with robust operation and minimal maintenance for
the next decade or more at APO.
---------------------------------------------------------
Title: Flares In Time-Domain Surveys
Authors: Kowalski, Adam; Hawley, Suzanne; Davenport, James; Berlicki,
Arkadiusz; Cauzzi, Gianna; Fletcher, Lyndsay; Heinzel, Petr; Notsu,
Yuta; Loyd, Parke; Martinez Oliveros, Juan Carlos; Pugh, Chloe;
Schmidt, Sarah Jane; Karmakar, Subhajeet; Pye, John; Flaccomio, Ettore
2016csss.confE.126K Altcode:
Proceedings for the splinter session "Flares in Time-Domain Surveys"
convened at Cool Stars 19 on June 07, 2016 in Uppsala, Sweden. Contains
a two page summary of the splinter session, links to YouTube talks,
and a PDF copy of the slides from the presenters.
---------------------------------------------------------
Title: Maximizing Science in the Era of LSST, Stars Study Group
Report: Rotation and Magnetic Activity in the Galactic Field
Population and in Open Star Clusters
Authors: Hawley, Suzanne L.; Angus, Ruth; Buzasi, Derek; Davenport,
James R. A.; Giampapa, Mark; Kashyap, Vinay; Meibom, Soren
2016arXiv160704302H Altcode:
This is the stars chapter of the Kavli workshop report, which resulted
from the community-based study of needed US OIR capabilities in
the LSST era. The full report, which will include this chapter,
is anticipated to be available in Fall 2016. See NOAO website
(http://www.noao.edu/meetings/lsst-oir-study/) for more details.
---------------------------------------------------------
Title: The MUSCLES Treasury Survey. I. Motivation and Overview
Authors: France, Kevin; Loyd, R. O. Parke; Youngblood, Allison;
Brown, Alexander; Schneider, P. Christian; Hawley, Suzanne L.;
Froning, Cynthia S.; Linsky, Jeffrey L.; Roberge, Aki; Buccino,
Andrea P.; Davenport, James R. A.; Fontenla, Juan M.; Kaltenegger,
Lisa; Kowalski, Adam F.; Mauas, Pablo J. D.; Miguel, Yamila; Redfield,
Seth; Rugheimer, Sarah; Tian, Feng; Vieytes, Mariela C.; Walkowicz,
Lucianne M.; Weisenburger, Kolby L.
2016ApJ...820...89F Altcode: 2016arXiv160209142F
Ground- and space-based planet searches employing radial velocity
techniques and transit photometry have detected thousands
of planet-hosting stars in the Milky Way. With so many planets
discovered, the next step toward identifying potentially habitable
planets is atmospheric characterization. While the Sun-Earth system
provides a good framework for understanding the atmospheric chemistry
of Earth-like planets around solar-type stars, the observational
and theoretical constraints on the atmospheres of rocky planets in
the habitable zones (HZs) around low-mass stars (K and M dwarfs) are
relatively few. The chemistry of these atmospheres is controlled by the
shape and absolute flux of the stellar spectral energy distribution
(SED), however, flux distributions of relatively inactive low-mass
stars are poorly understood at present. To address this issue, we
have executed a panchromatic (X-ray to mid-IR) study of the SEDs of
11 nearby planet-hosting stars, the Measurements of the Ultraviolet
Spectral Characteristics of Low-mass Exoplanetary Systems (MUSCLES)
Treasury Survey. The MUSCLES program consists visible observations from
Hubble and ground-based observatories. Infrared and astrophysically
inaccessible wavelengths (EUV and Lyα) are reconstructed using
stellar model spectra to fill in gaps in the observational data. In
this overview and the companion papers describing the MUSCLES survey,
we show that energetic radiation (X-ray and ultraviolet) is present from
magnetically active stellar atmospheres at all times for stars as late
as M6. The emission line luminosities of C IV and Mg II are strongly
correlated with band-integrated luminosities and we present empirical
relations that can be used to estimate broadband FUV and XUV (≡X-ray +
EUV) fluxes from individual stellar emission line measurements. We find
that while the slope of the SED, FUV/NUV, increases by approximately
two orders of magnitude form early K to late M dwarfs (≈0.01-1), the
absolute FUV and XUV flux levels at their corresponding HZ distances
are constant to within factors of a few, spanning the range 10-70 erg
cm<SUP>-2</SUP> s<SUP>-1</SUP> in the HZ. Despite the lack of strong
stellar activity indicators in their optical spectra, several of the
M dwarfs in our sample show spectacular UV flare emission in their
light curves. We present an example with flare/quiescent ultraviolet
flux ratios of the order of 100:1 where the transition region
energy output during the flare is comparable to the total quiescent
luminosity of the star E<SUB>flare</SUB>(UV) ∼ 0.3 L<SUB>*</SUB>Δt
(Δt = 1 s). Finally, we interpret enhanced L(line)/L<SUB>Bol</SUB>
ratios for C IV and N v as tentative observational evidence for the
interaction of planets with large planetary mass-to-orbital distance
ratios (M<SUB>plan</SUB>/a<SUB>plan</SUB>) with the transition regions
of their host stars. <P />Based on observations made with the NASA/ESA
Hubble Space Telescope, obtained from the data archive at the Space
Telescope Science Institute. STScI is operated by the Association
of Universities for Research in Astronomy, Inc. under NASA contract
NAS 5-26555.
---------------------------------------------------------
Title: M Dwarf Flare Continuum Variations on One-second Timescales:
Calibrating and Modeling of ULTRACAM Flare Color Indices
Authors: Kowalski, Adam F.; Mathioudakis, Mihalis; Hawley, Suzanne L.;
Wisniewski, John P.; Dhillon, Vik S.; Marsh, Tom R.; Hilton, Eric J.;
Brown, Benjamin P.
2016ApJ...820...95K Altcode: 2016arXiv160204879K
We present a large data set of high-cadence dMe flare light curves
obtained with custom continuum filters on the triple-beam, high-speed
camera system ULTRACAM. The measurements provide constraints for models
of the near-ultraviolet (NUV) and optical continuum spectral evolution
on timescales of ≈1 s. We provide a robust interpretation of the
flare emission in the ULTRACAM filters using simultaneously obtained
low-resolution spectra during two moderate-sized flares in the dM4.5e
star YZ CMi. By avoiding the spectral complexity within the broadband
Johnson filters, the ULTRACAM filters are shown to characterize
bona fide continuum emission in the NUV, blue, and red wavelength
regimes. The NUV/blue flux ratio in flares is equivalent to a Balmer
jump ratio, and the blue/red flux ratio provides an estimate for the
color temperature of the optical continuum emission. We present a new
“color-color” relationship for these continuum flux ratios at the
peaks of the flares. Using the RADYN and RH codes, we interpret the
ULTRACAM filter emission using the dominant emission processes from a
radiative-hydrodynamic flare model with a high nonthermal electron beam
flux, which explains a hot, T ≈ 10<SUP>4</SUP> K, color temperature
at blue-to-red optical wavelengths and a small Balmer jump ratio as
observed in moderate-sized and large flares alike. We also discuss the
high time resolution, high signal-to-noise continuum color variations
observed in YZ CMi during a giant flare, which increased the NUV flux
from this star by over a factor of 100. <P />Based on observations
obtained with the Apache Point Observatory 3.5 m telescope, which is
owned and operated by the Astrophysical Research Consortium, based on
observations made with the William Herschel Telescope operated on the
island of La Palma by the Isaac Newton Group in the Spanish Observatorio
del Roque de los Muchachos of the Instituto de Astrofsica de Canarias,
and observations, and based on observations made with the ESO Telescopes
at the La Silla Paranal Observatory under programme ID 085.D-0501(A).
---------------------------------------------------------
Title: Synergy between solar and stellar flares: challenges and
perspectives
Authors: Hawley, Suzanne L.
2016IAUS..320..419H Altcode:
I will review the current status of stellar flare observations and
models, highlight similarities and differences with solar flares,
and plead for additional data and insight from the “Sun as a Star”.
---------------------------------------------------------
Title: Examining the ages of M7-L8 dwarfs with the BOSS Ultracool
Dwarf sample
Authors: Schmidt, Sarah J.; Hawley, Suzanne L.; West, Andrew A.;
Bochanski, John J.
2016AAS...22712103S Altcode:
We present the latest results from the BOSS Ultracool Dwarfs (BUD)
sample of 12998 M7-L8 dwarfs, identified from a combination of
photometry and spectroscopy from the Sloan Digital Sky Survey
(SDSS). Using a cross-match of the BUD sample to the Two Micron
All-Sky Survey (2MASS) and the Wide-field Infrared Survey Explorer
(WISE) catalogs, we measure both colors and proper motions for the
majority of the sample. The proper motions, combined with radial
velocities from SDSS spectra and updated distance estimates based on
i-Ks colors, yield three-dimensional velocities for 9121 ultracool
dwarfs. We usethese velocities as statistical proxies for age to
identify and test other potential age indicators, including H<span
style="line-height:20.8px">α</span> emission, atomic line
strengths, molecular band depths, and broad-band colors.
---------------------------------------------------------
Title: Solar and Stellar Flares and their Effects on Planets
Authors: Kosovichev, A. G.; Hawley, S. L.; Heinzel, P.
2016IAUS..320.....K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: New Insights into White-Light Flare Emission from
Radiative-Hydrodynamic Modeling of a Chromospheric Condensation
Authors: Kowalski, Adam F.; Hawley, S. L.; Carlsson, M.; Allred,
J. C.; Uitenbroek, H.; Osten, R. A.; Holman, G.
2015SoPh..290.3487K Altcode: 2015SoPh..tmp...61K; 2015arXiv150307057K
The heating mechanism at high densities during M-dwarf flares is
poorly understood. Spectra of M-dwarf flares in the optical and
near-ultraviolet wavelength regimes have revealed three continuum
components during the impulsive phase: 1) an energetically dominant
blackbody component with a color temperature of T ≈10<SUP>4</SUP>K
in the blue-optical, 2) a smaller amount of Balmer continuum emission
in the near-ultraviolet at λ ≤3 646 Å, and 3) an apparent
pseudo-continuum of blended high-order Balmer lines between λ =3
646 Å and λ ≈3 900 Å. These properties are not reproduced by
models that employ a typical "solar-type" flare heating level of
≤10<SUP>11</SUP>ergcm−<SUP>2</SUP>s−<SUP>1</SUP> in nonthermal
electrons, and therefore our understanding of these spectra is
limited to a phenomenological three-component interpretation. We
present a new 1D radiative-hydrodynamic model of an M-dwarf flare
from precipitating nonthermal electrons with a high energy flux of
10<SUP>13</SUP>ergcm−<SUP>2</SUP>s−<SUP>1</SUP>. The simulation
produces bright near-ultraviolet and optical continuum emission from a
dense (n >10<SUP>15</SUP>cm−<SUP>3</SUP>), hot (T ≈12 000 -13 500
K) chromospheric condensation. For the first time, the observed color
temperature and Balmer jump ratio are produced self-consistently in a
radiative-hydrodynamic flare model. We find that a T ≈10<SUP>4</SUP>K
blackbody-like continuum component and a low Balmer jump ratio result
from optically thick Balmer (∞ →n =2 ) and Paschen recombination
(∞ →n =3 ) radiation, and thus the properties of the flux spectrum
are caused by blue (λ ≈4 300 Å) light escaping over a larger
physical depth range than by red (λ ≈6 700 Å) and near-ultraviolet
(λ ≈3 500 Å) light. To model the near-ultraviolet pseudo-continuum
previously attributed to overlapping Balmer lines, we include the
extra Balmer continuum opacity from Landau-Zener transitions that
result from merged, high-order energy levels of hydrogen in a dense,
partially ionized atmosphere. This reveals a new diagnostic of ambient
charge density in the densest regions of the atmosphere that are heated
during dMe and solar flares.
---------------------------------------------------------
Title: Using Transiting Exoplanets to Study Starspots with Kepler
Authors: Davenport, James R. A.; Hebb, Leslie; Hawley, Suzanne
2015IAUGA..2257832D Altcode:
Starspots are a fundamental manifestation of stellar dynamos that
constrain the surface magnetic field strength and topology. Kepler
has already produced the first ensemble studies of starspots,
discovering rotation periods and rough spot properties for thousands
of stars across the main sequence. Here we study the G dwarf Kepler
17, which hosts a transiting 2.5 Jupiter mass exoplanet on a 1.5 day
orbit. Starspots are frequently occulted during transit, allowing us to
probe smaller-scale starspot regions on the stellar surface along the
projected path of the planet. These planet-spot occultations reveal the
presence of at least 7 unique starspot groups on the stellar surface
at any time. The spot crossings also give an empirical estimate of
the starspot temperature contrast, which we find are consistent
with the Solar umbra. Using over 4 years of data for Kepler 17,
we observe changes in the starspot positions and sizes indicative of
differential rotation and active region diffusion. Using an MCMC-based
light curve modeling code, we determine the positions and sizes of each
spot group over time. Our approach is novel in modeling both the in-
and out-of transit features in the light curve, allowing us to break
fundamental degeneracies between spot size, latitude, and contrast. This
technique constrains key properties for understanding stellar dynamos,
including the stellar rotation period, differential rotation rate,
and spot diffusion timescales.
---------------------------------------------------------
Title: Properties of Flares on GKM Stars in Kepler
Authors: Hawley, Suzanne; Davenport, James R. A.; Hebb, Leslie;
Kowalski, Adam Francis; Wisniewski, John
2015IAUGA..2253855H Altcode:
We analyze Kepler observations of G and K stars and determine flare
properties, frequencies and energies from both long and short cadence
data. We compare these with our previous results for M dwarfs and
investigate correlations with rotation, starspot phase, differential
rotation and starspot evolution.
---------------------------------------------------------
Title: Synergy Between Solar and Stellar Flares: Challenges and
Perspectives
Authors: Hawley, Suzanne
2015IAUGA..2250517H Altcode:
I will review the current status of stellar flare observations and
models, highlight similarities and differences with solar flares,
and plead for additional data and insight from the "Sun as a Star".
---------------------------------------------------------
Title: The search for star-planet interactions in eccentric systems
Authors: Hodgson, John, II; Christian, Damian; Hawley, Suzanne
2015IAUGA..2256241H Altcode:
We have undertaken a study to determine if the orbital geometry of
exoplanets affects the activity of their host stars by observing a
sample of planetary systems known to contain massive planets on short
period, highly elliptical orbits. While recent studies in the optical,
UV, and X-Ray have shown enhanced chromospheric activity for stars
hosting exoplanets with orbital semi-major axes less than 0.1 AU [1,
2, 3, 4], it is not yet clear whether this activity is driven by
magnetic or tidal interactions. In this study, we are probing the
dependence of star-planet interactions (SPI) on orbital geometry
in a selection of eccentric systems by analyzing the Ca II H &
K emission lines for variability phased with the planet's orbit. We
have obtained high resolution spectra of this systems with the ARCES on
the APO 3.5m from the Keck Observatory Archive. We shall describe our
methodology and review our results on how the orbital geometry of the
planet affects the activity of its host star.References[1] Krejcova,
T., & Budaj, J., 2012, A&A, 540, A82[2] Shkolnik, E., 2013,
ApJ pre-print from arXiv:1301.6192v1[3] Kashyap, V.L., Drake, J.J.,
& Saar, S.H., 2008, ApJ, 687, 1339[4] Poppenhaeger, K., Robrade,
J., & Schmitt, J.H., 2010, A&A, 515, A98
---------------------------------------------------------
Title: The Eleventh and Twelfth Data Releases of the Sloan Digital
Sky Survey: Final Data from SDSS-III
Authors: Alam, Shadab; Albareti, Franco D.; Allende Prieto, Carlos;
Anders, F.; Anderson, Scott F.; Anderton, Timothy; Andrews, Brett
H.; Armengaud, Eric; Aubourg, Éric; Bailey, Stephen; Basu, Sarbani;
Bautista, Julian E.; Beaton, Rachael L.; Beers, Timothy C.; Bender,
Chad F.; Berlind, Andreas A.; Beutler, Florian; Bhardwaj, Vaishali;
Bird, Jonathan C.; Bizyaev, Dmitry; Blake, Cullen H.; Blanton, Michael
R.; Blomqvist, Michael; Bochanski, John J.; Bolton, Adam S.; Bovy,
Jo; Shelden Bradley, A.; Brandt, W. N.; Brauer, D. E.; Brinkmann,
J.; Brown, Peter J.; Brownstein, Joel R.; Burden, Angela; Burtin,
Etienne; Busca, Nicolás G.; Cai, Zheng; Capozzi, Diego; Carnero
Rosell, Aurelio; Carr, Michael A.; Carrera, Ricardo; Chambers,
K. C.; Chaplin, William James; Chen, Yen-Chi; Chiappini, Cristina;
Chojnowski, S. Drew; Chuang, Chia-Hsun; Clerc, Nicolas; Comparat,
Johan; Covey, Kevin; Croft, Rupert A. C.; Cuesta, Antonio J.; Cunha,
Katia; da Costa, Luiz N.; Da Rio, Nicola; Davenport, James R. A.;
Dawson, Kyle S.; De Lee, Nathan; Delubac, Timothée; Deshpande,
Rohit; Dhital, Saurav; Dutra-Ferreira, Letícia; Dwelly, Tom; Ealet,
Anne; Ebelke, Garrett L.; Edmondson, Edward M.; Eisenstein, Daniel J.;
Ellsworth, Tristan; Elsworth, Yvonne; Epstein, Courtney R.; Eracleous,
Michael; Escoffier, Stephanie; Esposito, Massimiliano; Evans, Michael
L.; Fan, Xiaohui; Fernández-Alvar, Emma; Feuillet, Diane; Filiz Ak,
Nurten; Finley, Hayley; Finoguenov, Alexis; Flaherty, Kevin; Fleming,
Scott W.; Font-Ribera, Andreu; Foster, Jonathan; Frinchaboy, Peter M.;
Galbraith-Frew, J. G.; García, Rafael A.; García-Hernández, D. A.;
García Pérez, Ana E.; Gaulme, Patrick; Ge, Jian; Génova-Santos,
R.; Georgakakis, A.; Ghezzi, Luan; Gillespie, Bruce A.; Girardi, Léo;
Goddard, Daniel; Gontcho, Satya Gontcho A.; González Hernández, Jonay
I.; Grebel, Eva K.; Green, Paul J.; Grieb, Jan Niklas; Grieves, Nolan;
Gunn, James E.; Guo, Hong; Harding, Paul; Hasselquist, Sten; Hawley,
Suzanne L.; Hayden, Michael; Hearty, Fred R.; Hekker, Saskia; Ho,
Shirley; Hogg, David W.; Holley-Bockelmann, Kelly; Holtzman, Jon A.;
Honscheid, Klaus; Huber, Daniel; Huehnerhoff, Joseph; Ivans, Inese
I.; Jiang, Linhua; Johnson, Jennifer A.; Kinemuchi, Karen; Kirkby,
David; Kitaura, Francisco; Klaene, Mark A.; Knapp, Gillian R.; Kneib,
Jean-Paul; Koenig, Xavier P.; Lam, Charles R.; Lan, Ting-Wen; Lang,
Dustin; Laurent, Pierre; Le Goff, Jean-Marc; Leauthaud, Alexie; Lee,
Khee-Gan; Lee, Young Sun; Licquia, Timothy C.; Liu, Jian; Long,
Daniel C.; López-Corredoira, Martín; Lorenzo-Oliveira, Diego;
Lucatello, Sara; Lundgren, Britt; Lupton, Robert H.; Mack, Claude E.,
III; Mahadevan, Suvrath; Maia, Marcio A. G.; Majewski, Steven R.;
Malanushenko, Elena; Malanushenko, Viktor; Manchado, A.; Manera, Marc;
Mao, Qingqing; Maraston, Claudia; Marchwinski, Robert C.; Margala,
Daniel; Martell, Sarah L.; Martig, Marie; Masters, Karen L.; Mathur,
Savita; McBride, Cameron K.; McGehee, Peregrine M.; McGreer, Ian D.;
McMahon, Richard G.; Ménard, Brice; Menzel, Marie-Luise; Merloni,
Andrea; Mészáros, Szabolcs; Miller, Adam A.; Miralda-Escudé, Jordi;
Miyatake, Hironao; Montero-Dorta, Antonio D.; More, Surhud; Morganson,
Eric; Morice-Atkinson, Xan; Morrison, Heather L.; Mosser, Benôit;
Muna, Demitri; Myers, Adam D.; Nandra, Kirpal; Newman, Jeffrey A.;
Neyrinck, Mark; Nguyen, Duy Cuong; Nichol, Robert C.; Nidever,
David L.; Noterdaeme, Pasquier; Nuza, Sebastián E.; O'Connell,
Julia E.; O'Connell, Robert W.; O'Connell, Ross; Ogando, Ricardo
L. C.; Olmstead, Matthew D.; Oravetz, Audrey E.; Oravetz, Daniel J.;
Osumi, Keisuke; Owen, Russell; Padgett, Deborah L.; Padmanabhan,
Nikhil; Paegert, Martin; Palanque-Delabrouille, Nathalie; Pan, Kaike;
Parejko, John K.; Pâris, Isabelle; Park, Changbom; Pattarakijwanich,
Petchara; Pellejero-Ibanez, M.; Pepper, Joshua; Percival, Will J.;
Pérez-Fournon, Ismael; Pérez-Ràfols, Ignasi; Petitjean, Patrick;
Pieri, Matthew M.; Pinsonneault, Marc H.; Porto de Mello, Gustavo
F.; Prada, Francisco; Prakash, Abhishek; Price-Whelan, Adrian M.;
Protopapas, Pavlos; Raddick, M. Jordan; Rahman, Mubdi; Reid, Beth A.;
Rich, James; Rix, Hans-Walter; Robin, Annie C.; Rockosi, Constance M.;
Rodrigues, Thaíse S.; Rodríguez-Torres, Sergio; Roe, Natalie A.;
Ross, Ashley J.; Ross, Nicholas P.; Rossi, Graziano; Ruan, John J.;
Rubiño-Martín, J. A.; Rykoff, Eli S.; Salazar-Albornoz, Salvador;
Salvato, Mara; Samushia, Lado; Sánchez, Ariel G.; Santiago, Basílio;
Sayres, Conor; Schiavon, Ricardo P.; Schlegel, David J.; Schmidt,
Sarah J.; Schneider, Donald P.; Schultheis, Mathias; Schwope, Axel
D.; Scóccola, C. G.; Scott, Caroline; Sellgren, Kris; Seo, Hee-Jong;
Serenelli, Aldo; Shane, Neville; Shen, Yue; Shetrone, Matthew; Shu,
Yiping; Silva Aguirre, V.; Sivarani, Thirupathi; Skrutskie, M. F.;
Slosar, Anže; Smith, Verne V.; Sobreira, Flávia; Souto, Diogo;
Stassun, Keivan G.; Steinmetz, Matthias; Stello, Dennis; Strauss,
Michael A.; Streblyanska, Alina; Suzuki, Nao; Swanson, Molly E. C.;
Tan, Jonathan C.; Tayar, Jamie; Terrien, Ryan C.; Thakar, Aniruddha
R.; Thomas, Daniel; Thomas, Neil; Thompson, Benjamin A.; Tinker,
Jeremy L.; Tojeiro, Rita; Troup, Nicholas W.; Vargas-Magaña, Mariana;
Vazquez, Jose A.; Verde, Licia; Viel, Matteo; Vogt, Nicole P.; Wake,
David A.; Wang, Ji; Weaver, Benjamin A.; Weinberg, David H.; Weiner,
Benjamin J.; White, Martin; Wilson, John C.; Wisniewski, John P.;
Wood-Vasey, W. M.; Ye`che, Christophe; York, Donald G.; Zakamska,
Nadia L.; Zamora, O.; Zasowski, Gail; Zehavi, Idit; Zhao, Gong-Bo;
Zheng, Zheng; Zhou, Xu; Zhou, Zhimin; Zou, Hu; Zhu, Guangtun
2015ApJS..219...12A Altcode: 2015arXiv150100963A
The third generation of the Sloan Digital Sky Survey (SDSS-III) took
data from 2008 to 2014 using the original SDSS wide-field imager, the
original and an upgraded multi-object fiber-fed optical spectrograph,
a new near-infrared high-resolution spectrograph, and a novel optical
interferometer. All of the data from SDSS-III are now made public. In
particular, this paper describes Data Release 11 (DR11) including all
data acquired through 2013 July, and Data Release 12 (DR12) adding data
acquired through 2014 July (including all data included in previous
data releases), marking the end of SDSS-III observing. Relative to our
previous public release (DR10), DR12 adds one million new spectra of
galaxies and quasars from the Baryon Oscillation Spectroscopic Survey
(BOSS) over an additional 3000 deg<SUP>2</SUP> of sky, more than
triples the number of H-band spectra of stars as part of the Apache
Point Observatory (APO) Galactic Evolution Experiment (APOGEE), and
includes repeated accurate radial velocity measurements of 5500 stars
from the Multi-object APO Radial Velocity Exoplanet Large-area Survey
(MARVELS). The APOGEE outputs now include the measured abundances of
15 different elements for each star. In total, SDSS-III added 5200
deg<SUP>2</SUP> of ugriz imaging; 155,520 spectra of 138,099 stars as
part of the Sloan Exploration of Galactic Understanding and Evolution
2 (SEGUE-2) survey; 2,497,484 BOSS spectra of 1,372,737 galaxies,
294,512 quasars, and 247,216 stars over 9376 deg<SUP>2</SUP>; 618,080
APOGEE spectra of 156,593 stars; and 197,040 MARVELS spectra of 5513
stars. Since its first light in 1998, SDSS has imaged over 1/3 of
the Celestial sphere in five bands and obtained over five million
astronomical spectra.
---------------------------------------------------------
Title: Detecting Differential Rotation and Starspot Evolution on
the M Dwarf GJ 1243 with Kepler
Authors: Davenport, James R. A.; Hebb, Leslie; Hawley, Suzanne L.
2015ApJ...806..212D Altcode: 2015arXiv150501524D
We present an analysis of the starspots on the active M4 dwarf GJ
1243, using 4 years of time series photometry from Kepler. A rapid P =
0.592596 ± 0.00021 days rotation period is measured due to the ∼2.2%
starspot-induced flux modulations in the light curve. We first use a
light curve modeling approach, using a Monte Carlo Markov Chain sampler
to solve for the longitudes and radii of the two spots within 5 day
windows of data. Within each window of time the starspots are assumed
to be unchanging. Only a weak constraint on the starspot latitudes
can be implied from our modeling. The primary spot is found to be
very stable over many years. A secondary spot feature is present in
three portions of the light curve, decays on 100-500 day timescales,
and moves in longitude over time. We interpret this longitude shearing
as the signature of differential rotation. Using our models we measure
an average shear between the starspots of 0.0047 rad day<SUP>-1</SUP>,
which corresponds to a differential rotation rate of Δ{Ω } = 0.012 ±
0.002 rad day<SUP>-1</SUP>. We also fit this starspot phase evolution
using a series of bivariate Gaussian functions, which provides a
consistent shear measurement. This is among the slowest differential
rotation shear measurements yet measured for a star in this temperature
regime, and provides an important constraint for dynamo models of
low-mass stars.
---------------------------------------------------------
Title: The Time Domain Spectroscopic Survey: Variable Selection and
Anticipated Results
Authors: Morganson, Eric; Green, Paul J.; Anderson, Scott F.; Ruan,
John J.; Myers, Adam D.; Eracleous, Michael; Kelly, Brandon; Badenes,
Carlos; Bañados, Eduardo; Blanton, Michael R.; Bershady, Matthew
A.; Borissova, Jura; Brandt, William Nielsen; Burgett, William
S.; Chambers, Kenneth; Draper, Peter W.; Davenport, James R. A.;
Flewelling, Heather; Garnavich, Peter; Hawley, Suzanne L.; Hodapp,
Klaus W.; Isler, Jedidah C.; Kaiser, Nick; Kinemuchi, Karen; Kudritzki,
Rolf P.; Metcalfe, Nigel; Morgan, Jeffrey S.; Pâris, Isabelle;
Parvizi, Mahmoud; Poleski, Radosław; Price, Paul A.; Salvato, Mara;
Shanks, Tom; Schlafly, Eddie F.; Schneider, Donald P.; Shen, Yue;
Stassun, Keivan; Tonry, John T.; Walter, Fabian; Waters, Chris Z.
2015ApJ...806..244M Altcode: 2015arXiv150500760M
We present the selection algorithm and anticipated results for the
Time Domain Spectroscopic Survey (TDSS). TDSS is an Sloan Digital
Sky Survey (SDSS)-IV Extended Baryon Oscillation Spectroscopic Survey
(eBOSS) subproject that will provide initial identification spectra
of approximately 220,000 luminosity-variable objects (variable stars
and active galactic nuclei across 7500 deg<SUP>2</SUP> selected from a
combination of SDSS and multi-epoch Pan-STARRS1 photometry. TDSS will be
the largest spectroscopic survey to explicitly target variable objects,
avoiding pre-selection on the basis of colors or detailed modeling of
specific variability characteristics. Kernel Density Estimate analysis
of our target population performed on SDSS Stripe 82 data suggests our
target sample will be 95% pure (meaning 95% of objects we select have
genuine luminosity variability of a few magnitudes or more). Our final
spectroscopic sample will contain roughly 135,000 quasars and 85,000
stellar variables, approximately 4000 of which will be RR Lyrae stars
which may be used as outer Milky Way probes. The variability-selected
quasar population has a smoother redshift distribution than a
color-selected sample, and variability measurements similar to those
we develop here may be used to make more uniform quasar samples in
large surveys. The stellar variable targets are distributed fairly
uniformly across color space, indicating that TDSS will obtain spectra
for a wide variety of stellar variables including pulsating variables,
stars with significant chromospheric activity, cataclysmic variables,
and eclipsing binaries. TDSS will serve as a pathfinder mission to
identify and characterize the multitude of variable objects that will
be detected photometrically in even larger variability surveys such
as Large Synoptic Survey Telescope.
---------------------------------------------------------
Title: Characterizing the Habitable Zones of Exoplanetary Systems
with a Large Ultraviolet/Visible/Near-IR Space Observatory
Authors: France, Kevin; Shkolnik, Evgenya; Linsky, Jeffrey; Roberge,
Aki; Ayres, Thomas; Barman, Travis; Brown, Alexander; Davenport,
James; Desert, Jean-Michel; Domagal-Goldman, Shawn; Fleming, Brian;
Fontenla, Juan; Fossati, Luca; Froning, Cynthia; Hallinan, Gregg;
Hawley, Suzanne; Hu, Renyu; Kaltenegger, Lisa; Kasting, James;
Kowlaski, Adam; Loyd, Parke; Mauas, Pablo; Miguel, Yamila; Osten,
Rachel; Redfield, Seth; Rugheimer, Sarah; Schneider, Christian; Segura,
Antigona; Stocke, John; Tian, Feng; Tumlinson, Jason; Vieytes, Mariela;
Walkowicz, Lucianne; Wood, Brian; Youngblood, Allison
2015arXiv150501840F Altcode:
Understanding the surface and atmospheric conditions of Earth-size,
rocky planets in the habitable zones (HZs) of low-mass stars is
currently one of the greatest astronomical endeavors. Knowledge of
the planetary effective surface temperature alone is insufficient
to accurately interpret biosignature gases when they are observed
in the coming decades. The UV stellar spectrum drives and regulates
the upper atmospheric heating and chemistry on Earth-like planets,
is critical to the definition and interpretation of biosignature
gases, and may even produce false-positives in our search for biologic
activity. This white paper briefly describes the scientific motivation
for panchromatic observations of exoplanetary systems as a whole (star
and planet), argues that a future NASA UV/Vis/near-IR space observatory
is well-suited to carry out this work, and describes technology
development goals that can be achieved in the next decade to support
the development of a UV/Vis/near-IR flagship mission in the 2020s.
---------------------------------------------------------
Title: BOSS Ultracool Dwarfs. I. Colors and Magnetic Activity of M
and L Dwarfs
Authors: Schmidt, Sarah J.; Hawley, Suzanne L.; West, Andrew A.;
Bochanski, John J.; Davenport, James R. A.; Ge, Jian; Schneider,
Donald P.
2015AJ....149..158S Altcode: 2014arXiv1410.0014S
We present the colors and activity of ultracool (M7-L8) dwarfs from the
Tenth Data Release of the Sloan Digital Sky Survey (SDSS). We combine
previous samples of SDSS M and L dwarfs with new data obtained from
the Baryon Oscillation Sky Survey (BOSS) to produce the BOSS Ultracool
Dwarf (BUD) sample of 11820 M7-L8 dwarfs. By combining SDSS data with
photometry from 2MASS and the Wide-field Infrared Sky Explorer (WISE)
mission, we present ultracool dwarf colors from i-z to W2-W3 as a
function of spectral type, and extend the SDSS-2MASS-WISE color locus to
include ultracool dwarfs. The i-z, i-J, and z-J colors provide the best
indication of spectral type for M7-L3 dwarfs. We also examine ultracool
dwarf chromospheric activity through the presence and strength of Hα
emission. The fraction of active dwarfs rises through the M spectral
sequence until it reaches ∼90% at spectral type L0. The fraction
of active dwarfs then declines to 50% at spectral type L5; no Hα
emission is observed in the late-L dwarfs in the BUD sample. The
fraction of active L0-L5 dwarfs is much higher than previously
observed. The strength of activity declines with spectral type from
M7 through L3, after which the data do not show a clear trend. Using
one-dimensional chromosphere models, we explore the range of filling
factors and chromospheric temperature structures that are consistent
with Hα observations of M0-L7 dwarfs. M dwarf chromospheres have a
similar, smoothly varying range of temperature and surface coverage,
while L dwarf chromospheres are cooler and have smaller filling factors.
---------------------------------------------------------
Title: State-of-the-Art Observations and Modeling of Stellar Flares
Authors: Kowalski, Adam F.; Hawley, Suzanne L.
2015HiA....16...99K Altcode:
Flares are observed on a wide variety of stellar types, ranging from
closely orbiting binary systems consisting of an evolved member (RS
CVn's) and young, nearby super-active M dwarfs (dMe's). The timescales
and energies of flares span many orders of magnitude and typically
far exceed the scales of even the largest solar flares observed. In
particular, the active M dwarfs produce an energetic signature in
the near-UV and optical continuum, which is often referred to as
the white-light continuum. White-light emission has been studied in
Johnson UBVR filters during a few large-amplitude flares, and the best
emission mechanism that fits the broadband color distribution is a
T~10<SUP>4</SUP> K blackbody (Hawley & Fisher 1992). Time-resolved
blue spectra have revealed a consistent picture, with little or
no Balmer jump and a smoothly rising continuum toward the near-UV
(Hawley & Pettersen 1991). However, the most recent self-consistent
radiative-hydrodynamic (RHD) models, which use a solar-type flare
heating function from accelerated, nonthermal electrons, do not
reproduce this emission spectrum. Instead, these models predict that
the white-light is dominated by Balmer continuum emission from Hydrogen
recombination in the chromosphere (Allred et al. 2006). Moreover, Allred
et al. (2006) showed that the Johnson colors of the model prediction
exhibit a broadband distribution similar to a blackbody with T~9000 K.
---------------------------------------------------------
Title: Serendipitous Discovery of a Dwarf Nova in the Kepler Field
Near the G Dwarf KIC 5438845
Authors: Brown, Alexander; Neff, James E.; Ayres, Thomas R.; Kowalski,
Adam; Hawley, Suzanne; Berdyugina, Svetlana; Harper, Graham M.;
Korhonen, Heidi; Piskunov, Nikolai; Saar, Steven; Walkowicz, Lucianne;
Wells, Mark A.
2015AJ....149...67B Altcode:
The Kepler satellite provides a unique window into stellar temporal
variability by observing a wide variety of stars with multi-year,
near-continuous, high precision, optical photometric time series. While
most Kepler targets are faint stars with poorly known physical
properties, many unexpected discoveries should result from a long
photometric survey of such a large area of sky. During our Kepler
Guest Observer programs that monitored late-type stars for starspot and
flaring variability, we discovered a previously unknown dwarf nova that
lies within a few arcseconds of the mid-G dwarf star KIC 5438845. This
dwarf nova underwent nine outbursts over a 4 year time span. The two
largest outbursts lasted ∼17-18 days and show strong modulations with
a 110.8 minute period and a declining amplitude during the outburst
decay phase. These properties are characteristic of an SU UMa-type
cataclysmic variable. By analogy with other dwarf nova light curves,
we associate the 110.8 minute (1.847 hr) period with the superhump
period, close to but slightly longer than the orbital period of the
binary. No precursor outbursts are seen before the super-outbursts
and the overall super-outburst morphology corresponds to Osaki &
Meyer “Case B” outbursts, which are initiated when the outer edge
of the disk reaches the tidal truncation radius. “Case B” outbursts
are rare within the Kepler light curves of dwarf novae. The dwarf nova
is undergoing relatively slow mass transfer, as evidenced by the long
intervals between outbursts, but the mass transfer rate appears to
be steady, because the smaller “normal” outbursts show a strong
correlation between the integrated outburst energy and the elapsed time
since the previous outburst. At super-outburst maximum the system was
at V ∼ 18, but in quiescence it is fainter than V ∼ 22, which will
make any detailed quiescent follow-up of this system difficult.
---------------------------------------------------------
Title: Kepler Flares III: Stellar Activity on GJ 1245A and B
Authors: Lurie, John C.; Davenport, James R. A.; Hawley, Suzanne L.;
Wilkinson, Tessa D.; Wisniewski, John P.; Kowalski, Adam F.; Hebb,
Leslie
2015ApJ...800...95L Altcode: 2014arXiv1412.6109L
We present the flare occurrence rates and starspot evolution for GJ
1245A and B, two active M5 stars, based on nine months of Kepler short
cadence observations, and four years of nearly continuous long cadence
observations. The A component is separated from the B component by 7”,
and the stars are not resolved in the Kepler pipeline processing due
to Kepler's large plate scale of 4” pixel<SUP>-1</SUP>. Analyzing
the target pixel data, we have generated separate light curves for
components A and B using the PyKE pixel response function modeling
procedures, and note the effects of CCD saturation and nonlinear
response to high-energy flares. In our sample, GJ 1245A and B exhibit
an average of 3.0 and 2.6 flares per day, respectively. We introduce
a new metric, L<SUB>fl</SUB> /L <SUB>Kp</SUB>, to compare the flare
rates between stars, and discuss this in the context of GJ 1245A and
B. Both stars exhibit starspot features that evolve on long timescales,
with the slower rotating B component showing evidence of differential
rotation. Intriguingly, the angular separation between the A and B
component photocenters decreases during the four years of observations
in a manner consistent with a shift in the position of the A photocenter
due to the orbit of its unseen M8 companion (GJ 1245C), which is ~94%
less bright. Among the most detailed photometric studies of fully
convective M dwarfs in a multiple system, these results provide an
important constraint on stellar age-rotation-activity models.
---------------------------------------------------------
Title: Flare Rate and Statistics for the M Dwarf GJ 1243 With Kepler
Authors: Johnson, Emily; Davenport, James R. A.; Hawley, Suzanne L.
2015AAS...22523902J Altcode:
Light curve data taken from the Kepler space telescope have been used
to detect stellar flares. These data are a valuable resource for the
study of flare rates and morphology, but currently flare samples must
be validated by hand. FBEye (Flares By Eye) is an interactive program
created to detect and manually validate these flares, with the goal
of removing the need for human input. As a first year undergraduate
student, I participated in this project by analyzing Kepler light
curves and vetting stellar flares. Using 11 months of one-minute
cadence data from GJ 1243, an M dwarf star, we classified each flare
by energy and morphology. This work has been used to refine the FBEye
program, which will eventually be applied to the entire catalogue of
Kepler data. It is also part of a research paper on GJ 1243, which is
currently in the publication process.
---------------------------------------------------------
Title: Time-Resolved Near-Ultraviolet Flare Spectra with the Hubble
Space Telescope / Cosmic Origins Spectrograph
Authors: Kowalski, Adam F.; Hawley, Suzanne L.; Johns-Krull,
Christopher M.; Schmidt, Sarah J.; Brown, Alexander; Wisniewski, John
P.; Davenport, James R. A.; Farina, Cecilia; Pietro Gentile Fusillo,
Nicola; Xilouris, Manolis; Mathioudakis, Mihalis; Osten, Rachel A.;
Holtzman, Jon A.; Phan-Bao, Ngoc; Valenti, Jeff A.; Walkowicz, Lucianne
2015AAS...22544903K Altcode:
A large amount of the radiated energy during solar and stellar flares
is emitted as white-light continuum emission, extending through the
ultraviolet and optical wavelength regimes. Broadband photometry
and optical spectral observations of M dwarf flares suggest that the
white-light peak is located in the near-ultraviolet wavelength regime
similar to a blackbody with T ~ 10,000 K, whereas radiative-hydrodynamic
models using a solar-type flare heating mechanism (nonthermal electrons
with a flux ~ 10<SUP>11</SUP> erg / s / cm<SUP>2</SUP> accelerated in
the corona) predict that the peak lies at redder wavelengths at the
head of the Balmer continuum. We have completed a successful flare
monitoring campaign on the dM4e star GJ 1243, in order to constrain
the time-evolution of the peak of the white-light continuum. The
campaign took place over 12 hours on Aug 31/Sept 1, 2014, and included
optical monitoring from nine ground-based telescopes as the Hubble
Space Telescope recorded time-tagged spectra in the near-ultraviolet
(2450-2840 Å) with the Cosmic Origins Spectrograph. Two flares occurred
during the HST observations, and we show preliminary results relating
the continuum and line (Fe II and Mg II) emission to the simultaneous
ground-based optical spectra and photometry. This dataset provides new
constraints for radiative-hydrodynamic modeling of the lower flaring
atmosphere in addition to input for models of the effects of flares
on biomarkers and habitability around M dwarfs.
---------------------------------------------------------
Title: The Continued Optical to Mid-Infrared Evolution of V838
Monocerotis
Authors: Loebman, S. R.; Wisniewski, J. P.; Schmidt, S. J.; Kowalski,
A. F.; Barry, R. K.; Bjorkman, K. S.; Hammel, H. B.; Hawley, S. L.;
Hebb, L.; Kasliwal, M. M.; Lynch, D. K.; Russell, R. W.; Sitko, M. L.;
Szkody, P.
2015AJ....149...17L Altcode: 2014arXiv1409.2513L
The eruptive variable V838 Monocerotis (V838 Mon) gained notoriety in
2002 when it brightened nine magnitudes in a series of three outbursts
and then rapidly evolved into an extremely cool supergiant. We
present optical, near-infrared (near-IR), and mid-IR spectroscopic
and photometric observations of V838 Mon obtained between 2008 and
2012 at the Apache Point Observatory 3.5 m, NASA IRTF 3 m, and Gemini
South 8 m telescopes. We contemporaneously analyze the optical and IR
spectroscopic properties of V838 Mon to arrive at a revised spectral
type L3 supergiant and effective temperature {{T}<SUB>eff</SUB>}∼
2000-2200 K. Because there are no existing optical observational
data for L supergiants, we speculate that V838 Mon may represent
the prototype for L supergiants in this wavelength regime. We find
a low level of Hα emission present in the system, consistent with
interaction between V838 Mon and its B3V binary; however, we cannot
rule out a stellar collision as the genesis event, which could result
in the observed Hα activity. Based upon a two-component blackbody
fit to all wavelengths of our data, we conclude that, as of 2009,
a shell of ejecta surrounded V838 Mon at a radius of R=263+/- 10 AU
with a temperature of T=285+/- 2 K. This result is consistent with
IR interferometric observations from the same era and predictions
from the Lynch et al. model of the expanding system, which provides a
simple framework for understanding this complicated system. <P />This
publication is partially based on observations obtained with the Apache
Point Observatory 3.5 m telescope, which is owned and operated by the
Astrophysical Research Consortium.
---------------------------------------------------------
Title: The Stellar Activity of an M Dwarf Binary from Deconvolved
Kepler Light Curves
Authors: Lurie, John C.; Davenport, James R. A.; Hawley, Suzanne L.;
Wilkinson, Tessa D.
2015AAS...22522906L Altcode:
The M5+M5 pair GJ 1245AB was monitored almost continuously by Kepler
for four years, providing a unique opportunity to study the stellar
activity of two coeval, nearly-equal mass M dwarfs that are fully
convective. The stars are 7" apart on the sky, and separate light
curves for each star cannot be generated via aperture photometry due
to Kepler's large 4"/pixel plate scale. Instead, we generated separate
light curves from the target pixel files using the PyKE pixel response
function modeling procedures. Intriguingly, the angular separation of
the two stars decreases over the four years of Kepler observations in
a manner consistent with an astrometric perturbation from the much
fainter, unseen M8 (GJ 1245C) companion to GJ 1245A. Analyzing the
separated light curves, we observe long lived starspot features on
both stars that evolve on multi-year timescales. Both stars flare at
nearly the same rate, despite having rotation rates that differ by
almost a factor of three. Consistent with recent studies of active M
dwarf binaries, these results provide further insight into the roles
of age and rotation rate in stellar activity.
---------------------------------------------------------
Title: The APOGEE Low-Mass Star Ancillary Project
Authors: Blake, Cullen; Mahadevan, Suvrath; Deshpande, Rohit; Bender,
Chad F.; Terrien, Ryan; Crepp, Justin R.; Carlberg, Joleen K.;
Nidever, David L.; Stassun, Keivan; Hawley, Suzanne L.; Hearty, Fred;
Allende-Prieto, Carlos
2015AAS...22530205B Altcode:
As a high-resolution, near-infrared, fiber-fed instrument, APOGEE
presents a unique opportunity to obtain multi-epoch radial velocity
measurements of a large number of low-mass stars. These observations
will reveal unseen companions, improving our understanding of
stellar multiplicity at the bottom of the Main Sequence, and may even
identify candidate sub-stellar companions. These same data contains an
unprecedented wealth of information about the kinematics, rotation,
and metallicities of these stars. I will describe the status of our
Ancillary Science program, and ongoing efforts to get the best possible
radial velocity precision from the APOGEE data.
---------------------------------------------------------
Title: Ground-based Data on Kepler Eclipsing Binaries
Authors: Wilkinson, Tessa D.; Hawley, S. L.; Davenport, J. R. A.;
Hebb, Leslie; Weisenburger, K. L.; Garofali, K.; Kruse, E.; Luger,
R.; Lurie, J. C.; Morris, B. M.; Ruan, J. J.; Sanderbeck, P. U.;
Suberlak, K.; Telford, O. G.; Windemuth, D.
2015AAS...22513830W Altcode:
Kepler has provided precise photometry for more than 2500 eclipsing
binaries, which may be used to obtain fundamental stellar parameters
such as mass and radius. We report on the initial results of a new
ground-based program at Apache Point Observatory and Manastash Ridge
Observatory to obtain spectra and photometry of Kepler eclipsing
binaries. We present multi-color light curves, radial velocites,
and additional characterization of the stellar spectra. The new
ground-based data will be used to inform modeling efforts for these
objects (see companion poster by K. Weisenburger et al.).
---------------------------------------------------------
Title: Eclipsing the Need for Spectroscopy: Constraining Eclipsing
Binary Parameters Using Only Kepler Photometry
Authors: Weisenburger, Kolby L.; Windemuth, D.; Hawley, S.; Davenport,
J. R. A.; Hebb, Leslie; Wilkinson, T. D.; Garofali, K.; Kruse, E.;
Luger, R.; Lurie, J. C.; Morris, B. M.; Suberlak, K.; Telford, O.;
Upton Sanderbeck, P.
2015AAS...22513829W Altcode:
Eclipsing binary (EB) stars provide accurate measurements of stellar
mass and radius and therefore play a critical role in constraining
stellar evolution models. Despite their utility in understanding
the distribution of stellar properties, previous studies have been
limited by the observational challenges inherent to identifying and
characterizing EBs, namely, the need for both high-cadence, continuous
photometric monitoring and follow-up spectroscopy for radial velocity
(RV) measurements. Fortunately, the time-resolved data from the Kepler
mission offer a new opportunity to assemble large samples of EBs,
as well as place preliminary constraints on their masses and radii
without the need for additional observations. While current EB models
(e.g., JKTEBOP) and Kepler photometric data alone can be used to produce
estimates of stellar parameters, we investigate the accuracy of this
method by solving for orbital solutions with and without additional
ground-based data (multi-color photometry and RVs). Here we present
three Kepler EBs that have ground-based data from a new monitoring
program recently initiated at Apache Point Observatory and Manastash
Ridge Observatory (see corresponding poster by T. Wilkinson et al.),
and use these systems to investigate any discrepancies between the
two approaches. Considering the observational costs to targeting all
Kepler EBs (> 2500) for ground-based follow-up, using select EBs
such as these as test cases may allow for the development of a reliable
method to determine stellar radii and temperatures exclusively from
photometric data and thereby provide a useful tool for streamlining
future EB analyses.
---------------------------------------------------------
Title: Using Transiting Planets to Model Starspot Evolution with
Kepler
Authors: Davenport, James R. A.; Hebb, Leslie; Hawley, Suzanne L.
2015AAS...22522907D Altcode:
Photometry from Kepler has revealed the presence of cool starspots on
the surfaces of thousands of stars, presenting a wide range of spot
morphologies and lifetimes. Understanding the lifetime and evolution
of starspots across the main sequence reveals critical information
about the strength and nature of stellar dynamos. We probe the dynamo
by modeling starspot features observed in Kepler light curves, using
an MCMC-based light curve modeling code. We study planetary systems
like Kepler 17, where spot-occulting transits probe smaller-scale
starspot regions on the stellar surface along a fixed latitude
region. Our approach is novel in modeling both the in- and out-of
transit features in the light curve, allowing us to break fundamental
degeneracies between spot size, latitude, and contrast. With continuous
monitoring from Kepler we are able to observe small changes in the
positions and sizes of spots from many transits, spanning 4 years
of data. Additionally, for stars without transiting planets like GJ
1243, we are able to recover subtle, long term changes in spot sizes
and longitudes, leading to the slowest differential rotation rate yet
measured for a low mass star. These studies constrain properties that
are key to understanding the stellar dynamo, including rotation period,
differential rotation, and spot diffusion timescales.
---------------------------------------------------------
Title: Using Transiting Planets to Model Starspot Evolution
Authors: Davenport, James R. A.; Hebb, Leslie; Hawley, Suzanne L.
2015csss...18..399D Altcode: 2014arXiv1408.5201D
Photometry from Kepler has revealed the presence of cool starspots on
the surfaces of thousands of stars, presenting a wide range of spot
morphologies and lifetimes . Understanding the lifetime and evolution
of starspots across the main sequence reveals critical information
about the strength and nature of stellar dynamos. We probe the dynamo
by modeling the starspot properties over time using Kepler light
curves. In particular, we use planetary systems like Kepler 17 that show
in-transit starspot crossing features. Spot-occulting transits probe
smaller-scale starspot features on the stellar surface along a fixed
latitude region. Our approach is novel in modeling both the in- and
out-of transit light curve features, allowing us to break fundamental
degeneracies between spot size, latitude, and contrast. With continuous
monitoring from Kepler we are able to observe small changes in the
positions and sizes of spots from many transits, spanning 4 years of
data. Additionally, for stars without transiting planets like GJ 1243
we are able to recover subtle, long term changes in spot sizes and
longitudes, leading to some of the slowest differential rotation rates
yet measured. These studies constrain key physical parameters including
rotation period, differential rotation, and diffusion timescales,
and open the door to ensemble studies of detailed spot evolution in
the future.
---------------------------------------------------------
Title: Hα Emission From Active Equal-Mass, Wide M Dwarf Binaries
Authors: Gunning, Heather C.; Schmidt, Sarah J.; Davenport, James
R. A.; Dhital, Saurav; Hawley, Suzanne L.; West, Andrew A.
2014PASP..126.1081G Altcode: 2014arXiv1410.1514G
Not Available <P />This publication is partially based on observations
obtained with the Apache Point Observatory 3.5-meter telescope, which
is owned and operated by the Astrophysical Research Consortium.
---------------------------------------------------------
Title: Kepler Flares. II. The Temporal Morphology of White-light
Flares on GJ 1243
Authors: Davenport, James R. A.; Hawley, Suzanne L.; Hebb, Leslie;
Wisniewski, John P.; Kowalski, Adam F.; Johnson, Emily C.; Malatesta,
Michael; Peraza, Jesus; Keil, Marcus; Silverberg, Steven M.; Jansen,
Tiffany C.; Scheffler, Matthew S.; Berdis, Jodi R.; Larsen, Daniel M.;
Hilton, Eric J.
2014ApJ...797..122D Altcode: 2014arXiv1411.3723D
We present the largest sample of flares ever compiled for a single M
dwarf, the active M4 star GJ 1243. Over 6100 individual flare events,
with energies ranging from 10<SUP>29</SUP> to 10<SUP>33</SUP> erg, are
found in 11 months of 1 minute cadence data from Kepler. This sample
is unique for its completeness and dynamic range. We have developed
automated tools for finding flares in short-cadence Kepler light curves,
and performed extensive validation and classification of the sample by
eye. From this pristine sample of flares we generate a median flare
template. This template shows that two exponential cooling phases
are present during the white-light flare decay, providing fundamental
constraints for models of flare physics. The template is also used as
a basis function to decompose complex multi-peaked flares, allowing us
to study the energy distribution of these events. Only a small number
of flare events are not well fit by our template. We find that complex,
multi-peaked flares occur in over 80% of flares with a duration of 50
minutes or greater. The underlying distribution of flare durations for
events 10 minutes and longer appears to follow a broken power law. Our
results support the idea that sympathetic flaring may be responsible
for some complex flare events.
---------------------------------------------------------
Title: Kepler Flares. I. Active and Inactive M Dwarfs
Authors: Hawley, Suzanne L.; Davenport, James R. A.; Kowalski, Adam F.;
Wisniewski, John P.; Hebb, Leslie; Deitrick, Russell; Hilton, Eric J.
2014ApJ...797..121H Altcode: 2014arXiv1410.7779H
We analyzed Kepler short-cadence M dwarf observations. Spectra from the
Astrophysical Research Consortium 3.5 m telescope identify magnetically
active (Hα in emission) stars. The active stars are of mid-M spectral
type, have numerous flares, and have well-defined rotational modulation
due to starspots. The inactive stars are of early M type, exhibit less
starspot signature, and have fewer flares. A Kepler to U-band energy
scaling allows comparison of the Kepler flare frequency distributions
with previous ground-based data. M dwarfs span a large range of flare
frequency and energy, blurring the distinction between active and
inactive stars designated solely by the presence of Hα. We analyzed
classical and complex (multiple peak) flares on GJ 1243, finding strong
correlations between flare energy, amplitude, duration, and decay time,
with only a weak dependence on rise time. Complex flares last longer and
have higher energy at the same amplitude, and higher energy flares are
more likely to be complex. A power law fits the energy distribution for
flares with log E<SUB>K_p</SUB> \gt 31 erg, but the predicted number of
low-energy flares far exceeds the number observed, at energies where
flares are still easily detectable, indicating that the power-law
distribution may flatten at low energy. There is no correlation of
flare occurrence or energy with starspot phase, the flare waiting
time distribution is consistent with flares occurring randomly in
time, and the energies of consecutive flares are uncorrelated. These
observations support a scenario where many independent active regions
on the stellar surface are contributing to the observed flare rate.
---------------------------------------------------------
Title: Calibrating Ultracool Dwarfs: Optical Template Spectra,
Bolometric Corrections, and χ Values
Authors: Schmidt, Sarah J.; West, Andrew A.; Bochanski, John J.;
Hawley, Suzanne L.; Kielty, Collin
2014PASP..126..642S Altcode: 2014arXiv1406.1228S
Not Available <P />This publication is partially based on observations
obtained with the Apache Point Observatory 3.5 meter telescope, which
is owned and operated by the Astrophysical Research Consortium.
---------------------------------------------------------
Title: The Hammer: An IDL Spectral Typing Suite
Authors: Covey, Kevin R.; West, Andrew A.; Bochanski, John J.; Hawley,
Suzanne L.
2014ascl.soft05003C Altcode:
The Hammer can classify spectra in a variety of formats with targets
spanning the MK spectral sequence. It processes a list of input
spectra by automatically estimating each object's spectral type and
measuring activity and metallicity tracers in late type stars. Once
automatic processing is complete, an interactive interface allows the
user to manually tweak the final assigned spectral type through visual
comparison with a set of templates.
---------------------------------------------------------
Title: The Tenth Data Release of the Sloan Digital Sky Survey:
First Spectroscopic Data from the SDSS-III Apache Point Observatory
Galactic Evolution Experiment
Authors: Ahn, Christopher P.; Alexandroff, Rachael; Allende Prieto,
Carlos; Anders, Friedrich; Anderson, Scott F.; Anderton, Timothy;
Andrews, Brett H.; Aubourg, Éric; Bailey, Stephen; Bastien, Fabienne
A.; Bautista, Julian E.; Beers, Timothy C.; Beifiori, Alessandra;
Bender, Chad F.; Berlind, Andreas A.; Beutler, Florian; Bhardwaj,
Vaishali; Bird, Jonathan C.; Bizyaev, Dmitry; Blake, Cullen H.;
Blanton, Michael R.; Blomqvist, Michael; Bochanski, John J.; Bolton,
Adam S.; Borde, Arnaud; Bovy, Jo; Shelden Bradley, Alaina; Brandt,
W. N.; Brauer, Dorothée; Brinkmann, J.; Brownstein, Joel R.; Busca,
Nicolás G.; Carithers, William; Carlberg, Joleen K.; Carnero, Aurelio
R.; Carr, Michael A.; Chiappini, Cristina; Chojnowski, S. Drew; Chuang,
Chia-Hsun; Comparat, Johan; Crepp, Justin R.; Cristiani, Stefano;
Croft, Rupert A. C.; Cuesta, Antonio J.; Cunha, Katia; da Costa, Luiz
N.; Dawson, Kyle S.; De Lee, Nathan; Dean, Janice D. R.; Delubac,
Timothée; Deshpande, Rohit; Dhital, Saurav; Ealet, Anne; Ebelke,
Garrett L.; Edmondson, Edward M.; Eisenstein, Daniel J.; Epstein,
Courtney R.; Escoffier, Stephanie; Esposito, Massimiliano; Evans,
Michael L.; Fabbian, D.; Fan, Xiaohui; Favole, Ginevra; Femenía
Castellá, Bruno; Fernández Alvar, Emma; Feuillet, Diane; Filiz
Ak, Nurten; Finley, Hayley; Fleming, Scott W.; Font-Ribera, Andreu;
Frinchaboy, Peter M.; Galbraith-Frew, J. G.; García-Hernández, D. A.;
García Pérez, Ana E.; Ge, Jian; Génova-Santos, R.; Gillespie, Bruce
A.; Girardi, Léo; González Hernández, Jonay I.; Gott, J. Richard,
III; Gunn, James E.; Guo, Hong; Halverson, Samuel; Harding, Paul;
Harris, David W.; Hasselquist, Sten; Hawley, Suzanne L.; Hayden,
Michael; Hearty, Frederick R.; Herrero Davó, Artemio; Ho, Shirley;
Hogg, David W.; Holtzman, Jon A.; Honscheid, Klaus; Huehnerhoff,
Joseph; Ivans, Inese I.; Jackson, Kelly M.; Jiang, Peng; Johnson,
Jennifer A.; Kinemuchi, K.; Kirkby, David; Klaene, Mark A.; Kneib,
Jean-Paul; Koesterke, Lars; Lan, Ting-Wen; Lang, Dustin; Le Goff,
Jean-Marc; Leauthaud, Alexie; Lee, Khee-Gan; Lee, Young Sun; Long,
Daniel C.; Loomis, Craig P.; Lucatello, Sara; Lupton, Robert H.;
Ma, Bo; Mack, Claude E., III; Mahadevan, Suvrath; Maia, Marcio
A. G.; Majewski, Steven R.; Malanushenko, Elena; Malanushenko,
Viktor; Manchado, A.; Manera, Marc; Maraston, Claudia; Margala,
Daniel; Martell, Sarah L.; Masters, Karen L.; McBride, Cameron K.;
McGreer, Ian D.; McMahon, Richard G.; Ménard, Brice; Mészáros,
Sz.; Miralda-Escudé, Jordi; Miyatake, Hironao; Montero-Dorta,
Antonio D.; Montesano, Francesco; More, Surhud; Morrison, Heather
L.; Muna, Demitri; Munn, Jeffrey A.; Myers, Adam D.; Nguyen, Duy
Cuong; Nichol, Robert C.; Nidever, David L.; Noterdaeme, Pasquier;
Nuza, Sebastián E.; O'Connell, Julia E.; O'Connell, Robert W.;
O'Connell, Ross; Olmstead, Matthew D.; Oravetz, Daniel J.; Owen,
Russell; Padmanabhan, Nikhil; Palanque-Delabrouille, Nathalie; Pan,
Kaike; Parejko, John K.; Parihar, Prachi; Pâris, Isabelle; Pepper,
Joshua; Percival, Will J.; Pérez-Ràfols, Ignasi; Dotto Perottoni,
Hélio; Petitjean, Patrick; Pieri, Matthew M.; Pinsonneault, M. H.;
Prada, Francisco; Price-Whelan, Adrian M.; Raddick, M. Jordan; Rahman,
Mubdi; Rebolo, Rafael; Reid, Beth A.; Richards, Jonathan C.; Riffel,
Rogério; Robin, Annie C.; Rocha-Pinto, H. J.; Rockosi, Constance
M.; Roe, Natalie A.; Ross, Ashley J.; Ross, Nicholas P.; Rossi,
Graziano; Roy, Arpita; Rubiño-Martin, J. A.; Sabiu, Cristiano G.;
Sánchez, Ariel G.; Santiago, Basílio; Sayres, Conor; Schiavon,
Ricardo P.; Schlegel, David J.; Schlesinger, Katharine J.; Schmidt,
Sarah J.; Schneider, Donald P.; Schultheis, Mathias; Sellgren, Kris;
Seo, Hee-Jong; Shen, Yue; Shetrone, Matthew; Shu, Yiping; Simmons,
Audrey E.; Skrutskie, M. F.; Slosar, Anže; Smith, Verne V.; Snedden,
Stephanie A.; Sobeck, Jennifer S.; Sobreira, Flavia; Stassun, Keivan
G.; Steinmetz, Matthias; Strauss, Michael A.; Streblyanska, Alina;
Suzuki, Nao; Swanson, Molly E. C.; Terrien, Ryan C.; Thakar, Aniruddha
R.; Thomas, Daniel; Thompson, Benjamin A.; Tinker, Jeremy L.; Tojeiro,
Rita; Troup, Nicholas W.; Vandenberg, Jan; Vargas Magaña, Mariana;
Viel, Matteo; Vogt, Nicole P.; Wake, David A.; Weaver, Benjamin A.;
Weinberg, David H.; Weiner, Benjamin J.; White, Martin; White, Simon
D. M.; Wilson, John C.; Wisniewski, John P.; Wood-Vasey, W. M.;
Yèche, Christophe; York, Donald G.; Zamora, O.; Zasowski, Gail;
Zehavi, Idit; Zhao, Gong-Bo; Zheng, Zheng; Zhu, Guangtun
2014ApJS..211...17A Altcode: 2013arXiv1307.7735A
The Sloan Digital Sky Survey (SDSS) has been in operation since 2000
April. This paper presents the Tenth Public Data Release (DR10) from
its current incarnation, SDSS-III. This data release includes the first
spectroscopic data from the Apache Point Observatory Galaxy Evolution
Experiment (APOGEE), along with spectroscopic data from the Baryon
Oscillation Spectroscopic Survey (BOSS) taken through 2012 July. The
APOGEE instrument is a near-infrared R ~ 22,500 300 fiber spectrograph
covering 1.514-1.696 μm. The APOGEE survey is studying the chemical
abundances and radial velocities of roughly 100,000 red giant star
candidates in the bulge, bar, disk, and halo of the Milky Way. DR10
includes 178,397 spectra of 57,454 stars, each typically observed three
or more times, from APOGEE. Derived quantities from these spectra
(radial velocities, effective temperatures, surface gravities, and
metallicities) are also included. DR10 also roughly doubles the number
of BOSS spectra over those included in the Ninth Data Release. DR10
includes a total of 1,507,954 BOSS spectra comprising 927,844 galaxy
spectra, 182,009 quasar spectra, and 159,327 stellar spectra selected
over 6373.2 deg<SUP>2</SUP>.
---------------------------------------------------------
Title: Mapping small-scale starspots on Kepler transiting planet
host stars
Authors: Hebb, Leslie; Davenport, J. R.; Hawley, S. L.; Jardine,
M. M.; Llama, J.
2014AAS...22344135H Altcode:
High precision, near-continuous time series photometry of large numbers
of transiting planet host stars is now available from the Kepler
satellite archive. Using short cadence light curves of transiting
planet host stars with sub-millimag photometric precision we are now,
for the first time, able to map relative brightness variations due to
small-scale starspots on the surfaces of stars other than the Sun. Here,
we present a new project whose goal is to derive the detailed time
evolution of the starspot distribution on the surface of tens of stars
with a range of masses and rotation rates. We have developed an eclipse
mapping code which we are using to determine the lifetime of individual
starspots and starspot groups by identifying and modeling brightness
variations during planetary transits caused by the planet crossing
in front of a starspot on the stellar surface. In order to reduce the
degeneracy of the light curve inversion problem, we are using precise
knowledge of the planet's position and comprehensively modeling the in-
and out- of transit data to strengthen the constraints on the positions
of the surface spots. Here, we describe our overall project, explain our
eclipse mapping technique in detail, and present preliminary results
on the transiting planet host star, Kepler-17. Preliminary results
on the spot evolution of additional systems (Kepler-17, Kepler-63,
HAT-P-11, and GJ1243) are presented in a corresponding presentation
by J.R.A. Davenport.
---------------------------------------------------------
Title: Double the Lightcurves, Double the Fun: Stellar Activity on
the M Dwarfs GJ 1245 A and B with Kepler
Authors: Lurie, John C.; Davenport, J. R.; Hawley, S. L.
2014AAS...22344140L Altcode:
GJ 1245ABC is a nearby triple system comprised of two M5 components
(A and B) and a very low mass stellar companion (C) to A. As a Kepler
target, this system presents a unique opportunity to study the stellar
activity of two coeval, nearly-equal mass M dwarfs. Components AC and
B are separated by 7". Given Kepler's large plate scale of 4"/pixel,
this system is not resolved in the Kepler pipeline processing. Time
series analysis reveals two strong periodic signals due to starspots
on components A and B, which have different rotation periods. The
C component is ~3 magnitudes fainter than A, and as such does not
contribute significantly to the flux from A. Examining the Kepler
pixel files directly, we are able to use these periodic signals
to disentangle the A and B components. Here we demonstrate this
novel technique, and present preliminary separated lightcurves for
GJ 1245 A and B. Ultimately, we will determine the individual flare
occurrence rates for A and B, providing an important test for stellar
age-activity-rotation models.
---------------------------------------------------------
Title: The Atmospheric Response to High Fluxes of Nonthermal Electrons
during M Dwarf Flares
Authors: Kowalski, Adam; Allred, J. C.; Carlsson, M.; Hawley, S. L.;
Holman, G. D.; Mathioudakis, M.; Osten, R. A.; Uitenbroek, H.
2014AAS...22315117K Altcode:
Flares are thought to be the result of magnetic fields in the stellar
corona that undergo reconnection and accelerate charged particles
into the lower atmosphere. Spectra of M dwarf flares in the optical
and near-ultraviolet wavelength regimes can be used to constrain the
heating mechanism of the lower stellar atmosphere. These observations
show several ubiquitous properties of the continuum emission, which
is not reproduced by models that use typical “solar-type” heating
functions. We present results from a grid of new flare models using the
RADYN code, which simultaneously calculates the radiative transfer and
hydrodynamics on short timescales. We explore the atmospheric response
to a short ~2 second burst of a very high heating rate from nonthermal
electrons using a solar-type heating function, and we propose a new
“M dwarf-type” heating variation that explains a range of observed
spectral properties, such as ~10,000 K blackbody emission and a smooth
continuum across the Balmer jump wavelength (3646A).
---------------------------------------------------------
Title: Using exoplanet systems with highly elliptical orbits to
search for star-planet interactions
Authors: Hodgson, John R.; Christian, Damian J.; Bodewits, Dennis;
Hawley, Suzanne
2014IAUS..299..291H Altcode:
We are investigating if the orbital geometry of exoplanets affects
the activity of their host star by studying a sample of planetary
systems known to contain massive planets on short period, highly
elliptical orbits. While recent studies in the optical, UV, and X-Ray
have shown enhanced chromospheric activity for stars hosting exoplanets
with orbital semi-major axes less than 0.1 AU (Krejcova 2012, Shkolnik
2013, Kashyap 2008, Poppenhaeger 2010), it is not yet clear whether this
activity is driven by magnetic or tidal interactions. We are probing the
dependence of star-planet interactions (SPI) on the orbital geometry
of the planetary systems by analyzing chromospheric lines (such as Ca
II H & K) for variability phased with the exoplanet's orbit. We
have obtained high resolution spectra of several systems with the
McDonald 2.1-m Sandiford echelle spectrograph, ARCES on the APO 3.5-m,
and for HIRES on Keck I from the Keck Observatory Archive. We describe
our methodology and review how our results will use orbital geometry
to deduce how planets may affect the activity of their host stars.
---------------------------------------------------------
Title: Tracing Detailed Starspot Evolution with Kepler
Authors: Davenport, James R.; Hebb, L.; Hawley, S. L.
2014AAS...22331503D Altcode:
Modeling sinusoidal flux variations in high precision photometry due to
starspots, and their evolution over time, reveals critical information
about the strength and nature of stellar magnetic fields. Photometry
from the Kepler mission has discovered the presence of cool starspots
on the surfaces of thousands of main sequence stars. Here we show
preliminary results from our campaign to model the detailed time
evolution of starspots on four stars. The rapidly rotating M4 star,
GJ 1243, exhibits a remarkably stable polar starspot spanning three
years of observation. A secondary polar spot is also seen, with an
evolution timescale of hundreds of days. Three G/K stars with a wide
range of rotation periods have also been studied, KOI-63, Kepler 17,
and HAT-P-11. These systems all have planetary transits in their
light curves, which we exploit to break degeneracies between spot
surface coverage area and spot latitude. These transits can also probe
smaller-scale starspot features on the stellar surface along a fixed
latitude. By modeling the in- and out-of-eclipse light curves (see
corresponding poster by L. Hebb) we are able to trace the detailed
starspot evolution for several years in each system. This will help
to constrain key physical parameters, such as mean rotation period,
differential rotation, and diffusion timescales.
---------------------------------------------------------
Title: The properties of flare kernels observed by the Dunn Solar
Telescope
Authors: Fletcher, Lyndsay; Kowalski, A.; Cauzzi, G.; Hawley, S. L.;
Hudson, H. S.
2013SPD....44...67F Altcode:
We report on a campaign at the Dunn Solar Telescope which resulted in
successful imaging and spectroscopic observations of a C1.1 solar flare
on 18th August 2011. This flare exhibited ribbons with complicated
fine structure at the resolution of the DST/IBIS instrument, and a
number of bright kernels with sizes comparable to the smallest scales
sampled by IBIS, around 2-4 pixels (0."3-0."6) FWHM. We focus on these
bright kernels, describing their spatial characteristics in the core
and wing of H alpha and Ca II 8542, and in the UV and EUV with SDO. We
also show preliminary broad-band spectroscopy of the kernels which may
demonstrate the presence of an optical continuum in this small flare.
---------------------------------------------------------
Title: Time-resolved Properties and Global Trends in dMe Flares from
Simultaneous Photometry and Spectra
Authors: Kowalski, Adam F.; Hawley, Suzanne L.; Wisniewski, John P.;
Osten, Rachel A.; Hilton, Eric J.; Holtzman, Jon A.; Schmidt, Sarah
J.; Davenport, James R. A.
2013ApJS..207...15K Altcode: 2013arXiv1307.2099K
We present a homogeneous analysis of line and continuum emission
from simultaneous high-cadence spectra and photometry covering
near-ultraviolet and optical wavelengths for 20 M dwarf flares. These
data were obtained to study the white-light continuum components at
bluer and redder wavelengths than the Balmer jump. Our goals were
to break the degeneracy between emission mechanisms that have been
fit to broadband colors of flares and to provide constraints for
radiative-hydrodynamic (RHD) flare models that seek to reproduce the
white-light flare emission. The main results from the analysis are
the following: (1) the detection of Balmer continuum (in emission)
that is present during all flares and with a wide range of relative
contributions to the continuum flux at bluer wavelengths than the
Balmer jump; (2) a blue continuum at flare maximum that is linearly
decreasing with wavelength from λ = 4000-4800 Å, indicative of hot,
blackbody emission with typical temperatures of T <SUB>BB</SUB>
~ 9000-14, 000 K (3) a redder continuum apparent at wavelengths
longer than Hβ (λ >~ 4900 Å) which becomes relatively more
important to the energy budget during the late gradual phase. The hot
blackbody component and redder continuum component have been detected
in previous studies of flares. However, we have found that although
the hot blackbody emission component is relatively well-represented
by a featureless, single-temperature Planck function, this component
includes absorption features and has a continuum shape strikingly
similar to the spectrum of an A-type star as directly observed in
our flare spectra. New model constraints are presented for the time
evolution among the hydrogen Balmer lines and between Ca II K and the
blackbody continuum emission. We calculate Balmer jump flux ratios and
compare to the solar-type flare heating predictions from RHD models. The
model ratios are too large and the blue-optical (λ = 4000-4800 Å)
slopes are too red in both the impulsive and gradual decay phases of
all 20 flares. This discrepancy implies that further work is needed
to understand the heating at high column mass during dMe flares. <P
/>Based on observations obtained with the Apache Point Observatory
3.5 m telescope, which is owned and operated by the Astrophysical
Research Consortium.
---------------------------------------------------------
Title: WIYN Observatory: Partnerships
Authors: Hawley, Suzanne L.; Walterbos, R. A.; Gillespie, B. A.
2013AAS...22220404H Altcode:
As part of its "meeting-in-a-meeting" highlighting the scientific
contributions and the new instrumentation available at WIYN, the
Observatory partners are providing a forum for discussion of potential
partnership arrangements for national 4-meter class telescopes. In this
session, WIYN and other operators of 4-meter class telescopes will
join in a panel discussion that features their plans for the future,
possible strategies for broadening the user base from the community,
and potential synergies and partnerships with existing and planned large
survey projects and facilities. This session is intended to facilitate
a conversation within the national community that explores potential
future partnership arrangements to provide stable operational models
for moderate aperture facilities that currently serve a large user
base in the US.
---------------------------------------------------------
Title: VizieR Online Data Catalog: M dwarf flare spectra (Kowalski+,
2013)
Authors: Kowalski, A. F.; Hawley, S. L.; Wisniewski, J. P.; Osten,
R. A.; Hilton, E. J.; Holtzman, J. A.; Schmidt, S. J.; Davenport,
J. R. A.
2013yCat..22070015K Altcode:
The spectral data are contained in FITS files (to be read into IDL with
mrdfits.pro), and the photometry data are contained in two column .dat
files. <P />Spectra were obtained with the Dual-Imaging Spectrograph
(DIS) on the ARC 3.5m telescope at the Apache Point Observatory (APO)
in low-resolution. The observing log for each target star is given in
Table 2. <P />(5 data files).
---------------------------------------------------------
Title: The Very Short Period M Dwarf Binary SDSS J001641-000925
Authors: Davenport, James R. A.; Becker, Andrew C.; West, Andrew
A.; Bochanski, John J.; Hawley, Suzanne L.; Holtzman, Jon; Gunning,
Heather C.; Hilton, Eric J.; Munshi, Ferah A.; Albright, Meagan
2013ApJ...764...62D Altcode: 2012arXiv1206.6056D
We present follow-up observations and analysis of the recently
discovered short period low-mass eclipsing binary, SDSS
J001641-000925. With an orbital period of 0.19856 days, this
system has one of the shortest known periods for an M dwarf binary
system. Medium-resolution spectroscopy and multi-band photometry for
the system are presented. Markov Chain Monte Carlo modeling of the light
curves and radial velocities yields estimated masses for the stars of M
<SUB>1</SUB> = 0.54 ± 0.07 M <SUB>⊙</SUB> and M <SUB>2</SUB> = 0.34
± 0.04 M <SUB>⊙</SUB>, and radii of R <SUB>1</SUB> = 0.68 ± 0.03
R <SUB>⊙</SUB> and R <SUB>2</SUB> = 0.58 ± 0.03 R <SUB>⊙</SUB>,
respectively. This solution places both components above the critical
Roche overfill limit, providing strong evidence that SDSS J001641-000925
is the first verified M-dwarf contact binary system. Within the
follow-up spectroscopy we find signatures of non-solid body rotation
velocities, which we interpret as evidence for mass transfer or loss
within the system. In addition, our photometry samples the system
over nine years, and we find strong evidence for period decay at the
rate of \dot{P}\sim 8 s yr<SUP>-1</SUP>. Both of these signatures
raise the intriguing possibility that the system is in over-contact,
and actively losing angular momentum, likely through mass loss. This
places SDSS J001641-000925 as not just the first M-dwarf over-contact
binary, but one of the few systems of any spectral type known to be
actively undergoing coalescence. Further study of SDSS J001641-000925
is ongoing to verify the nature of the system, which may prove to be
a unique astrophysical laboratory. <P />Based on observations obtained
with the Apache Point Observatory 3.5 m telescope, which is owned and
operated by the Astrophysical Research Consortium. This paper includes
data gathered with the 6.5 m Magellan Telescopes located at Las Campanas
Observatory, Chile. Support for the design and construction of the
Magellan Echellette Spectrograph was received from the Observatories
of the Carnegie Institution of Washington, the School of Science of
the Massachusetts Institute of Technology, and the National Science
Foundation in the form of a collaborative Major Research Instrument
grant to Carnegie and MIT (AST0215989).
---------------------------------------------------------
Title: Measuring the ages of low-mass stars and brown dwarfs
Authors: Bochanski, J. J.; Hawley, S. L.; Covey, K. R.; Agüeros,
M. A.; Baraffe, I.; Catalán, S.; Mohanty, S.; Rice, E. L.; West, A. A.
2013AN....334...44B Altcode: 2013csss...17...44B
Age is among the most elusive, yet important, fundamental properties
of low-mass stars and brown dwarfs. M dwarfs have main-sequence
lifetimes that are estimated to be trillions of years, with little
change in luminosity. In contrast, brown dwarfs cool and dim with
time, resulting in a significant degeneracy between mass, age, and
luminosity. Despite these inherent challenges, there have been recent
efforts on both observational and theoretical fronts that may yield
precise ages for low-mass stars and brown dwarfs. We feature some
current observational efforts focused on estimating ages of these
objects as presented in our Cool Stars 17 splinter session.
---------------------------------------------------------
Title: MMT Hectochelle Spectral Variability of Active Late-type
Stars in the Kepler Field (2013A)
Authors: Brown, Alexander; Walkowicz, Lucianne; Saar, Steven; Hawley,
Suzanne; Kowalski, Adam; Furesz, Gabor; Piskunov, Nikolai
2013noao.prop..286B Altcode:
We have on-going it Kepler photometric monitoring of over 300 active
late-type (mid-A - K) stars as part of our Cycles 1/2/3/4 Guest
Observer (GO) programs with the aim of studying starspot evolution,
differential rotation, activity cycles, and flares. We propose to
use the MMT Hectochelle multiobject spectrograph to observe over
140 of these stars to determine a range of basic physical properties
for the stars, such as radial velocity variations due to binarity,
chromospheric activity levels from Ca II H+K and H(alpha), projected
rotational velocities for comparison to the rotational periods
measured directly by it Kepler, age/youth as indicated by Li I, and
better effective temperature and luminosity estimates. In addition,
to provide a superior sample for statistical studies another 800 GKM
dwarf stars showing either starspot modulation from the it Kepler
Team's data or from our deep XMM X-ray survey will be observed using
the unassigned fibers in each field. These measurements require the
32,000 spectral resolution provided by Hectochelle, which is hard to
obtain efficiently for 13-15th magnitude stars any other way.
---------------------------------------------------------
Title: Mapping the Local Halo: Statistical Parallax Analysis of SDSS
Low-mass Subdwarfs
Authors: Bochanski, John J.; Savcheva, Antonia; West, Andrew A.;
Hawley, Suzanne L.
2013AJ....145...40B Altcode: 2012arXiv1211.6104B
We present a statistical parallax study of nearly 2000 M subdwarfs
with photometry and spectroscopy from the Sloan Digital Sky Survey
(SDSS). Statistical parallax analysis yields the mean absolute
magnitudes, mean velocities, and velocity ellipsoids for homogenous
samples of stars. We selected homogeneous groups of subdwarfs based
on their photometric colors and spectral appearance. We examined
the color-magnitude relations of low-mass subdwarfs and quantified
their dependence on the newly refined metallicity parameter, ζ. We
also developed a photometric metallicity parameter, δ<SUB>(g -
r)</SUB>, based on the g - r and r - z colors of low-mass stars and
used it to select stars with similar metallicities. The kinematics
of low-mass subdwarfs as a function of color and metallicity were
also examined and compared to main-sequence M dwarfs. We find that
the SDSS subdwarfs share similar kinematics to the inner halo and
thick disk. The color-magnitude relations derived in this analysis
will be a powerful tool for identifying and characterizing low-mass
metal-poor subdwarfs in future surveys such as Gaia and LSST, making
them important and plentiful tracers of the stellar halo.
---------------------------------------------------------
Title: A Large Sample of Magnetically-Active Stars Observed With
Kepler
Authors: Wells, Mark; Neff, J. E.; Brown, A.; Ayres, T. R.; Basri,
G. S.; Berdyugina, S.; Harper, G.; Hawley, S. L.; Korhonen, H.;
Kowalski, A.; Micela, G.; Piskunov, N. E.; Ramsey, L. W.; Saar, S. H.;
Walkowicz, L. M.
2013AAS...22135415W Altcode:
We have observed about 325 stars in our Kepler Guest Observer
programs (Cycles 1 through 4). For most of these targets, we are
analyzing extremely high-precision light curves that have been
continuously sampled every 30 minutes for up to 3 years. Our sample
of candidate magnetically-active stars was selected primarily using
GALEX colors. Starspots, pulsations, and variations due to eclipsing
and contact binaries combine to produce a rich variety of light
curves. We have developed semi-automated procedures to characterize
this variability and thus to classify the targets and identify the
physical mechanisms that dominate their Kepler light curves. We will
describe these procedures and discuss the range of physical properties
covered by our final classification scheme. We are using this Kepler
database of variability over timescales of minutes to years to provide
diagnostics of flares, starspot formation, evolution, migration, and
ultimately of stellar cycles in general. This work contains results
obtained using the NASA Kepler satellite and from the Apache Point
Observatory, the MMT (using NOAO community access time), and the
Hobby-Eberly Telescope. Funding is provided by NASA Kepler grants
NNX10AC51G, NNX11AC79G, and NNX12AC85G to the University of Colorado,
by NSF grant AST-1109695 to the College of Charleston, and by a grant
from the South Carolina Space Grant consortium.
---------------------------------------------------------
Title: First Results From The BOSS Ultracool Dwarf (BUD) Sample
Authors: Schmidt, Sarah J.; Hawley, S. L.; Davenport, J. R.; West,
A. A.; Bochanski, J. J.
2013AAS...22115821S Altcode:
We introduce the BOSS Ultracool Dwarf (BUD) sample of 12,085 M7-L8
dwarfs selected from the Sloan Digital Sky Survey (SDSS) photometry
and spectroscopy. The BUD sample includes ultracool dwarfs selected
from the SDSS seventh data release in addition to new dwarfs from the
Baryon Oscillation Sky Survey (BOSS). We present the izJHKW1W2W3 color
locus from a cross-match between the BUD sample and the 2MASS and
WISE catalogs. In addition to colors, we also examine chromospheric
activity based on the presence and strength of Hα emission. When we
restrict our activity search to spectra with S/N > 3 in the region
surrounding Hα, we find that over 80% of nearby early-L dwarfs are
active. The fraction of active ultracool dwarfs is larger closer to
the galactic plane, indicating that ultracool dwarfs follow an age
activity relationship similar to more massive M dwarfs.
---------------------------------------------------------
Title: Young Star Populations in the Kepler Field
Authors: Brown, Alexander; Neff, J. E.; Wells, M.; Saar, S.; Furesz,
G.; Walkowicz, L. M.; Ayres, T. R.; Basri, G. S.; Berdyugina, S.;
Harper, G.; Hawley, S. L.; Korhonen, H.; Kowalski, A.; Micela, G.;
Piskunov, N. E.; Ramsey, L. W.
2013AAS...22135414B Altcode:
The Kepler satellite is providing spectacular optical photometric
light-curves of unprecedented precision and duration that routinely
allow detailed studies of stellar magnetic activity on late-type stars
that were difficult previously. Kepler provides multi-year duration
light-curves that allow investigation of how activity phenomena --
such as the growth, migration, and decay of star-spots, differential
rotation, activity cycles, and flaring -- operate on a wide variety of
single and binary stars. The 105 square degree Kepler Field contains
tens of thousands of late-type stars showing rotational modulation due
to star-spots with periods ranging from one day to a “solar-like”
month. Short rotation periods and high levels of magnetic activity are
strongly correlated. However, there are only two basic reasons why stars
with rotation periods of a few days possess such high angular momentum
--- either they are close binaries or they are young stars. During
Kepler GO Cycles 1 through 4 we have been studying the Long-cadence
(30 minute sampling) photometry of hundreds of active late-type stars
and as an absolutely essential complement we have been obtaining high
resolution optical spectra to understand the physical properties of
these stars. We present results from a spectroscopic survey using the
MMT Hectochelle multi-object echelle of 4 square degrees of the Kepler
Field. We have discovered a significant population of young stars with
Li I absorption indicating ages of ~100 Myr or less at a spatial density
of at least 20 stars per square degree. Our detected young star sample
comprises at least 80 stars and represents a dramatic advance compared
to the previously known sample over the full Kepler Field of three
stars in this age range. Roughly one sixth of the stars observed are
young and a similar number short-period binaries based on 2-4 radial
velocities. We show how the rotational properties of the stars and their
physical properties are related. This work is based on data obtained
with the NASA Kepler satellite and the MMT Hectochelle spectrograph
using NOAO community access time. Support by NASA Kepler grants to the
University of Colorado and by NSF grant to the College of Charleston.
---------------------------------------------------------
Title: The Ninth Data Release of the Sloan Digital Sky Survey:
First Spectroscopic Data from the SDSS-III Baryon Oscillation
Spectroscopic Survey
Authors: Ahn, Christopher P.; Alexandroff, Rachael; Allende Prieto,
Carlos; Anderson, Scott F.; Anderton, Timothy; Andrews, Brett H.;
Aubourg, Éric; Bailey, Stephen; Balbinot, Eduardo; Barnes, Rory;
Bautista, Julian; Beers, Timothy C.; Beifiori, Alessandra; Berlind,
Andreas A.; Bhardwaj, Vaishali; Bizyaev, Dmitry; Blake, Cullen H.;
Blanton, Michael R.; Blomqvist, Michael; Bochanski, John J.; Bolton,
Adam S.; Borde, Arnaud; Bovy, Jo; Brandt, W. N.; Brinkmann, J.; Brown,
Peter J.; Brownstein, Joel R.; Bundy, Kevin; Busca, N. G.; Carithers,
William; Carnero, Aurelio R.; Carr, Michael A.; Casetti-Dinescu,
Dana I.; Chen, Yanmei; Chiappini, Cristina; Comparat, Johan;
Connolly, Natalia; Crepp, Justin R.; Cristiani, Stefano; Croft,
Rupert A. C.; Cuesta, Antonio J.; da Costa, Luiz N.; Davenport,
James R. A.; Dawson, Kyle S.; de Putter, Roland; De Lee, Nathan;
Delubac, Timothée; Dhital, Saurav; Ealet, Anne; Ebelke, Garrett L.;
Edmondson, Edward M.; Eisenstein, Daniel J.; Escoffier, S.; Esposito,
Massimiliano; Evans, Michael L.; Fan, Xiaohui; Femenía Castellá,
Bruno; Fernández Alvar, Emma; Ferreira, Leticia D.; Filiz Ak, N.;
Finley, Hayley; Fleming, Scott W.; Font-Ribera, Andreu; Frinchaboy,
Peter M.; García-Hernández, D. A.; García Pérez, A. E.; Ge,
Jian; Génova-Santos, R.; Gillespie, Bruce A.; Girardi, Léo;
González Hernández, Jonay I.; Grebel, Eva K.; Gunn, James E.; Guo,
Hong; Haggard, Daryl; Hamilton, Jean-Christophe; Harris, David W.;
Hawley, Suzanne L.; Hearty, Frederick R.; Ho, Shirley; Hogg, David W.;
Holtzman, Jon A.; Honscheid, Klaus; Huehnerhoff, J.; Ivans, Inese I.;
Ivezić, Željko; Jacobson, Heather R.; Jiang, Linhua; Johansson,
Jonas; Johnson, Jennifer A.; Kauffmann, Guinevere; Kirkby, David;
Kirkpatrick, Jessica A.; Klaene, Mark A.; Knapp, Gillian R.; Kneib,
Jean-Paul; Le Goff, Jean-Marc; Leauthaud, Alexie; Lee, Khee-Gan;
Lee, Young Sun; Long, Daniel C.; Loomis, Craig P.; Lucatello, Sara;
Lundgren, Britt; Lupton, Robert H.; Ma, Bo; Ma, Zhibo; MacDonald,
Nicholas; Mack, Claude E.; Mahadevan, Suvrath; Maia, Marcio A. G.;
Majewski, Steven R.; Makler, Martin; Malanushenko, Elena; Malanushenko,
Viktor; Manchado, A.; Mandelbaum, Rachel; Manera, Marc; Maraston,
Claudia; Margala, Daniel; Martell, Sarah L.; McBride, Cameron K.;
McGreer, Ian D.; McMahon, Richard G.; Ménard, Brice; Meszaros,
Sz.; Miralda-Escudé, Jordi; Montero-Dorta, Antonio D.; Montesano,
Francesco; Morrison, Heather L.; Muna, Demitri; Munn, Jeffrey A.;
Murayama, Hitoshi; Myers, Adam D.; Neto, A. F.; Nguyen, Duy Cuong;
Nichol, Robert C.; Nidever, David L.; Noterdaeme, Pasquier; Nuza,
Sebastián E.; Ogando, Ricardo L. C.; Olmstead, Matthew D.; Oravetz,
Daniel J.; Owen, Russell; Padmanabhan, Nikhil; Palanque-Delabrouille,
Nathalie; Pan, Kaike; Parejko, John K.; Parihar, Prachi; Pâris,
Isabelle; Pattarakijwanich, Petchara; Pepper, Joshua; Percival,
Will J.; Pérez-Fournon, Ismael; Pérez-Ràfols, Ignasi; Petitjean,
Patrick; Pforr, Janine; Pieri, Matthew M.; Pinsonneault, Marc H.;
Porto de Mello, G. F.; Prada, Francisco; Price-Whelan, Adrian M.;
Raddick, M. Jordan; Rebolo, Rafael; Rich, James; Richards, Gordon
T.; Robin, Annie C.; Rocha-Pinto, Helio J.; Rockosi, Constance M.;
Roe, Natalie A.; Ross, Ashley J.; Ross, Nicholas P.; Rossi, Graziano;
Rubiño-Martin, J. A.; Samushia, Lado; Sanchez Almeida, J.; Sánchez,
Ariel G.; Santiago, Basílio; Sayres, Conor; Schlegel, David J.;
Schlesinger, Katharine J.; Schmidt, Sarah J.; Schneider, Donald P.;
Schultheis, Mathias; Schwope, Axel D.; Scóccola, C. G.; Seljak,
Uros; Sheldon, Erin; Shen, Yue; Shu, Yiping; Simmerer, Jennifer;
Simmons, Audrey E.; Skibba, Ramin A.; Skrutskie, M. F.; Slosar, A.;
Sobreira, Flavia; Sobeck, Jennifer S.; Stassun, Keivan G.; Steele,
Oliver; Steinmetz, Matthias; Strauss, Michael A.; Streblyanska, Alina;
Suzuki, Nao; Swanson, Molly E. C.; Tal, Tomer; Thakar, Aniruddha R.;
Thomas, Daniel; Thompson, Benjamin A.; Tinker, Jeremy L.; Tojeiro,
Rita; Tremonti, Christy A.; Vargas Magaña, M.; Verde, Licia; Viel,
Matteo; Vikas, Shailendra K.; Vogt, Nicole P.; Wake, David A.; Wang,
Ji; Weaver, Benjamin A.; Weinberg, David H.; Weiner, Benjamin J.;
West, Andrew A.; White, Martin; Wilson, John C.; Wisniewski, John P.;
Wood-Vasey, W. M.; Yanny, Brian; Yèche, Christophe; York, Donald G.;
Zamora, O.; Zasowski, Gail; Zehavi, Idit; Zhao, Gong-Bo; Zheng, Zheng;
Zhu, Guangtun; Zinn, Joel C.
2012ApJS..203...21A Altcode: 2012arXiv1207.7137S
The Sloan Digital Sky Survey III (SDSS-III) presents the first
spectroscopic data from the Baryon Oscillation Spectroscopic Survey
(BOSS). This ninth data release (DR9) of the SDSS project includes
535,995 new galaxy spectra (median z ~ 0.52), 102,100 new quasar
spectra (median z ~ 2.32), and 90,897 new stellar spectra, along
with the data presented in previous data releases. These spectra were
obtained with the new BOSS spectrograph and were taken between 2009
December and 2011 July. In addition, the stellar parameters pipeline,
which determines radial velocities, surface temperatures, surface
gravities, and metallicities of stars, has been updated and refined with
improvements in temperature estimates for stars with T <SUB>eff</SUB>
< 5000 K and in metallicity estimates for stars with [Fe/H] >
-0.5. DR9 includes new stellar parameters for all stars presented in
DR8, including stars from SDSS-I and II, as well as those observed as
part of the SEGUE-2. The astrometry error introduced in the DR8 imaging
catalogs has been corrected in the DR9 data products. The next data
release for SDSS-III will be in Summer 2013, which will present the
first data from the APOGEE along with another year of data from BOSS,
followed by the final SDSS-III data release in 2014 December.
---------------------------------------------------------
Title: DRAFTS: A Deep, Rapid Archival Flare Transient Search in the
Galactic Bulge
Authors: Osten, Rachel A.; Kowalski, Adam; Sahu, Kailash; Hawley,
Suzanne L.
2012ApJ...754....4O Altcode: 2012arXiv1205.1485O
We utilize the Sagittarius Window Eclipsing Extrasolar Planet Search
Hubble Space Telescope/Advanced Camera for Surveys data set for a Deep
Rapid Archival Flare Transient Search to constrain the flare rate toward
the older stellar population in the Galactic bulge. During seven days
of monitoring 229,293 stars brighter than V = 29.5, we find evidence for
flaring activity in 105 stars between V = 20 and V = 28. We divided the
sample into non-variable stars and variable stars whose light curves
contain large-scale variability. The flare rate on variable stars is
~700 times that of non-variable stars, with a significant correlation
between the amount of underlying stellar variability and peak flare
amplitude. The flare energy loss rates are generally higher than
those of nearby well-studied single dMe flare stars. The distribution
of proper motions is consistent with the flaring stars being at the
distance and age of the Galactic bulge. If they are single dwarfs,
then they span a range of ≈1.0-0.25 M <SUB>⊙</SUB>. A majority of
the flaring stars exhibit periodic photometric modulations with P <
3 days. If these are tidally locked magnetically active binary systems,
then their fraction in the bulge is enhanced by a factor of ~20 compared
to the local value. These stars may be useful for placing constraints
on the angular momentum evolution of cool close binary stars. Our
results expand the type of stars studied for flares in the optical
band, and suggest that future sensitive optical time-domain studies
will have to contend with a larger sample of flaring stars than the
M dwarf flare stars usually considered.
---------------------------------------------------------
Title: MOST Observations of the Flare Star AD Leo
Authors: Hunt-Walker, Nicholas M.; Hilton, Eric J.; Kowalski, Adam F.;
Hawley, Suzanne L.; Matthews, Jaymie M.
2012PASP..124..545H Altcode: 2012arXiv1206.5019H
We present continuous, high-precision photometric monitoring data
with 1 minute cadence of the dM3e flare star AD Leo with the MOST
satellite. We observed 19 flares in 5.8 days and found a flare
frequency distribution that is similar to previous studies. The light
curve reveals a sinusoidal modulation with a period of days that we
attribute to the rotation of a stellar spot rotating into and out
of view. We see no correlation between the occurrence of flares and
rotational phase, indicating that there may be many spots distributed
at different longitudes or, possibly, that the modulation is caused
by varying surface coverage of a large polar spot that is viewed
nearly pole-on. The data show no correlation between flare energy
and the time since the previous flare. We use these results to reject
a simple model in which all magnetic energy is stored in one active
region and released only during flares. <P />Based on observations
obtained with the Apache Point Observatory 3.5 m telescope, which is
owned and operated by the Astrophysical Research Consortium.
---------------------------------------------------------
Title: Erratum: "The Luminosity and Mass Functions of
Low-mass Stars in the Galactic Disk. II. The Field" <A
href="/abs/2010AJ....139.2679B">(2010, AJ, 139, 2679)</A>
Authors: Bochanski, John J.; Hawley, Suzanne L.; Covey, Kevin R.;
West, Andrew A.; Reid, I. Neill; Golimowski, David A.; Ivezić, Željko
2012AJ....143..152B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Time-resolved NUV And Optical Spectra Of A Stellar Megaflare
On YZ CMi With SALT/RSS
Authors: Brown, Benjamin; Kowalski, A. F.; Mathioudakis, M.; Hooper,
E. J.; Hawley, S. L.; Osten, R. A.; Wisniewski, J. P.
2012AAS...22020452B Altcode:
The primary mode of radiative energy release in stellar flares is
in the optical and near-ultraviolet (NUV) continuum. Active M-dwarf
stares flare more frequently than the Sun, and their flares can be
substantially more energetic. The dominant component in solar flare
white light is thought to be Hydrogen recombination, whereas for stellar
M dwarf flares, the dominant component is thought to be T 10,000 K
blackbody emission. Recently we have obtained very high time-cadence
spectral observations of the flaring M-dwarf YZ CMi (3200-6000A) using
the Robert Stobie Spectrograph on the 11-meter South African Large
Telescope (SALT/RSS), achieving 100x better temporal resolution than
has previously been possible at the atmospheric limit. We observed
a megaflare of over 100x flux enhancement in the NUV emission. Here
we discuss the evolution of the stellar flare spectrum during the
rapid impulsive phase of the flare and the implications for stellar
flare models.
---------------------------------------------------------
Title: Using Kepler Data to Characterize the Flare Properties of
GK Stars
Authors: Kowalski, Adam F.; Deitrick, Russell J.; Brown, Alex;
Davenport, Jim R. A.; Hawley, Suzanne L.; Hilton, Eric J.; Ayres,
Thomas R.; Berdyugina, Svetlana V.; Harper, Graham M.; Korhonen,
Heidi; Walkowicz, Lucianne M.
2012decs.confE.120K Altcode:
Due to their high occurrence rate and large contrast against the
background stellar emission, white-light flares on a handful of
very active low-mass M stars have been the primary source for our
understanding of optical flare emission. Kepler's high-precision, long
baseline light curves have opened up the characterization of white-light
emission to new domains of stars, including active G dwarfs. We present
the properties of white-light flares on GALEX-selected solar-type stars
from GO data in Q1-Q7. The flares are discussed in relation to intrinsic
stellar properties, which are constrained by a vast amount of follow-up
characterization of the sample. We compare the flare properties to
large white-light flares observed on the Sun. These high-precision
state-of-the-art observations will provide important constraints for
models of internal magnetic dynamos and NLTE radiative-hydrodynamic
simulations of energy deposition in the lower atmospheric layers.
---------------------------------------------------------
Title: Multi-wavelength Characterization of Stellar Flares on Low-mass
Stars Using SDSS and 2MASS Time-domain Surveys
Authors: Davenport, James R. A.; Becker, Andrew C.; Kowalski, Adam
F.; Hawley, Suzanne L.; Schmidt, Sarah J.; Hilton, Eric J.; Sesar,
Branimir; Cutri, Roc
2012ApJ...748...58D Altcode: 2012arXiv1202.1902D
We present the first rates of flares from M dwarf stars in both red
optical and near-infrared (NIR) filters. We have studied ~50,000 M
dwarfs from the Sloan Digital Sky Survey (SDSS) Stripe 82 area and
1321 M dwarfs from the Two Micron All Sky Survey (2MASS) Calibration
Scan Point Source Working Database that overlap SDSS imaging fields. We
assign photometric spectral types from M0 to M6 using (r - i) and (i -
z) colors for every star in our sample. Stripe 82 stars each have 50-100
epochs of data, while 2MASS Calibration stars have ~1900 epochs. From
these data we estimate the observed rates and theoretical detection
thresholds for flares in eight photometric bands as a function of
spectral type. Optical flare rates are found to be in agreement with
previous studies, while the frequency per hour of NIR flare detections
is found to be more than two orders of magnitude lower. An excess
of small-amplitude flux increases in all bands exhibits a power-law
distribution, which we interpret as the result of flares below our
detection thresholds. In order to investigate the recovery efficiency
for flares in each filter, we extend a two-component flare model into
the NIR. Quiescent M0-M6 spectral templates were used with the model
to predict the photometric response of flares from u to K<SUB>s</SUB>
. We determine that red optical filters are sensitive to flares with
u-band amplitudes gsim2 mag, and NIR filters to flares with Δu gsim
4.5 mag. Our model predicts that M0 stars have the best color contrast
for J-band detections, but M4-M6 stars should yield the highest rate of
NIR flares with amplitudes of ΔJ >= 0.01 mag. Characterizing flare
rates and photometric variations at longer wavelengths is important for
predicting the signatures of M dwarf variability in next-generation
surveys, and we discuss their impact on surveys such as the Large
Synoptic Survey Telescope.
---------------------------------------------------------
Title: The Multiple Continuum Components in the White-Light Flare
of 16 January 2009 on the dM4.5e Star YZ CMi
Authors: Kowalski, A. F.; Hawley, S. L.; Holtzman, J. A.; Wisniewski,
J. P.; Hilton, E. J.
2012SoPh..277...21K Altcode: 2011arXiv1109.0837K
The white light during M dwarf flares has long been known to exhibit
the broadband shape of a T≈10 000 K blackbody, and the white
light in solar-flares is thought to arise primarily from hydrogen
recombination. Yet, a current lack of broad-wavelength coverage
solar flare spectra in the optical/near-UV region prohibits a direct
comparison of the continuum properties to determine if they are indeed
so different. New spectroscopic observations of a secondary flare
during the decay of a megaflare on the dM4.5e star YZ CMi have revealed
multiple components in the white-light continuum of stellar flares,
including both a blackbody-like spectrum and a hydrogen-recombination
spectrum. One of the most surprising findings is that these two
components are anti-correlated in their temporal evolution. We combine
initial phenomenological modeling of the continuum components with
spectra from radiative hydrodynamic models to show that continuum
veiling causes the measured anti-correlation. This modeling allows us
to use the components' inferred properties to predict how a similar
spatially resolved, multiple-component, white-light continuum might
appear using analogies to several solar-flare phenomena. We also
compare the properties of the optical stellar flare white light to
Ellerman bombs on the Sun.
---------------------------------------------------------
Title: MMT Hectochelle Spectral Variability of Active Late-type
Stars in the Kepler Field (2012A)
Authors: Brown, Alexander; Walkowicz, Lucianne; Hawley, Suzanne;
Kowalski, Adam; Saar, Steven; Furesz, Gabor
2012noao.prop..332B Altcode:
We have on-going Kepler photometric monitoring of over 200 active
late-type (mid-A - K) stars as part of our Cycles 1/2/3 Guest Observer
(GO) programs with the aim of studying starspot evolution, differential
rotation, activity cycles, and flares. We propose to use the MMT
Hectochelle multiobject spectrograph to observe over 120 of these stars
to determine a range of basic physical properties for the stars, such
as radial velocity variations due to binarity, chromospheric activity
levels from Ca II H+K and H(alpha), projected rotational velocities
for comparison to the rotational periods measured directly by Kepler,
age/youth as indicated by Li I, and better effective temperature and
luminosity estimates. In addition, to provide a superior sample for
statistical studies another ~1,000 GKM dwarf stars showing either
starspot modulation from the Kepler Team's data or from our on-going
deep XMM X-ray survey will be observed using the unassigned fibers in
each field. These measurements require the 32,000 spectral resolution
provided by Hectochelle, which is hard to obtain efficiently for
13-15th magnitude stars any other way.
---------------------------------------------------------
Title: Hα Emission Variability in Active M Dwarfs
Authors: Bell, Keaton J.; Hilton, Eric J.; Davenport, James R. A.;
Hawley, Suzanne L.; West, Andrew A.; Rogel, Allen B.
2012PASP..124...14B Altcode: 2011arXiv1112.1411B
We use ∼12,000 spectra of ∼3500 magnetically active M0-M9 dwarfs
from the Sloan Digital Sky Survey taken at 10-15 minute intervals,
together with ∼300 spectra of ∼60 M0-M8 stars obtained hourly
with the Hydra multiobject spectrometer, to probe Hα variability on
timescales of minutes to weeks. With multiple observations for every
star examined, we are able to characterize fluctuations in Hα emission
as a function of activity strength and spectral type. Stars with greater
magnetic activity (as quantified by L<SUB>Hα</SUB>/L<SUB>bol</SUB>)
are found to be less variable at all spectral types. We attribute this
result to the stronger level of persistent emission in the high-activity
stars, requiring a larger heating event in order to produce measurable
variability. We also construct Hα structure functions to constrain
the timescale of variability. The more active objects with lower
variability exhibit a characteristic timescale longer than 1 hr,
likely due to larger, longer lasting heating events, while the less
active objects with higher variability have a characteristic timescale
shorter than 15 minutes.
---------------------------------------------------------
Title: Probing the Flare Atmospheres of M Dwarfs Using Infrared
Emission Lines
Authors: Schmidt, Sarah J.; Kowalski, Adam F.; Hawley, Suzanne L.;
Hilton, Eric J.; Wisniewski, John P.; Tofflemire, Benjamin M.
2012ApJ...745...14S Altcode: 2011arXiv1111.7072S
We present the results of a campaign to monitor active M dwarfs
using infrared spectroscopy, supplemented with optical photometry and
spectroscopy. We detected 16 flares during nearly 50 hr of observations
on EV Lac, AD Leo, YZ CMi, and VB 8. The three most energetic flares
also showed infrared emission, including the first reported detections
of Pβ, Pγ, He I λ10830, and Brγ during an M dwarf flare. The
strongest flare (Δu = 4.02 on EV Lac) showed emission from Hγ, Hδ,
He I λ4471, and Ca II K in the UV/blue and Pβ, Pγ, Pδ, Brγ,
and He I λ10830 in the infrared. The weaker flares (Δu = 1.68 on
EV Lac and ΔU = 1.38 on YZ CMi) were only observed with photometry
and infrared spectroscopy; both showed emission from Pβ, Pγ, and
He I λ10830. The strongest infrared emission line, Pβ, occurred in
the active mid-M dwarfs with a duty cycle of ~3%-4%. To examine the
most energetic flare, we used the static NLTE radiative transfer code
RH to produce model spectra based on a suite of one-dimensional model
atmospheres. Using a hotter chromosphere than previous one-dimensional
atmospheric models, we obtain line ratios that match most of the
observed emission lines. <P />Based on observations obtained with the
Apache Point Observatory 3.5 m telescope, which is owned and operated
by the Astrophysical Research Consortium.
---------------------------------------------------------
Title: The Implications of M Dwarf Flares on the Detection and
Characterization of Exoplanets at Infrared Wavelengths
Authors: Tofflemire, Benjamin M.; Wisniewski, John P.; Kowalski,
Adam F.; Schmidt, Sarah J.; Kundurthy, Praveen; Hilton, Eric J.;
Holtzman, Jon A.; Hawley, Suzanne L.
2012AJ....143...12T Altcode: 2011arXiv1111.1793T
We present the results of an observational campaign which obtained
high-cadence, high-precision, simultaneous optical and IR photometric
observations of three M dwarf flare stars for 47 hr. The campaign
was designed to characterize the behavior of energetic flare events,
which routinely occur on M dwarfs, at IR wavelengths to millimagnitude
precision, and quantify to what extent such events might influence
current and future efforts to detect and characterize extrasolar
planets surrounding these stars. We detected and characterized four
highly energetic optical flares having U-band total energies of
~7.8 × 10<SUP>30</SUP> to ~1.3 × 10<SUP>32</SUP> erg, and found no
corresponding response in the J, H, or Ks bandpasses at the precision of
our data. For active dM3e stars, we find that a ~1.3 × 10<SUP>32</SUP>
erg U-band flare (ΔU <SUB>max</SUB> ~ 1.5 mag) will induce <8.3
(J), <8.5 (H), and <11.7 (Ks) mmag of a response. A flare of
this energy or greater should occur less than once per 18 hr. For
active dM4.5e stars, we find that a ~5.1 × 10<SUP>31</SUP> erg
U-band flare (ΔU <SUB>max</SUB> ~ 1.6 mag) will induce <7.8 (J),
<8.8 (H), and <5.1 (Ks) mmag of a response. A flare of this
energy or greater should occur less than once per 10 hr. No evidence
of stellar variability not associated with discrete flare events was
observed at the level of ~3.9 mmag over 1 hr timescales and at the
level of ~5.6 mmag over 7.5 hr timescales. We therefore demonstrate
that most M dwarf stellar activity and flares will not influence IR
detection and characterization studies of M dwarf exoplanets above
the level of ~5-11 mmag, depending on the filter and spectral type. We
speculate that the most energetic megaflares on M dwarfs, which occur
at rates of once per month, are likely to be easily detected in IR
observations with sensitivity of tens of millimagnitudes. We also
discuss how recent detections of line flux enhancements during M dwarf
flares could influence IR transmission spectroscopic observations of
M dwarf exoplanets.
---------------------------------------------------------
Title: Long-Term Optical and Near-Infrared Spectroscopic Monitoring
of ɛ Aurigae During the 2009-11 Eclipse
Authors: Barentine, John C.; Ketzeback, W. F.; Dembicky, J. M.;
Huehnerhoff, J.; McMillan, R.; Saurage, G.; Sheldon, A.; Coughlin,
J.; Ule, N.; Hawley, S.; Schmidt, S.; Wallerstein, G.; Leadbeater,
R.; York, D. G.
2012AAS...21943312B Altcode:
We present the results of a program to spectroscopically monitor
the long-period (P ∼ 27 y) eclipsing binary ɛ Aurigae during
the primary eclipse of 2009-11 with the ARC 3.5m telescope at Apache
Point. Spectroscopic data from 3500-10000Å were obtained at a resolving
power of R 38000 and from 0.9-2.5μm at R 3000 with a temporal cadence
of approximately one week for the full duration of the eclipse. By
noting the velocity centroids of certain weak metal lines (e.g., Na I D
and K I 7699Å associated with the presumed optically-thick disk around
the unseen secondary, we confirm a mid-eclipse epoch of HJD 2455384. The
same lines indicate disk absorption with equivalent widths equal to or
greater than the corresponding lines in the primary photosphere. The
components of Hα and their evolution through the eclipse suggest
the presence of weak ionized hydrogen, possibly distributed in a
circumstellar ring or shell, and a separate, broad ionized component
associated with the secondary disk in the form of a disk atmosphere or
wind. Overall, our observations support the "consensus model” of ɛ
Aur, consisting of a 2 M⊙, F0 post-asymptotic giant branch primary
and a dust-enshrouded, 6 M⊙ B8 dwarf. Variability of the profiles
of certain lines such as Hα outside of eclipse encourages continued
long-term synoptic monitoring of ɛ Aur between primary eclipses to
better understand the circumstellar environment of the system.
---------------------------------------------------------
Title: White-Light Continuum Emission in M Dwarf Flares
Authors: Kowalski, Adam; Hawley, S. L.
2012AAS...21910403K Altcode:
A primary mode of radiative energy release in stellar flares
is the optical and near-ultraviolet (NUV) continuum. However,
radiative-hydrodynamic models of stellar flares using a solar flare
paradigm and the sparse observations of solar and stellar flare continua
are all seemingly in disagreement over the type(s) of emission that
contribute to the optical/NUV continuum during flares. We have completed
a long-term flare monitoring campaign using simultaneous low-resolution
(3400-9200A) spectroscopic and broadband photometric observations to
fully characterize the optical/NUV white light continuum emission on
short timescales. To date, our most significant results come from
observations during the decay phase of a megaflare on the dM4.5e
star YZ CMi, where we have detected multiple continuum components
that contribute to the white light near the Balmer jump (3646A). We
present a time-resolved spectral analysis of the continuum components
and emission lines for this flare and for several other large and small
flares obtained during our spectroscopic monitoring campaign. We compare
these data to phenomenological flare models with the RH code and to
preliminary results from the next-generation of radiative-hydrodynamic
1D flare models with the RADYN code. <P />Funding for this project
has been provided by NSF AST 0807205. Observations were obtained
with the ARC 3.5m, the NMSU 1m, and the ARCSAT 0.5m at the Apache
Point Observatory.
---------------------------------------------------------
Title: Kinematics, Colors, And Ages Of Ultracool Dwarfs
Authors: Schmidt, Sarah J.; Hawley, S. L.
2012AAS...21933006S Altcode:
We present results from multiple spectroscopic and photometric datasets
for late-M and L dwarfs in the field. These include L dwarfs selected
in SDSS data release 7, ultracool dwarfs within 20pc of the Sun as
part of the Brown Dwarfs Kinematics Project, and first results from
our SDSS-III ancillary program to obtain spectra of late-M and L
dwarfs. Combining radial velocities, proper motions, and colors from
each of these complementary datasets, we examine the ages of field L
dwarfs and investigate relations between color and age.
---------------------------------------------------------
Title: Hα Variability in Active Equal-Mass M Dwarf Wide Binaries
Authors: Gunning, Heather C.; Schmidt, S. J.; Davenport, J. R. A.;
Hawley, S. L.; Dhital, S.
2012AAS...21934516G Altcode:
We present monitoring of equal-mass, active mid-M dwarf wide binaries
using the mid-resolution optical spectrograph on the Astrophysical
Research Consortium 3.5-m telescope. We selected our sample for
spectroscopic follow-up from the Sloan Low-mass Wide Pairs of
Kinematically Equivalent Stars (SLoWPoKES) catalog. Our goal is to
examine the differences in activity level, as measured by the equivalent
width of Hα, of stars of similar masses, metallicities, and ages. We
will compare both the mean and the normalized variability of Hα
between the companions of each of our wide binary pairs. Additionally,
we will examine the variation in molecular bands, such as the
temperature-sensitive TiO feature, over time.
---------------------------------------------------------
Title: The Sloan Digital Sky Survey Data Release 7 M Dwarf
Spectroscopic Catalog
Authors: West, A. A.; Morgan, D. P.; Bochanski, J. J.; Andersen,
J. M.; Bell, K. J.; Kowalski, A. F.; Davenport, J. R. A.; Hawley,
S. L.; Schmidt, S. J.; Bernat, D.; Hilton, E. J.; Muirhead, P.;
Covey, K. R.; Rojas-Ayala, B.; Schlawin, E.; Gooding, M.; Schluns,
K.; Dhital, S.; Pineda, J. S.; Jones, D. O.
2011ASPC..448.1407W Altcode: 2010arXiv1012.3766W; 2011csss...16.1407W
We present a spectroscopic catalog of 70,841 visually inspected M
dwarfs from the seventh data release (DR7) of the Sloan Digital Sky
Survey (SDSS). For each spectrum, we provide measurements of the
spectral type, a number of molecular bandheads, and the Hα, Hβ,
Hγ, Hδ and Ca II K emission lines. In addition, we calculate the
metallicity-sensitive parameter ζ and 3D space motions for most of the
stars in the sample. Our catalog is cross-matched to Two Micron All Sky
Survey (2MASS) infrared data, and contains photometric distances for
each star. Future studies will use these data to thoroughly examine
magnetic activity and kinematics in late-type M dwarfs and examine
the chemical and dynamical history of the local Milky Way.
---------------------------------------------------------
Title: Mining Databases for M Dwarf Variability
Authors: Davenport, J. R. A.; Becker, A. C.; Hawley, S. L.; Kowalski,
A. F.; Sesar, B.; Cutri, R. M.
2011ASPC..448..983D Altcode: 2011csss...16..983D; 2011arXiv1101.1363D
Time-resolved databases with large spatial coverage are quickly
becoming a standard tool for all types of astronomical studies. We
report preliminary results from our search for stellar flares in the
2MASS calibration fields. A sample of 4343 M dwarfs, spatially matched
between the SDSS and the 2MASS calibration fields, each with hundreds
to thousands of epochs in near infrared bandpasses, is analyzed using
a modified Welch-Stetson index to characterize the variability. A
Monte Carlo model was used to assess the noise of the variability
index. We find significnat residuals above the noise with power-law
slopes of -3.37 and -4.05 for our JH and HK<SUB>s</SUB> distributions
respectively. This is evidence for flares being observed from M dwarfs
in infrared photometry.
---------------------------------------------------------
Title: M Dwarf Flares: Exoplanet Detection Implications
Authors: Tofflemire, B. M.; Wisniewski, J. P.; Hilton, E. J.; Kowalski,
A. F.; Kundurthy, P.; Schmidt, S. J.; Hawley, S. L.; Holtzman, J. A.
2011ASPC..448.1287T Altcode: 2011csss...16.1287T
Low mass stars such as M dwarfs have become prime targets for exoplanet
transit searches as their low luminosities and small stellar radii
could enable the detection of super-Earths residing in their habitable
zones. While promising transit targets, M dwarfs are also inherently
variable and can exhibit up to ∼6 magnitude flux enhancements in
the optical U-band. This is significantly higher than the predicted
transit depths of habitable zone super-Earths (0.005 magnitude
flux decrease). The behavior of flares at infrared (IR) wavelengths,
particularly those likely to be used to study and characterize M dwarf
exoplanets using facilities such as the James Web Space Telescope
(JWST), remains largely unknown. To address these uncertainties, we
are executing a coordinated, contemporaneous monitoring program of
the optical and IR flux of M dwarfs known to regularly flare. A suite
of telescopes located at the Kitt Peak National Observatory and the
Apache Point Observatory are used for the observations. We present
the initial results of this program.
---------------------------------------------------------
Title: L Dwarf Kinematics
Authors: Schmidt, S. J.; West, A. A.; Hawley, S. L.
2011ASPC..448..333S Altcode: 2011csss...16..333S
The L spectral class is composed of both stars and brown dwarfs. Because
brown dwarfs cool as they age, it is not possible to assign a mass to
an L dwarf based on its T<SUB>eff</SUB>/spectral type. Due to this
degeneracy between mass, age, and spectral type, it is especially
important to determine the ages of L dwarfs. Indirect estimates of age,
such as a relationship between age and J-K<SUB>S</SUB> color have
been proposed, but a better calibration is needed. Kinematics have
proven to be a useful age calibrator, and will likely be instrumental
in future studies of L dwarf ages. We examine the differences between
the kinematics of a large, magnitude limited sample of L dwarfs from
the Sloan Digital Sky Survey, and a smaller, volume-limited sample of
L dwarfs within 20pc. Both samples show a kinematically hot component,
suggestive of an older population of stars. Additionally, L dwarfs
with bluer J-K<SUB>S</SUB> colors have hotter kinematics than redder
L dwarfs, indicating a relationship between J-K<SUB>S</SUB> color and
age in both samples.
---------------------------------------------------------
Title: White Light Flare Continuum Observations with ULTRACAM
Authors: Kowalski, A. F.; Mathioudakis, M.; Hawley, S. L.; Hilton,
E. J.; Dhillon, V. S.; Marsh, T. R.; Copperwheat, C. M.
2011ASPC..448.1157K Altcode: 2011arXiv1103.0822K; 2011csss...16.1157K
We present sub-second, continuous-coverage photometry of three flares
on the dM3.5e star, EQ Peg A, using custom continuum filters with
WHT/ULTRACAM. These data provide a new view of flare continuum emission,
with each flare exhibiting a very distinct light curve morphology. The
spectral shape of flare emission for the two large-amplitude flares
is compared with synthetic ULTRACAM measurements taken from the
spectra during the large 'megaflare' event on a similar type flare
star. The white light shape during the impulsive phase of the EQ
Peg flares is consistent with the range of colors derived from the
megaflare continuum, which is known to contain a Hydrogen recombination
component and compact, blackbody-like components. Tentative evidence
in the ULTRACAM photometry is found for an anti-correlation between
the emission of these components.
---------------------------------------------------------
Title: Statistical Parallax Analysis of SDSS M Dwarfs
Authors: Hawley, S. L.; Bochanski, J. J.; West, A. A.
2011ASPC..448.1359H Altcode: 2011csss...16.1359H; 2010arXiv1012.3505H
We report on the analysis of ∼ 22,000 M dwarfs using a statistical
parallax method. This technique employs a maximum-likelihood formulation
to simultaneously solve for the absolute magnitude, velocity ellipsoid
parameters and reflex solar motion of a homogeneous stellar sample,
and has previously been applied to Galactic RR Lyrae and Cepheid
populations and to the Palomar/Michigan State University (PMSU) survey
of nearby low-mass stars. We analyze subsamples of the most recent
spectroscopic catalog of M dwarfs in the Sloan Digital Sky Survey (SDSS)
to determine absolute magnitudes and kinematic properties as a function
of spectral type, color, chromospheric activity and metallicity. We
find new, independent spectral type-absolute magnitude relations, and
color-absolute magnitude relations in the SDSS filters, and compare
to those found from other methods. Active stars have brighter absolute
magnitudes and lower metallicity stars have fainter absolute magnitudes
for stars of type M0-M4. Our kinematic analysis confirms previous
results for the solar motion and velocity dispersions, with more distant
stars possessing larger peculiar motions, and chromospherically active
(younger) stars having smaller velocity dispersions than their inactive
counterparts. We find some evidence for systematic differences in the
mean U and W velocities of samples subdivided by color.
---------------------------------------------------------
Title: The Galactic M Dwarf Flare Rate
Authors: Hilton, E. J.; Hawley, S. L.; Kowalski, A. F.; Holtzman, J.
2011ASPC..448..197H Altcode: 2011csss...16..197H
M dwarfs are known to flare on timescales from minutes to hours,
with flux increases of several magnitudes in the blue/near-UV. These
frequent, powerful events, which are caused by magnetic reconnection,
will have a strong observational signature in large, time-domain
surveys. The radiation and particle fluxes from flares may also exert
a significant influence on the atmospheres of orbiting planets, and
affect their habitability. We present a statistical model of flaring
M dwarfs in the Galaxy that allows us to predict the observed flare
rate along a given line of sight for a particular survey depth and
cadence. The parameters that enter the model are the Galactic structure,
the distribution of magnetically active and inactive M dwarfs, and
the flare frequency distribution (FFD) of both populations. The FFD is
a function of spectral type, activity, and Galactic height. Although
inactive M dwarfs make up the majority of stars in a magnitude-limited
survey, the FFD of inactive stars is very poorly constrained. We
have organized a flare monitoring campaign comprising hundreds of
hours of new observations from both the ground and space to better
constrain flare rates. Incorporating the new observations into our
model provides more accurate predictions of stellar variability caused
by flares on M dwarfs. We pay particular attention to the likelihood
of flares appearing as optical transients (i.e., host star not seen
in quiescent data).
---------------------------------------------------------
Title: Splinter Session "Solar and Stellar Flares"
Authors: Fletcher, L.; Hudson, H.; Cauzzi, G.; Getman, K. V.; Giampapa,
M.; Hawley, S. L.; Heinzel, P.; Johnstone, C.; Kowalski, A. F.; Osten,
R. A.; Pye, J.
2011ASPC..448..441F Altcode: 2011csss...16..441F; 2012arXiv1206.3997F
This summary reports on papers presented at the Cool Stars-16 meeting in
the splinter session "Solar and Stellar flares." Although many topics
were discussed, the main themes were the commonality of interests,
and of physics, between the solar and stellar flare communities,
and the opportunities for important new observations in the near future.
---------------------------------------------------------
Title: SDSS-III: Massive Spectroscopic Surveys of the Distant
Universe, the Milky Way, and Extra-Solar Planetary Systems
Authors: Eisenstein, Daniel J.; Weinberg, David H.; Agol, Eric; Aihara,
Hiroaki; Allende Prieto, Carlos; Anderson, Scott F.; Arns, James
A.; Aubourg, Éric; Bailey, Stephen; Balbinot, Eduardo; Barkhouser,
Robert; Beers, Timothy C.; Berlind, Andreas A.; Bickerton, Steven J.;
Bizyaev, Dmitry; Blanton, Michael R.; Bochanski, John J.; Bolton,
Adam S.; Bosman, Casey T.; Bovy, Jo; Brandt, W. N.; Breslauer, Ben;
Brewington, Howard J.; Brinkmann, J.; Brown, Peter J.; Brownstein,
Joel R.; Burger, Dan; Busca, Nicolas G.; Campbell, Heather; Cargile,
Phillip A.; Carithers, William C.; Carlberg, Joleen K.; Carr, Michael
A.; Chang, Liang; Chen, Yanmei; Chiappini, Cristina; Comparat, Johan;
Connolly, Natalia; Cortes, Marina; Croft, Rupert A. C.; Cunha, Katia;
da Costa, Luiz N.; Davenport, James R. A.; Dawson, Kyle; De Lee,
Nathan; Porto de Mello, Gustavo F.; de Simoni, Fernando; Dean, Janice;
Dhital, Saurav; Ealet, Anne; Ebelke, Garrett L.; Edmondson, Edward M.;
Eiting, Jacob M.; Escoffier, Stephanie; Esposito, Massimiliano; Evans,
Michael L.; Fan, Xiaohui; Femenía Castellá, Bruno; Dutra Ferreira,
Leticia; Fitzgerald, Greg; Fleming, Scott W.; Font-Ribera, Andreu;
Ford, Eric B.; Frinchaboy, Peter M.; García Pérez, Ana Elia; Gaudi,
B. Scott; Ge, Jian; Ghezzi, Luan; Gillespie, Bruce A.; Gilmore, G.;
Girardi, Léo; Gott, J. Richard; Gould, Andrew; Grebel, Eva K.; Gunn,
James E.; Hamilton, Jean-Christophe; Harding, Paul; Harris, David
W.; Hawley, Suzanne L.; Hearty, Frederick R.; Hennawi, Joseph F.;
González Hernández, Jonay I.; Ho, Shirley; Hogg, David W.; Holtzman,
Jon A.; Honscheid, Klaus; Inada, Naohisa; Ivans, Inese I.; Jiang,
Linhua; Jiang, Peng; Johnson, Jennifer A.; Jordan, Cathy; Jordan,
Wendell P.; Kauffmann, Guinevere; Kazin, Eyal; Kirkby, David; Klaene,
Mark A.; Knapp, G. R.; Kneib, Jean-Paul; Kochanek, C. S.; Koesterke,
Lars; Kollmeier, Juna A.; Kron, Richard G.; Lampeitl, Hubert; Lang,
Dustin; Lawler, James E.; Le Goff, Jean-Marc; Lee, Brian L.; Lee,
Young Sun; Leisenring, Jarron M.; Lin, Yen-Ting; Liu, Jian; Long,
Daniel C.; Loomis, Craig P.; Lucatello, Sara; Lundgren, Britt; Lupton,
Robert H.; Ma, Bo; Ma, Zhibo; MacDonald, Nicholas; Mack, Claude;
Mahadevan, Suvrath; Maia, Marcio A. G.; Majewski, Steven R.; Makler,
Martin; Malanushenko, Elena; Malanushenko, Viktor; Mandelbaum, Rachel;
Maraston, Claudia; Margala, Daniel; Maseman, Paul; Masters, Karen L.;
McBride, Cameron K.; McDonald, Patrick; McGreer, Ian D.; McMahon,
Richard G.; Mena Requejo, Olga; Ménard, Brice; Miralda-Escudé,
Jordi; Morrison, Heather L.; Mullally, Fergal; Muna, Demitri; Murayama,
Hitoshi; Myers, Adam D.; Naugle, Tracy; Neto, Angelo Fausti; Nguyen,
Duy Cuong; Nichol, Robert C.; Nidever, David L.; O'Connell, Robert
W.; Ogando, Ricardo L. C.; Olmstead, Matthew D.; Oravetz, Daniel J.;
Padmanabhan, Nikhil; Paegert, Martin; Palanque-Delabrouille, Nathalie;
Pan, Kaike; Pandey, Parul; Parejko, John K.; Pâris, Isabelle;
Pellegrini, Paulo; Pepper, Joshua; Percival, Will J.; Petitjean,
Patrick; Pfaffenberger, Robert; Pforr, Janine; Phleps, Stefanie;
Pichon, Christophe; Pieri, Matthew M.; Prada, Francisco; Price-Whelan,
Adrian M.; Raddick, M. Jordan; Ramos, Beatriz H. F.; Reid, I. Neill;
Reyle, Celine; Rich, James; Richards, Gordon T.; Rieke, George H.;
Rieke, Marcia J.; Rix, Hans-Walter; Robin, Annie C.; Rocha-Pinto,
Helio J.; Rockosi, Constance M.; Roe, Natalie A.; Rollinde, Emmanuel;
Ross, Ashley J.; Ross, Nicholas P.; Rossetto, Bruno; Sánchez, Ariel
G.; Santiago, Basilio; Sayres, Conor; Schiavon, Ricardo; Schlegel,
David J.; Schlesinger, Katharine J.; Schmidt, Sarah J.; Schneider,
Donald P.; Sellgren, Kris; Shelden, Alaina; Sheldon, Erin; Shetrone,
Matthew; Shu, Yiping; Silverman, John D.; Simmerer, Jennifer; Simmons,
Audrey E.; Sivarani, Thirupathi; Skrutskie, M. F.; Slosar, Anže; Smee,
Stephen; Smith, Verne V.; Snedden, Stephanie A.; Stassun, Keivan G.;
Steele, Oliver; Steinmetz, Matthias; Stockett, Mark H.; Stollberg,
Todd; Strauss, Michael A.; Szalay, Alexander S.; Tanaka, Masayuki;
Thakar, Aniruddha R.; Thomas, Daniel; Tinker, Jeremy L.; Tofflemire,
Benjamin M.; Tojeiro, Rita; Tremonti, Christy A.; Vargas Magaña,
Mariana; Verde, Licia; Vogt, Nicole P.; Wake, David A.; Wan, Xiaoke;
Wang, Ji; Weaver, Benjamin A.; White, Martin; White, Simon D. M.;
Wilson, John C.; Wisniewski, John P.; Wood-Vasey, W. Michael; Yanny,
Brian; Yasuda, Naoki; Yèche, Christophe; York, Donald G.; Young,
Erick; Zasowski, Gail; Zehavi, Idit; Zhao, Bo
2011AJ....142...72E Altcode: 2011arXiv1101.1529E
Building on the legacy of the Sloan Digital Sky Survey (SDSS-I
and II), SDSS-III is a program of four spectroscopic surveys on
three scientific themes: dark energy and cosmological parameters,
the history and structure of the Milky Way, and the population of
giant planets around other stars. In keeping with SDSS tradition,
SDSS-III will provide regular public releases of all its data,
beginning with SDSS Data Release 8 (DR8), which was made public
in 2011 January and includes SDSS-I and SDSS-II images and spectra
reprocessed with the latest pipelines and calibrations produced for the
SDSS-III investigations. This paper presents an overview of the four
surveys that comprise SDSS-III. The Baryon Oscillation Spectroscopic
Survey will measure redshifts of 1.5 million massive galaxies and
Lyα forest spectra of 150,000 quasars, using the baryon acoustic
oscillation feature of large-scale structure to obtain percent-level
determinations of the distance scale and Hubble expansion rate at z <
0.7 and at z ≈ 2.5. SEGUE-2, an already completed SDSS-III survey
that is the continuation of the SDSS-II Sloan Extension for Galactic
Understanding and Exploration (SEGUE), measured medium-resolution
(R = λ/Δλ ≈ 1800) optical spectra of 118,000 stars in a
variety of target categories, probing chemical evolution, stellar
kinematics and substructure, and the mass profile of the dark matter
halo from the solar neighborhood to distances of 100 kpc. APOGEE,
the Apache Point Observatory Galactic Evolution Experiment, will
obtain high-resolution (R ≈ 30,000), high signal-to-noise ratio
(S/N >= 100 per resolution element), H-band (1.51 μm < λ
< 1.70 μm) spectra of 10<SUP>5</SUP> evolved, late-type stars,
measuring separate abundances for ~15 elements per star and creating
the first high-precision spectroscopic survey of all Galactic stellar
populations (bulge, bar, disks, halo) with a uniform set of stellar
tracers and spectral diagnostics. The Multi-object APO Radial Velocity
Exoplanet Large-area Survey (MARVELS) will monitor radial velocities
of more than 8000 FGK stars with the sensitivity and cadence (10-40
m s<SUP>-1</SUP>, ~24 visits per star) needed to detect giant planets
with periods up to two years, providing an unprecedented data set for
understanding the formation and dynamical evolution of giant planet
systems. As of 2011 January, SDSS-III has obtained spectra of more
than 240,000 galaxies, 29,000 z >= 2.2 quasars, and 140,000 stars,
including 74,000 velocity measurements of 2580 stars for MARVELS.
---------------------------------------------------------
Title: Erratum: "The Eighth Data Release of the Sloan
Digital Sky Survey: First Data from SDSS-III" <A
href="/abs/2011ApJS..193...29A">(2011, ApJS, 193, 29)</A>
Authors: Aihara, Hiroaki; Allende Prieto, Carlos; An, Deokkeun;
Anderson, Scott F.; Aubourg, Éric; Balbinot, Eduardo; Beers, Timothy
C.; Berlind, Andreas A.; Bickerton, Steven J.; Bizyaev, Dmitry;
Blanton, Michael R.; Bochanski, John J.; Bolton, Adam S.; Bovy, Jo;
Brandt, W. N.; Brinkmann, J.; Brown, Peter J.; Brownstein, Joel R.;
Busca, Nicolas G.; Campbell, Heather; Carr, Michael A.; Chen, Yanmei;
Chiappini, Cristina; Comparat, Johan; Connolly, Natalia; Cortes,
Marina; Croft, Rupert A. C.; Cuesta, Antonio J.; da Costa, Luiz N.;
Davenport, James R. A.; Dawson, Kyle; Dhital, Saurav; Ealet, Anne;
Ebelke, Garrett L.; Edmondson, Edward M.; Eisenstein, Daniel J.;
Escoffier, Stephanie; Esposito, Massimiliano; Evans, Michael L.; Fan,
Xiaohui; Femenía Castellá, Bruno; Font-Ribera, Andreu; Frinchaboy,
Peter M.; Ge, Jian; Gillespie, Bruce A.; Gilmore, G.; González
Hernández, Jonay I.; Gott, J. Richard; Gould, Andrew; Grebel, Eva
K.; Gunn, James E.; Hamilton, Jean-Christophe; Harding, Paul; Harris,
David W.; Hawley, Suzanne L.; Hearty, Frederick R.; Ho, Shirley; Hogg,
David W.; Holtzman, Jon A.; Honscheid, Klaus; Inada, Naohisa; Ivans,
Inese I.; Jiang, Linhua; Johnson, Jennifer A.; Jordan, Cathy; Jordan,
Wendell P.; Kazin, Eyal A.; Kirkby, David; Klaene, Mark A.; Knapp,
G. R.; Kneib, Jean-Paul; Kochanek, C. S.; Koesterke, Lars; Kollmeier,
Juna A.; Kron, Richard G.; Lampeitl, Hubert; Lang, Dustin; Le Goff,
Jean-Marc; Lee, Young Sun; Lin, Yen-Ting; Long, Daniel C.; Loomis,
Craig P.; Lucatello, Sara; Lundgren, Britt; Lupton, Robert H.; Ma,
Zhibo; MacDonald, Nicholas; Mahadevan, Suvrath; Maia, Marcio A. G.;
Makler, Martin; Malanushenko, Elena; Malanushenko, Viktor; Mandelbaum,
Rachel; Maraston, Claudia; Margala, Daniel; Masters, Karen L.; McBride,
Cameron K.; McGehee, Peregrine M.; McGreer, Ian D.; Ménard, Brice;
Miralda-Escudé, Jordi; Morrison, Heather L.; Mullally, F.; Muna,
Demitri; Munn, Jeffrey A.; Murayama, Hitoshi; Myers, Adam D.; Naugle,
Tracy; Neto, Angelo Fausti; Nguyen, Duy Cuong; Nichol, Robert C.;
O'Connell, Robert W.; Ogando, Ricardo L. C.; Olmstead, Matthew D.;
Oravetz, Daniel J.; Padmanabhan, Nikhil; Palanque-Delabrouille,
Nathalie; Pan, Kaike; Pandey, Parul; Pâris, Isabelle; Percival, Will
J.; Petitjean, Patrick; Pfaffenberger, Robert; Pforr, Janine; Phleps,
Stefanie; Pichon, Christophe; Pieri, Matthew M.; Prada, Francisco;
Price-Whelan, Adrian M.; Raddick, M. Jordan; Ramos, Beatriz H. F.;
Reylé, Céline; Rich, James; Richards, Gordon T.; Rix, Hans-Walter;
Robin, Annie C.; Rocha-Pinto, Helio J.; Rockosi, Constance M.; Roe,
Natalie A.; Rollinde, Emmanuel; Ross, Ashley J.; Ross, Nicholas P.;
Rossetto, Bruno M.; Sánchez, Ariel G.; Sayres, Conor; Schlegel,
David J.; Schlesinger, Katharine J.; Schmidt, Sarah J.; Schneider,
Donald P.; Sheldon, Erin; Shu, Yiping; Simmerer, Jennifer; Simmons,
Audrey E.; Sivarani, Thirupathi; Snedden, Stephanie A.; Sobeck,
Jennifer S.; Steinmetz, Matthias; Strauss, Michael A.; Szalay,
Alexander S.; Tanaka, Masayuki; Thakar, Aniruddha R.; Thomas, Daniel;
Tinker, Jeremy L.; Tofflemire, Benjamin M.; Tojeiro, Rita; Tremonti,
Christy A.; Vandenberg, Jan; Vargas Magaña, M.; Verde, Licia; Vogt,
Nicole P.; Wake, David A.; Wang, Ji; Weaver, Benjamin A.; Weinberg,
David H.; White, Martin; White, Simon D. M.; Yanny, Brian; Yasuda,
Naoki; Yeche, Christophe; Zehavi, Idit
2011ApJS..195...26A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: An “A star” on an M star during a flare within a flare
Authors: Kowalski, Adam F.; Hawley, Suzanne L.; Holtzman, Jon A.;
Wisniewski, John P.; Hilton, Eric J.
2011IAUS..273..261K Altcode: 2010arXiv1010.0452K
M dwarfs produce explosive flare emission in the near-UV and optical
continuum, and the mechanism responsible for this phenomenon is not
well-understood. We present a near-UV/optical flare spectrum from the
rise phase of a secondary flare, which occurred during the decay of
a much larger flare. The newly formed flare emission resembles the
spectrum of an early-type star, with the Balmer lines and continuum
in absorption. We model this observation phenomenologically as a
temperature bump (hot spot) near the photosphere of the M dwarf. The
amount of heating implied by our model (ΔT<SUB>phot</SUB> ~ 16,000 K)
is far more than predicted by chromospheric backwarming in current 1D
RHD flare models (ΔT<SUB>phot</SUB> ~ 1200 K).
---------------------------------------------------------
Title: Starspot variability and evolution from modeling Kepler
photometry of active late-type stars
Authors: Brown, Alexander; Korhonen, Heidi; Berdyugina, Svetlana;
Tofany, Barton; Ayres, Thomas R.; Kowalski, Adam; Hawley, Suzanne;
Harper, Graham; Piskunov, Nikolai
2011IAUS..273...78B Altcode:
The Kepler satellite provides a unique opportunity to study the detailed
optical photometric variability of late-type stars with unprecedentedly
long (several year) continuous monitoring and sensitivity to very
small-scale variations. We are studying a sample of over two hundred
cool (mid-A - late-K spectral type) stars using Kepler long-cadence
(30 minute sampling) observations. These stars show a remarkable
range of photometric variability, but in this paper we concentrate on
rotational modulation due to starspots and flaring. Modulation at the
0.1% level is readily discernable. We highlight the rapid timescales
of starspot evolution seen on solar-like stars with rotational periods
between 2 and 7 days.
---------------------------------------------------------
Title: The First Detection of Time-Variable Infrared Line Emission
During M Dwarf Flares
Authors: Schmidt, Sarah J.; Hilton, E. J.; Tofflemire, B.; Wisniewski,
J. P.; Kowalski, A. F.; Holtzman, J.; Hawley, S. L.
2011AAS...21832604S Altcode: 2011BAAS..43G32604S
M dwarfs are notorious for their active chromospheres, characterized by
quiescent line emission at optical wavelengths in addition to dramatic
flare events. These flares have been well-studied at X-ray, radio,
UV, and optical wavelengths, but so far there is only one single-epoch
detection of high-order Paschen emission lines in a red optical spectrum
(Schmidt et al. 2007). In order to investigate infrared line emission
during flares, we have conducted a monitoring campaign totaling
about 60 hours on 5 active M dwarfs. We have obtained infrared (0.9
to 2.4 micron) spectroscopy using the TripleSpec instrument on the
Apache Point Observatory 3.5-m, simultaneous optical/UV photometry
on the NMSU 1-m and ARC 0.8-m, and optical spectroscopy on the DAO
1.8-m for one run. During the three brightest flares observed on EV
Lac and YZ CMi (> 2 magnitudes in U), we observed emission from
Hydrogen Paschen beta, gamma, and delta; Brackett gamma, and Helium
10830A. We characterize the strength and time variation of these
lines and investigate the heating needed to produce infrared emission
during flares.
---------------------------------------------------------
Title: Light Curves, Energetics and Rates of M Dwarf Flares
Authors: Hilton, Eric J.; Hawley, S. L.; Kowalski, A. F.; Schmidt,
S. J.; Davenport, J. R. A.; Wisniewski, J. P.; Bell, K. J.; Tofflemire,
B.; Holtzman, J.
2011AAS...21832502H Altcode: 2011BAAS..43G32502H
The magnetic reconnection events that power stellar flares lead to a
wide variety of light curve shapes, hinting at the complex underlying
magnetic field topologies. Using our quantitative definition of a flare
event, we find more than 100 flares during 600 hours of photometric
monitoring of two dozen stars. The sample includes both active and
inactive M dwarfs with a range of spectral type. We fit models for the
light curve evolution to our photometric flare catalogue and present
an analysis of the rise and decay times as well as flare colors. We
additionally present the distribution of flare rates as a function of
energy and equivalent duration. The flare frequency distribution is
used to characterize the impact of M dwarf flares seen in time domain
surveys, and is also necessary to model the effect of flares on the
atmospheres of exoplanets orbiting an M dwarf host.
---------------------------------------------------------
Title: High Cadence Kepler Observations of Flare Stars
Authors: Hawley, Suzanne L.; Kowalski, A. F.; Wisniewski, J. P.;
Hilton, E. J.; Walkowicz, L. M.; Brown, A.
2011AAS...21822705H Altcode: 2011BAAS..43G22705H
We report on preliminary results from our Kepler Cycle 2 GO program to
observe low mass stars at high cadence (one observation per minute). The
outstanding fidelity of the Kepler light curves reveals both starspot
modulation and a large number of stellar flares. We investigate the
flare amplitude, frequency and energy distributions and relate these
to the better-known nearby flare stars in the solar neighborhood.
---------------------------------------------------------
Title: Hα Variability in Active M Dwarf Spectra on Intermediate
Timescales
Authors: Bell, Keaton; Hilton, E. J.; Hawley, S. L.; Rogel, A. B.
2011AAS...21832605B Altcode: 2011BAAS..43G32605B
The strength of Hα emission in magnetically active M dwarfs has been
observed to increase on very short (seconds) timescales during flares,
and to decrease on very long (millions-billions of years) timescales
with stellar aging. We utilize a set of 13,000 time-resolved active M
dwarf spectra taken on several-minute intervals from the Sloan Digital
Sky Survey and an independent set of 312 Hydra spectra taken hourly with
the WIYN 3.5-meter telescope to study Hα variability on intermediate
timescales. With several observations per target, and with many targets
observed on multiple nights, we are able to probe variability in the
equivalent width measurements of Hα on timescales from minutes to
weeks. We will present the variability structure function and discuss
it in the context of previous results.
---------------------------------------------------------
Title: UV Diagnostics of Stellar and Solar Flares
Authors: Kowalski, Adam; Hawley, S. L.; Hudson, H. S.
2011AAS...21821303K Altcode: 2011BAAS..43G21303K
The UV spectral regime provides a comprehensive view of the plasma
dynamics and atmospheric temperature structure during stellar flares. We
review the major developments in UV spectroscopy of flares on low mass
stars that shape our understanding of the flare process and challenge
the predictions of current radiative hydrodynamic models. We put the
ultraviolet properties in context with the radiation in the neighboring
X-ray and visible wavelength regimes. We also show how SDO/EVE data
of several Cycle 24 solar flares allow for new comparisons to be made
between solar and stellar flares.
---------------------------------------------------------
Title: M Dwarf Photometric Variability In The Optical And NIR
Authors: Davenport, James R. A.; Becker, A. C.; Kowalski, A. F.;
Hawley, S. L.; Hilton, E. J.
2011AAS...21832603D Altcode: 2011BAAS..43G32603D
We present limits on the observability of stochastic flare events from
M dwarfs in SDSS and 2MASS filters. We have studied 30,000 M dwarfs
from the SDSS Stripe 82 time-domain catalog, and 4300 M dwarfs from the
2MASS Calibration Scan Point Source Working Database which overlap the
SDSS DR7 single-epoch data. M dwarfs are chosen based on their SDSS
r,i,z colors. Stripe 82 stars each have 50-100 epochs of data, while
2MASS Calibration stars have 2000-3000. An M dwarf continuum spectral
model is used to predict observed flare signatures in each band. From
these data we estimate the observed rates and theoretical detection
thresholds for flares in eight photometric bands as a function of
spectral type. The structure function of the variability for each
spectral type bin is also calculated for all eight bands. These
rates of flares and photometric variations at longer wavelengths
will be important for predicting the impact of M dwarf variability in
next-generation instruments such as JWST.
---------------------------------------------------------
Title: Kepler Observations of Starspot Evolution, Differential
Rotation, and Flares on Late-Type Stars
Authors: Brown, Alexander; Korhonen, H.; Berdyugina, S.; Walkowicz,
L.; Kowalski, A.; Hawley, S.; Neff, J.; Ramsey, L.; Redman, S.; Saar,
S.; Furesz, G.; Piskunov, N.; Harper, G.; Ayres, T.; Tofany, B.
2011AAS...21820502B Altcode: 2011BAAS..43G20502B
The Kepler satellite is providing spectacular optical photometric
light-curves of unprecedented precision and duration that
routinely allow detailed studies of stellar magnetic activity on
late-type stars that were difficult, if not impossible, to attempt
previously. Rotational modulation due to starspots is commonly seen
in the Kepler light-curves of late-type stars, allowing detailed
study of the surface distribution of their photospheric magnetic
activity. Kepler is providing multi-year duration light-curves that
allow us to investigate how activity phenomena -- such as the growth,
migration, and decay of starspots, differential rotation, activity
cycles, and flaring -- operate on single and binary stars with a
wide range of mass and convection zone depth. <P />We present the
first results from detailed starspot modeling using newly-developed
light-curve inversion codes for a range of GALEX-selected stars with
typical rotation periods of a few days, that we have observed as part of
our 200 target Kepler Cycle 1/2 Guest Observer programs. The physical
properties of the stars have been measured using high resolution
optical spectroscopy, which allows the Kepler results to be placed
within the existing framework of knowledge regarding stellar magnetic
activity. These results demonstrate the powerful diagnostic capability
provided by tracking starspot evolution essentially continuously for
more than 16 months. The starspots are clearly sampling the stellar
rotation rate at different latitudes, enabling us to measure the
differential rotation and starspot lifetimes. As would be expected,
stars with few day rotation show frequent flaring that is easily seen
as "white-light" flares in Kepler light-curves. We compare the observed
flare rates and occurrence with the starspot properties. <P />This work
contains results obtained using the NASA Kepler satellite and from the
Apache Point Observatory, the MMT (using NOAO community access time),
and the Hobby-Eberly Telescope. Funding is provided by NASA Kepler
grants NNX10AC51G and NNX11AC79G.
---------------------------------------------------------
Title: Kepler Observations of Pulsations In A Sample of
Magnetically-Active Stars
Authors: Neff, James E.; Brown, A.; Hawley, S.; Kowalski, A.;
Walkowicz, L.; Saar, S.
2011AAS...21822704N Altcode: 2011BAAS..43G22704N
We have observed about 200 targets in Kepler Cycle 1/2 Guest Observer
programs. The sample of active star candidates was selected primarily
using GALEX colors, and the Kepler light curves have revealed a rich
variety of variability. Rotational modulation (typical periods a few
days) due to starspots over the multi-year timeline of the Kepler
observations will permit us to measure surface differential rotation
and stellar magnetic cycles. On shorter timescales, the Kepler data
show dramatic evidence of stellar pulsations across much of the HR
diagram. Our selection criteria yielded a sample of magnetically active
G and K dwarfs, which might show solar-like pulsations. It also yielded
subsamples of several well-known pulsators (e.g., Delta Scuti stars)
as well as pulsators that currently defy easy classification. We are
systematically classifying and analyzing the pulsating stars in the our
Kepler GO program. We are particularly interested in using pulsations
to probe the interior properties of active G and K dwarfs, while the
starspots serve as a probe of the convection zone and surface layers. We
will present summary results for several different types of pulsation,
and we will provide a detailed asteroseismic analysis of those stars
in our sample that were observed to have both pulsations and magnetic
activity. <P />This work contains results obtained using the NASA
Kepler satellite and from the Apache Point Observatory, the MMT (using
NOAO community access time), and the Hobby-Eberly Telescope. Funding
is provided by NASA Kepler grants NNX10AC51G and NNX11AC79G.
---------------------------------------------------------
Title: Periodic Variability of Low-mass Stars in Sloan Digital Sky
Survey Stripe 82
Authors: Becker, A. C.; Bochanski, J. J.; Hawley, S. L.; Ivezić,
Ž.; Kowalski, A. F.; Sesar, B.; West, A. A.
2011ApJ...731...17B Altcode: 2011arXiv1102.1387B
We present a catalog of periodic stellar variability in the "Stripe
82" region of the Sloan Digital Sky Survey. After aggregating
and re-calibrating catalog-level data from the survey, we ran a
period-finding algorithm (Supersmoother) on all point-source light
curves. We used color selection to identify systems that are likely to
contain low-mass stars, in particular M dwarfs and white dwarfs. In
total, we found 207 candidates, the vast majority of which appear to
be in eclipsing binary systems. The catalog described in this paper
includes 42 candidate M dwarf/white dwarf pairs, four white dwarf
pairs, 59 systems whose colors indicate they are composed of two
M dwarfs and whose light-curve shapes suggest they are in detached
eclipsing binaries, and 28 M dwarf systems whose light-curve shapes
suggest they are in contact binaries. We find no detached systems
with periods longer than 3 days, thus the majority of our sources
are likely to have experienced orbital spin-up and enhanced magnetic
activity. Indeed, 26 of 27 M dwarf systems that we have spectra for
show signs of chromospheric magnetic activity, far higher than the 24%
seen in field stars of the same spectral type. We also find binaries
composed of stars that bracket the expected boundary between partially
and fully convective interiors, which will allow the measurement of the
stellar mass-radius relationship across this transition. The majority
of our contact systems have short orbital periods, with small variance
(0.02 days) in the sample near the observed cutoff of 0.22 days. The
accumulation of these stars at short orbital period suggests that the
process of angular momentum loss, leading to period evolution, becomes
less efficient at short periods. These short-period systems are in a
novel regime for studying the effects of orbital spin-up and enhanced
magnetic activity, which are thought to be the source of discrepancies
between mass-radius predictions and measurements of these properties
in eclipsing binaries.
---------------------------------------------------------
Title: The Eighth Data Release of the Sloan Digital Sky Survey:
First Data from SDSS-III
Authors: Aihara, Hiroaki; Allende Prieto, Carlos; An, Deokkeun;
Anderson, Scott F.; Aubourg, Éric; Balbinot, Eduardo; Beers, Timothy
C.; Berlind, Andreas A.; Bickerton, Steven J.; Bizyaev, Dmitry;
Blanton, Michael R.; Bochanski, John J.; Bolton, Adam S.; Bovy, Jo;
Brandt, W. N.; Brinkmann, J.; Brown, Peter J.; Brownstein, Joel R.;
Busca, Nicolas G.; Campbell, Heather; Carr, Michael A.; Chen, Yanmei;
Chiappini, Cristina; Comparat, Johan; Connolly, Natalia; Cortes,
Marina; Croft, Rupert A. C.; Cuesta, Antonio J.; da Costa, Luiz N.;
Davenport, James R. A.; Dawson, Kyle; Dhital, Saurav; Ealet, Anne;
Ebelke, Garrett L.; Edmondson, Edward M.; Eisenstein, Daniel J.;
Escoffier, Stephanie; Esposito, Massimiliano; Evans, Michael L.; Fan,
Xiaohui; Femenía Castellá, Bruno; Font-Ribera, Andreu; Frinchaboy,
Peter M.; Ge, Jian; Gillespie, Bruce A.; Gilmore, G.; González
Hernández, Jonay I.; Gott, J. Richard; Gould, Andrew; Grebel, Eva
K.; Gunn, James E.; Hamilton, Jean-Christophe; Harding, Paul; Harris,
David W.; Hawley, Suzanne L.; Hearty, Frederick R.; Ho, Shirley; Hogg,
David W.; Holtzman, Jon A.; Honscheid, Klaus; Inada, Naohisa; Ivans,
Inese I.; Jiang, Linhua; Johnson, Jennifer A.; Jordan, Cathy; Jordan,
Wendell P.; Kazin, Eyal A.; Kirkby, David; Klaene, Mark A.; Knapp,
G. R.; Kneib, Jean-Paul; Kochanek, C. S.; Koesterke, Lars; Kollmeier,
Juna A.; Kron, Richard G.; Lampeitl, Hubert; Lang, Dustin; Le Goff,
Jean-Marc; Lee, Young Sun; Lin, Yen-Ting; Long, Daniel C.; Loomis,
Craig P.; Lucatello, Sara; Lundgren, Britt; Lupton, Robert H.; Ma,
Zhibo; MacDonald, Nicholas; Mahadevan, Suvrath; Maia, Marcio A. G.;
Makler, Martin; Malanushenko, Elena; Malanushenko, Viktor; Mandelbaum,
Rachel; Maraston, Claudia; Margala, Daniel; Masters, Karen L.; McBride,
Cameron K.; McGehee, Peregrine M.; McGreer, Ian D.; Ménard, Brice;
Miralda-Escudé, Jordi; Morrison, Heather L.; Mullally, F.; Muna,
Demitri; Munn, Jeffrey A.; Murayama, Hitoshi; Myers, Adam D.; Naugle,
Tracy; Neto, Angelo Fausti; Nguyen, Duy Cuong; Nichol, Robert C.;
O'Connell, Robert W.; Ogando, Ricardo L. C.; Olmstead, Matthew D.;
Oravetz, Daniel J.; Padmanabhan, Nikhil; Palanque-Delabrouille,
Nathalie; Pan, Kaike; Pandey, Parul; Pâris, Isabelle; Percival, Will
J.; Petitjean, Patrick; Pfaffenberger, Robert; Pforr, Janine; Phleps,
Stefanie; Pichon, Christophe; Pieri, Matthew M.; Prada, Francisco;
Price-Whelan, Adrian M.; Raddick, M. Jordan; Ramos, Beatriz H. F.;
Reylé, Céline; Rich, James; Richards, Gordon T.; Rix, Hans-Walter;
Robin, Annie C.; Rocha-Pinto, Helio J.; Rockosi, Constance M.; Roe,
Natalie A.; Rollinde, Emmanuel; Ross, Ashley J.; Ross, Nicholas P.;
Rossetto, Bruno M.; Sánchez, Ariel G.; Sayres, Conor; Schlegel,
David J.; Schlesinger, Katharine J.; Schmidt, Sarah J.; Schneider,
Donald P.; Sheldon, Erin; Shu, Yiping; Simmerer, Jennifer; Simmons,
Audrey E.; Sivarani, Thirupathi; Snedden, Stephanie A.; Sobeck,
Jennifer S.; Steinmetz, Matthias; Strauss, Michael A.; Szalay,
Alexander S.; Tanaka, Masayuki; Thakar, Aniruddha R.; Thomas, Daniel;
Tinker, Jeremy L.; Tofflemire, Benjamin M.; Tojeiro, Rita; Tremonti,
Christy A.; Vandenberg, Jan; Vargas Magaña, M.; Verde, Licia; Vogt,
Nicole P.; Wake, David A.; Wang, Ji; Weaver, Benjamin A.; Weinberg,
David H.; White, Martin; White, Simon D. M.; Yanny, Brian; Yasuda,
Naoki; Yeche, Christophe; Zehavi, Idit
2011ApJS..193...29A Altcode: 2011arXiv1101.1559S
The Sloan Digital Sky Survey (SDSS) started a new phase in 2008 August,
with new instrumentation and new surveys focused on Galactic structure
and chemical evolution, measurements of the baryon oscillation feature
in the clustering of galaxies and the quasar Lyα forest, and a radial
velocity search for planets around ~8000 stars. This paper describes
the first data release of SDSS-III (and the eighth counting from the
beginning of the SDSS). The release includes five-band imaging of
roughly 5200 deg<SUP>2</SUP> in the southern Galactic cap, bringing
the total footprint of the SDSS imaging to 14,555 deg<SUP>2</SUP>,
or over a third of the Celestial Sphere. All the imaging data have
been reprocessed with an improved sky-subtraction algorithm and
a final, self-consistent photometric recalibration and flat-field
determination. This release also includes all data from the second
phase of the Sloan Extension for Galactic Understanding and Exploration
(SEGUE-2), consisting of spectroscopy of approximately 118,000 stars
at both high and low Galactic latitudes. All the more than half a
million stellar spectra obtained with the SDSS spectrograph have been
reprocessed through an improved stellar parameter pipeline, which has
better determination of metallicity for high-metallicity stars.
---------------------------------------------------------
Title: The Sloan Digital Sky Survey Data Release 7 Spectroscopic M
Dwarf Catalog. II. Statistical Parallax Analysis
Authors: Bochanski, John J.; Hawley, Suzanne L.; West, Andrew A.
2011AJ....141...98B Altcode: 2011arXiv1101.3549B
We present a statistical parallax analysis of low-mass dwarfs from the
Sloan Digital Sky Survey. We calculate absolute r-band magnitudes
(M<SUB>r</SUB> ) as a function of color and spectral type and
investigate changes in M<SUB>r</SUB> with location in the Milky
Way. We find that magnetically active M dwarfs are intrinsically
brighter in M<SUB>r</SUB> than their inactive counterparts at the same
color or spectral type. Metallicity, as traced by the proxy ζ, also
affects M<SUB>r</SUB> , with metal-poor stars having fainter absolute
magnitudes than higher metallicity M dwarfs at the same color or
spectral type. Additionally, we measure the velocity ellipsoid and solar
reflex motion for each subsample of M dwarfs. We find good agreement
between our measured solar peculiar motion and previous results for
similar populations, as well as some evidence for differing motions
of early and late M-type populations in U and W velocities that
cannot be attributed to asymmetric drift. The reflex solar motion
and the velocity dispersions both show that younger populations,
as traced by magnetic activity and location near the Galactic plane,
have experienced less dynamical heating. We introduce a new parameter,
the independent position altitude (IPA), to investigate populations
as a function of vertical height from the Galactic plane. M dwarfs at
all types exhibit an increase in velocity dispersion when analyzed in
comparable IPA subgroups.
---------------------------------------------------------
Title: The Sloan Digital Sky Survey Data Release 7 Spectroscopic M
Dwarf Catalog. I. Data
Authors: West, Andrew A.; Morgan, Dylan P.; Bochanski, John J.;
Andersen, Jan Marie; Bell, Keaton J.; Kowalski, Adam F.; Davenport,
James R. A.; Hawley, Suzanne L.; Schmidt, Sarah J.; Bernat, David;
Hilton, Eric J.; Muirhead, Philip; Covey, Kevin R.; Rojas-Ayala,
Bárbara; Schlawin, Everett; Gooding, Mary; Schluns, Kyle; Dhital,
Saurav; Pineda, J. Sebastian; Jones, David O.
2011AJ....141...97W Altcode: 2011arXiv1101.1082W
We present a spectroscopic catalog of 70,841 visually inspected M dwarfs
from the seventh data release of the Sloan Digital Sky Survey. For each
spectrum, we provide measurements of the spectral type, a number of
molecular band heads, and the Hα, Hβ, Hγ, Hδ, and Ca II K emission
lines. In addition, we calculate the metallicity-sensitive parameter ζ
and identify a relationship between ζ and the g - r and r - z colors
of M dwarfs. We assess the precision of our spectral types (which were
assigned by individual examination), review the bulk attributes of
the sample, and examine the magnetic activity properties of M dwarfs,
in particular those traced by the higher order Balmer transitions. Our
catalog is cross-matched to Two Micron All Sky Survey infrared data,
and contains photometric distances for each star. Finally, we identify
eight new late-type M dwarfs that are possibly within 25 pc of the
Sun. Future studies will use these data to thoroughly examine magnetic
activity and kinematics in late-type M dwarfs and examine the chemical
and dynamical history of the local Milky Way.
---------------------------------------------------------
Title: M Dwarf Flares: Exoplanet Implications
Authors: Wisniewski, John; Kowalski, Adam; Schmidt, Sarah; Kundurthy,
Praveen; Hawley, Suzanne; Tofflemire, Ben; Holtzman, Jon
2011noao.prop..106W Altcode:
M dwarfs are attractive stars for exoplanet transit research as their
low luminosities and small stellar radii could enable detection of
super-Earths residing in their habitable zones. M dwarf flare events
can cause <0.1 to 6.0 magnitude flux enhancements in the optical U-
band, which is significantly higher than the predicted transit depths
of super-Earths (~0.005 magnitude flux decrease). While Solar flares
have been observed to cause infrared continuum enhancements (Xu et al
2006); surprisingly, it is not known whether energetic flares associated
with M dwarfs can induce IR variability in filters relevant to future
transiting exoplanet characterization studies (e.g. using JWST). We
propose to monitor the optical & IR flux of a M dwarf known to
regularly flare, to determine what effect flares could have on future IR
characterization studies of M dwarf exoplanets. This proposal represents
a resubmission of our approved 2009B program, which lost >80% of
its on-sky time due to Tropical Storm Olaf (but did demonstrate the
ability to achieve 5 milli-mag IR photometry with the KPNO 2.1m). We
request 5 nights in 2011A to complete our science goals.
---------------------------------------------------------
Title: Extending M Dwarf Variability Studies to Longer Wavelengths
Authors: Davenport, James R. A.; Becker, A.; Kowalski, A. F.; Hilton,
E. J.; Hawley, S. L.
2011AAS...21724213D Altcode: 2011BAAS...4324213D
Flares on M dwarfs occur stochastically, and the statistical frequency
of such events is well characterized in the optical. Flares and stellar
variability are a source of confusion for large time-domain surveys,
and a unified physical model of these magnetically driven events across
all spectral types still awaits discovery. To correctly predict the
occurrence rate of M dwarf variability in future astronomical surveys,
we must understand the full SED of these events as completely as
possible. We have constructed a sample of 4000 M dwarfs with a broad
range of properties, each with thousands of epochs of observation. This
matched data set comes from the SDSS Stripe 82 and LINEAR databases
in the optical, and 2MASS Calibration Scan database in the NIR. We
present preliminary results that extend the flaring rate and variability
signature to longer wavelengths, where many future scientific missions
such as LSST, JWST, and others will operate.
---------------------------------------------------------
Title: M Dwarf Atomic and Molecular Features in SDSS DR7 Spectra
Authors: Spencer, Meghin; Davenport, J. R. A.; West, A. A.; Hawley,
S. L.
2011AAS...21724220S Altcode: 2011BAAS...4324220S
Large, homogenous spectroscopic datasets offer the opportunity to
investigate the behavior of stellar atmospheres as a function of various
stellar parameters with unprecedented statistical accuracy. We use the
SDSS DR7 spectroscopic catalog of 70,000 low mass stars to investigate
the changes in atomic and molecular features that occur with differing
mass, temperature, metallicity, and level of magnetic activity.
---------------------------------------------------------
Title: Optical and NIR Spectroscopy of ɛ Aurigae at Apache Point
Observatory, the First Half of the Eclipse
Authors: Ketzeback, William F.; Barentine, J.; Leadbeater, R.;
McMillan, R.; Dembicky, J.; Saurage, G.; Huehnerhoff, J.; Schmidt,
S.; Hawley, S.; Wallerstein, G.; Coughlin, J.; York, D.
2011AAS...21725705K Altcode: 2011BAAS...4325705K
Epsilon Aurigae (ɛ Aur), first confirmed as a variable in 1821,
is an eclipsing binary star system with a period of 27.1 years,
one of the longest known. The primary, a pulsating F supergiant
star with a variability out of eclipse of approximately 60 days and
possible overtones of hundreds of days, is orbited by the secondary,
a B-star enveloped by an enormous, cool, spectrally gray disk producing
no evident wavelength dependence to the light output variations. The
eclipse lasts for over 700 days; the current eclipse began first contact
in July, 2009, and August 4, 2010 marked the estimated midway point
of the eclipse. Although the components of the system have now been
identified, much is still unclear such as the origin, composition and
structure of the disk. Modern digital spectroscopy of bright stars
not only enables asteroseismology and planetary detection, but the
eclipsing binary epsilon Aurigae is an unusual case in which precise
spectroscopic study of the now transiting dark disk is enabled. At
Apache Point Observatory, our team has conducted high-resolution
optical and NIR spectroscopic monitoring of this mysterious eclipsing
system since February, 2009. We present major changes in the spectra
attributable to the disk from the first half of the eclipse in the
0.4 - 2.2 μm range using ARCES, an optical echelle spectrograph
(λ/Δλ=31,500), and Triplespec, a NIR cross-dispersed spectrograph
(λ/Δλ=3500), on the ARC 3.5-meter telescope.
---------------------------------------------------------
Title: Revealing Stellar Magnetic Fields Through M Dwarf Flares
Authors: Hilton, Eric J.; Hawley, S. L.; Kowalski, A. F.
2011AAS...21730702H Altcode: 2011BAAS...4330702H
Magnetic reconnection on M dwarfs powers explosive flares with flux
increases of several magnitudes in the blue/near-UV on timescales
of minutes to hours. We obtained over 500 hours of flare monitoring
observations at the Apache Point Observatory to make the first
measurements of the flare frequency distribution of inactive early
and mid M dwarfs and active late M dwarfs. These new measurements
combined with our studies of flare rates from both SDSS photometry and
spectroscopy have allowed us to construct a model of M dwarf flaring in
the Galaxy that predicts the number and magnitude of flares expected
in a given survey. In addition to the implications for time-domain
surveys such as LSST, Pan-STARRS, and PTF, and for planet-habitability,
the rate of flaring on stars of different mass and age informs our
knowledge of the formation and evolution of stellar magnetic fields. We
find that the flare star distribution is more concentrated toward the
Galactic mid-plane than the active star population, implying that they
are younger. Active stars flare more frequently and with more energy
than inactive stars. Flares on late-type active M dwarfs are less
energetic than those on earlier types. <P />We acknowledge support
from NSF grant AST <P />08-07205.
---------------------------------------------------------
Title: An Optical Flare Rate Census of Galactic Bulge Dwarf Stars
Authors: Kowalski, Adam; Osten, R. A.; Sahu, K. C.; Hawley, S. L.
2011AAS...21734207K Altcode: 2011BAAS...4334207K
Flare emission is thought to be the observational consequence of
transiently heated plasma by the dynamic interaction of magnetic fields
throughout the stellar atmosphere. Other magnetic activity measures
indicate that age may be a fundamental parameter for the generation and
presence of surface magnetic fields. However, flares have been observed
on both old and young stars, and the importance of age on the flare
rate of a stellar population is not well known, as previous flare rate
studies have been limited to the surrounding solar neighborhood and
young disk population. The SWEEPS project monitored a 202x202 arcsec
dense stellar field in the Sagittarius window of the Galactic bulge for
a continuous seven-day period using the HST/ACS F606W (V) and F814W (I)
filters. These data were aimed at a search for transiting exoplanets,
but the high-cadence light curves, consisting of 260 epochs in each
filter, provide a unique repository to mine for flare incidence in an
evolved stellar population of dwarfs. We employ a customized algorithm
to search for flares on 200,000 cool dwarfs of intermediate-old age,
and we study the stellar flare rate and flare properties as a function
of mass, V - I color, and the degree of underlying variability. These
rates allow us to compare to the flare rates of younger stars and to
extend the investigation of the evolution of magnetic activity to an
older stellar population.
---------------------------------------------------------
Title: Making The Most Of Flaring M Dwarfs
Authors: Hunt-Walker, Nicholas; Hilton, E.; Kowalski, A.; Hawley,
S.; Matthews, J.; Holtzman, J.
2011AAS...21724224H Altcode: 2011BAAS...4324224H
We present observations of flare activity using the Microvariability
and Oscillations of Stars (MOST) satellite in conjunction with
simultaneous spectroscopic and photometric observations from the ARC
3.5-meter, NMSU 1.0-meter, and ARCSAT 0.5-meter telescopes at the
Apache Point Observatory. The MOST observations enable unprecedented
completeness with regard to observing frequent, low-energy flares on
the well-known dMe flare star AD Leo with broadband photometry. The
observations span approximately one week with a 60-second cadence and
are sensitive to flares as small as 0.01-magnitudes. The time-resolved,
ground-based spectroscopy gives measurements of Hα and other important
chromospheric emission lines, whereas the Johnson U-, SDSS u-, and SDSS
g-band photometry provide color information during the flare events
and allow us to relate the MOST observations to decades of previous
broadband observations. Understanding the rates and energetics of flare
events on M dwarfs will help characterize this source of variability in
large time-domain surveys such as LSST and Pan-STARRS. Flare rates are
also of interest to astrobiology, since flares affect the habitability
of exoplanets orbiting M dwarfs.
---------------------------------------------------------
Title: X-ray and Radio Observations of LP349-25
Authors: Schmidt, Sarah J.; Osten, R. A.; Hawley, S. L.; Ngoc, P.;
Reid, N.
2011AAS...21724218S Altcode: 2011BAAS...4324218S
For a long time ultracool dwarfs (stellar objects with spectral types
later than M7) were not thought to display any of the characteristics
associated with the presence and action of strong magnetic fields, but
surprisingly, recent observations have demonstrated the continuation
of chromospheric and coronal indicators into this regime. The radio
and X-ray behavior of ultracool dwarfs in particular show strikingly
different behaviors when compared to what is seen in higher mass stars:
objects detected at X-ray wavelengths show the decline of plasma
heating with effective temperature but with examples of flare-like
behavior which suggest some continuation in behavior from early-mid M
dwarf stars. Radio detections of ultracool dwarfs are characterized by
variability which occurs on timescales associated with the rotation
period, and the dominant emission mechanism may switch from the
incoherent gyrosynchrotron seen on earlier M stars to a coherent maser
process. There is a discontinuity between radio-detected ultracool
dwarfs (which tend to be X-ray weak or undetected) and X-ray detected
ultracool dwarfs, which tend to be radio weak or undetected. The young
brown dwarf binary LP 349-25 is a peculiar radio emitter due to its
lack of radio variability on both long and short timescales. The lack
of rotational modulation presents difficulties for the generation
of radio emission in strong large scale magnetic fields. To further
investigate the conditions of LP349-25, we present simultaneous radio
and x-ray observations of LP349-25. Initial analysis of the data shows
that the radio emission continues to be constant and that LP349-25
additionally shows quiescent x-ray emission. This allows us to place
additional constraints on the mechanism for radio emission in LP349-25
and explore the conditions which cause disparate high energy behaviors
in ultracool dwarfs.
---------------------------------------------------------
Title: M Dwarf Flares from Time-resolved Sloan Digital Sky Survey
Spectra
Authors: Hilton, Eric J.; West, Andrew A.; Hawley, Suzanne L.;
Kowalski, Adam F.
2010AJ....140.1402H Altcode: 2010arXiv1009.1158H
We have identified 63 flares on M dwarfs from the individual component
spectra in the Sloan Digital Sky Survey (SDSS) using a novel measurement
of emission-line strength called the Flare Line Index. Each of the
~38,000 M dwarfs in the SDSS low-mass star spectroscopic sample of West
et al. was observed several times (usually 3-5) in exposures that were
typically 9-25 minutes in duration. Our criteria allowed us to identify
flares that exhibit very strong Hα and Hβ emission-line strength
and/or significant variability in those lines throughout the course of
the exposures. The flares we identified have characteristics consistent
with flares observed by classical spectroscopic monitoring. The flare
duty cycle for the objects in our sample is found to increase from 0.02%
for early M dwarfs to 3% for late M dwarfs. We find that the flare duty
cycle is larger in the population near the Galactic plane and that
the flare stars are more spatially restricted than the magnetically
active but non-flaring stars. This suggests that flare frequency may
be related to stellar age (younger stars are more likely to flare)
and that the flare stars are younger than the mean active population.
---------------------------------------------------------
Title: Solar Flares and the Chromosphere
Authors: Fletcher, L.; Turkmani, R.; Hudson, H. S.; Hawley, S. L.;
Kowalski, A.; Berlicki, A.; Heinzel, P.
2010arXiv1011.4650F Altcode:
A white paper prepared for the Space Studies Board, National Academy
of Sciences (USA), for its Decadal Survey of Solar and Space Physics
(Heliophysics), reviewing and encouraging studies of flare physics in
the chromosphere.
---------------------------------------------------------
Title: Solar Flares and the Chromosphere: A white paper for the
Decadal Survey
Authors: Hudson, H. S.; Fletcher, L.; Turkmani, R.; Hawley, S. L.;
Kowalski, A. F.; Berlicki, A.; Heinzel, P.
2010helio2010....1H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Effect of a Strong Stellar Flare on the Atmospheric
Chemistry of an Earth-like Planet Orbiting an M Dwarf
Authors: Segura, Antígona; Walkowicz, Lucianne M.; Meadows, Victoria;
Kasting, James; Hawley, Suzanne
2010AsBio..10..751S Altcode: 2010arXiv1006.0022S
Main sequence M stars pose an interesting problem for astrobiology:
their abundance in our galaxy makes them likely targets in the hunt
for habitable planets, but their strong chromospheric activity produces
high-energy radiation and charged particles that may be detrimental to
life. We studied the impact of the 1985 April 12 flare from the M dwarf
AD Leonis (AD Leo), simulating the effects from both UV radiation and
protons on the atmospheric chemistry of a hypothetical, Earth-like
planet located within its habitable zone. Based on observations of
solar proton events and the Neupert effect, we estimated a proton flux
associated with the flare of 5.9×10<SUP>8</SUP> protons cm<SUP>-2</SUP>
sr<SUP>-1</SUP> s<SUP>-1</SUP> for particles with energies >10
MeV. Then we calculated the abundance of nitrogen oxides produced by the
flare by scaling the production of these compounds during a large solar
proton event called the Carrington event. The simulations were performed
with a 1-D photochemical model coupled to a 1-D radiative/convective
model. Our results indicate that the UV radiation emitted during the
flare does not produce a significant change in the ozone column depth of
the planet. When the action of protons is included, the ozone depletion
reaches a maximum of 94% two years after the flare for a planet with no
magnetic field. At the peak of the flare, the calculated UV fluxes that
reach the surface, in the wavelength ranges that are damaging for life,
exceed those received on Earth during less than 100 s. Therefore, flares
may not present a direct hazard for life on the surface of an orbiting
habitable planet. Given that AD Leo is one of the most magnetically
active M dwarfs known, this conclusion should apply to planets around
other M dwarfs with lower levels of chromospheric activity.
---------------------------------------------------------
Title: OT1_shawley_2: Synchrotron Radiation in Stellar Flares
Authors: Hawley, S.
2010hers.prop..879H Altcode:
Stellar flares emit copious radiation at X-ray, optical and
radio wavelengths but have not yet been investigated in the
far-infrared. Recent observations at millimeter wavelengths
provide tantalizing evidence that a population of ultrarelativistic
electrons may be accelerated during flares and may provide significant
synchrotron radiation in the far-infrared and sub-millimeter wavelength
regimes. Herschel observations of two very active stars with a history
of strong, frequent and energetic flares will probe this wavelength
regime for the first time. Ultrarelativistic electrons may hold the
key to explaining the photospheric flare heating that is necessary
to produce the observed white light flare emission which carries more
than half of the total flare energy. Our team brings together experts
in stellar flare optical and radio observations, particle acceleration
and plasma physics, and radiative hydrodynamical atmosphere modeling. We
propose to carry out a Herschel flare observing campaign together with
several ground-based optical and radio observatories and to produce
a new generation of flare models that include the ultrarelativistic
electron population.
---------------------------------------------------------
Title: The Milky Way Tomography with SDSS. III. Stellar Kinematics
Authors: Bond, Nicholas A.; Ivezić, Željko; Sesar, Branimir; Jurić,
Mario; Munn, Jeffrey A.; Kowalski, Adam; Loebman, Sarah; Roškar,
Rok; Beers, Timothy C.; Dalcanton, Julianne; Rockosi, Constance M.;
Yanny, Brian; Newberg, Heidi J.; Allende Prieto, Carlos; Wilhelm, Ron;
Lee, Young Sun; Sivarani, Thirupathi; Majewski, Steven R.; Norris,
John E.; Bailer-Jones, Coryn A. L.; Re Fiorentin, Paola; Schlegel,
David; Uomoto, Alan; Lupton, Robert H.; Knapp, Gillian R.; Gunn,
James E.; Covey, Kevin R.; Allyn Smith, J.; Miknaitis, Gajus; Doi,
Mamoru; Tanaka, Masayuki; Fukugita, Masataka; Kent, Steve; Finkbeiner,
Douglas; Quinn, Tom R.; Hawley, Suzanne; Anderson, Scott; Kiuchi,
Furea; Chen, Alex; Bushong, James; Sohi, Harkirat; Haggard, Daryl;
Kimball, Amy; McGurk, Rosalie; Barentine, John; Brewington, Howard;
Harvanek, Mike; Kleinman, Scott; Krzesinski, Jurek; Long, Dan; Nitta,
Atsuko; Snedden, Stephanie; Lee, Brian; Pier, Jeffrey R.; Harris,
Hugh; Brinkmann, Jonathan; Schneider, Donald P.
2010ApJ...716....1B Altcode: 2009arXiv0909.0013B
We study Milky Way kinematics using a sample of 18.8 million
main-sequence stars with r < 20 and proper-motion measurements
derived from Sloan Digital Sky Survey (SDSS) and POSS astrometry,
including ~170,000 stars with radial-velocity measurements from the
SDSS spectroscopic survey. Distances to stars are determined using a
photometric-parallax relation, covering a distance range from ~100
pc to 10 kpc over a quarter of the sky at high Galactic latitudes
(|b|>20°). We find that in the region defined by 1 kpc <Z<
5 kpc and 3 kpc <R< 13 kpc, the rotational velocity for disk
stars smoothly decreases, and all three components of the velocity
dispersion increase, with distance from the Galactic plane. In contrast,
the velocity ellipsoid for halo stars is aligned with a spherical
coordinate system and appears to be spatially invariant within the
probed volume. The velocity distribution of nearby (Z < 1 kpc) K/M
stars is complex, and cannot be described by a standard Schwarzschild
ellipsoid. For stars in a distance-limited subsample of stars (<100
pc), we detect a multi-modal velocity distribution consistent with
that seen by HIPPARCOS. This strong non-Gaussianity significantly
affects the measurements of the velocity-ellipsoid tilt and vertex
deviation when using the Schwarzschild approximation. We develop and
test a simple descriptive model for the overall kinematic behavior
that captures these features over most of the probed volume, and can be
used to search for substructure in kinematic and metallicity space. We
use this model to predict further improvements in kinematic mapping of
the Galaxy expected from Gaia and the Large Synoptic Survey Telescope.
---------------------------------------------------------
Title: The Luminosity and Mass Functions of Low-mass Stars in the
Galactic Disk. II. The Field
Authors: Bochanski, John J.; Hawley, Suzanne L.; Covey, Kevin R.;
West, Andrew A.; Reid, I. Neill; Golimowski, David A.; Ivezić, Željko
2010AJ....139.2679B Altcode: 2010arXiv1004.4002B
We report on new measurements of the luminosity function (LF) and mass
function (MF) of field low-mass dwarfs derived from Sloan Digital Sky
Survey Data Release 6 photometry. The analysis incorporates ~15 million
low-mass stars (0.1 {\cal M}_\odot {\cal M} < 0.8\,{\cal M}_\odot),
spread over 8400 deg<SUP>2</SUP>. Stellar distances are estimated
using new photometric parallax relations, constructed from ugriz
photometry of nearby low-mass stars with trigonometric parallaxes. We
use a technique that simultaneously measures Galactic structure and
the stellar LF from 7 < M<SUB>r</SUB> < 16. We compare the LF
to previous studies and convert to an MF using the mass-luminosity
relations of Delfosse et al. The system MF, measured over -1.0< log
{\cal M} / {\cal M}_\odot <-0.1, is well described by a lognormal
distribution with {\cal M}_{\circ } = 0.25 {\cal M}_\odot. We stress
that our results should not be extrapolated to other mass regimes. Our
work generally agrees with prior low-mass stellar MFs and places strong
constraints on future theoretical star formation studies.
---------------------------------------------------------
Title: Colors and Kinematics of L Dwarfs from the Sloan Digital
Sky Survey
Authors: Schmidt, Sarah J.; West, Andrew A.; Hawley, Suzanne L.;
Pineda, J. Sebastian
2010AJ....139.1808S Altcode: 2010arXiv1001.3402S
We present a sample of 484 L dwarfs, 210 of which are newly discovered
from the Sloan Digital Sky Survey (SDSS) Data Release 7 spectroscopic
database. We combine this sample with known L dwarfs to investigate
their izJHK<SUB>S</SUB> colors. Our spectroscopically selected sample
has ~0.1 mag bluer median J - K<SUB>S</SUB> color at a given spectral
type (for L0-L4) than previously known L dwarfs, which reflects a
bias toward redder L dwarfs in past selection criteria. We present
photometric distance relations based on i - z and i - J colors and
derive distances to our L dwarf sample. We combine the distances
with SDSS/2MASS proper motions in order to examine the tangential
velocities. For the majority of our spectroscopic sample, we measured
radial velocities and present three-dimensional kinematics. We also
provide Hα detections for the fraction of our sample with sufficient
quality spectra. Comparison of the velocities of our L dwarf sample
to a kinematic model shows evidence for both cold and hot dynamical
populations, consistent with young and old disk components. The
dispersions of these components are similar to those found for M
dwarfs. We also show that J - K<SUB>S</SUB> color is correlated with
velocity dispersion, confirming a relationship between J - K<SUB>S</SUB>
color and age.
---------------------------------------------------------
Title: A White Light Megaflare on the dM4.5e Star YZ CMi
Authors: Kowalski, Adam F.; Hawley, Suzanne L.; Holtzman, Jon A.;
Wisniewski, John P.; Hilton, Eric J.
2010ApJ...714L..98K Altcode: 2010arXiv1003.3057K
On UT 2009 January 16, we observed a white light megaflare on the dM4.5e
star YZ CMi as part of a long-term spectroscopic flare-monitoring
campaign to constrain the spectral shape of optical flare continuum
emission. Simultaneous U-band photometric and 3350-9260 Å spectroscopic
observations were obtained during 1.3 hr of the flare decay. The event
persisted for more than 7 hr and at flare peak, the U-band flux was
almost 6 mag brighter than in the quiescent state. The properties of
this flare mark it as one of the most energetic and longest-lasting
white light flares ever to be observed on an isolated low-mass star. We
present the U-band flare energetics and a flare continuum analysis. For
the first time, we show convincingly with spectra that the shape
of the blue continuum from 3350 Å to 4800 Å can be represented
as a sum of two components: a Balmer continuum as predicted by the
Allred et al. radiative hydrodynamic flare models and a T~ 10,000 K
blackbody emission component as suggested by many previous studies of
the broadband colors and spectral distributions of flares. The areal
coverage of the Balmer continuum and blackbody emission regions vary
during the flare decay, with the Balmer continuum emitting region
always being significantly (~3-16 times) larger. These data will
provide critical constraints for understanding the physics underlying
the mysterious blue continuum radiation in stellar flares. <P />Based on
observations obtained with the Apache Point Observatory 3.5 m Telescope,
which is owned and operated by the Astrophysical Research Consortium.
---------------------------------------------------------
Title: Discovery of an Unusually Blue L Dwarf Within 10 pc of the Sun
Authors: Schmidt, Sarah J.; West, Andrew A.; Burgasser, Adam J.;
Bochanski, John J.; Hawley, Suzanne L.
2010AJ....139.1045S Altcode: 2009arXiv0912.3565S
We report the discovery of an unusually blue L5 dwarf within 10 pc of
the Sun from a search of Sloan Digital Sky Survey (SDSS) spectra. A
spectrophotometric distance estimate of 8.0 ± 1.6 pc places SDSS
J141624.08+134826.7 among the six closest known L dwarfs. SDSS
1416+13 was overlooked in infrared color-based searches because of
its unusually blue J - K <SUB> S </SUB> color, which also identifies
it as the nearest member of the blue L dwarf subclass. We present
additional infrared and optical spectroscopy from the IRTF/SpeX and
Magellan/MagE spectrographs and determine UVW motions that indicate thin
disk kinematics. The inclusion of SDSS 1416+13 in the 20 pc sample of
L dwarfs increases the number of L5 dwarfs by 20% suggesting that the
L dwarf luminosity function may be far from complete. <P />This paper
includes data gathered with the 6.5 m Magellan Telescopes located at
Las Campanas Observatory, Chile.
---------------------------------------------------------
Title: A White Light Megaflare on the dM4.5e Star YZ CMi
Authors: Kowalski, Adam; Hawley, S. L.; Holtzman, J. A.; Wisniewski,
J. P.; Hilton, E. J.
2010AAS...21542411K Altcode: 2010BAAS...42..332K
Due to their strong and persistent surface magnetic fields, some M
dwarfs frequently produce very explosive and energetic flares in the
optical and near-UV. However, observations and radiative hydrodynamic
simulations of flares are in stark disagreement over the type of
emission which characterizes the continuum at these wavelengths. On
January 16, 2009, we observed a white light megaflare on the dM4.5e star
YZ CMi as part of a long-term spectroscopic flare-monitoring campaign
to constrain the spectral shape of optical flare emission. This flare
was observed with simultaneous U-band photometry and 3400 A - 9000 A
spectroscopy with the NMSU 1 m and ARC 3.5 m telescopes at the Apache
Point Observatory. The event persisted for over 7.5 hours and at the
flare peak, YZ CMi's U-band flux was 5.8 magnitudes brighter than in
its quiescent state. The properties of this flare mark it as one of the
most energetic and long-lasting white light flares ever to be observed
on an isolated star. We present the detailed light curve properties and
a time-resolved spectral analysis of the continuum and emission lines
using over 160 spectra obtained during 1.3 hours of the decay phase of
the flare, during which there were complex light curve variations with
the U-band flux still elevated at 15-38 times the quiescent level. <P
/>AFK, SLH, & EJH acknowledge support from NSF grant AST 0807205
<P />JPW acknowledges support from NSF Astronomy & Astrophysics
Postdoctoral Fellowship AST 08-02230
---------------------------------------------------------
Title: Stellar Population Science with LSST
Authors: Covey, Kevin R.; Saha, A.; Beers, T. C.; Bochanski, J. J.;
Boeshaar, P.; Burgasser, A.; Cargile, P.; Chu, Y.; Claver, C.; Cook,
K.; Dhital, S.; Hawley, S. L.; Hebb, L.; Henry, T. J.; Hilton, E.;
Holberg, J. B.; Ivezic, Z.; Juric, M. L.; Kafka, S.; Kalirai, J.;
Lepine, S.; Macri, L.; McGehee, P. M.; Monet, D.; Olsen, K.; Pepper,
J.; Prsa, A.; Sarajedini, A.; Silvestri, N.; Stassun, K.; Thorman,
P.; West, A. A.; Williams, B. F.
2010AAS...21540108C Altcode: 2010BAAS...42..218C
The LSST will produce a multi-color photometric catalog of half the
sky to r=27.6 (AB mag; 5-sigma). Multi-epoch observations over the
survey's ten year baseline will allow variability, proper motion and
parallax measurements for objects as faint as r=24.7. These capabilities
allow LSST to identify and characterize resolved stellar populations
in unprecedented breadth and detail, enabling a more comprehensive
and nuanced understanding of the star formation history of the
Milky Way and nearby galaxies. The stellar populations science that
LSST will enable includes: completing the solar neighborhood census
by measuring accurate parallaxes (sigma<SUB>pi</SUB> = 6 mas) and
proper motions (sigma<SUB>pm</SUB> = 2 mas/yr) for low--mass stars
and brown dwarfs to a very faint limit (y < 21.4); assembling
large samples of eclipsing binaries, subdwarfs and white dwarfs to
measure fundamental physical parameters of stars and stellar systems;
enabling photometric metallicity determinations (down to [Fe/H]
= -2.5, or lower) for main-sequence stars in the LSST footprint;
constructing a comprehensive, homogeneous census of southern star
clusters to characterize stellar evolution as a function of age and
chemical composition; measure the star formation history of the Milky
Way's thin disk over the last 2-3 Gyrs by interpreting rotation periods
of solar analogs with calibrated gyrochronology relations; mapping the
location, chemistry, and ages of stars turning off the main-sequence
(MS) at all distances within the Galaxy, Magellanic Clouds, and dwarf
satellites of the Milky Way; map out the star formation history and
structure of the Magellanic clouds to distances exceeding 15 degrees
and surface brightness densities below 35 mags. per square arc sec;
fine tuning the extragalactic distance scale by examining properties
of RR Lyraes and Cepheids as a function of parent populations.
---------------------------------------------------------
Title: Connecting the Time Domain Photometry of M Dwarfs with
Low-Resolution Spectroscopy
Authors: West, Andrew A.; Kowlaski, A. F.; Becker, A. C.; Bochanski,
J. J.; Hawley, S. L.
2010AAS...21542420W Altcode: 2010BAAS...42R.333W
We present a study of the lightcurves and spectra of 18,000 M dwarfs
from the Sloan Digital Sky Survey (SDSS). Our sample was selected to
have both multi-epoch observations from SDSS's Stripe 82 (resulting in
60 separate observations in each band), as well as SDSS low-resolution
spectra for each star. A majority of the photometric variation in these
stars is thought to be caused by long-lived star spots that modulate
the light as the star rotates. The amplitude of the variation in all of
the SDSS bands gives us important insight into the spot coverage and
temperature. We investigate how this amplitude changes as a function
of various quantities derived from the spectra, namely spectral type,
magnetic activity (thought to be connected to the star spots), and
dynamical age. This sample and its ties to spectroscopic observations
will help inform and add value to upcoming (and current) time domain
surveys such as LSST.
---------------------------------------------------------
Title: M Dwarf Flares: Exoplanet Implications
Authors: Tofflemire, Benjamin M.; Wisniewski, J. P.; Kowalski, A. F.;
Schmidt, S. J.; Kundurthy, P.; Hawley, S. L.; Hilton, E. J.
2010AAS...21542315T Altcode: 2010BAAS...42..328T
Low mass stars such as M dwarfs are prime targets for exoplanet
transit searches as their low luminosities and small stellar radii
could enable detection of super-Earths residing in their habitable
zones. While promising targets for transit searches, M dwarfs are also
inherently variable and can exhibit up to 6 magnitude flux enhancements
in the optical U-band. This is significantly higher than the predicted
transit depths of super-Earths (0.005 magnitude flux decrease). The
behavior of flares at IR wavelengths, particularly those likely to
be used to study and characterize M dwarf exoplanets using facilities
such as JWST, remains largely unknown. To address these uncertainties,
we have executed a coordinated, contemporaneous monitoring program of
the optical and IR flux of M dwarfs known to regularly flare. A suite
of telescopes located at the Kitt Peak National Observatory and the
Apache Point Observatory were used for the observations. We present
the initial results of this program and discuss how flare events could
influence future exoplanet detection and characterization studies
in the IR. <P />JPW acknowledges support from a NSF Astronomy and
Astrophysics Postdoctoral Fellowship, AST 08-02230.
---------------------------------------------------------
Title: TYC 1240-945-1b: First Brown Dwarf Candidate from the
SDSS-III-MARVELS Planet Search
Authors: Lee, Brian L.; Ge, J.; Fleming, S. W.; Mahadevan, S.;
Sivarani, T.; De Lee, N.; Dou, L.; Jiang, P.; Xie, J.; Gaudi, B. S.;
Eastman, J.; Pepper, J.; Stassun, K.; Gary, B.; Wisniewski, J. P.;
Barnes, R.; Kane, S. R.; van Eyken, J. C.; Wang, J.; Chang, L.;
Costello, E.; Fletcher, A.; Groot, J.; Guo, P.; Hanna, K.; Malik, M.;
Rohan, P.; Varosi, F.; Wan, X.; Zhao, B.; Hearty, F.; Shelden, A.;
Leger, F.; Long, D.; Agol, E.; Ford, E. B.; Ford, H. C.; Holtzman,
J. A.; Schneider, D.; Weinberg, D. H.; Eisenstein, D.; Hawley,
S.; Snedden, S.; Bizyaev, D.; Brewington, H.; Malanushenko, V.;
Malanushenko, E.; Oravetz, D.; Pan, K.; Simmons, A.
2010AAS...21547204L Altcode: 2010BAAS...42..519L
We present a new brown dwarf candidate, TYC 1240-945-1b, discovered in
the first year of MARVELS, a multi-object radial velocity (RV) planet
search which is part of the Sloan Digital Sky Survey (SDSS-III). From
our RV discovery data taken at 15 epochs spread over a 100d time
baseline at the SDSS 2.5-m telescope, we derive a preliminary
characterization of the orbit with semi-amplitude K=2.5 km/s, period
P=5.9d, and no detectable eccentricity. Adopting a mass of 1.2 solar
masses for the F9V host star TYC 1240-945-1, we infer that the candidate
has Msini 26M<SUB>Jup</SUB> and semimajor axis 0.068AU. In addition
to exhibiting the discovery data, we show the pre-survey and follow-up
spectroscopic observations that have been taken to further refine the
stellar parameters for the host star. <P />This work was supported by
the W.M. Keck Foundation, NSF, SDSS-III consortium, NASA, and UF.
---------------------------------------------------------
Title: The Continued Optical to Mid-IR Evolution of V838 Monocerotis
Authors: Loebman, Sarah; Wisniewski, J. P.; Kowalski, A. F.; Barry,
R. K.; Bjorkman, K. S.; Bond, H. E.; Clampin, M.; Hammel, H. B.;
Hawley, S. L.; Lynch, D. K.; Munshi, F. A.; Russell, R. W.; Schmidt,
S. J.; Sitko, M. L.
2010AAS...21543115L Altcode: 2010BAAS...42..364L
V838 Monocerotis is an eruptive variable which gained notoriety in
2002 when it brightened by 9 magnitudes in a series of outbursts,
and eventually developed a spectacular light echo. The star's mid-IR
flux increased by a factor of 2 between 2004 and 2007, suggesting that
new dust was condensing from the expanding ejecta of the outbursts,
while more recent optical spectroscopic observations suggest that these
expanding ejecta have engulfed the system's B3V binary companion. We
present new optical, near-IR, and mid-IR spectroscopic and mid-IR
photometric observations of V838 Monocerotis obtained between 2008-2009
at the Apache Point Observatory 3.5m, NASA IRTF 3m, and Gemini South 8m
telescopes. We discuss the chemistry and continued evolution of recently
formed dust in the system in the context of previously published
photometric, spectroscopic, and spectro-polarimetric observations of
the system. <P />This work is supported at The Aerospace Corporation
by the Independent Research and Development program; JPW acknowledges
support from a NSF Astronomy & Astrophysics Postdoctoral Fellowship,
AST 08-02230.
---------------------------------------------------------
Title: The SDSS-III MARVELS Survey: The First Year
Authors: De Lee, Nathan M.; Ge, J.; Lee, B.; Mahadevan, S.; Fleming,
S. W.; Sivarani, T.; Wan, X.; Groot, J.; Zhao, B.; Varosi, F.; Hanna,
K.; Hearty, F.; Chang, L.; Liu, J.; Rohan, P.; van Eyken, J. C.;
Wang, J.; Guo, P.; Malik, M.; Shelden, A.; Kane, S. R.; Costello,
E.; Fletcher, A.; Ford, E. B.; Agol, E.; Bochanski, J. J.; Ford, H.;
Gaudi, S.; Holtzman, J.; Schneider, D. P.; Seager, S.; Weinberg, D.;
Eisenstein, D.; Leger, F.; Long, D.; Snedden, S.; Pan, K.; Bizyaev,
D.; Brewington, H.; Malanushenko, E.; Malanushenko, V.; Oravetz, D.;
Simmons, A.; Hawley, S.
2010AAS...21547205D Altcode: 2010BAAS...42..519D
The Sloan Digital Sky Survey (SDSS-III) MARVELS (Multi-object Apache
point observatory Radial Velocity Exo-planet Large-area Survey)
project is currently in its second year of operation. The MARVELS
survey is currently searching for giant planets around a large and
diverse set of host stars from F, G, and K dwarfs and subgiants to G
and K giants. The MARVELS survey has already canvassed over 2500 stars
primarily ranging in V magnitude from 7.6 to 12. <P />This presentation
will cover an overview of the MARVELS Survey including operations and
data processing during the first year of observing. There will also
be a discussion of the ongoing analysis of the MARVELS radial velocity
curves. This analysis will consider identification of variable objects,
period searching, and ultimately identifying MARVELS candidates for
binaries, brown dwarfs, and planets. Early results from the first year
of operation will be shown. <P />We wish to acknowledge support from
the W.M. Keck Foundation, NSF, SDSS-III consortium, NASA and UF.
---------------------------------------------------------
Title: Flares on M Dwarfs from a Time-Resolved SDSS Spectral Sample
Authors: Hilton, Eric J.; Hawley, S. L.; West, A. A.; Kowalski, A. F.
2010AAS...21542410H Altcode: 2010BAAS...42..332H
We present flare rates and analysis of individual flares using
time-resolved spectra of M dwarfs from the Sloan Digital Sky Survey
Data Release 5. Each of the 40,000 M dwarf spectra from the West et
al. (2008) DR5 sample represents a co-addition of several shorter
(9-15 min) spectra. We analyze nearly 200,000 of these short spectra,
subdividing them by spectral type and by signal-to-noise ratio and use
statistical methods to assign variability and flaring status. These
data allow us to investigate the spectroscopic time-domain properties
of low-mass stars.
---------------------------------------------------------
Title: Color and Kinematics of L dwarfs From the Sloan Digital
Sky Survey
Authors: Schmidt, Sarah J.; West, A. A.; Hawley, S. L.; Pineda, J. S.
2010AAS...21542426S Altcode: 2010BAAS...42Q.335S
We present a sample of 484 L dwarfs from the Sloan Digital Sky Survey
(SDSS) spectroscopic database, selected primarily using spectroscopic
criteria. Our SDSS L dwarf sample has a bluer median J-Ks color at
each spectral type than samples of L dwarfs selected using infrared
colors, which reflects a bias towards redder J-Ks in previously known L
dwarfs. Distances are estimated using newly derived photometric parallax
relations in i-z and i-J, and are combined with radial velocities and
proper motions to calculate full space motions. As a single population,
L dwarfs do not appear to be kinematically cooler (younger) than M
dwarfs. However, our sample is better fit by a two-population model
with hot and cold components, consistent with young and old disk
populations. We also find that bluer objects have a larger velocity
dispersion than redder objects of the same spectral type, indicating
that the J-Ks color may be a good tracer of age.
---------------------------------------------------------
Title: Early Results of a High-Resolution Spectroscopic Monitoring
Program of the Mysterious Eclipsing Binary
Authors: Ketzeback, W.; McMillan, R.; Dembicky, J.; Saurage, G.;
Huehnerhoff, J.; Coughlin, J.; Barentine, J.; Schmidt, S.; Hawley,
S.; Wallerstein, G.
2010neme.confP...2K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Flare Rates in Low-Mass Stars
Authors: Krogsrud, David; Davenport, J. R. A.; Reid, I. N.; Hawley,
S. L.
2009AAS...21360102K Altcode:
Low-mass stars constitute a large majority of the total population
of stars in our galaxy, yet relatively little is known about their
properties. This is largely a consequence of the difficulty of observing
them due to their intrinsic dimness. As they are so common, low-mass
stars are a large potential source of noise in numerous variability
studies including extra-solar planet and novae surveys. Flare rates for
these stars are also important in constraining the characteristics of
their magnetic dynamos. In this study, we look at the open cluster IC
2391, observing three fields in U and I Johnson-Cousins filters. The
data come from the CTIO 0.9m telescope. Twenty-three late-type stars
are monitored, half of which have previously published I magnitudes. We
present preliminary results <P />of the activity rates of these stars.
---------------------------------------------------------
Title: LSST Science Book, Version 2.0
Authors: LSST Science Collaboration; Abell, Paul A.; Allison, Julius;
Anderson, Scott F.; Andrew, John R.; Angel, J. Roger P.; Armus, Lee;
Arnett, David; Asztalos, S. J.; Axelrod, Tim S.; Bailey, Stephen;
Ballantyne, D. R.; Bankert, Justin R.; Barkhouse, Wayne A.; Barr,
Jeffrey D.; Barrientos, L. Felipe; Barth, Aaron J.; Bartlett, James
G.; Becker, Andrew C.; Becla, Jacek; Beers, Timothy C.; Bernstein,
Joseph P.; Biswas, Rahul; Blanton, Michael R.; Bloom, Joshua S.;
Bochanski, John J.; Boeshaar, Pat; Borne, Kirk D.; Bradac, Marusa;
Brandt, W. N.; Bridge, Carrie R.; Brown, Michael E.; Brunner, Robert
J.; Bullock, James S.; Burgasser, Adam J.; Burge, James H.; Burke,
David L.; Cargile, Phillip A.; Chandrasekharan, Srinivasan; Chartas,
George; Chesley, Steven R.; Chu, You-Hua; Cinabro, David; Claire,
Mark W.; Claver, Charles F.; Clowe, Douglas; Connolly, A. J.; Cook,
Kem H.; Cooke, Jeff; Cooray, Asantha; Covey, Kevin R.; Culliton,
Christopher S.; de Jong, Roelof; de Vries, Willem H.; Debattista,
Victor P.; Delgado, Francisco; Dell'Antonio, Ian P.; Dhital, Saurav;
Di Stefano, Rosanne; Dickinson, Mark; Dilday, Benjamin; Djorgovski,
S. G.; Dobler, Gregory; Donalek, Ciro; Dubois-Felsmann, Gregory;
Durech, Josef; Eliasdottir, Ardis; Eracleous, Michael; Eyer, Laurent;
Falco, Emilio E.; Fan, Xiaohui; Fassnacht, Christopher D.; Ferguson,
Harry C.; Fernandez, Yanga R.; Fields, Brian D.; Finkbeiner, Douglas;
Figueroa, Eduardo E.; Fox, Derek B.; Francke, Harold; Frank, James
S.; Frieman, Josh; Fromenteau, Sebastien; Furqan, Muhammad; Galaz,
Gaspar; Gal-Yam, A.; Garnavich, Peter; Gawiser, Eric; Geary, John;
Gee, Perry; Gibson, Robert R.; Gilmore, Kirk; Grace, Emily A.; Green,
Richard F.; Gressler, William J.; Grillmair, Carl J.; Habib, Salman;
Haggerty, J. S.; Hamuy, Mario; Harris, Alan W.; Hawley, Suzanne L.;
Heavens, Alan F.; Hebb, Leslie; Henry, Todd J.; Hileman, Edward;
Hilton, Eric J.; Hoadley, Keri; Holberg, J. B.; Holman, Matt J.;
Howell, Steve B.; Infante, Leopoldo; Ivezic, Zeljko; Jacoby, Suzanne
H.; Jain, Bhuvnesh; R; Jedicke; Jee, M. James; Garrett Jernigan,
J.; Jha, Saurabh W.; Johnston, Kathryn V.; Jones, R. Lynne; Juric,
Mario; Kaasalainen, Mikko; Styliani; Kafka; Kahn, Steven M.; Kaib,
Nathan A.; Kalirai, Jason; Kantor, Jeff; Kasliwal, Mansi M.; Keeton,
Charles R.; Kessler, Richard; Knezevic, Zoran; Kowalski, Adam;
Krabbendam, Victor L.; Krughoff, K. Simon; Kulkarni, Shrinivas;
Kuhlman, Stephen; Lacy, Mark; Lepine, Sebastien; Liang, Ming;
Lien, Amy; Lira, Paulina; Long, Knox S.; Lorenz, Suzanne; Lotz,
Jennifer M.; Lupton, R. H.; Lutz, Julie; Macri, Lucas M.; Mahabal,
Ashish A.; Mandelbaum, Rachel; Marshall, Phil; May, Morgan; McGehee,
Peregrine M.; Meadows, Brian T.; Meert, Alan; Milani, Andrea; Miller,
Christopher J.; Miller, Michelle; Mills, David; Minniti, Dante; Monet,
David; Mukadam, Anjum S.; Nakar, Ehud; Neill, Douglas R.; Newman,
Jeffrey A.; Nikolaev, Sergei; Nordby, Martin; O'Connor, Paul; Oguri,
Masamune; Oliver, John; Olivier, Scot S.; Olsen, Julia K.; Olsen,
Knut; Olszewski, Edward W.; Oluseyi, Hakeem; Padilla, Nelson D.;
Parker, Alex; Pepper, Joshua; Peterson, John R.; Petry, Catherine;
Pinto, Philip A.; Pizagno, James L.; Popescu, Bogdan; Prsa, Andrej;
Radcka, Veljko; Raddick, M. Jordan; Rasmussen, Andrew; Rau, Arne; Rho,
Jeonghee; Rhoads, James E.; Richards, Gordon T.; Ridgway, Stephen
T.; Robertson, Brant E.; Roskar, Rok; Saha, Abhijit; Sarajedini,
Ata; Scannapieco, Evan; Schalk, Terry; Schindler, Rafe; Schmidt,
Samuel; Schmidt, Sarah; Schneider, Donald P.; Schumacher, German;
Scranton, Ryan; Sebag, Jacques; Seppala, Lynn G.; Shemmer, Ohad;
Simon, Joshua D.; Sivertz, M.; Smith, Howard A.; Allyn Smith, J.;
Smith, Nathan; Spitz, Anna H.; Stanford, Adam; Stassun, Keivan G.;
Strader, Jay; Strauss, Michael A.; Stubbs, Christopher W.; Sweeney,
Donald W.; Szalay, Alex; Szkody, Paula; Takada, Masahiro; Thorman,
Paul; Trilling, David E.; Trimble, Virginia; Tyson, Anthony; Van
Berg, Richard; Vanden Berk, Daniel; VanderPlas, Jake; Verde, Licia;
Vrsnak, Bojan; Walkowicz, Lucianne M.; Wandelt, Benjamin D.; Wang,
Sheng; Wang, Yun; Warner, Michael; Wechsler, Risa H.; West, Andrew
A.; Wiecha, Oliver; Williams, Benjamin F.; Willman, Beth; Wittman,
David; Wolff, Sidney C.; Wood-Vasey, W. Michael; Wozniak, Przemek;
Young, Patrick; Zentner, Andrew; Zhan, Hu
2009arXiv0912.0201L Altcode:
A survey that can cover the sky in optical bands over wide fields to
faint magnitudes with a fast cadence will enable many of the exciting
science opportunities of the next decade. The Large Synoptic Survey
Telescope (LSST) will have an effective aperture of 6.7 meters and an
imaging camera with field of view of 9.6 deg^2, and will be devoted
to a ten-year imaging survey over 20,000 deg^2 south of +15 deg. Each
pointing will be imaged 2000 times with fifteen second exposures in six
broad bands from 0.35 to 1.1 microns, to a total point-source depth
of r~27.5. The LSST Science Book describes the basic parameters of
the LSST hardware, software, and observing plans. The book discusses
educational and outreach opportunities, then goes on to describe
a broad range of science that LSST will revolutionize: mapping the
inner and outer Solar System, stellar populations in the Milky Way and
nearby galaxies, the structure of the Milky Way disk and halo and other
objects in the Local Volume, transient and variable objects both at low
and high redshift, and the properties of normal and active galaxies at
low and high redshift. It then turns to far-field cosmological topics,
exploring properties of supernovae to z~1, strong and weak lensing,
the large-scale distribution of galaxies and baryon oscillations, and
how these different probes may be combined to constrain cosmological
models and the physics of dark energy.
---------------------------------------------------------
Title: VizieR Online Data Catalog: X-emitting stars identified from
the RASS/SDSS (Agueros+, 2009)
Authors: Agueros, M. A.; Anderson, S. F.; Covey, K. R.; Hawley,
S. L.; Margon, B.; Newsom, E. R.; Posselt, B.; Silvestri, N. M.;
Szkody, P.; Voges, W.
2009yCat..21810444A Altcode:
The ROSAT All-Sky Survey (RASS) was the first imaging X-ray survey of
the entire sky. Combining the RASS Bright and Faint Source Catalogs
(Cat. <IX/10>, 1RXS and <IX/29>) yields an average of
about three X-ray sources per square degree. However, while X-ray
source counterparts are known to range from distant quasars to nearby
M dwarfs, the RASS data alone are often insufficient to determine
the nature of an X-ray source. As a result, large-scale follow-up
programs are required to construct samples of known X-ray emitters. We
use optical data produced by the Sloan Digital Sky Survey (SDSS) to
identify 709 stellar X-ray emitters cataloged in the RASS and falling
within the SDSS Data Release 1 footprint. Most of these are bright
stars with coronal X-ray emission unsuitable for SDSS spectroscopy,
which is designed for fainter objects (g>15[mag]). Instead, we use
SDSS photometry, correlations with the Two Micron All Sky Survey and
other catalogs, and spectroscopy from the Apache Point Observatory
3.5m telescope to identify these stellar X-ray counterparts. Our
sample of 707 X-ray-emitting F, G, K, and M stars is one of the largest
X-ray-selected samples of such stars. We identify 17 new X-ray-emitting
DA (hydrogen) WDs, of which three are newly identified WDs. We report
on follow-up observations of three candidate cool X-ray-emitting WDs
(one DA and two DB (helium) WDs); we have not confirmed X-ray emission
from these WDs. <P />(7 data files).
---------------------------------------------------------
Title: Spectroscopic Study of NSVS RR Lyrae Stars: Preliminary
Metallicity Results
Authors: Kinemuchi, K.; Wallerstein, G.; Preston, G.; Walkowicz, L.;
Fraser, O.; Bochanski, J.; Hawley, S.
2009AIPC.1170..191K Altcode:
The Northern Sky Variability Survey (NSVS) is an all-sky photometric
survey of variable objects found down to V~15. The NSVS probes the
disk and inner halo components of the Milky Way Galaxy. Field RR
Lyrae (RRL) variable stars have been identified and analyzed. We
have begun a campaign to obtain spectra for many of these new RRL
stars. Mid-resolution spectra were obtained using the Dual Imaging
Spectrograph on the ARC 3.5 m telescope at Apache Point Observatory
over a span of 2 years. We have collected 89 spectra of RRL stars,
which were selected for their possible membership of the thick and thin
disk components. We have also included RRL stars with long periods
(P>0.75 days). We present the driving science and goals of these
projects, and preliminary results from the mid-resolution spectra.
---------------------------------------------------------
Title: Steady and Transient Radio Emission from Ultracool Dwarfs
Authors: Osten, Rachel A.; Phan-Bao, N.; Hawley, Suzanne L.; Reid,
I. Neill; Ojha, Roopesh
2009ApJ...700.1750O Altcode: 2009arXiv0905.4197O
We present the results of multi-frequency radio observing campaigns
designed to elucidate the nature of radio emission from very low mass
stars. We detect radio emission in an additional two epochs of the
ultracool dwarf binary LP 349-25, finding that the observed emission
is broad band and steady on timescales between 10 s and 10.7 hr, as
well as on timescales of 0.6 and 1.6 years. This system is unusual for
ultracool dwarfs with detectable radio emission, in exhibiting a lack
of any large-scale variability, particularly the bursting (periodic
or aperiodic) behavior exhibited by the other objects with detectable
levels of radio emission. We explore the constraints that the lack of
variability on long- and short-timescales, and flat spectral index,
imply about the radio-emitting structures and mechanism. The temporal
constraints argue for a high latitude emitting region with a large
inclination so that it is always in view, and survives for at least 0.6
years. Temporal constraints also limit the plasma conditions, implying
that the electron density be n<SUB>e</SUB> < 4 × 10<SUP>5</SUP>
cm<SUP>-3</SUP> and B< 130 G in order not to see time variations
due to collisional or radiative losses from high-energy particles. The
observations and constraints provided by them are most compatible
with a nonthermal radio emission mechanism, likely gyrosynchrotron
emission from a spatially homogeneous or inhomogeneous source. This
indicates that, similar to behaviors noted for chromospheric, transition
region, and coronal plasmas in ultracool dwarfs, the magnetic activity
patterns observed in active higher mass stars can survive to the
substellar boundary. We also present new epochs of multi-frequency
radio observations for the ultracool dwarfs 2MASS 05233822-140322 and
2MASS14563831-2809473(=LHS 3003); each has been detected in at least one
previous epoch but are not detected in the epochs reported here. The
results here suggest that magnetic configurations in ultracool dwarfs
can be long-lasting, and support the need for further radio monitoring
using a simultaneous, multi-frequency observing approach.
---------------------------------------------------------
Title: M Dwarfs in Sloan Digital Sky Survey Stripe 82: Photometric
Light Curves and Flare Rate Analysis
Authors: Kowalski, Adam F.; Hawley, Suzanne L.; Hilton, Eric J.;
Becker, Andrew C.; West, Andrew A.; Bochanski, John J.; Sesar, Branimir
2009AJ....138..633K Altcode: 2009arXiv0906.2030K
We present a flare rate analysis of 50,130 M dwarf light curves in
Sloan Digital Sky Survey Stripe 82. We identified 271 flares using
a customized variability index to search ~2.5 million photometric
observations for flux increases in the u and g bands. Every image
of a flaring observation was examined by eye and with a point-spread
function-matching and image subtraction tool to guard against false
positives. Flaring is found to be strongly correlated with the
appearance of Hα in emission in the quiet spectrum. Of the 99 flare
stars that have spectra, we classify eight as relatively inactive. The
flaring fraction is found to increase strongly in stars with redder
colors during quiescence, which can be attributed to the increasing
flare visibility and increasing active fraction for redder stars. The
flaring fraction is strongly correlated with |Z| distance such that
most stars that flare are within 300 pc of the Galactic plane. We derive
flare u-band luminosities and find that the most luminous flares occur
on the earlier-type m dwarfs. Our best estimate of the lower limit
on the flaring rate (averaged over Stripe 82) for flares with Δu
>= 0.7 mag on stars with u < 22 is 1.3 flares hr<SUP>-1</SUP>
deg<SUP>-2</SUP> but can vary significantly with the line of sight. <P
/>Based on observations obtained with the Apache Point Observatory
3.5 m telescope, which is owned and operated by the Astrophysical
Research Consortium.
---------------------------------------------------------
Title: M Dwarf Flares: Exoplanet Implications
Authors: Wisniewski, John; Kowalski, Adam; Schmidt, Sarah; Hawley,
Suzanne; Kundurthy, Praveen
2009noao.prop..280W Altcode:
Low mass M dwarfs are attractive stars for exoplanet transit research as
their low luminosities and small stellar radii could enable detection
of super-Earths residing in their habitable zones using existing
technology. Future IR facilities such as JWST will undoubtedly attempt
to characterize these systems through detailed transit observations. M
dwarfs can exhibit highly energetic flare events which cause <0.1
to 6.0 magnitude flux enhancements in the optical U-band, which is
significantly higher than the predicted transit depths of super- Earths
(~0.005 magnitude flux decrease). While Solar flares have been observed
to cause IR continuum enhancements (Xu et al 2006); surprisingly, it is
not known whether energetic flares associated with M dwarfs similarly
induce IR variability. We propose to contemporaneously monitor the
optical & IR flux of two M dwarfs known to regularly flare, to
determine what effect flares could have on future IR characterization
studies of M dwarf exoplanets.
---------------------------------------------------------
Title: The Seventh Data Release of the Sloan Digital Sky Survey
Authors: Abazajian, Kevork N.; Adelman-McCarthy, Jennifer K.; Agüeros,
Marcel A.; Allam, Sahar S.; Allende Prieto, Carlos; An, Deokkeun;
Anderson, Kurt S. J.; Anderson, Scott F.; Annis, James; Bahcall,
Neta A.; Bailer-Jones, C. A. L.; Barentine, J. C.; Bassett, Bruce
A.; Becker, Andrew C.; Beers, Timothy C.; Bell, Eric F.; Belokurov,
Vasily; Berlind, Andreas A.; Berman, Eileen F.; Bernardi, Mariangela;
Bickerton, Steven J.; Bizyaev, Dmitry; Blakeslee, John P.; Blanton,
Michael R.; Bochanski, John J.; Boroski, William N.; Brewington,
Howard J.; Brinchmann, Jarle; Brinkmann, J.; Brunner, Robert J.;
Budavári, Tamás; Carey, Larry N.; Carliles, Samuel; Carr, Michael
A.; Castander, Francisco J.; Cinabro, David; Connolly, A. J.; Csabai,
István; Cunha, Carlos E.; Czarapata, Paul C.; Davenport, James R. A.;
de Haas, Ernst; Dilday, Ben; Doi, Mamoru; Eisenstein, Daniel J.;
Evans, Michael L.; Evans, N. W.; Fan, Xiaohui; Friedman, Scott D.;
Frieman, Joshua A.; Fukugita, Masataka; Gänsicke, Boris T.; Gates,
Evalyn; Gillespie, Bruce; Gilmore, G.; Gonzalez, Belinda; Gonzalez,
Carlos F.; Grebel, Eva K.; Gunn, James E.; Györy, Zsuzsanna; Hall,
Patrick B.; Harding, Paul; Harris, Frederick H.; Harvanek, Michael;
Hawley, Suzanne L.; Hayes, Jeffrey J. E.; Heckman, Timothy M.; Hendry,
John S.; Hennessy, Gregory S.; Hindsley, Robert B.; Hoblitt, J.; Hogan,
Craig J.; Hogg, David W.; Holtzman, Jon A.; Hyde, Joseph B.; Ichikawa,
Shin-ichi; Ichikawa, Takashi; Im, Myungshin; Ivezić, Željko;
Jester, Sebastian; Jiang, Linhua; Johnson, Jennifer A.; Jorgensen,
Anders M.; Jurić, Mario; Kent, Stephen M.; Kessler, R.; Kleinman,
S. J.; Knapp, G. R.; Konishi, Kohki; Kron, Richard G.; Krzesinski,
Jurek; Kuropatkin, Nikolay; Lampeitl, Hubert; Lebedeva, Svetlana; Lee,
Myung Gyoon; Lee, Young Sun; French Leger, R.; Lépine, Sébastien;
Li, Nolan; Lima, Marcos; Lin, Huan; Long, Daniel C.; Loomis, Craig P.;
Loveday, Jon; Lupton, Robert H.; Magnier, Eugene; Malanushenko, Olena;
Malanushenko, Viktor; Mandelbaum, Rachel; Margon, Bruce; Marriner,
John P.; Martínez-Delgado, David; Matsubara, Takahiko; McGehee,
Peregrine M.; McKay, Timothy A.; Meiksin, Avery; Morrison, Heather
L.; Mullally, Fergal; Munn, Jeffrey A.; Murphy, Tara; Nash, Thomas;
Nebot, Ada; Neilsen, Eric H., Jr.; Newberg, Heidi Jo; Newman, Peter
R.; Nichol, Robert C.; Nicinski, Tom; Nieto-Santisteban, Maria; Nitta,
Atsuko; Okamura, Sadanori; Oravetz, Daniel J.; Ostriker, Jeremiah P.;
Owen, Russell; Padmanabhan, Nikhil; Pan, Kaike; Park, Changbom; Pauls,
George; Peoples, John, Jr.; Percival, Will J.; Pier, Jeffrey R.; Pope,
Adrian C.; Pourbaix, Dimitri; Price, Paul A.; Purger, Norbert; Quinn,
Thomas; Raddick, M. Jordan; Re Fiorentin, Paola; Richards, Gordon
T.; Richmond, Michael W.; Riess, Adam G.; Rix, Hans-Walter; Rockosi,
Constance M.; Sako, Masao; Schlegel, David J.; Schneider, Donald P.;
Scholz, Ralf-Dieter; Schreiber, Matthias R.; Schwope, Axel D.; Seljak,
Uroš; Sesar, Branimir; Sheldon, Erin; Shimasaku, Kazu; Sibley, Valena
C.; Simmons, A. E.; Sivarani, Thirupathi; Allyn Smith, J.; Smith,
Martin C.; Smolčić, Vernesa; Snedden, Stephanie A.; Stebbins, Albert;
Steinmetz, Matthias; Stoughton, Chris; Strauss, Michael A.; SubbaRao,
Mark; Suto, Yasushi; Szalay, Alexander S.; Szapudi, István; Szkody,
Paula; Tanaka, Masayuki; Tegmark, Max; Teodoro, Luis F. A.; Thakar,
Aniruddha R.; Tremonti, Christy A.; Tucker, Douglas L.; Uomoto, Alan;
Vanden Berk, Daniel E.; Vandenberg, Jan; Vidrih, S.; Vogeley, Michael
S.; Voges, Wolfgang; Vogt, Nicole P.; Wadadekar, Yogesh; Watters,
Shannon; Weinberg, David H.; West, Andrew A.; White, Simon D. M.;
Wilhite, Brian C.; Wonders, Alainna C.; Yanny, Brian; Yocum, D. R.;
York, Donald G.; Zehavi, Idit; Zibetti, Stefano; Zucker, Daniel B.
2009ApJS..182..543A Altcode: 2008arXiv0812.0649A
This paper describes the Seventh Data Release of the Sloan Digital
Sky Survey (SDSS), marking the completion of the original goals of
the SDSS and the end of the phase known as SDSS-II. It includes 11,663
deg<SUP>2</SUP> of imaging data, with most of the ~2000 deg<SUP>2</SUP>
increment over the previous data release lying in regions of low
Galactic latitude. The catalog contains five-band photometry for 357
million distinct objects. The survey also includes repeat photometry
on a 120° long, 2fdg5 wide stripe along the celestial equator in
the Southern Galactic Cap, with some regions covered by as many as
90 individual imaging runs. We include a co-addition of the best of
these data, going roughly 2 mag fainter than the main survey over
250 deg<SUP>2</SUP>. The survey has completed spectroscopy over
9380 deg<SUP>2</SUP> the spectroscopy is now complete over a large
contiguous area of the Northern Galactic Cap, closing the gap that
was present in previous data releases. There are over 1.6 million
spectra in total, including 930,000 galaxies, 120,000 quasars, and
460,000 stars. The data release includes improved stellar photometry
at low Galactic latitude. The astrometry has all been recalibrated
with the second version of the USNO CCD Astrograph Catalog, reducing
the rms statistical errors at the bright end to 45 milliarcseconds
per coordinate. We further quantify a systematic error in bright
galaxy photometry due to poor sky determination; this problem is less
severe than previously reported for the majority of galaxies. Finally,
we describe a series of improvements to the spectroscopic reductions,
including better flat fielding and improved wavelength calibration at
the blue end, better processing of objects with extremely strong narrow
emission lines, and an improved determination of stellar metallicities.
---------------------------------------------------------
Title: Using magnetic activity and Galactic dynamics to constrain
the ages of M dwarfs
Authors: West, Andrew A.; Hawley, Suzanne L.; Bochanski, John J.;
Covey, Kevin R.; Burgasser, Adam J.
2009IAUS..258..327W Altcode: 2008arXiv0812.1223W
We present a study of the dynamics and magnetic activity of M
dwarfs using the largest spectroscopic sample of low-mass stars
ever assembled. The age at which strong surface magnetic activity
(as traced by Hα) ceases in M dwarfs has been inferred to have a
strong dependence on mass (spectral type, surface temperature) and
explains previous results showing a large increase in the fraction
of active stars at later spectral types. Using spectral observations
of more than 40000 M dwarfs from the Sloan Digital Sky Survey, we
show that the fraction of active stars decreases as a function of
vertical distance from the Galactic plane (a statistical proxy for
age), and that the magnitude of this decrease changes significantly
for different M spectral types. Adopting a simple dynamical model for
thin disk vertical heating, we assign an age for the activity decline
at each spectral type, and thus determine the activity lifetimes for M
dwarfs. In addition, we derive a statistical age-activity relation for
each spectral type using the dynamical model, the vertical distance from
the Plane and the Hα emission line luminosity of each star (the latter
of which also decreases with vertical height above the Galactic plane).
---------------------------------------------------------
Title: Short Period Variability Of An M-dwarf In SDSS Stripe-82
Authors: Munshi, Ferah; Becker, A.; Hawley, S. L.; Bochanski, J. J.;
Sesar, B.; Kowalski, A.
2009AAS...21443007M Altcode:
We present analysis of a unique short-period object selected from the
SDSS-II Stripe 82 photometric time-domain database. This object stands
out in color-period space, having the colors and spectrum of an early
M-dwarf (M0-M1) but a photometric period of 0.1 days, an amplitude of
0.2 magnitudes, and a sinusoidal lightcurve. It is unusual to find
<P />such a red object with such a short period. We have obtained
multiple epochs of spectroscopy with the MAGE spectrograph at Magellan
to constrain any radial velocity variations. We examine the possible
<P />interpretations of this system, including : an M-dwarf/M-dwarf
eclipsing system, which would be near the Algol limit; stellar rotation
with persistent star spots; and stellar pulsation.
---------------------------------------------------------
Title: X-Ray-Emitting Stars Identified from the ROSAT All-Sky Survey
and the Sloan Digital Sky Survey
Authors: Agüeros, Marcel A.; Anderson, Scott F.; Covey, Kevin R.;
Hawley, Suzanne L.; Margon, Bruce; Newsom, Emily R.; Posselt, Bettina;
Silvestri, Nicole M.; Szkody, Paula; Voges, Wolfgang
2009ApJS..181..444A Altcode: 2009arXiv0903.4202A
The ROSAT All-Sky Survey (RASS) was the first imaging X-ray survey
of the entire sky. Combining the RASS Bright and Faint Source
Catalogs yields an average of about three X-ray sources per square
degree. However, while X-ray source counterparts are known to range
from distant quasars to nearby M dwarfs, the RASS data alone are often
insufficient to determine the nature of an X-ray source. As a result,
large-scale follow-up programs are required to construct samples
of known X-ray emitters. We use optical data produced by the Sloan
Digital Sky Survey (SDSS) to identify 709 stellar X-ray emitters
cataloged in the RASS and falling within the SDSS Data Release 1
footprint. Most of these are bright stars with coronal X-ray emission
unsuitable for SDSS spectroscopy, which is designed for fainter objects
(g > 15 [mag]). Instead, we use SDSS photometry, correlations with
the Two Micron All Sky Survey and other catalogs, and spectroscopy
from the Apache Point Observatory 3.5 m telescope to identify these
stellar X-ray counterparts. Our sample of 707 X-ray-emitting F, G,
K, and M stars is one of the largest X-ray-selected samples of such
stars. We derive distances to these stars using photometric parallax
relations appropriate for dwarfs on the main sequence, and use these
distances to calculate L<SUB>X</SUB> . We also identify a previously
unknown cataclysmic variable (CV) as a RASS counterpart. Separately,
we use correlations of the RASS and the SDSS spectroscopic catalogs
of CVs and white dwarfs (WDs) to study the properties of these rarer
X-ray-emitting stars. We examine the relationship between (f<SUB>X</SUB>
/f<SUB>g</SUB> ) and the equivalent width of the Hβ emission line
for 46 X-ray-emitting CVs and discuss tentative classifications for a
subset based on these quantities. We identify 17 new X-ray-emitting DA
(hydrogen) WDs, of which three are newly identified WDs. We report
on follow-up observations of three candidate cool X-ray-emitting WDs
(one DA and two DB (helium) WDs); we have not confirmed X-ray emission
from these WDs. <P />Includes observations obtained with the Apache
Point Observatory 3.5 m telescope, which is owned and operated by the
Astrophysical Research Consortium.
---------------------------------------------------------
Title: Observations and Models of Quiescent M Dwarf Chromospheres
Authors: Walkowicz, Lucianne M.; Hawley, Suzanne L.
2009AIPC.1094..696W Altcode: 2009csss...15..696W
Using simultaneous observations of the Hα and Ca II K lines for a
sample of M3 dwarfs, we investigate the temperature structure required
to produce the spectral signatures of chromospheric activity in
low mass stars. Combined, the Hα and Ca II K data provide a rich
set of observational challenges to theory. We apply these data as
empirical constraints for new static models of quiescent M dwarf
atmospheres. Using these models, we find that single component model
atmospheres are able to provide a satisfactory description of weakly
active M dwarfs, but more active stars require two component models,
with different temperature structures for active and basal regions of
the chromosphere.
---------------------------------------------------------
Title: M Dwarf Flares from Time-Resolved SDSS Spectra
Authors: Hilton, Eric J.; Hawley, Suzanne; West, Andrew A.; Kowalski,
Adam
2009AIPC.1094..652H Altcode: 2009csss...15..652H
Flares on low-mass dwarfs are a major source of variability in
the optical and UV in the Galaxy. In addition to being a source of
optical transients, these flares may have an important effect on
the habitability of planets orbiting low-mass dwarfs. We present a
study of flares on M dwarfs determined from Sloan Digital Sky Survey
time-resolved spectra. Our sample consists of tens of thousands of M
dwarfs whose SDSS spectra were formed from co-adds of several (typically
3-5) consecutive shorter (typically 9-15 minute) exposures. We present
the Flare Line Index as a way to identify flares in these individual
component spectra with crude time-resolution, and investigate the
short-term variability of the Balmer and Ca II emission lines.
---------------------------------------------------------
Title: Tracers of Chromospheric Structure. I. Observations of Ca II
K and Hα in M Dwarfs
Authors: Walkowicz, Lucianne M.; Hawley, Suzanne L.
2009AJ....137.3297W Altcode: 2008arXiv0811.1778W
We report on our observing program<SUP>4</SUP>This paper is based
on observations obtained with the Apache Point Observatory 3.5 m
telescope, which is owned and operated by the Astrophysical Research
Consortium. Some of the data presented herein were obtained at the
W. M. Keck Observatory, which is operated as a scientific partnership
among the California Institute of Technology, the University of
California and the National Aeronautics and Space Administration. The
Observatory was made possible by the generous financial support of the
W. M. Keck Foundation. to capture simultaneous spectra of Ca II and
Balmer lines in a sample of nearby M3 dwarfs. Our goal is to investigate
the chromospheric temperature structure required to produce these
lines at the observed levels. We find a strong positive correlation
between instantaneous measurements of Ca II K and the Balmer lines in
active stars, although these lines may not be positively correlated in
time-resolved measurements. The relationship between Hα and Ca II K
remains ambiguous for weak and intermediate activity stars, with Hα
absorption corresponding to a range of Ca II K emission. A similar
relationship is also observed between Ca II K and the higher-order
Balmer lines. As our sample consists of a single spectral type,
correlations between these important chromospheric tracers cannot be
ascribed to continuum effects, as suggested by other authors. These data
confirm prior nonsimultaneous observations of the Hα line behavior with
increasing activity, showing an initial increase in the Hα absorption
with increasing Ca II K emission, prior to Hα filling in and eventually
becoming a pure emission line in the most active stars. We also compare
our optical measurements with archival UV and X-ray measurements,
finding a positive correlation between the chromospheric and coronal
emission for both high and intermediate activity stars. We compare our
results with previous determinations of the active fraction of low-mass
stars, and discuss them in the context of surface inhomogeneity. Lastly,
we discuss the application of these data as empirical constraints on
new static models of quiescent M dwarf atmospheres.
---------------------------------------------------------
Title: Our Nearest 15 Million Neighbors: The Field Low-Mass Stellar
Luminosity and Mass Functions
Authors: Bochanski, John J.; Hawley, Suzanne L.; Reid, I. Neill; Covey,
Kevin R.; West, Andrew A.; Golimowski, David A.; Ivezić, Željko
2009AIPC.1094..977B Altcode: 2008arXiv0810.2343B; 2009csss...15..977B
We report on a new measurement of the luminosity function (LF) and
mass function (MF) of field low-mass dwarfs using Sloan Digital Sky
Survey (SDSS) photometry. The final catalog is composed of ~15 million
low-mass stars (0.1 M<SUB>solar</SUB><M<0.8 M<SUB>solar</SUB>),
spread over 8,400 square degrees. Distances to the stars are estimated
using new photometric parallax relations, constructed from ugriz
photometry of nearby low-mass stars with trigonometric parallaxes. The
LF is measured with a novel technique, which simultaneously measures
Galactic structure and the stellar LF. The resulting LF is compared
to previous studies and converted to a MF. The MF is well-described by
a log-normal distribution, with M<SUB>°</SUB> = 0.27 M<SUB>solar</SUB>.
---------------------------------------------------------
Title: On-sky Commissioning and Early Results from the
SDSS-III-MARVELS Planet Search
Authors: Lee, Brian L.; Ge, J.; Mahadevan, S.; Fleming, S. W.;
Wan, X.; Groot, J.; Zhao, B.; Hearty, F.; Chang, L.; Varosi, F.;
Hanna, K.; Liu, J.; van Eyken, J. C.; Guo, P.; Malik, M.; Shelden,
A.; Sivarani, T.; De Lee, N.; Kane, S. R.; Wang, J.; Costello, E.;
Rohan, P.; Fletcher, A.; Ford, E. B.; Agol, E.; Bochanski, J. J.;
Ford, H.; Gaudi, B. S.; Holtzman, J. A.; Schneider, D. P.; Seager,
S.; Weinberg, D. H.; Eisenstein, D. J.; Hawley, S. L.
2009AAS...21340506L Altcode: 2009BAAS...41..198L
The Multi-object APO Radial Velocity Large-area Survey (MARVELS)
commenced operations as an SDSS-III bright-time survey in
Sep. 2008. MARVELS will be used to monitor 11000 stars for RV
variations during SDSS-III, using time baselines of 1.5 years,
to <10-30m/s radial velocity (RV) precision for stars with
brightnesses 7.6<V<12. The first MARVELS instrument is a dispersed
fixed-delay interferometer (DFDI) with a 60-object fibre-fed input,
mounted at the ARC 2.5-m telescope at Apache Point Observatory. Both
interferometer output beams are recorded, producing fringing spectra
over wavelengths 500-570nm with resolving power R 12000. The instrument
is environmentally stabilized such that no iodine cell is needed in
the stellar beam path, and instrument drift calibrations are simply
taken before and after each stellar exposure. <P />We outline our
DFDI RV data reduction procedure and show calibration lamp image
stability equivalent to 3m/s RMS stellar RV precision. On-sky, even in
the presence of higher than normal environmental disturbances during
our Sep. commissioning observations, our first preliminary analysis
achieved 12m/s RMS RV precision (on 9m/s photon noise) on the RV-stable
star HD 9407 (V=6.5) in 144 sec. exposures, and 30m/s RMS RV precision
(on 20m/s photon noise) on the known planet-bearing star TrES-2 (V=11.4)
in 40-60 min. exposures, over 6 commissioning nights. Finally, we show
candidate radial velocity variables garnered after moving to normal
survey operations during Oct.-Dec. 2008, acquired using an operations
strategy designed to deliver optimum extrasolar planet yield over
the six-year lifecycle of SDSS-III. <P />We would like to thank the
W.M. Keck Foundation, Sloan Foundation, NSF, NASA and UF for support.
---------------------------------------------------------
Title: Flare Rates on M Dwarfs: Observing Program
Authors: Hilton, Eric J.; Hawley, S.; Ule, N.; Kowalski, A.; Gomez,
T.; Grammer, S.; Holtzman, J.; Huang, M.; Huehnerhoff, J.; Morgan, D.
2009AAS...21343416H Altcode: 2009BAAS...41..305H
Determining the magnitude and rate at which low mass stars flare is
an important problem in stellar astrophysics because flares are a
major source of variability in large time domain surveys, affect the
atmospheres of orbiting planetary systems, and are manifestations
of magnetic field production and reconfiguration, processes which
are not well understood on M dwarfs. We present early results from
a multi-year observing campaign to statistically determine M dwarf
flare rates and energies as a function of spectral type and activity
level. Our observations consist of over 100 hours of monitoring M
dwarfs on three telescopes. In addition to preliminary flare rates,
we discuss our method of determining energy and duration.
---------------------------------------------------------
Title: The Sdss-iii Multi-object Apo Radial-velocity Exoplanet
Large-area Survey (marvels) And Its Early Results
Authors: Ge, Jian; Lee, B.; Mahadevan, S.; Wan, X.; Groot, J.; Zhao,
B.; Hearty, F.; Fleming, S.; van Eyken, J.; Hanna, K.; Varosi, F.;
Chang, L.; Thirupathi, S.; Chen, Z.; Shelden, A.; Liu, J.; De Lee,
N.; Malik, M.; Rohan, P.; Kane, S.; Guo, P.; Leger, F.; Wang, J.;
Ford, E. B.; Agol, E.; Gaudi, S.; Ford, H.; Schneider, D.; Holtzman,
J.; Harding, P.; Blanton, M.; Snedden, S.; Pan, K.; Fletcher, A.;
Costello, E.; Bochanski, J.; Seager, S.; Weinberg, D.; Eisenstein,
D.; Gunn, J.; Hawley, S.
2009AAS...21333602G Altcode: 2009BAAS...41..397G
MARVELS, as one of the four on-going Sloan Digital Sky Survey (SDSS) III
survey projects, is conducting the largest ground-based radial velocity
planet survey using a next-generation, multiple-object , dispersed
fixed-delay interferometer Doppler instrument in 2008-2014. Over the
next six years, MARVELS plans on monitoring a total of 11,000 late
F, G and K stars (90% main sequence and subgiants; 10% giant stars)
with V magnitude 7.6-12 over $\sim$800 square degrees. The survey
aims to detect and characterize a single large, statistically well
defined sample of hundreds of new giant planets with periods ? days
orbiting host stars with well-understood selection biases. The first
MARVELS instrument with 60 object capability was commissioned at the
SDSS telescope at Apache Point Observatory in September 2008 and will
be used to conduct the science survey starting in October 2008. The
early commissioning results show that the instrument has reached about
6mK (peak-to-valley) long-term thermal stability, 2-3 m/s Doppler
precision with bright calibration light sources, and 20 m/s photon
noise error for TrES-2 (a V=11.4 G0V star) in a 40 min exposure. The
early science results and instrument performance from the first three
months of operation will be reported. <P />We would like to thank the
W.M. Keck Foundation, Sloan Foundation, NSF, NASA and UF for support.
---------------------------------------------------------
Title: The Time-Dependent Effect of a Stellar Flare on Terrestrial
Planet Habitability and Biosignatures
Authors: Walkowicz, Lucianne M.; Segura, A.; Meadows, V.; Kasting,
J.; Hawley, S.
2009AAS...21342802W Altcode: 2009BAAS...41..259W
Due to their low stellar luminosities, M dwarf habitable zones (as
defined by Kasting et al. 1993) lie very near the star ( 0.2 AU or
less), making planets in the habitable zone especially vulnerable
to the effects of stellar activity. Although M dwarfs emit the bulk
of their flux in the optical and near infrared, activity on these
stars produces energetic radiation, from X rays to ultraviolet (UV),
that may be dangerous for life on a planet in the habitable zone (HZ)
of the star. In particular, stellar activity is a concern for the
continuity of habitability on the planetary surface, as starspots or
flares may cause the stellar irradiance to vary strongly with time. <P
/>Using a convective/radiative model coupled to a photochemical model,
we simulated the atmosphere of an Earth-like planet located in the
habitable zone of the active M dwarf AD Leo over the course of a
large flare. We present the time-dependent atmospheric temperature and
composition profiles for water, methane and ozone, finding that while
water and ozone are photolyzed in the stratosphere, the temperature
profile and methane column depth are relatively unperturbed. Ozone
number density decreases in the stratosphere during the impulsive
phase of the flare, but quickly recovers to preflare levels
thereafter. While the UV flux at the planetary surface changes with
the ozone concentration during the flare, we find that the planetary
surface UV flux is less than that received on Earth's surface except
during the very peak of the flare. We conclude that even large flares
may not be detrimental to life on planets with Earth-like atmospheres.
---------------------------------------------------------
Title: Statement from ACCORD for ASTRO2010
Authors: Alcock, Charles; Bolte, Michael; Freedman, Wendy; Kudritzki,
Rolf-Peter; Kulkarni, Shri; Martin, Pierre; Smith, William;
Strittmatter, Peter; Hawley, Suzanne
2009astro2010P..27A Altcode: 2009astro2010P..27K
No abstract at ADS
---------------------------------------------------------
Title: M Dwarf Flare Rate Analysis of SDSS Stripe 82
Authors: Kowalski, Adam; Hawley, S. L.; Hilton, E. J.; Becker, A. C.;
Bochanski, J. J.; West, A. A.
2009AAS...21343402K Altcode: 2009BAAS...41..303K
M dwarfs produce intense flares from the X-ray to the radio,
including the optical by a physical mechanism which is still poorly
understood. Since M dwarfs comprise about 70% of the stars in the
Galaxy, their flares will be a significant source of optical transients
in future time domain surveys, such as LSST, Pan-STARRS, and GAIA. Using
a Flare Index to select flaring events from 40,000 low-cadence M dwarf
light curves, we present the flaring rate as a function of intrinsic
stellar properties, such as spectral type, level of magnetic activity,
and distance from the Galactic plane. We also discuss our results
in light of our understanding of flare physics and how our derived
flaring rates and luminosities compare to the Lacy, Moffett, &
Evans (1976) classical study of nearby active flare stars.
---------------------------------------------------------
Title: χ Values for Blue Emission Lines in M Dwarfs
Authors: West, Andrew A.; Hawley, Suzanne L.
2008PASP..120.1161W Altcode: 2008arXiv0812.1221W
We compute χ values for blue emission lines in active M dwarfs. Using
flux-calibrated spectra from nearby M dwarfs and spectral M dwarf
templates from SDSS, we derive analytical relations that describe how
the χ values for the Ca II H and K as well as the Hβ, Hγ, Hδ, Hɛ,
and H8 Balmer emission lines vary as a function of spectral type and
color. These derived values are important for numerous M dwarf studies
where the intrinsic luminosity of emission lines cannot be estimated
due to uncertain distances and/or non-flux-calibrated spectra. We use
these results to estimate the mean properties of blue emission lines
in active-field M dwarfs from SDSS.
---------------------------------------------------------
Title: The Luminosity and Mass Functions of Low-Mass Stars in the
Galactic Disk. I. The Calibration Region
Authors: Covey, Kevin R.; Hawley, Suzanne L.; Bochanski, John J.;
West, Andrew A.; Reid, I. Neill; Golimowski, David A.; Davenport,
James R. A.; Henry, Todd; Uomoto, Alan; Holtzman, Jon A.
2008AJ....136.1778C Altcode: 2008arXiv0807.2452C
We present measurements of the luminosity and mass functions of
low-mass stars constructed from a catalog of matched Sloan Digital Sky
Survey (SDSS) and Two Micron All Sky Survey (2MASS) detections. This
photometric catalog contains more than 25,000 matched SDSS and 2MASS
point sources spanning ~30 deg<SUP>2</SUP> on the sky. We have obtained
follow-up spectroscopy, complete to J = 16, of more than 500 low-mass
dwarf candidates within a 1 deg<SUP>2</SUP> subsample, and thousands of
additional dwarf candidates in the remaining 29 deg<SUP>2</SUP>. This
spectroscopic sample verifies that the photometric sample is complete,
uncontaminated, and unbiased at the 99% level globally, and at the 95%
level in each color range. We use this sample to derive the luminosity
and mass functions of low-mass stars over nearly a decade in mass (0.7
M <SUB>sun</SUB> > M <SUB>*</SUB> > 0.1 M <SUB>sun</SUB>). The
luminosity function of the Galactic disk is statistically consistent
with that measured from volume-complete samples in the solar
neighborhood. We find that the logarithmically binned mass function
is best fit with an M<SUB>c</SUB> = 0.29 log-normal distribution,
with a 90% confidence interval of M<SUB>c</SUB> = 0.20-0.50. These
90% confidence intervals correspond to linearly binned mass functions
peaking between 0.27 M <SUB>sun</SUB> and 0.12 M <SUB>sun</SUB>, where
the best fit MF turns over at 0.17 M <SUB>sun</SUB>. A power-law fit
to the entire mass range sampled here, however, returns a best fit
of α = 1.1 (where the Salpeter slope is α = 2.35); a broken power
law returns α = 2.04 at masses greater than log M = -0.5 (M = 0.32 M
<SUB>sun</SUB>), and α = 0.2 at lower masses. These results agree well
with most previous investigations, though differences in the analytic
formalisms adopted to describe those mass functions, as well as the
range over which the data are fit, can give the false impression of
disagreement. Given the richness of modern-day astronomical data sets,
we are entering the regime whereby stronger conclusions can be drawn by
comparing the actual datapoints measured in different mass functions,
rather than the results of analytic analyses that impose structure
on the data a priori. Having validated this method to generate
a low-mass luminosity function from matched SDSS/2MASS data sets,
future studies will extend this technique to the entirety of the SDSS
footprint. <P />Based in part on observations obtained with the Apache
Point Observatory 3.5 m telescope, which is owned and operated by the
Astrophysical Research Consortium.
---------------------------------------------------------
Title: The Properties of Long-Period Variables in the Large Magellanic
Cloud from MACHO
Authors: Fraser, Oliver J.; Hawley, Suzanne L.; Cook, Kem H.
2008AJ....136.1242F Altcode: 2008arXiv0808.1737F
We present a new analysis of the long-period variables in
the Large Magellanic Cloud (LMC) from the MACHO Variable Star
Catalog. Three-quarters of our sample of evolved, variable stars have
periodic light curves. We characterize the stars in our sample using
the multiple periods found in their frequency spectra. Additionally, we
use single-epoch Two Micron All Sky Survey measurements to construct
the average infrared light curves for different groups of these
stars. Comparison with evolutionary models shows that stars on the red
giant branch (RGB) or the early asymptotic giant branch (AGB) often
show non-periodic variability, but begin to pulsate with periods on the
two shortest period-luminosity (P-L) sequences (3 & 4) when they
brighten to K <SUB>s</SUB> ≈ 13. The stars on the thermally pulsing
AGB are more likely to pulsate with longer periods that lie on the
next two P-L sequences (1 & 2), including the sequence associated
with the Miras in the LMC. The Petersen diagram and its variants show
that multi-periodic stars on each pair of these sequences (3 &
4, and 1 & 2) typically pulsate with periods associated only with
that pair. The periods in these multi-periodic stars become longer and
stronger as the star evolves. We further constrain the mechanism behind
the long secondary periods (LSPs) seen in half of our sample, and find
that there is a close match between the luminosity functions of the
LSP stars and all of the stars in our sample, and that these star's
pulsation amplitudes are relatively wavelength independent. Although
this is characteristic of stellar multiplicity, the large number of
these variables is problematic for that explanation.
---------------------------------------------------------
Title: The Milky Way Tomography with SDSS. II. Stellar Metallicity
Authors: Ivezić, Željko; Sesar, Branimir; Jurić, Mario; Bond,
Nicholas; Dalcanton, Julianne; Rockosi, Constance M.; Yanny, Brian;
Newberg, Heidi J.; Beers, Timothy C.; Allende Prieto, Carlos;
Wilhelm, Ron; Lee, Young Sun; Sivarani, Thirupathi; Norris, John E.;
Bailer-Jones, Coryn A. L.; Re Fiorentin, Paola; Schlegel, David;
Uomoto, Alan; Lupton, Robert H.; Knapp, Gillian R.; Gunn, James E.;
Covey, Kevin R.; Allyn Smith, J.; Miknaitis, Gajus; Doi, Mamoru;
Tanaka, Masayuki; Fukugita, Masataka; Kent, Steve; Finkbeiner, Douglas;
Munn, Jeffrey A.; Pier, Jeffrey R.; Quinn, Tom; Hawley, Suzanne;
Anderson, Scott; Kiuchi, Furea; Chen, Alex; Bushong, James; Sohi,
Harkirat; Haggard, Daryl; Kimball, Amy; Barentine, John; Brewington,
Howard; Harvanek, Mike; Kleinman, Scott; Krzesinski, Jurek; Long,
Dan; Nitta, Atsuko; Snedden, Stephanie; Lee, Brian; Harris, Hugh;
Brinkmann, Jonathan; Schneider, Donald P.; York, Donald G.
2008ApJ...684..287I Altcode: 2008arXiv0804.3850I
Using effective temperature and metallicity derived from SDSS
spectra for ~60,000 F- and G-type main-sequence stars (0.2 <
g - r < 0.6), we develop polynomial models for estimating these
parameters from the SDSS u - g and g - r colors. These photometric
estimates have similar error properties as those determined from SDSS
spectra. We apply this method to SDSS photometric data for over 2
million F/G stars and measure the unbiased metallicity distribution
for a complete volume-limited sample of stars at distances between
500 pc and 8 kpc. The metallicity distribution can be exquisitely
modeled using two components with a spatially varying number ratio,
which correspond to disk and halo. The two components also possess
the kinematics expected for disk and halo stars. The metallicity
of the halo component is spatially invariant, while the median disk
metallicity smoothly decreases with distance from the Galactic plane
from -0.6 at 500 pc to -0.8 beyond several kiloparsecs. The absence of
a correlation between metallicity and kinematics for disk stars is in a
conflict with the traditional decomposition in terms of thin and thick
disks. We detect coherent substructures in the kinematics-metallicity
space, such as the Monoceros stream, which rotates faster than the LSR,
and has a median metallicity of [Fe/H] = -0.95, with an rms scatter of
only ~0.15 dex. We extrapolate our results to the performance expected
from the Large Synoptic Survey Telescope (LSST) and estimate that LSST
will obtain metallicity measurements accurate to 0.2 dex or better,
with proper-motion measurements accurate to ~0.5 mas yr<SUP>-1</SUP>,
for about 200 million F/G dwarf stars within a distance limit of ~100
kpc (g < 23.5).
---------------------------------------------------------
Title: Evidence for Distinct Components of the Galactic Stellar Halo
from 838 RR Lyrae Stars Discovered in the LONEOS-I Survey
Authors: Miceli, Antonino; Rest, Armin; Stubbs, Christopher W.;
Hawley, Suzanne L.; Cook, Kem H.; Magnier, Eugene A.; Krisciunas,
Kevin; Bowell, Edward; Koehn, Bruce
2008ApJ...678..865M Altcode: 2007arXiv0706.1583M
We present 838 ab-type RR Lyrae stars from the Lowell Observatory
Near Earth Objects Survey Phase I (LONEOS-I). These objects cover
1430 deg<SUP>2</SUP> and span distances ranging from 3 to 30 kpc from
the Galactic center. Object selection is based on phased, photometric
data with 28-50 epochs. We use this large sample to explore the bulk
properties of the stellar halo, including the spatial distribution. The
period-amplitude distribution of this sample shows that the majority
of these RR Lyrae stars resemble Oosterhoff type I, but there is a
significant fraction (26%) which have longer periods and appear to be
Oosterhoff type II. We find that the radial distributions of these two
populations have significantly different profiles (ρ<SUB>OoI</SUB>
~ R<SUP>-2.26 +/- 0.07</SUP> and ρ<SUB>OoII</SUB> ~ R<SUP>-2.88 +/-
0.11</SUP>). This suggests that the stellar halo was formed by at
least two distinct accretion processes and supports dual-halo models.
---------------------------------------------------------
Title: Characterizing the Near-UV Environment of M Dwarfs
Authors: Walkowicz, Lucianne M.; Johns-Krull, Christopher M.; Hawley,
Suzanne L.
2008ApJ...677..593W Altcode: 2007arXiv0711.1861W
We report the results of our Hubble Space Telescope (HST) snapshot
survey with the ACS HRC PR200L prism, designed to measure the
near-UV emission in a sample of nearby M dwarfs. Thirty-three stars
were observed, spanning the mass range from 0.1 to 0.6 solar masses
(T<SUB>eff</SUB> ~ 2200-4000 K) where the UV energy distributions vary
widely between active and inactive stars. These observations provide
much needed constraints on models of the habitability zone and the
atmospheres of possible terrestrial planets orbiting M dwarf hosts
and will be useful in refining the target selection for future space
missions such as Terrestrial Planet Finder (TPF). We compare our data
with a new generation of M dwarf atmospheric models and discuss their
implications for the chromospheric energy budget. These NUV data will
also be valuable in conjunction with existing optical, FUV, and X-ray
data to explore unanswered questions regarding the dynamo generation
and magnetic heating in low-mass stars.
---------------------------------------------------------
Title: The Sixth Data Release of the Sloan Digital Sky Survey
Authors: Adelman-McCarthy, Jennifer K.; Agüeros, Marcel A.; Allam,
Sahar S.; Allende Prieto, Carlos; Anderson, Kurt S. J.; Anderson,
Scott F.; Annis, James; Bahcall, Neta A.; Bailer-Jones, C. A. L.;
Baldry, Ivan K.; Barentine, J. C.; Bassett, Bruce A.; Becker, Andrew
C.; Beers, Timothy C.; Bell, Eric F.; Berlind, Andreas A.; Bernardi,
Mariangela; Blanton, Michael R.; Bochanski, John J.; Boroski,
William N.; Brinchmann, Jarle; Brinkmann, J.; Brunner, Robert J.;
Budavári, Tamás; Carliles, Samuel; Carr, Michael A.; Castander,
Francisco J.; Cinabro, David; Cool, R. J.; Covey, Kevin R.; Csabai,
István; Cunha, Carlos E.; Davenport, James R. A.; Dilday, Ben; Doi,
Mamoru; Eisenstein, Daniel J.; Evans, Michael L.; Fan, Xiaohui;
Finkbeiner, Douglas P.; Friedman, Scott D.; Frieman, Joshua A.;
Fukugita, Masataka; Gänsicke, Boris T.; Gates, Evalyn; Gillespie,
Bruce; Glazebrook, Karl; Gray, Jim; Grebel, Eva K.; Gunn, James
E.; Gurbani, Vijay K.; Hall, Patrick B.; Harding, Paul; Harvanek,
Michael; Hawley, Suzanne L.; Hayes, Jeffrey; Heckman, Timothy M.;
Hendry, John S.; Hindsley, Robert B.; Hirata, Christopher M.; Hogan,
Craig J.; Hogg, David W.; Hyde, Joseph B.; Ichikawa, Shin-ichi;
Ivezić, Željko; Jester, Sebastian; Johnson, Jennifer A.; Jorgensen,
Anders M.; Jurić, Mario; Kent, Stephen M.; Kessler, R.; Kleinman,
S. J.; Knapp, G. R.; Kron, Richard G.; Krzesinski, Jurek; Kuropatkin,
Nikolay; Lamb, Donald Q.; Lampeitl, Hubert; Lebedeva, Svetlana; Lee,
Young Sun; French Leger, R.; Lépine, Sébastien; Lima, Marcos; Lin,
Huan; Long, Daniel C.; Loomis, Craig P.; Loveday, Jon; Lupton, Robert
H.; Malanushenko, Olena; Malanushenko, Viktor; Mandelbaum, Rachel;
Margon, Bruce; Marriner, John P.; Martínez-Delgado, David; Matsubara,
Takahiko; McGehee, Peregrine M.; McKay, Timothy A.; Meiksin, Avery;
Morrison, Heather L.; Munn, Jeffrey A.; Nakajima, Reiko; Neilsen,
Eric H., Jr.; Newberg, Heidi Jo; Nichol, Robert C.; Nicinski, Tom;
Nieto-Santisteban, Maria; Nitta, Atsuko; Okamura, Sadanori; Owen,
Russell; Oyaizu, Hiroaki; Padmanabhan, Nikhil; Pan, Kaike; Park,
Changbom; Peoples, John, Jr.; Pier, Jeffrey R.; Pope, Adrian C.;
Purger, Norbert; Raddick, M. Jordan; Re Fiorentin, Paola; Richards,
Gordon T.; Richmond, Michael W.; Riess, Adam G.; Rix, Hans-Walter;
Rockosi, Constance M.; Sako, Masao; Schlegel, David J.; Schneider,
Donald P.; Schreiber, Matthias R.; Schwope, Axel D.; Seljak, Uroš;
Sesar, Branimir; Sheldon, Erin; Shimasaku, Kazu; Sivarani, Thirupathi;
Allyn Smith, J.; Snedden, Stephanie A.; Steinmetz, Matthias; Strauss,
Michael A.; SubbaRao, Mark; Suto, Yasushi; Szalay, Alexander S.;
Szapudi, István; Szkody, Paula; Tegmark, Max; Thakar, Aniruddha R.;
Tremonti, Christy A.; Tucker, Douglas L.; Uomoto, Alan; Vanden Berk,
Daniel E.; Vandenberg, Jan; Vidrih, S.; Vogeley, Michael S.; Voges,
Wolfgang; Vogt, Nicole P.; Wadadekar, Yogesh; Weinberg, David H.;
West, Andrew A.; White, Simon D. M.; Wilhite, Brian C.; Yanny, Brian;
Yocum, D. R.; York, Donald G.; Zehavi, Idit; Zucker, Daniel B.
2008ApJS..175..297A Altcode: 2007arXiv0707.3413A
This paper describes the Sixth Data Release of the Sloan Digital Sky
Survey. With this data release, the imaging of the northern Galactic cap
is now complete. The survey contains images and parameters of roughly
287 million objects over 9583 deg<SUP>2</SUP>, including scans over
a large range of Galactic latitudes and longitudes. The survey also
includes 1.27 million spectra of stars, galaxies, quasars, and blank
sky (for sky subtraction) selected over 7425 deg<SUP>2</SUP>. This
release includes much more stellar spectroscopy than was available in
previous data releases and also includes detailed estimates of stellar
temperatures, gravities, and metallicities. The results of improved
photometric calibration are now available, with uncertainties of
roughly 1% in g, r, i, and z, and 2% in u, substantially better than
the uncertainties in previous data releases. The spectra in this data
release have improved wavelength and flux calibration, especially
in the extreme blue and extreme red, leading to the qualitatively
better determination of stellar types and radial velocities. The
spectrophotometric fluxes are now tied to point-spread function
magnitudes of stars rather than fiber magnitudes. This gives more robust
results in the presence of seeing variations, but also implies a change
in the spectrophotometric scale, which is now brighter by roughly 0.35
mag. Systematic errors in the velocity dispersions of galaxies have
been fixed, and the results of two independent codes for determining
spectral classifications and redshifts are made available. Additional
spectral outputs are made available, including calibrated spectra from
individual 15 minute exposures and the sky spectrum subtracted from
each exposure. We also quantify a recently recognized underestimation
of the brightnesses of galaxies of large angular extent due to poor sky
subtraction; the bias can exceed 0.2 mag for galaxies brighter than r =
14 mag.
---------------------------------------------------------
Title: Constraining the Age-Activity Relation for Cool Stars: The
Sloan Digital Sky Survey Data Release 5 Low-Mass Star Spectroscopic
Sample
Authors: West, Andrew A.; Hawley, Suzanne L.; Bochanski, John J.;
Covey, Kevin R.; Reid, I. Neill; Dhital, Saurav; Hilton, Eric J.;
Masuda, Michael
2008AJ....135..785W Altcode: 2007arXiv0712.1590W
We present a spectroscopic analysis of over 38,000 low-mass stars from
the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5). Analysis of
this unprecedentedly large sample confirms the previously detected
decrease in the fraction of magnetically active stars (as traced by
Hα emission) as a function of the vertical distance from the Galactic
plane. The magnitude and slope of this effect vary as a function of
spectral type. Using simple 1D dynamical models, we demonstrate that
the drop in activity fraction can be explained by thin-disk dynamical
heating and a rapid decrease in magnetic activity. The timescale for
this rapid activity decrease changes according to the spectral type. By
comparing our data to the simulations, we calibrate the age-activity
relation at each M dwarf spectral type. We also present evidence for
a possible decrease in the metallicity as a function of height above
the Galactic plane. In addition to our activity analysis, we provide
line measurements, molecular band indices, colors, radial velocities,
3D space motions, and mean properties as a function of spectral type
for the SDSS DR5 low-mass star sample.
---------------------------------------------------------
Title: Externally Induced or Internally Produced: What is the Source
of the Extreme Magnetic Activity Observed in Very Low Mass Stars?
Authors: Howell, Steve B.; Giampapa, Mark; Harrison, Thomas; Hawley,
Suzanne; Hill, Frank; Honeycutt, Kent; Kafka, Stella; Silvestri,
Nicole; Szkody, Paula; Walter, Fred; West, Andrew
2008noao.prop...95H Altcode:
Recent observations of the very low mass donor stars in short
period interacting binaries have revealed the presence of active
chromospheres. Our group has obtained initial spectra for five such
systems to date and found evidence of stellar activity in all of
them, including a brown dwarf mass (0.055 M-sun) donor star. The
Washington group has obtained a SDSS sample of a number of close, but
non-interacting white dwarf + red dwarf binaries and find H(alpha)
emission related to activity. We plan to perform the first detailed
phase-resolved spectroscopic study of the active chromospheres in
this set of rapidly rotating (<0.3 day), low mass (<0.25 M-sun),
fully convective late-type stars and brown dwarfs. Our observational
goals are to study the extent, nature and short-term changes of these
active chromospheres on the low mass stars of close binaries. Is
the extreme activity caused by the low mass star itself or externally
driven by tidal or magnetic forces? The long term goals are to complete
a large enough sample (~10 systems) to provide statistically useful
measurements and to use the extended time allocation to obtain long term
“coverage" spectra of each system to monitor, measure, and understand
the solar-type cycles likely to be present.
---------------------------------------------------------
Title: Stellar SEDs from 0.3 to 2.5 μm: Tracing the Stellar Locus
and Searching for Color Outliers in the SDSS and 2MASS
Authors: Covey, K. R.; Ivezić, Ž.; Schlegel, D.; Finkbeiner, D.;
Padmanabhan, N.; Lupton, R. H.; Agüeros, M. A.; Bochanski, J. J.;
Hawley, S. L.; West, A. A.; Seth, A.; Kimball, A.; Gogarten, S. M.;
Claire, M.; Haggard, D.; Kaib, N.; Schneider, D. P.; Sesar, B.
2007AJ....134.2398C Altcode: 2007arXiv0707.4473C
The Sloan Digital Sky Survey (SDSS) and Two Micron All Sky Survey
(2MASS) are rich resources for studying stellar astrophysics and the
structure and formation history of the Galaxy. As new surveys and
instruments adopt similar filter sets, it is increasingly important to
understand the properties of the ugrizJHK<SUB>s</SUB> stellar locus,
both to inform studies of "normal" main-sequence stars and enable
robust searches for point sources with unusual colors. Using a sample
of ~600,000 point sources detected by SDSS and 2MASS, we tabulate
the position and width of the ugrizJHK<SUB>s</SUB> stellar locus as a
function of g - i color, and provide accurate polynomial fits. We map
the Morgan-Keenan spectral type sequence to the median stellar locus
by using synthetic photometry of spectral standards and by analyzing
3000 SDSS stellar spectra with a custom spectral typing pipeline,
described in the Appendix to this paper. We develop an algorithm to
calculate a point source's minimum separation from the stellar locus in
a seven-dimensional color space, and use it to robustly identify objects
with unusual colors, as well as spurious SDSS/2MASS matches. Analysis
of a final catalog of 2117 color outliers identifies 370 white-dwarf/M
dwarf (WDMD) pairs, 93 QSOs, and 90 M giant/carbon star candidates,
and demonstrates that WDMD pairs and QSOs can be distinguished on the
basis of their J - K<SUB>s</SUB> and r - z colors. We also identify
a group of objects with correlated offsets in the u - g versus g -
r and g - r versus r - i color-color spaces, but subsequent follow-up
is required to reveal the nature of these objects. Future applications
of this algorithm to a matched SDSS-UKIDSS catalog may well identify
additional classes of objects with unusual colors by probing new areas
of color-magnitude space.
---------------------------------------------------------
Title: Improved Photometric Calibrations for Red Stars Observed with
the SDSS Photometric Telescope
Authors: Davenport, James R. A.; Bochanski, John J.; Covey, Kevin R.;
Hawley, Suzanne L.; West, Andrew A.; Schneider, Donald P.
2007AJ....134.2430D Altcode: 2007arXiv0708.0889D
We present a new set of photometric transformations for red stars
observed with the Sloan Digital Sky Survey (SDSS) 0.5 m Photometric
Telescope (PT) and the SDSS 2.5 m telescope at the Apache Point
Observatory in New Mexico. Nightly PT observations of US Naval
Observatory standards are used to determine extinction corrections and
calibration terms for SDSS 2.5 m photometry. Systematic differences
between the PT and native SDSS 2.5 m ugriz photometry require
conversions between the two systems which have previously been undefined
for the reddest stars. By matching ~43,000 stars observed with both the
PT and SDSS 2.5 m, we extend the present relations to include low-mass
stars with colors 0.6 <= r - i <= 1.7. These corrections will
allow us to place photometry of bright, low-mass trigonometric parallax
stars previously observed with the PT on the 2.5 m system. We present
new transformation equations and discuss applications of these data
to future low-mass star studies using the SDSS.
---------------------------------------------------------
Title: Exploring the Local Milky Way: M Dwarfs as Tracers of Galactic
Populations
Authors: Bochanski, John J.; Munn, Jeffrey A.; Hawley, Suzanne L.;
West, Andrew A.; Covey, Kevin R.; Schneider, Donald P.
2007AJ....134.2418B Altcode: 2007arXiv0708.0044B
We have assembled a spectroscopic sample of low-mass dwarfs observed
as part of the Sloan Digital Sky Survey along one Galactic sight line,
designed to investigate the observable properties of the thin and
thick disks. This sample of ~7400 K and M stars also has measured
ugriz photometry, proper motions, and radial velocities. We compute
UVW space-motion distributions, and investigate their structure
with respect to vertical distance from the Galactic plane. We place
constraints on the velocity dispersions of the thin and thick disks,
using two-component Gaussian fits. We also compare these kinematic
distributions to a leading Galactic model. Finally, we investigate
other possible observable differences between the thin and thick disks,
such as color, active fraction, and metallicity.
---------------------------------------------------------
Title: Our 3 Million Nearest Neighbors: The Field Luminosity and
Mass Functions of M Dwarfs from Matched SDSS & 2MASS Observations
Authors: Bochanski, John J.; Hawley, S. L.; Covey, K. R.; Reid, N.;
West, A. A.; SDSS Collaboration
2007AAS...211.2103B Altcode: 2007BAAS...39R.772B
We present the initial results of our investigation into the field
luminosity and mass functions of M dwarfs. We have assembled a database
of matched SDSS and 2MASS observations of 3 million low-mass stars, two
orders of magnitude larger than any previous study on this topic. The
observations span the entire SDSS footprint, about 8,400 square
degrees. Using this 8-color photometry and improved color-absolute
magnitude relations, we derive luminosities and masses for each star
in our sample. We quantify the uncertainties in our analysis using
results from a calibration region of 30 square degrees, where we have
spectroscopic observations of several thousand stars. Additionally, we
measure the structure of the local Milky Way, determining the density
profiles of the thin and thick disks. <P />The authors gratefully
acknowledge the support of NSF grant AST06-07644 and NASA ADP grant
NAG5-13111.
---------------------------------------------------------
Title: Galactic M Dwarf Flare Rates
Authors: Hawley, Suzanne L.; Hilton, E. J.; Kowalski, A. F.; Bochanski,
J. J.; West, A. A.
2007AAS...21110306H Altcode: 2007BAAS...39..920H
We present preliminary results from our effort to model M dwarf flare
rates in the Galaxy. Using existing flare data and new determinations of
the M dwarf luminosity function and activity fractions from SDSS data,
we have developed numerical simulations to model the number of flares
seen along a given Galactic sightline. We compare the simulations with
data from the SDSS repeat scans obtained in the equatorial region. These
simulations will be useful for predicting the detection of M dwarf
variability in new time domain surveys such as PanSTARRs and LSST. <P
/>Based on data from the Sloan Digital Sky Survey (www.sdss.org)
---------------------------------------------------------
Title: Pulsation and Mass-Loss in Long Period Variables
Authors: Fraser, Oliver J.; Hawley, S. L.; Cook, K. H.
2007AAS...211.2504F Altcode: 2007BAAS...39..776F
We present a new analysis of the long period variables in the
Large Magellanic Cloud from the MACHO Variable Star Catalog. Of
our sample of 61,587 evolved stars with non-constant light curves,
80 percent have periodic light curves. We characterize these stars
using the multiple periods, harmonics, and mixing terms found in
their frequency spectra. Additionally, we use single-epoch 2MASS
measurements to construct the average infrared light curve of each
of the well-known period-luminosity sequences. We further constrain
the mechanism behind the long secondary periods seen in many of these
stars, and find that an explanation due to binarity is indeed likely. We
describe the characteristic variability at each of the stages of RGB
and AGB evolution by comparison with population synthesis models. RGB
and early AGB stars vary with either periodic or chaotic pulsations,
the latter explain the large number of stars (22 percent of our sample)
with periods clearly due to the annual observing cycle on Earth. Stars
in the thermally pulsing AGB pulsate periodically with longer periods
than those earlier in their evolution, and are also the most likely to
undergo heavy mass loss. We also compare the long period variables in
the MACHO catalogs of the SMC and the Galactic Bulge with our results.
---------------------------------------------------------
Title: The Active Lives of M Dwarfs: The Activity, Dynamical and
Metallicity Evolution of Most Milky Way Stars
Authors: West, Andrew A.; Hawley, S. L.; Bochanski, J. J.; Covey,
K. R.; Reid, I. N.
2007AAS...211.2106W Altcode: 2007BAAS...39R.772W
We present the results from a study of the dynamics and magnetic
activity of M dwarfs using the largest spectroscopic sample of low-mass
stars ever assembled. The age at which strong surface magnetic activity
ceases in M dwarfs has been inferred to have a strong dependence
on mass (spectral type, surface temperature) and explains previous
results showing a large increase in the fraction of active stars
at later spectral types. Using spectral observations of more than
40,000 M dwarfs from the SDSS, we show that the fraction of active
stars decreases as a function of vertical distance from the Galactic
plane, and that the magnitude of this decrease changes significantly
for different M spectral types. Adopting a simple dynamical model for
thin disk vertical heating, we assign an age for the activity decline
at each spectral type, and thus determine an activity-age relation
for M dwarfs. These results provide constraints for dynamo models
that seek to describe the production of surface magnetic fields in
low mass stars. In addition, we will show how M dwarfs can be used to
probe both the metallicity evolution as well as the dynamical heating
and structure of the Milky Way thin disk.
---------------------------------------------------------
Title: The SDSS-III Multi-object Apo Radial-velocity Exoplanet
Large-area Survey
Authors: Ge, Jian; Mahadevan, S.; Lee, B.; Wan, X.; Zhao, B.; van
Eyken, J.; Kane, S.; Guo, P.; Ford, E. B.; Agol, E.; Gaudi, S.;
Fleming, S.; Crepp, J.; Cohen, R.; Groot, J.; Galvez, M.; Liu, J.;
Ford, H.; Schneider, D.; Seager, S.; Hawley, S. L.; Weinberg, D.;
Eisenstein, D.
2007AAS...21113209G Altcode: 2007BAAS...39..962G
As part of SDSS-III survey in 2008-2014, the Multi-object APO
Radial-Velocity Exoplanet Large-area Survey (MARVELS) will conduct
the largest ground-based Doppler planet survey to date using the SDSS
telescope and new generation multi-object Doppler instruments with
120 object capability and 10-20 m/s Doppler precision. The baseline
survey plan is to monitor a total of 11,000 V=8-12 stars ( 10,000 main
sequence stars and 1000 giant stars) over 800 square degrees over the
6 years. The primary goal is to produce a large, statistically well
defined sample of giant planets ( 200) with a wide range of masses (
0.2-10 Jupiter masses) and orbits (1 day-2 years) drawn from a large
of host stars with a diverse set of masses, compositions, and ages
for studying the diversity of extrasolar planets and constraining
planet formation, migration & dynamical evolution of planetary
systems. The survey data will also be used for providing a statistical
sample for theoretical comparison and discovering rare systems and
identifying signposts for lower-mass or more distant planets. Early
science results from the pilot program will be reported. <P />We would
like to thank the SDSS MC for allocation of the telescope time and
the W.M. Keck Foundation, NSF, NASA and UF for support.
---------------------------------------------------------
Title: Self-Consistent Quiescent Model Atmospheres for M Dwarfs
Authors: Walkowicz, Lucianne M.; Hawley, S. L.
2007AAS...211.2105W Altcode: 2007BAAS...39Q.772W
H alpha and Ca II K are two of the strongest emission lines in M
dwarf chromospheres, responsible for <P />cooling the atmosphere,
balancing the magnetic heating, and determining the resulting
equilibrium structure. To investigate the relationship between these
two important lines, I captured simultaneous observations of Ca II
K and H alpha for 85 dM3 stars of varying activity strength. The
results of my observing program reveal a complex relationship between
the two, where even so-called "inactive" stars (those with H alpha in
absorption) may display substantial Ca II K emission. A new generation
of quiescent model atmospheres is required to further investigate the
chromospheric heating required to produce both of these lines at the
observed levels. I present the observed results, and discuss their
application as empirical constraints on static models of quiescent M
dwarf atmospheres. I also present initial model calculations and place
them in the context of the data.
---------------------------------------------------------
Title: The Apache Point Observatory Galactic Evolution Experiment
(APOGEE)
Authors: Majewski, Steven R.; Skrutskie, M. F.; Schiavon, R. P.;
Wilson, J. C.; O'Connell, R. W.; Smith, V. V.; Shetrone, M.; Cunha,
K.; Frinchaboy, P. M.; Reid, I. N.; Allende Prieto, C.; Eisenstein,
D.; Indebetouw, R.; Nelson, M. J.; Patterson, R. J.; Rood, R. T.;
Beers, T.; Bullock, J.; Crane, J. D.; Geisler, D.; Hawley, S. L.;
Holtzman, J.; Johnston, K. V.; McWilliam, A.; Munn, J. A.; Spergel,
D. N.; Weinberg, D.; Weinberg, M.
2007AAS...21113208M Altcode: 2007BAAS...39..962M
APOGEE is a large-scale, NIR, high-resolution (R 20,000) spectroscopic
survey of Galactic stars, and is one of the four experiments in
the SDSS-III suite. APOGEE will provide, by orders of magnitude,
the largest uniform database of chemical abundances, spectroscopic
parallaxes and kinematics for Galactic stars across the bulge, disk,
and halo. The survey will be conducted with a dedicated, 300-fiber,
cryogenic, spectrograph operating in the H-band, to be built at the
University of Virginia. APOGEE will use approximately half of the time
on 150 bright nights each year during a three-year period to observe,
at high S/N, of order 100,000 giant stars selected directly from 2MASS
down to a flux limit of H 13.5. Many of the targets will be located
in the inner Galaxy, towards the Galactic bulge/bar and disk, often in
regions never accessed by optical observations. With its high resolution
and S/N, APOGEE will determine, for a vast sample, accurate abundance
patterns, spanning numerous chemical species, and precision radial
velocities, with better than 0.5 km/s accuracy. Some of the scientific
objectives of this survey are to (1) provide extensive chemodynamical
data on the inner Galaxy (thin/thick disk, bar/bulge, low latitude
halo substructure) sufficient to constrain formation/evolution models,
(2) place constraints on the first stars from unbiased metallicity
distribution functions of these stellar populations, (3) constrain
and understand physical processes of star formation, feedback, mixing
in the formation of the Galaxy, (4) survey the dynamics of the bulge
and disk, and place constraints on the nature and influence of the
Galactic bar and spiral arms, (5) attempt to isolate what portion of
the disk and bulge come from accretion versus formation in situ.
---------------------------------------------------------
Title: The Fifth Data Release of the Sloan Digital Sky Survey
Authors: Adelman-McCarthy, Jennifer K.; Agüeros, Marcel A.;
Allam, Sahar S.; Anderson, Kurt S. J.; Anderson, Scott F.; Annis,
James; Bahcall, Neta A.; Bailer-Jones, Coryn A. L.; Baldry, Ivan K.;
Barentine, J. C.; Beers, Timothy C.; Belokurov, V.; Berlind, Andreas;
Bernardi, Mariangela; Blanton, Michael R.; Bochanski, John J.; Boroski,
William N.; Bramich, D. M.; Brewington, Howard J.; Brinchmann, Jarle;
Brinkmann, J.; Brunner, Robert J.; Budavári, Tamás; Carey, Larry N.;
Carliles, Samuel; Carr, Michael A.; Castander, Francisco J.; Connolly,
A. J.; Cool, R. J.; Cunha, Carlos E.; Csabai, István; Dalcanton,
Julianne J.; Doi, Mamoru; Eisenstein, Daniel J.; Evans, Michael L.;
Evans, N. W.; Fan, Xiaohui; Finkbeiner, Douglas P.; Friedman, Scott D.;
Frieman, Joshua A.; Fukugita, Masataka; Gillespie, Bruce; Gilmore,
G.; Glazebrook, Karl; Gray, Jim; Grebel, Eva K.; Gunn, James E.;
de Haas, Ernst; Hall, Patrick B.; Harvanek, Michael; Hawley, Suzanne
L.; Hayes, Jeffrey; Heckman, Timothy M.; Hendry, John S.; Hennessy,
Gregory S.; Hindsley, Robert B.; Hirata, Christopher M.; Hogan, Craig
J.; Hogg, David W.; Holtzman, Jon A.; Ichikawa, Shin-ichi; Ichikawa,
Takashi; Ivezić, Željko; Jester, Sebastian; Johnston, David E.;
Jorgensen, Anders M.; Jurić, Mario; Kauffmann, Guinevere; Kent,
Stephen M.; Kleinman, S. J.; Knapp, G. R.; Kniazev, Alexei Yu.; Kron,
Richard G.; Krzesinski, Jurek; Kuropatkin, Nikolay; Lamb, Donald Q.;
Lampeitl, Hubert; Lee, Brian C.; Leger, R. French; Lima, Marcos; Lin,
Huan; Long, Daniel C.; Loveday, Jon; Lupton, Robert H.; Mandelbaum,
Rachel; Margon, Bruce; Martínez-Delgado, David; Matsubara, Takahiko;
McGehee, Peregrine M.; McKay, Timothy A.; Meiksin, Avery; Munn, Jeffrey
A.; Nakajima, Reiko; Nash, Thomas; Neilsen, Eric H., Jr.; Newberg,
Heidi Jo; Nichol, Robert C.; Nieto-Santisteban, Maria; Nitta, Atsuko;
Oyaizu, Hiroaki; Okamura, Sadanori; Ostriker, Jeremiah P.; Padmanabhan,
Nikhil; Park, Changbom; Peoples, John, Jr.; Pier, Jeffrey R.; Pope,
Adrian C.; Pourbaix, Dimitri; Quinn, Thomas R.; Raddick, M. Jordan;
Re Fiorentin, Paola; Richards, Gordon T.; Richmond, Michael W.; Rix,
Hans-Walter; Rockosi, Constance M.; Schlegel, David J.; Schneider,
Donald P.; Scranton, Ryan; Seljak, Uroš; Sheldon, Erin; Shimasaku,
Kazu; Silvestri, Nicole M.; Smith, J. Allyn; Smolčić, Vernesa;
Snedden, Stephanie A.; Stebbins, Albert; Stoughton, Chris; Strauss,
Michael A.; SubbaRao, Mark; Suto, Yasushi; Szalay, Alexander S.;
Szapudi, István; Szkody, Paula; Tegmark, Max; Thakar, Aniruddha R.;
Tremonti, Christy A.; Tucker, Douglas L.; Uomoto, Alan; Vanden Berk,
Daniel E.; Vandenberg, Jan; Vidrih, S.; Vogeley, Michael S.; Voges,
Wolfgang; Vogt, Nicole P.; Weinberg, David H.; West, Andrew A.; White,
Simon D. M.; Wilhite, Brian; Yanny, Brian; Yocum, D. R.; York, Donald
G.; Zehavi, Idit; Zibetti, Stefano; Zucker, Daniel B.
2007ApJS..172..634A Altcode: 2007arXiv0707.3380A
This paper describes the Fifth Data Release (DR5) of the Sloan Digital
Sky Survey (SDSS). DR5 includes all survey quality data taken through
2005 June and represents the completion of the SDSS-I project (whose
successor, SDSS-II, will continue through mid-2008). It includes
five-band photometric data for 217 million objects selected over 8000
deg<SUP>2</SUP> and 1,048,960 spectra of galaxies, quasars, and stars
selected from 5713 deg<SUP>2</SUP> of that imaging data. These numbers
represent a roughly 20% increment over those of the Fourth Data Release;
all the data from previous data releases are included in the present
release. In addition to “standard” SDSS observations, DR5 includes
repeat scans of the southern equatorial stripe, imaging scans across
M31 and the core of the Perseus Cluster of galaxies, and the first
spectroscopic data from SEGUE, a survey to explore the kinematics and
chemical evolution of the Galaxy. The catalog database incorporates
several new features, including photometric redshifts of galaxies,
tables of matched objects in overlap regions of the imaging survey,
and tools that allow precise computations of survey geometry for
statistical investigations.
---------------------------------------------------------
Title: New Close Binary Systems from the SDSS-I (Data Release Five)
and the Search for Magnetic White Dwarfs in Cataclysmic Variable
Progenitor Systems
Authors: Silvestri, Nicole M.; Lemagie, Mara P.; Hawley, Suzanne L.;
West, Andrew A.; Schmidt, Gary D.; Liebert, James; Szkody, Paula;
Mannikko, Lee; Wolfe, Michael A.; Barentine, J. C.; Brewington,
Howard J.; Harvanek, Michael; Krzesinski, Jurik; Long, Dan; Schneider,
Donald P.; Snedden, Stephanie A.
2007AJ....134..741S Altcode: 2007arXiv0704.0789S
We present the latest catalog of more than 1200 spectroscopically
selected close binary systems observed with the Sloan Digital Sky Survey
through Data Release Five. We use the catalog to search for magnetic
white dwarfs in cataclysmic variable progenitor systems. Given that
approximately 25% of cataclysmic variables contain a magnetic white
dwarf, and that our large sample of close binary systems should contain
many progenitors of cataclysmic variables, it is quite surprising that
we find only two potential magnetic white dwarfs in this sample. The
candidate magnetic white dwarfs, if confirmed, would possess relatively
low magnetic field strengths (B<SUB>WD</SUB><10 MG) that are similar
to those of intermediate Polars but are much less than the average field
strength of the current Polar population. Additional observations of
these systems are required to definitively cast the white dwarfs as
magnetic. Even if these two systems prove to be the first evidence of
detached magnetic white dwarf + M dwarf binaries, there is still a large
disparity between the properties of the presently known cataclysmic
variable population and the presumed close binary progenitors.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Luminosity function of M7-L8
ultracool dwarfs (Cruz+, 2007)
Authors: Cruz, K. L.; Reid, I. N.; Kirkpatrick, J. D.; Burgasser,
A. J.; Liebert, J.; Solomon, A. R.; Schmidt, S. J.; Allen, P. R.;
Hawley, S. L.; Covey, K. R.
2007yCat..51330439C Altcode:
We present a 20pc, volume-limited sample of M7-L8 dwarfs created through
spectroscopic follow-up of sources selected from the Two Micron All Sky
Survey Second Incremental Release Point Source Catalog. In this paper we
present optical spectroscopy of 198 candidate nearby ultracool dwarfs,
including 12 late-M and L dwarfs likely to be within 20pc of the Sun and
94 more distant late-type dwarfs. We have also identified five ultracool
dwarfs with spectral signatures of low gravity. Combining these data
with previous results, we define a sample of 99 ultracool dwarfs in
91 systems within 20pc. These are used to estimate the J- and K-band
luminosity functions for dwarfs with optical spectral types between M7
and L8 (10.5<M<SUB>J</SUB><15, 9.5<M<SUB>Ks</SUB><13). We
find a space density of 4.9x10<SUP>-3</SUP>/pc<SUP>3</SUP> for late-M
dwarfs (M7-M9.5) and a lower limit of 3.8x10<SUP>-3</SUP>/pc<SUP>3</SUP>
for L dwarfs. <P />(8 data files).
---------------------------------------------------------
Title: Characterizing The Near-UV Environment Of M Dwarfs
Authors: Walkowicz, Lucianne M.; Johns-Krull, C. M.; Hawley, S. L.
2007AAS...210.1705W Altcode: 2007BAAS...39Q.118W
We report the results of our HST snapshot survey with the ACS HRC PR200L
prism, designed to measure the near-UV emission in a sample of nearby M
dwarfs. 33 stars were observed, spanning the mass range from 0.1 - 0.6
solar masses (T 2200K - 4000K) where the UV energy distributions vary
widely between active and inactive stars. The strength and distribution
of this UV emission can have critical consequences for the atmospheres
of attendant planets. These observations provide much-needed constraints
on models of the habitability zone and the atmospheres of possible
terrestrial planets orbiting M dwarf hosts, and will be used to refine
the target selection for future space missions such as TPF. These NUV
data will also be used in conjunction with existing optical, FUV and
X-ray data to constrain a new generation of M dwarf atmospheric models,
and to explore unanswered questions regarding the dynamo generation
and magnetic heating in these low-mass stars.
---------------------------------------------------------
Title: Meeting the Cool Neighbors. IX. The Luminosity Function of
M7-L8 Ultracool Dwarfs in the Field
Authors: Cruz, Kelle L.; Reid, I. Neill; Kirkpatrick, J. Davy;
Burgasser, Adam J.; Liebert, James; Solomon, Adam R.; Schmidt, Sarah
J.; Allen, Peter R.; Hawley, Suzanne L.; Covey, Kevin R.
2007AJ....133..439C Altcode: 2006astro.ph..9648C
We present a 20 pc, volume-limited sample of M7-L8 dwarfs created
through spectroscopic follow-up of sources selected from the Two Micron
All Sky Survey Second Incremental Release Point Source Catalog. In
this paper we present optical spectroscopy of 198 candidate nearby
ultracool dwarfs, including 12 late-M and L dwarfs likely to be
within 20 pc of the Sun and 94 more distant late-type dwarfs. We
have also identified five ultracool dwarfs with spectral signatures
of low gravity. Combining these data with previous results, we define
a sample of 99 ultracool dwarfs in 91 systems within 20 pc. These are
used to estimate the J- and K-band luminosity functions for dwarfs with
optical spectral types between M7 and L8 (10.5<M<SUB>J</SUB><15,
9.5<M<SUB>K<SUB>S</SUB></SUB><13). We find a space density
of 4.9×10<SUP>-3</SUP> pc<SUP>-3</SUP> for late-M dwarfs (M7-M9.5)
and a lower limit of 3.8×10<SUP>-3</SUP> pc<SUP>-3</SUP> for L dwarfs.
---------------------------------------------------------
Title: Low-Mass Dwarf Template Spectra from the Sloan Digital
Sky Survey
Authors: Bochanski, John J.; West, Andrew A.; Hawley, Suzanne L.;
Covey, Kevin R.
2007AJ....133..531B Altcode: 2006astro.ph.10639B
We present template spectra of low-mass (M0-L0) dwarfs derived from
over 4000 Sloan Digital Sky Survey spectra. These composite spectra
are suitable for use as medium-resolution (R~1800) radial velocity
standards. We report mean spectral properties (molecular band-head
strengths, equivalent widths) and use the templates to investigate the
effects of magnetic activity and metallicity on the spectroscopic and
photometric properties of low-mass stars.
---------------------------------------------------------
Title: Near-Ultraviolet Spectra of Flares on YZ CMi
Authors: Hawley, Suzanne L.; Walkowicz, Lucianne M.; Allred, Joel C.;
Valenti, Jeff A.
2007PASP..119...67H Altcode: 2006astro.ph.11074H
Near-ultraviolet spectroscopic data obtained with the Hubble Space
Telescope STIS (Space Telescope Imaging Spectrograph) instrument on
the dMe flare star YZ Canis Minoris (YZ CMi) were analyzed. Flare
and quiet intervals were identified from the broadband near-UV light
curve, and the spectrum of each flare was separately extracted. Mg II
and Fe II line profiles show similar behavior during the flares. Two
large flares allowed time-resolved spectra to be analyzed, revealing a
very broad component to the Mg II k line profile in at least one flare
spectrum (F9b). If interpreted as a velocity, this component requires
chromospheric material to be moving with FWHM ~ 250 km s<SUP>-1</SUP>,
implying kinetic energy far in excess of the radiative energy. The Mg II
k flare line profiles were compared to recent radiative hydrodynamic
models of flare atmospheres undergoing electron beam heating. The
models successfully predict red enhancements in the line profile, with
a typical velocity of a few km s<SUP>-1</SUP>, but do not reproduce
the flares showing blue enhancements, or the strongly broadened line
observed in flare F9b. A more complete calculation of redistribution
into the line wings, including the effect of collisions with the
electron beam, may resolve the origin of the excess line broadening.
---------------------------------------------------------
Title: Measuring the Luminosity Function of Low-Mass Stars with
Matched Survey Datasets
Authors: Covey, Kevin R.; Bochanski, J. J.; Hawley, S. L.; Davenport,
J.; Reid, I.; Golimowski, D.
2006AAS...209.2708C Altcode: 2006BAAS...38S.940C
We present an initial measurement of the luminosity and mass functions
of low mass stars as constructed from a catalog of matched Sloan
Digital Sky Survey (SDSS) and 2 Micron All Sky Survey (2MASS) point
sources. We have assembled a photometric catalog of 25,000+ matched
SDSS and 2MASS point sources, spanning over 30 square degrees on the
sky. We have also obtained follow-up spectroscopy, complete to J=16,
of 500+ low mass dwarf candidates within a 1 square degree sub-sample,
and thousands of additional dwarf candidates in the remaining 29 square
degrees. This spectroscopic sample verifies that less than 1% of the
photometric catalog is affected by incompleteness, contamination, or
bias. Using this sample, we derive the luminosity and mass functions of
low-mass stars over nearly a decade in mass ( 0.7 M<SUB>solar </SUB><
M<SUB>*</SUB> < 0.1 M<SUB>solar</SUB>), and compare our findings
to previous results. Having validated this method to generate a low
mass luminosity function from matched SDSS/2MASS datasets, future
studies will enable extending this technique to the entirety of the
SDSS/2MASS overlap.
---------------------------------------------------------
Title: Exploring the Local Milky Way: M Dwarfs as Tracers of Galactic
Populations
Authors: Bochanski, John J.; Hawley, S. L.; Munn, J. A.; Covey, K. R.;
West, A. A.; Walkowicz, L. M.
2006AAS...20917214B Altcode: 2006BAAS...38.1149B
We utilize Sloan Digital Sky Survey observations of over 8,000 low-mass
dwarfs to examine Galactic structure and kinematics in the Southern (b
-60 deg) Milky Way. Combining medium-resolution (R 1,800) spectroscopy,
five band (ugriz) photometry and proper motion measurements, this
dataset represents a powerful tool for examining the local structure and
kinematics of the thin and thick disks. For each star, we have measured
the activity (using the H-alpha luminosity) and UVW velocities. These
measurements, as functions of distance from the Galactic Plane, offer a
glimpse into the mean structural and kinematic properties of the thin
and thick disk populations. <P />The authors gratefully acknowledge
the support of NSF grants AST02-05875 and AST06-07644 and NASA ADP
grant NAG5-13111
---------------------------------------------------------
Title: New Close Binary Systems from the SDSS-I (Data Release
Five) and the Orbital Periods for a Subset of Close White Dwarf +
M Dwarf Systems
Authors: Silvestri, Nicole M.; Hawley, S. L.; Dang, L. C.; Krogsrud,
D. A.; Smoke, K.; Wolfe, M. A.; Mannikko, L.
2006AAS...20916218S Altcode: 2006BAAS...38Q1128S
We present the latest catalog of more than 1200 spectroscopically
selected close binary systems observed with the Sloan Digital Sky
Survey (SDSS) through the now public Data Release Five. We use
the systems from this catalog to study the influence of the binary
environment on the evolution of the low-mass (typically an M dwarf)
secondary star. We investigate how the properties of the M dwarf are
impacted by the presence of the white dwarf primary using a variety
of methods. Candidate systems with very active secondaries and/or
low-mass primaries are observed using time-series spectroscopy on the
ARC 3.5m to find their orbital periods. Preliminary orbital periods from
repeat observations from the SDSS are also presented. In addition to
the orbital period study, candidates are observed using photometric
time-series on the MDM 2.4m to search for variability (eclipses,
rotational modulation) and infrared photometry on the ARC 3.5m to
search for faint, low-mass companions. We have now compiled a sample of
systems with a wide range of spectral types, orbital periods and ages,
and will discuss our results on the properties of these systems.
---------------------------------------------------------
Title: Using the Galactic Dynamics of M7 Dwarfs to Infer the Evolution
of Their Magnetic Activity
Authors: West, Andrew A.; Bochanski, John J.; Hawley, Suzanne L.;
Cruz, Kelle L.; Covey, Kevin R.; Silvestri, Nicole M.; Reid, I. Neill;
Liebert, James
2006AJ....132.2507W Altcode: 2006astro.ph..9001W
We present a spectroscopic study and dynamical analysis of ~2600
M7 dwarfs. We confirm our previous finding that the fraction of
magnetically active stars decreases with vertical distance from
the Galactic plane. We also show that the mean luminosity of the
Hα emission has a small but statistically significant decrease
with distance. Using space motions for ~1300 stars and a simple
one-dimensional dynamical simulation, we demonstrate that the drop
in the activity fraction of M7 dwarfs can be explained by thin disk
dynamical heating and a rapid decrease of magnetic activity at a mean
stellar age of ~6-7 Gyr.
---------------------------------------------------------
Title: Time Variation in the Magnetic Activity of Cool Stars
Authors: West, Andrew A.; Wright, J. T.; Marcy, G. W.; Agueros, M.;
Walkowicz, L. M.; Hilton, E. J.; Hawley, S. L.; Bochanski, J. J.;
Covey, K. R.
2006AAS...209.8904W Altcode: 2006BAAS...38.1024W
We present results from the analysis of multi-epoch, spectral
observations of magnetically active M-dwarfs. Using data from the
California and Carnegie Planet Search Program, the Sloan Digital
Sky Survey, and follow-up observations at Apache Point Observatory,
we examine the time variation of chromospheric magnetic activity
(as traced by the H-alpha, H-beta and Calcium K emission lines). We
investigate the amplitude of activity variation in individual stars and
compare this to the spread in activity seen in large SDSS samples of
M-dwarfs. The data suggest that the activity variation of individual
stars cannot explain the range of activity seen in the SDSS sample,
indicating there is an intrinsic spread of activity strength in the
M-dwarf population. In addition, we examine differences in the observed
activity variation between the measured emission lines. Our analysis
puts important constraints on the range of chromospheric temperatures
predicted from models of M-dwarf dynamos.
---------------------------------------------------------
Title: Tracers of Chromospheric Structure: Observations of CaII K
and Hα in M Dwarfs
Authors: Walkowicz, Lucianne M.; Hawley, S. L.
2006AAS...209.1403W Altcode: 2006BAAS...38R.915W
We report on our observing program to capture simultaneous high
resolution spectra of Ca II and Balmer lines in a sample of nearby M3
dwarfs. Our goal is to investigate the chromospheric heating required
to produce both of these lines at the observed levels. We present the
results of our observing program so far, and discuss the application
of these results as empirical constraints on models of quiescent M
dwarf atmospheres. We also present initial model calculations and
place them in the context of the data.
---------------------------------------------------------
Title: Flare Rate Analysis of M-Dwarf Lightcurves
Authors: Kowalski, Adam F.; Hilton, E. J.; Becker, A. C.; Hawley, S. L.
2006AAS...209.8907K Altcode: 2006BAAS...38.1025K
We present a preliminary variability index analysis of lightcurves of
several thousand M-dwarfs extracted from the Sloan Digital Sky Survey
Equatorial Stripe. These objects have been subclassed by magnetic
activity and spectral type. This analysis will provide the rates of
flaring activity as a function of the above parameters as well as
characterizing the colors of these stars while active. M-dwarf flare
rates will be applicable to next-generation time domain surveys such
as the Large Synoptic Survey Telescope by predicting the fraction
of observed variable objects that are flaring M-dwarfs and not other
cosmological transients.
---------------------------------------------------------
Title: Improvement in the SDSS Photometric Calibration for Red Stars
Authors: Davenport, James R.; Bochanski, J.; Covey, K.; Hawley, S.
2006AAS...209.9712D Altcode: 2006BAAS...38.1037D
The SDSS has been an extremely fruitful survey for the study of
late-type stars and other inherently red objects. Because of the
breadth of the survey, it is important that all of the photometric
data be calibrated on the standard SDSS 2.5m ugriz system. However,
for stars redder than r-i > 0.6, the stellar locus measured with
the SDSS 2.5m telescope begins to diverge from the SDSS photometric
telescope calibration measurements using the presently derived color
transformations. We use photometry of hundreds of late type stars that
have been measured with both the SDSS 2.5m and the SDSS photometric
telescope to obtain improved color transformations between the two
telescopes for stars with red colors. These data will be particularly
useful for calibrating an improved photometric parallax relation for
low mass stars.
---------------------------------------------------------
Title: The Age-Activity Relation for M dwarfs Using 25,000 SDSS
Spectra
Authors: Hawley, Suzanne L.; West, A. A.; Bochanski, J. J.; Covey,
K. R.
2006AAS...209.8906H Altcode: 2006BAAS...38.1025H
The age at which strong surface magnetic activity ceases in M dwarfs
has been inferred to have a strong dependence on mass (spectral
type, surface temperature) to explain previous results showing a
large increase in the fraction of active stars at later spectral
types. Using spectral observations of 25,000 M dwarfs in the SDSS,
we show that the fraction of active stars decreases as a function of
vertical distance from the Galactic plane, and that the magnitude
of this decrease changes significantly for different M spectral
types. Adopting a simple dynamical model for thin disk vertical
heating, we assign an age for the activity decline at each spectral
type, and thus determine an activity-age relation for M dwarfs. These
results provide constraints for dynamo models that seek to describe
the production of surface magnetic fields in low mass stars.
---------------------------------------------------------
Title: From Radio to X-Ray: The Quiescent Atmosphere of the dMe
Flare Star EV Lacertae
Authors: Osten, Rachel A.; Hawley, Suzanne L.; Allred, Joel;
Johns-Krull, Christopher M.; Brown, Alexander; Harper, Graham M.
2006ApJ...647.1349O Altcode: 2006astro.ph..4255O
We report on multiwavelength observations spanning radio to X-ray
wavelengths of the M dwarf flare star EV Lacertae and probing
the characteristics of the outer atmospheric plasma from the upper
chromosphere to the corona. We detect the star at a wavelength of 2 cm
(15 GHz) for the first time. UV and FUV line profiles show evidence
of nonthermal broadening, and the velocity width appears to peak
at lower temperatures than in the Sun; this trend is confirmed in
another active M dwarf flare star. Electron density measurements
indicate nearly constant electron pressures between logT=5.2 and
6.4. At higher coronal temperatures, there is a sharp increase
of 2 orders of magnitude in density (n<SUB>e</SUB>~10<SUP>13</SUP>
cm<SUP>-3</SUP> at logT=6.9). X-ray, EUV, FUV, and NUV spectra constrain
the differential emission measure (DEM) from the upper chromosphere
through the corona. The coronal pressures are inconsistent with the
assumption of hydrostatic equilibrium, either through emission measure
(EM) modeling or application of scaling laws, and imply large conductive
loss rates and a large energy input at the highest temperatures. The
timescales for radiative and conductive losses in EV Lac's upper
atmosphere imply that significant continued heating must occur for
the corona to maintain its quiescent properties. The high-frequency
radio detection requires the high-temperature X-ray-emitting coronal
plasma to be spatially distinct from the radio emission source. Length
scales in the low-temperature corona are markedly larger than those in
the high-temperature corona, further suggestions of an inhomogeneous
mixture of thermal and nonthermal coronal plasma.
---------------------------------------------------------
Title: Radiative Hydrodynamic Models of Optical and Ultraviolet
Emission from M Dwarf Flares
Authors: Allred, Joel C.; Hawley, Suzanne L.; Abbett, William P.;
Carlsson, Mats
2006ApJ...644..484A Altcode: 2006astro.ph..3195A
We report on radiative hydrodynamic simulations of M dwarf stellar
flares and compare the model predictions to observations of several
flares. The flares were simulated by calculating the hydrodynamic
response of a model M dwarf atmosphere to a beam of nonthermal
electrons. Radiative back-warming through numerous soft X-ray,
extreme-ultraviolet, and ultraviolet transitions are also included. The
equations of radiative transfer and statistical equilibrium are treated
in non-LTE for many transitions of hydrogen, helium, and the Ca II
ion, allowing the calculation of detailed line profiles and continuum
radiation. Two simulations were carried out, with electron beam fluxes
corresponding to moderate and strong beam heating. In both cases we
find that the dynamics can be naturally divided into two phases: an
initial gentle phase in which hydrogen and helium radiate away much
of the beam energy and an explosive phase characterized by large
hydrodynamic waves. During the initial phase, lower chromospheric
material is evaporated into higher regions of the atmosphere, causing
many lines and continua to brighten dramatically. The He II 304 line
is especially enhanced, becoming the brightest line in the flaring
spectrum. The hydrogen Balmer lines also become much brighter and show
very broad line widths, in agreement with observations. We compare
our predicted Balmer decrements to decrements calculated for several
flare observations and find the predictions to be in general agreement
with the observations. During the explosive phase both condensation and
evaporation waves are produced. The moderate flare simulation predicts
a peak evaporation wave of ~130 km s<SUP>-1</SUP> and a condensation
wave of ~30 km s<SUP>-1</SUP>. The velocity of the condensation wave
matches velocities observed in several transition region lines. The
optical continuum also greatly intensifies, reaching a peak increase
of 130% (at 6000 Å) for the strong flare, but does not match observed
white-light spectra.
---------------------------------------------------------
Title: Erratum: “Spectroscopic Survey of M Dwarfs within 100
Parsecs of the Sun” (<A href="/abs/2005AJ.130.1871B">AJ, 130, 1871
[2005]</A>)
Authors: Bochanski, John J.; Hawley, Suzanne L.; Reid, I. Neill;
Covey, Kevin R.; West, Andrew A.; Tinney, C. G.; Gizis, John E.
2006AJ....131.3136B Altcode:
In Table 2 of the recent paper titled “Spectroscopic Survey of M
Dwarfs within 100 Parsecs of the Sun” by Bochanski et al., the authors
presented UVW space velocities, proper motions, radial velocities, and
distances to the 574 M dwarfs within their sample. The UVW motions were
then examined as a function of vertical distance from the Galactic
plane, with a discussion on the significance of the results and
their application to dynamic heating models. <P />The authors have
discovered an error in the calculation of the UVW motions. During
the preparation of the manuscript, the computed space motions were
not accurately recorded for a given star, resulting in sporadic
errors throughout Table 2 and the subsequent analysis. In addition,
the authors want to explicitly state that the UVW motions, corrected
to the local standard of rest, are in a right-handed system, with a
positive U-velocity in the direction of the Galactic center. <P />The
new space velocities for the M dwarfs within this sample affect Tables
2 and 4-6 and Figures 8 and 9. The new values are included below,
but the authors stress that the original conclusions presented in §
6 of the original paper remain valid. In the new version of Figure 9,
the general decrease in velocity dispersion of the broad component
(circles) with distance from the plane is preserved, along with the
mostly constant dispersion of the narrow velocity dispersion component
(squares). For completeness, a new illustrative demonstration of our
kinematic analysis is shown, along with updated versions of Tables 4-6,
which present the details of the kinematic analysis for UVW. <P />The
authors sincerely regret any confusion introduced by this error and
wish to thank Francesca Figueras for helpful discussion.
---------------------------------------------------------
Title: A Radiative Hydrodynamic Simulation of the 23 July 2002
Solar Flare
Authors: Allred, J. C.; Hawley, S. L.
2006AGUSMSH52A..01A Altcode:
We report on a simulation of the 23 July 2002 X-class solar flare. The
flare was simulated by modeling the radiative hydrodynamic response of
the solar atmosphere to a beam of non-thermal electrons. The electron
beam spectrum was inferred from X-ray spectra obtained by RHESSI during
the 23 July flare. The total beam flux and energy distribution vary as
a function of time allowing us to investigate temporal correlations of
the electron beam with the observed spectral response. In particular,
we investigate the correlation of the beam heating rate with the
white light increase. Our flare simulations include detailed non-LTE,
optically thick radiative transfer which is crucial for understanding
how energy is transported from the chromosphere deep into the
photosphere where the white light is produced. During the course of
the flare simulation we find the level of increase in white light
matches well with observations of similarly sized white light flares.
---------------------------------------------------------
Title: A Catalog of Spectroscopically Selected Close Binary Systems
from the Sloan Digital Sky Survey Data Release Four
Authors: Silvestri, Nicole M.; Hawley, Suzanne L.; West, Andrew A.;
Szkody, Paula; Bochanski, John J.; Eisenstein, Daniel J.; McGehee,
Peregrine; Schmidt, Gary D.; Smith, J. Allyn; Wolfe, Michael A.;
Harris, Hugh C.; Kleinman, Scot J.; Liebert, James; Nitta, Atsuko;
Barentine, J. C.; Brewington, Howard J.; Brinkmann, John; Harvanek,
Michael; Krzesiński, Jurek; Long, Dan; Neilsen, Eric H., Jr.;
Schneider, Donald P.; Snedden, Stephanie A.
2006AJ....131.1674S Altcode:
We present a spectroscopic sample of 747 detached close binary systems
from the Sloan Digital Sky Survey (SDSS) Fourth Data Release. The
majority of these binaries consist of a white dwarf primary and a
low-mass secondary (typically M dwarf) companion. We have determined
the temperature and gravity for 496 of the white dwarf primaries
and the spectral type and magnetic activity properties for 661 of
the low-mass secondaries. We have estimated the distances for each
of the white dwarf-main-sequence star binaries and use white dwarf
evolutionary grids to establish the age of each binary system from
the white dwarf cooling times. With respect to a spectroscopically
identified sample of ~8000 isolated M dwarf stars in the SDSS, the M
dwarf secondaries show enhanced activity with a higher active fraction
at a given spectral type. The white dwarf temperatures and gravities are
similar to the distribution of ~1900 DA white dwarfs from the SDSS. The
ages of the binaries in this study range from ~0.5 Myr to nearly 3 Gyr
(average age ~0.20 Gyr).
---------------------------------------------------------
Title: Optical Spectroscopy of a Flare on Barnard's Star
Authors: Paulson, Diane B.; Allred, Joel C.; Anderson, Ryan B.;
Hawley, Suzanne L.; Cochran, William D.; Yelda, Sylvana
2006PASP..118..227P Altcode: 2005astro.ph.11281P
We present optical spectra of a flare on Barnard's star. Several
photospheric and chromospheric species were enhanced by the flare
heating. An analysis of the Balmer lines shows that their shapes
are best explained by Stark broadening rather than chromospheric
mass motions. We estimate the temperature of the flaring region in
the lower atmosphere to be >=8000 K and the electron density to
be ~10<SUP>14</SUP> cm<SUP>-3</SUP>, similar to values observed in
other dM flares. Because Barnard's star is considered to be one of
our oldest neighbors, a flare of this magnitude is probably quite rare.
---------------------------------------------------------
Title: The Fourth Data Release of the Sloan Digital Sky Survey
Authors: Adelman-McCarthy, Jennifer K.; Agüeros, Marcel A.; Allam,
Sahar S.; Anderson, Kurt S. J.; Anderson, Scott F.; Annis, James;
Bahcall, Neta A.; Baldry, Ivan K.; Barentine, J. C.; Berlind, Andreas;
Bernardi, Mariangela; Blanton, Michael R.; Boroski, William N.;
Brewington, Howard J.; Brinchmann, Jarle; Brinkmann, J.; Brunner,
Robert J.; Budavári, Tamás; Carey, Larry N.; Carr, Michael A.;
Castander, Francisco J.; Connolly, A. J.; Csabai, István; Czarapata,
Paul C.; Dalcanton, Julianne J.; Doi, Mamoru; Dong, Feng; Eisenstein,
Daniel J.; Evans, Michael L.; Fan, Xiaohui; Finkbeiner, Douglas P.;
Friedman, Scott D.; Frieman, Joshua A.; Fukugita, Masataka; Gillespie,
Bruce; Glazebrook, Karl; Gray, Jim; Grebel, Eva K.; Gunn, James E.;
Gurbani, Vijay K.; de Haas, Ernst; Hall, Patrick B.; Harris, Frederick
H.; Harvanek, Michael; Hawley, Suzanne L.; Hayes, Jeffrey; Hendry, John
S.; Hennessy, Gregory S.; Hindsley, Robert B.; Hirata, Christopher M.;
Hogan, Craig J.; Hogg, David W.; Holmgren, Donald J.; Holtzman, Jon A.;
Ichikawa, Shin-ichi; Ivezić, Željko; Jester, Sebastian; Johnston,
David E.; Jorgensen, Anders M.; Jurić, Mario; Kent, Stephen M.;
Kleinman, S. J.; Knapp, G. R.; Kniazev, Alexei Yu.; Kron, Richard G.;
Krzesinski, Jurek; Kuropatkin, Nikolay; Lamb, Donald Q.; Lampeitl,
Hubert; Lee, Brian C.; Leger, R. French; Lin, Huan; Long, Daniel C.;
Loveday, Jon; Lupton, Robert H.; Margon, Bruce; Martínez-Delgado,
David; Mandelbaum, Rachel; Matsubara, Takahiko; McGehee, Peregrine
M.; McKay, Timothy A.; Meiksin, Avery; Munn, Jeffrey A.; Nakajima,
Reiko; Nash, Thomas; Neilsen, Eric H., Jr.; Newberg, Heidi Jo; Newman,
Peter R.; Nichol, Robert C.; Nicinski, Tom; Nieto-Santisteban, Maria;
Nitta, Atsuko; O'Mullane, William; Okamura, Sadanori; Owen, Russell;
Padmanabhan, Nikhil; Pauls, George; Peoples, John, Jr.; Pier, Jeffrey
R.; Pope, Adrian C.; Pourbaix, Dimitri; Quinn, Thomas R.; Richards,
Gordon T.; Richmond, Michael W.; Rockosi, Constance M.; Schlegel, David
J.; Schneider, Donald P.; Schroeder, Joshua; Scranton, Ryan; Seljak,
Uroš; Sheldon, Erin; Shimasaku, Kazu; Smith, J. Allyn; Smolčić,
Vernesa; Snedden, Stephanie A.; Stoughton, Chris; Strauss, Michael
A.; SubbaRao, Mark; Szalay, Alexander S.; Szapudi, István; Szkody,
Paula; Tegmark, Max; Thakar, Aniruddha R.; Tucker, Douglas L.; Uomoto,
Alan; Vanden Berk, Daniel E.; Vandenberg, Jan; Vogeley, Michael S.;
Voges, Wolfgang; Vogt, Nicole P.; Walkowicz, Lucianne M.; Weinberg,
David H.; West, Andrew A.; White, Simon D. M.; Xu, Yongzhong; Yanny,
Brian; Yocum, D. R.; York, Donald G.; Zehavi, Idit; Zibetti, Stefano;
Zucker, Daniel B.
2006ApJS..162...38A Altcode: 2005astro.ph..7711A
This paper describes the Fourth Data Release of the Sloan Digital
Sky Survey (SDSS), including all survey-quality data taken through
2004 June. The data release includes five-band photometric data
for 180 million objects selected over 6670 deg<SUP>2</SUP> and
673,280 spectra of galaxies, quasars, and stars selected from 4783
deg<SUP>2</SUP> of those imaging data using the standard SDSS target
selection algorithms. These numbers represent a roughly 27% increment
over those of the Third Data Release; all the data from previous data
releases are included in the present release. The Fourth Data Release
also includes an additional 131,840 spectra of objects selected using
a variety of alternative algorithms, to address scientific issues
ranging from the kinematics of stars in the Milky Way thick disk to
populations of faint galaxies and quasars.
---------------------------------------------------------
Title: Investigating the late stages of stellar evolution with long
period variables from MACHO and 2MASS
Authors: Fraser, Oliver J.; Hawley, Suzanne L.; Cook, Kem H.
2006MmSAI..77..519F Altcode: 2005astro.ph..9569F
We are re-analyzing the MACHO variable star database to explore the
relationships between pulsation, evolution, and mass loss in evolved
stars. We will analyze the multi-periodic properties of long period
variable (LPV) stars, 50% of which could not be assigned any period
in the original analysis. Recent results show that the missing
stars may be an important element in understanding the origin of
the period-luminosity sequences observed in the LMC. Our goal is to
characterize the morphology and periodic properties of these stars,
and then use the stars' 2MASS colors along with theoretical isochrones
to understand their mass loss and evolution. We will develop a
luminosity-independent criteria to classify the LMC LPVs, which can then
be applied to Galactic LPVs. This will enable a synthesis of knowledge
between LPVs in the LMC and the well-studied Galactic examples.
---------------------------------------------------------
Title: The Radio Spectrum of TVLM 513-46546: Constraints on the
Coronal Properties of a Late M Dwarf
Authors: Osten, Rachel A.; Hawley, Suzanne L.; Bastian, Timothy S.;
Reid, I. Neill
2006ApJ...637..518O Altcode: 2005astro.ph..9762O
We explore the radio emission from the M9 dwarf TVLM 513-46546 at
multiple radio frequencies, determining the flux spectrum of persistent
radio emission, as well as constraining the levels of circular
polarization. Detections at both 3.6 and 6 cm provide a spectral index
measurement α (where S<SUB>ν</SUB>~ν<SUP>α</SUP>) of -0.4+/-0.1. A
detection at 20 cm suggests that the spectral peak is between 1.4 and
5 GHz. The most stringent upper limits on circular polarization are
at 3.6 and 6 cm, with V/I<15%. These characteristics agree well
with those of typical parameters for early- to mid-type M dwarfs,
confirming that magnetic activity is present at levels comparable with
those extrapolated from earlier M dwarfs. We apply analytic models to
investigate the coronal properties under simple assumptions of dipole
magnetic field geometry and radially varying nonthermal electron
density distributions. Requiring the spectrum to be optically thin
at frequencies higher than 5 GHz and reproducing the observed 3.6 cm
fluxes constrains the magnetic field at the base to be less than about
500 G. There is no statistically significant periodicity in the 3.6
cm light curve, but it is consistent with low-level variability.
---------------------------------------------------------
Title: SDSS spectroscopic survey of stars.
Authors: Ivezić, Ž.; Schlegel, D.; Uomoto, A.; Bond, N.; Beers, T.;
Allende Prieto, C.; Wilhelm, R.; Lee, Y. Sun; Sivarani, T.; Jurić,
M.; Lupton, R.; Rockosi, C.; Knapp, G.; Gunn, J.; Yanny, B.; Jester,
S.; Kent, S.; Pier, J.; Munn, J.; Richards, G.; Newberg, H.; Blanton,
M.; Eisenstein, D.; Hawley, S.; Anderson, S.; Harris, H.; Kiuchi, F.;
Chen, A.; Bushong, J.; Sohi, H.; Haggard, D.; Kimball, A.; Barentine,
J.; Brewington, H.; Harvanek, M.; Kleinman, S.; Krzesinski, J.; Long,
D.; Nitta, A.; Snedden, S.; SDSS Collaboration
2006MmSAI..77.1057I Altcode: 2007astro.ph..1509I
In addition to optical photometry of unprecedented quality, the Sloan
Digital Sky Survey (SDSS) is also producing a massive spectroscopic
database. We discuss determination of stellar parameters, such as
effective temperature, gravity and metallicity from SDSS spectra,
describe correlations between kinematics and metallicity, and study
their variation as a function of the position in the Galaxy. We show
that stellar parameter estimates by Beers et al. show a good correlation
with the position of a star in the g-r vs. u-g color-color diagram,
thereby demonstrating their robustness as well as a potential for
photometric parameter estimation methods. Using Beers et al. parameters,
we find that the metallicity distribution of the Milky Way stars at
a few kpc from the galactic plane is bimodal with a local minimum at
[Z/Z_⊙] ∼ -1.3. The median metallicity for the low-metallicity
[Z/Z_⊙]< -1.3 subsample is nearly independent of Galactic
cylindrical coordinates R and z, while it decreases with z for the
high-metallicity [Z/Z_⊙]> -1.3 sample. We also find that the
low-metallicity sample has ∼2.5 times larger velocity dispersion and
that it does not rotate (at the ∼10 km/s level), while the rotational
velocity of the high-metallicity sample decreases smoothly with the
height above the galactic plane.
---------------------------------------------------------
Title: Low Mass Template Spectra from SDSS
Authors: Bochanski, J. J.; West, A. A.; Hawley, S. L.; Covey, K. R.
2005AAS...20713107B Altcode: 2005BAAS...37.1378B
We present mean template spectra of low mass dwarfs as observed by the
Sloan Digital Sky Survey (SDSS). These extremely high signal-to-noise
templates result from co-adding observations of stars with similar
spectral types. We make use of ∼ 12,000 unique low mass stellar
spectra to construct a set of templates spanning the spectral types,
M0-L2. We measure the spectral and photometric properties of these
mean templates, and report on H-alpha emission (due to chromospheric
activity) and molecular band strengths. These pristine spectra are
suitable for use as radial velocity cross-correlation templates as well
as illuminating many of the mean properties of low mass stars. <P />We
gratefully acknowledge the support of NSF grant AST02-05875 and NASA
ADP grant NAG5-13111.
---------------------------------------------------------
Title: Testing LMC Microlensing Scenarios: The Discrimination Power
of the SuperMACHO Microlensing Survey
Authors: Rest, A.; Stubbs, C.; Becker, A. C.; Miknaitis, G. A.; Miceli,
A.; Covarrubias, R.; Hawley, S. L.; Smith, R. C.; Suntzeff, N. B.;
Olsen, K.; Prieto, J. L.; Hiriart, R.; Welch, D. L.; Cook, K. H.;
Nikolaev, S.; Huber, M.; Prochtor, G.; Clocchiatti, A.; Minniti, D.;
Garg, A.; Challis, P.; Keller, S. C.; Schmidt, B. P.
2005ApJ...634.1103R Altcode: 2005astro.ph..9240R
Characterizing the nature and spatial distribution of the lensing
objects that produce the previously measured microlensing optical depth
toward the Large Magellanic Cloud (LMC) remains an open problem. We
present an appraisal of the ability of the SuperMACHO Project,
a next-generation microlensing survey directed toward the LMC, to
discriminate between various proposed lensing populations. We consider
two scenarios: lensing by a uniform foreground screen of objects and
self-lensing by LMC stars. The optical depth for “screen lensing” is
essentially constant across the face of the LMC, whereas the optical
depth for self-lensing shows a strong spatial dependence. We have
carried out extensive simulations, based on data obtained during the
first year of the project, to assess the SuperMACHO survey's ability
to discriminate between these two scenarios. In our simulations
we predict the expected number of observed microlensing events for
various LMC models for each of our fields by adding artificial stars
to the images and estimating the spatial and temporal efficiency of
detecting microlensing events using Monte Carlo methods. We find that
the event rate itself shows significant sensitivity to the choice of
the LMC luminosity function, limiting the conclusions that can be drawn
from the absolute rate. If instead we determine the differential event
rate across the LMC, we will decrease the impact of these systematic
biases and render our conclusions more robust. With this approach
the SuperMACHO Project should be able to distinguish between the two
categories of lens populations. This will provide important constraints
on the nature of the lensing objects and their contributions to the
Galactic dark matter halo.
---------------------------------------------------------
Title: Seven Days in the Life of AR Lac
Authors: Ayres, T. R.; Brown, A.; Harper, G. M.; Korhonen, H.;
Redfield, S.; Hawley, S. L.; Optical Support Team
2005AAS...20717505A Altcode: 2005BAAS...37.1445A
A week-long pointing on the short-period eclipsing RS CVn binary AR Lac
(K0IV+G4IV; P=2d) by the Far-Ultraviolet Spectroscopic Explorer was
coordinated with groundbased optical Doppler mapping, to provide an
unprecedented view of structure, energetics, and dynamics of subcoronal
activity, through time-resolved measurements of FUV diagnostics like
C III λ 977, O VI λ 1031, and (coronal forbidden line) Fe XVIII
λ 974. The observation was carried out over the period 29 November
to 7 December 2004, with a total exposure of 225 ks, covering four
revolutions of the binary. Three large flares were captured during
this period, and numerous smaller ones, mainly on the K subgiant
primary. We discuss the appearance of the FUV activity on the surfaces
of the two hyperactive companions, with special emphasis on the eclipse
intervals. <P />This work was supported by a FUSE Guest Investigator
grant.
---------------------------------------------------------
Title: The SDSS/2MASS Low Mass Stellar Luminosity Function: The
Calibration Region
Authors: Covey, K. R.; Hawley, S. L.; Bochanski, J. J.; SDSS
Collaboration
2005AAS...207.4204C Altcode: 2005BAAS...37.1227C
We present an initial measurement of the luminosity and mass functions
of low mass stars as constructed from a catalog of matched Sloan
Digital Sky Survey (SDSS) and 2 Micron All Sky Survey (2MASS) point
sources. We have assembled a photometric catalog of 25,000+ matched
SDSS and 2MASS point sources, spanning over 30 square degrees on the
sky. We have also obtained follow-up spectroscopy, complete to J=16,
of 500+ low mass dwarf candidates within a 1 square degree sub-sample,
and thousands of additional dwarf candidates in the remaining 29 square
degrees. We have used this spectroscopic sample to assess the impact
of, and correct for, photometric biases and contamination by distinct
classes of astronomical objects found in nearby regions of color space
(e.g. hi-z QSOs). Having validated this method to generate a low mass
luminosity function from matched SDSS/2MASS datasets, future studies
will enable extending this technique to the entirety of the SDSS/2MASS
overlap. <P />The authors gratefully acknowledge the NASA ADP and GSRP
programs for funding which enabled this work.
---------------------------------------------------------
Title: Spectroscopic Survey of M Dwarfs within 100 Parsecs of the Sun
Authors: Bochanski, John J.; Hawley, Suzanne L.; Reid, I. Neill;
Covey, Kevin R.; West, Andrew A.; Tinney, C. G.; Gizis, John E.
2005AJ....130.1871B Altcode:
We have constructed a sample of M dwarfs out to a distance of ~100
pc. This sample of 605 stars (574 M dwarfs and 31 K dwarfs) have been
spectroscopically observed, yielding spectral types, radial velocities,
Hα equivalent widths, and molecular band indices. Photometric
observations have been compiled, with photographic plates providing
RI magnitudes and JHK<SUB>s</SUB> magnitudes from Two Micron All
Sky Survey observations. Proper motions were determined by a match to
USNO-B, and distances were computed employing a spectroscopic parallax,
allowing the computation of UVW space motions. These data were used to
investigate the distribution of magnetically active stars within the
solar neighborhood. We find that there is no statistically significant
variation in activity for equidistant locations above and below the
Galactic plane. We also confirm prior kinematic analysis of large
samples of M dwarfs, finding that active stars form a dynamically
colder population.
---------------------------------------------------------
Title: VizieR Online Data Catalog: A preliminary 20pc census from
the NLTT catalogue (Reid+, 2004)
Authors: Reid, I. N.; Cruz, K. L.; Allen, P.; Mungall, F.; Kilkenny,
D.; Liebert, J.; Hawley, S. L.; Fraser, O. J.; Covey, K. R.; Lowrance,
P.; Kirkpatrick, J. D.; Burgasser, A. J.
2005yCat..51280463R Altcode:
Continuing our census of late-type dwarfs in the solar neighborhood,
we present BVRI photometry and optical spectroscopy of 800 mid-type M
dwarfs drawn from the NLTT proper-motion catalog. The targets are taken
both from our own cross-referencing of the NLTT Catalogue and the 2MASS
Second Incremental Data Release, and from the revised NLTT compiled
recently by Salim & Gould (Cat. <J/ApJ/582/1011>). All are
identified as nearby-star candidates based on their location in the
(m<SUB>r</SUB>, m<SUB>r</SUB>-K<SUB>s</SUB>) diagram. Three hundred
stars discussed here have previous astrometric, photometric, or
spectroscopic observations. We present new BVRI photometry for 101
stars, together with low-resolution spectroscopy of a further 400
dwarfs. <P />(10 data files).
---------------------------------------------------------
Title: Status of Abundance Determinations for Low Mass Dwarfs and
Subdwarfs
Authors: Hawley, S. L.
2005ASPC..336...69H Altcode:
In this talk, I will review the status of abundance determinations
for M dwarfs and M subdwarfs. Most results come from photometric data
(position of the star in a calibrated color magnitude diagram) and/or
low resolution studies of molecular band-strengths. These methods give
only rough estimates of the metallicity. A few high resolution studies
have been attempted, and more are in progress. The calibration of low
resolution abundance indicators using these high resolution studies
offers the best hope for obtaining metallicities of large samples of
stars in the future.
---------------------------------------------------------
Title: Radiative Hydrodynamic Models of the Optical and Ultraviolet
Emission from Solar Flares
Authors: Allred, Joel C.; Hawley, Suzanne L.; Abbett, William P.;
Carlsson, Mats
2005ApJ...630..573A Altcode: 2005astro.ph..7335A
We report on radiative hydrodynamic simulations of moderate and strong
solar flares. The flares were simulated by calculating the atmospheric
response to a beam of nonthermal electrons injected at the apex of a
one-dimensional closed coronal loop and include heating from thermal
soft X-ray, extreme ultraviolet, and ultraviolet (XEUV) emission. The
equations of radiative transfer and statistical equilibrium were
treated in non-LTE and solved for numerous transitions of hydrogen,
helium, and Ca II, allowing the calculation of detailed line profiles
and continuum emission. This work improves on previous simulations
by incorporating more realistic nonthermal electron beam models and
includes a more rigorous model of thermal XEUV heating. We find that
XEUV back-warming contributes less than 10% of the heating, even in
strong flares. The simulations show elevated coronal and transition
region densities resulting in dramatic increases in line and continuum
emission in both the UV and optical regions. The optical continuum
reaches a peak increase of several percent, which is consistent with
enhancements observed in solar white-light flares. For a moderate flare
(~M class), the dynamics are characterized by a long gentle phase of
near balance between flare heating and radiative cooling, followed
by an explosive phase with beam heating dominating over cooling and
characterized by strong hydrodynamic waves. For a strong flare (~X
class), the gentle phase is much shorter, and we speculate that for even
stronger flares the gentle phase may be essentially nonexistent. During
the explosive phase, synthetic profiles for lines formed in the upper
chromosphere and transition region show blueshifts corresponding to
a plasma velocity of ~120 km s<SUP>-1</SUP>, and lines formed in the
lower chromosphere show redshifts of ~40 km s<SUP>-1</SUP>.
---------------------------------------------------------
Title: Updated Colors for Cool Stars in the Sloan Digital Sky Survey
Authors: West, Andrew A.; Walkowicz, Lucianne M.; Hawley, Suzanne L.
2005PASP..117..706W Altcode:
We present updated colors for M and L dwarfs based on photometry from
the third data release of the Sloan Digital Sky Survey (SDSS). These
data are improved in quality and number from earlier results. We also
provide updated equations for determining photometric parallaxes from
SDSS colors of late-type stars. Walkowicz et al. have recently presented
new techniques for studying the magnetic activity of low-mass stars,
and their method relies on an accurate determination of SDSS color. We
derive new relationships between SDSS colors and other common passbands
and present updated formulas from Walkowicz et al. for determining
the level of magnetic activity in M and L dwarfs.
---------------------------------------------------------
Title: The Magnetic Properties of an L Dwarf Derived from Simultaneous
Radio, X-Ray, and Hα Observations
Authors: Berger, E.; Rutledge, R. E.; Reid, I. N.; Bildsten, L.;
Gizis, J. E.; Liebert, J.; Martín, E.; Basri, G.; Jayawardhana, R.;
Brandeker, A.; Fleming, T. A.; Johns-Krull, C. M.; Giampapa, M. S.;
Hawley, S. L.; Schmitt, J. H. M. M.
2005ApJ...627..960B Altcode: 2005astro.ph..2384B
We present the first simultaneous, multiwavelength observations of
an L dwarf, the L3.5 candidate brown dwarf 2MASS J00361617+1821104,
conducted with the Very Large Array, the Chandra X-Ray Observatory,
and the Kitt Peak 4 m telescope. We detect strongly variable
and periodic radio emission (P=3 hr) with a fraction of about
60% circular polarization. No X-ray emission is detected to a
limit of L<SUB>X</SUB>/L<SUB>bol</SUB><~2×10<SUP>-5</SUP>,
several hundred times below the saturation level observed in early
M dwarfs. Similarly, we do not detect Hα emission to a limit of
L<SUB>Hα</SUB>/L<SUB>bol</SUB><~2×10<SUP>-7</SUP>, the deepest for
any L dwarf observed to date. The ratio of radio to X-ray luminosity
is at least 4 orders of magnitude in excess of that observed in a
wide range of active stars (including M dwarfs), providing the first
direct confirmation that late-M and L dwarfs violate the radio/X-ray
correlation. The radio emission is due to gyrosynchrotron radiation
in a large-scale magnetic field of about 175 G, which is maintained
on timescales longer than 3 yr. The detected 3 hr period may be due
to (1) the orbital motion of a companion at a separation of about 5
stellar radii, similar to the configuration of RS CVn systems, (2)
an equatorial rotation velocity of about 37 km s<SUP>-1</SUP> and an
anchored, long-lived magnetic field, or (3) periodic release of magnetic
stresses in the form of weak flares. In the case of orbital motion, the
magnetic activity may be induced by the companion, possibly explaining
the unusual pattern of activity and the long-lived signal. We conclude
that fully convective stars can maintain a large-scale and stable
magnetic field, but the lack of X-ray and Hα emission indicates that
the atmospheric conditions are markedly different than in early-type
stars and even M dwarfs. Similar observations are therefore invaluable
for probing both the internal and external structure of low-mass stars
and substellar objects, and for providing constraints on dynamo models.
---------------------------------------------------------
Title: Characterizing the Near-UV Environment of M Dwarfs:
Implications for Extrasolar Planetary Searches and Astrobiology
Authors: Hawley, Suzanne
2005hst..prop10525H Altcode:
We propose SNAP observations with the ACS HRC PR200L prism, designed
to measure the near ultraviolet emission in a sample of 107 nearby M
dwarfs. The sample spans the mass range from 0.1 - 0.6 solar masses
{temperature range 2200K - 4000K} where the UV energy distributions
vary widely between active and inactive stars. The strength and
distribution of this UV emission can have critical consequences for the
atmospheres of attendant planets. Our proposed observations will provide
desperately needed constraints on models of the habitability zone and
the atmospheres of possible terrestrial planets orbiting M dwarf hosts,
and will be used to sharpen TPF target selection. In addition, the NUV
data will be used in conjunction with existing optical, FUV and X-ray
data to constrain a new generation of M dwarf atmospheric models,
and to explore unanswered questions regarding the dynamo generation
and magnetic heating in these low-mass stars.
---------------------------------------------------------
Title: The SuperMACHO Microlensing Survey
Authors: Becker, Andrew C.; Rest, A.; Stubbs, C.; Miknaitis, G. A.;
Miceli, A.; Covarrubias, R.; Hawley, S. L.; Aguilera, C.; Smith,
R. C.; Suntzeff, N. B.; Olsen, K.; Prieto, J. L.; Hiriart, R.; Garg,
A.; Welch, D. L.; Cook, K. H.; Nikolaev, S.; Clocchiatti, A.; Minniti,
D.; Keller, S. C.; Schmidt, B. P.
2005IAUS..225..357B Altcode: 2004astro.ph..9167B
We present the first results from our next-generation microlensing
survey, the SuperMACHO project. We are using the CTIO 4m Blanco
telescope and the MOSAIC imager to carry out a search for microlensing
toward the Large Magellanic Cloud (LMC). We plan to ascertain the nature
of the population responsible for the excess microlensing rate seen by
the MACHO project. Our observing strategy is optimized to measure the
differential microlensing rate across the face of the LMC. We find this
derivative to be relatively insensitive to the details of the LMC's
internal structure but a strong discriminant between Galactic halo
and LMC self lensing. In December 2003 we completed our third year
of survey operations. 2003 also marked the first year of real-time
microlensing alerts and photometric and spectroscopic followup. We
have extracted several dozen microlensing candidates, and we present
some preliminary light curves and related information. Similar to
the MACHO project, we find SNe behind the LMC to be a significant
contaminant - this background has not been completely removed from
our current single-color candidate sample. Our follow-up strategy is
optimized to discriminate between SNe and true microlensing.
---------------------------------------------------------
Title: Cool Stars: Red Dwarfs and Brown Dwarfs
Authors: Hawley, S. L.
2005AAS...206.2201H Altcode: 2005BAAS...37Q.463H
Low mass red dwarfs and brown dwarfs are the coolest stars in the
sky. I will review our current knowledge of these objects and discuss
some interesting problems in their formation and evolution.
---------------------------------------------------------
Title: The Chromospheric Activity and Ages of M Dwarf Stars in Wide
Binary Systems
Authors: Silvestri, Nicole M.; Hawley, Suzanne L.; Oswalt, Terry D.
2005AJ....129.2428S Altcode: 2005astro.ph..2305S
We investigate the relationship between age and chromospheric
activity for 139 M dwarf stars in wide binary systems with white dwarf
companions. The age of each system is determined from the cooling age of
its white dwarf component. The current limit for activity-age relations
found for M dwarfs in open clusters is 4 Gyr. Our unique approach to
finding ages for M stars allows for the exploration of this relationship
at ages older than 4 Gyr. The general trend of stars remaining active
for a longer time at a later spectral type is confirmed. However,
our larger sample and greater age range reveal additional complexity
in assigning age based on activity alone. We find that M dwarfs in
wide binaries older than 4 Gyr depart from the loglinear relation
for clusters and are found to have activity at magnitudes, colors,
and masses that are brighter, bluer, and more massive than predicted
by the cluster relation. In addition to our activity-age results,
we present the measured radial velocities and complete space motions
for 161 white dwarf stars in wide binaries. <P />Based on observations
obtained with the Apache Point Observatory 3.5 m telescope, which is
owned and operated by the Astrophysical Research Consortium; the Cerro
Tololo Inter-American Observatory 4.0 m telescope, which is operated by
the Association of Universities for Research in Astronomy (AURA), Inc.,
under a cooperative agreement with the National Science Foundation
(NSF) as part of the National Optical Astronomy Observatory (NOAO),
which also operates Kitt Peak National Observatory in Tucson, Arizona;
and the SARA Observatory 0.9 m telescope at Kitt Peak, which is owned
and operated by the Southeastern Association for Research in Astronomy
(http://www.saraobservatory.org).
---------------------------------------------------------
Title: Where Are the Magnetic White Dwarfs with Detached,
Nondegenerate Companions?
Authors: Liebert, James; Wickramasinghe, Dayal T.; Schmidt, Gary D.;
Silvestri, Nicole M.; Hawley, Suzanne L.; Szkody, Paula; Ferrario,
Lilia; Webbink, Ronald F.; Oswalt, Terry D.; Smith, J. Allyn; Lemagie,
Mara P.
2005AJ....129.2376L Altcode:
The Sloan Digital Sky Survey has already more than doubled the sample
of white dwarfs with spectral classifications, the subset with detached
M dwarf companions, and the subset of magnetic white dwarfs. In the
course of assessing these new discoveries, we have noticed a curious,
unexpected property of the total lists of magnetic white dwarfs and of
white dwarf plus main-sequence binaries: there appears to be virtually
zero overlap between the two samples! No confirmed magnetic white dwarf
has yet been found in such a pairing with a main-sequence star. The
same statement can be made for the samples of white dwarf-M dwarf
pairs in wide, common proper motion systems. This contrasts with the
situation for interacting binaries, in which an estimated 25% of the
accreting systems have a magnetic white dwarf primary. Alternative
explanations are discussed for the observed absence of magnetic
white dwarf-main-sequence pairs, but the recent discoveries of very
low accretion rate magnetic binaries pose difficulties for each. A
plausible explanation may be that the presence of the companion and
the likely large mass and small radius of the magnetic white dwarf
(relative to nonmagnetic degenerate dwarfs) may provide a selection
effect against the discovery of the latter in such binary systems. More
careful analysis of the existing samples may yet uncover members of
this class of binary, and the sample sizes will continue to grow. The
question of whether the mass and field distributions of the magnetic
primaries in interacting binaries are similar to those of the isolated
magnetic white dwarfs (including those in wider binaries) must also
be answered.
---------------------------------------------------------
Title: Status Report on the SDSS-II Supernova Survey
Authors: Kessler, R.; Adelman-McCarthy, J.; Barentine, J.; Becker,
A.; Boroski, W.; Brewington, H.; Connolly, A.; DeJongh, F.; Dembicky,
J.; Dilday, B.; Doi, M.; Frieman, J.; Gunn, J.; Harvanek, M.; Hawley,
S.; Hendry, J.; Hoeflich, P.; Hogan, C.; Holtzman, J.; Inkmann, J.;
Johnston, D.; Kaplan, J.; Ketzeback, B.; Kilper, G.; Kleinman, A.;
Kleinman, S.; Kron, R. G.; Krughoff, S.; Krzesinski, J.; Lamenti,
D.; Lampeitl, H.; Long, D.; Marriner, J.; McMillan, R.; Miknaitis,
G.; Newman, P. R.; Nichol, R.; Riess, A. G.; Romani, R.; Sako, M.;
Scranton, R.; Snedden, S.; Stoughton, C.; Subbarao, M.; Tucker, D.;
Wang, L.; Yasuda, N.; Yocum, D.; York, D.
2005AAS...206.1507K Altcode: 2005BAAS...37..457K
The SDSS-II Supernova Survey is a proposed optical survey to discover
supernovae in the redshift range 0.05 < z < 0.35, and to measure
their lightcurves for use as a probe of dark energy. The poster will
present preliminary results of a test campaign in the Fall of 2004, as
well as a proposal for a three-year run in 2005-2007. <P />A feasibility
study in September-November of 2004 used the 2.5 m SDSS telescope at APO
to repeat-scan 140 sq. degrees every other night. These scans were used
to discover SN and to measure their lightcurves. A reduction pipeline
running at APO was used to find SN candidates (g and r bands only)
within 2 days; spectra for these candidates were taken by the ARC 3.5
m and HET telescopes. This test run resulted in 16 spectroscopically
confirmed SN Ia, 5 type II and one type Ic. <P />The SDSS-II proposal is
a three-year program to measure 200 SN Ia lightcurves in the five SDSS
bands (ugriz). Compared to the 2004 test run, we anticipate lightcurve
yield improvements as follows: > 2 from longer campaigns, x2 from
increased sky coverage (along with scanning every night instead of every
other night), and better detection efficiency from improved software. In
addition to using the ARC 3.5 and HET telescopes for spectroscopy,
proposals are pending to use the Subaru 8m, WHT 4.2m, NTT 3.5m, VLT
10m, and the Calar Alto 3.5m. <P />Funding for the Sloan Digital Sky
Survey (SDSS) has been provided by the Alfred P. Sloan Foundation,
the Participating Institutions, the National Aeronautics and Space
Administration, the National Science Foundation, the U.S. Department
of Energy, the Japanese Monbukagakusho, and the Max Planck Society.
---------------------------------------------------------
Title: Updated Colors for Cool Stars in the SDSS
Authors: West, Andrew A.; Walkowicz, Lucianne M.; Hawley, Suzanne L.
2005astro.ph..4673W Altcode:
We present updated colors for M and L dwarfs based on photometry from
the third data release of the Sloan Digital Sky Survey (SDSS). These
data are improved in quality and number from earlier results. We also
provide updated equations for determining photometric parallaxes from
SDSS colors of late-type stars. Walkowicz, Hawley & West (2004)
have recently presented new techniques for studying the magnetic
activity of low-mass stars and their method relies on an accurate
determination of SDSS color. We derive new relationships between SDSS
colors and other common passbands and present updated formulas from
Walkowicz et al. (2004) for determining the level of magnetic activity
in M and L dwarfs.
---------------------------------------------------------
Title: The Third Data Release of the Sloan Digital Sky Survey
Authors: Abazajian, Kevork; Adelman-McCarthy, Jennifer K.; Agüeros,
Marcel A.; Allam, Sahar S.; Anderson, Kurt S. J.; Anderson, Scott
F.; Annis, James; Bahcall, Neta A.; Baldry, Ivan K.; Bastian, Steven;
Berlind, Andreas; Bernardi, Mariangela; Blanton, Michael R.; Bochanski,
John J., Jr.; Boroski, William N.; Brewington, Howard J.; Briggs,
John W.; Brinkmann, J.; Brunner, Robert J.; Budavári, Tamás;
Carey, Larry N.; Castander, Francisco J.; Connolly, A. J.; Covey,
Kevin R.; Csabai, István; Dalcanton, Julianne J.; Doi, Mamoru;
Dong, Feng; Eisenstein, Daniel J.; Evans, Michael L.; Fan, Xiaohui;
Finkbeiner, Douglas P.; Friedman, Scott D.; Frieman, Joshua A.;
Fukugita, Masataka; Gillespie, Bruce; Glazebrook, Karl; Gray, Jim;
Grebel, Eva K.; Gunn, James E.; Gurbani, Vijay K.; Hall, Patrick B.;
Hamabe, Masaru; Harbeck, Daniel; Harris, Frederick H.; Harris, Hugh
C.; Harvanek, Michael; Hawley, Suzanne L.; Hayes, Jeffrey; Heckman,
Timothy M.; Hendry, John S.; Hennessy, Gregory S.; Hindsley, Robert
B.; Hogan, Craig J.; Hogg, David W.; Holmgren, Donald J.; Holtzman,
Jon A.; Ichikawa, Shin-ichi; Ichikawa, Takashi; Ivezić, Željko;
Jester, Sebastian; Johnston, David E.; Jorgensen, Anders M.; Jurić,
Mario; Kent, Stephen M.; Kleinman, S. J.; Knapp, G. R.; Kniazev,
Alexei Yu.; Kron, Richard G.; Krzesinski, Jurek; Lamb, Donald Q.;
Lampeitl, Hubert; Lee, Brian C.; Lin, Huan; Long, Daniel C.; Loveday,
Jon; Lupton, Robert H.; Mannery, Ed; Margon, Bruce; Martínez-Delgado,
David; Matsubara, Takahiko; McGehee, Peregrine M.; McKay, Timothy
A.; Meiksin, Avery; Ménard, Brice; Munn, Jeffrey A.; Nash, Thomas;
Neilsen, Eric H., Jr.; Newberg, Heidi Jo; Newman, Peter R.; Nichol,
Robert C.; Nicinski, Tom; Nieto-Santisteban, Maria; Nitta, Atsuko;
Okamura, Sadanori; O'Mullane, William; Owen, Russell; Padmanabhan,
Nikhil; Pauls, George; Peoples, John; Pier, Jeffrey R.; Pope, Adrian
C.; Pourbaix, Dimitri; Quinn, Thomas R.; Raddick, M. Jordan; Richards,
Gordon T.; Richmond, Michael W.; Rix, Hans-Walter; Rockosi, Constance
M.; Schlegel, David J.; Schneider, Donald P.; Schroeder, Joshua;
Scranton, Ryan; Sekiguchi, Maki; Sheldon, Erin; Shimasaku, Kazu;
Silvestri, Nicole M.; Smith, J. Allyn; Smolčić, Vernesa; Snedden,
Stephanie A.; Stebbins, Albert; Stoughton, Chris; Strauss, Michael A.;
SubbaRao, Mark; Szalay, Alexander S.; Szapudi, István; Szkody, Paula;
Szokoly, Gyula P.; Tegmark, Max; Teodoro, Luis; Thakar, Aniruddha R.;
Tremonti, Christy; Tucker, Douglas L.; Uomoto, Alan; Vanden Berk,
Daniel E.; Vandenberg, Jan; Vogeley, Michael S.; Voges, Wolfgang;
Vogt, Nicole P.; Walkowicz, Lucianne M.; Wang, Shu-i.; Weinberg,
David H.; West, Andrew A.; White, Simon D. M.; Wilhite, Brian C.; Xu,
Yongzhong; Yanny, Brian; Yasuda, Naoki; Yip, Ching-Wa; Yocum, D. R.;
York, Donald G.; Zehavi, Idit; Zibetti, Stefano; Zucker, Daniel B.
2005AJ....129.1755A Altcode: 2004astro.ph.10239A
This paper describes the Third Data Release of the Sloan Digital Sky
Survey (SDSS). This release, containing data taken up through 2003
June, includes imaging data in five bands over 5282 deg<SUP>2</SUP>,
photometric and astrometric catalogs of the 141 million objects detected
in these imaging data, and spectra of 528,640 objects selected over 4188
deg<SUP>2</SUP>. The pipelines analyzing both images and spectroscopy
are unchanged from those used in our Second Data Release.
---------------------------------------------------------
Title: From Radio to X-Ray: Flares on the dMe Flare Star EV Lacertae
Authors: Osten, Rachel A.; Hawley, Suzanne L.; Allred, Joel C.;
Johns-Krull, Christopher M.; Roark, Christine
2005ApJ...621..398O Altcode: 2004astro.ph.11236O
We present the results of a campaign to observe flares on the M dwarf
flare star EV Lacertae over the course of two days in 2001 September,
utilizing a combination of radio continuum, optical photometric and
spectroscopic, ultraviolet spectroscopic, and X-ray spectroscopic
observations to characterize the multiwavelength nature of flares from
this active, single, late-type star. We find flares in every wavelength
region in which we observed. A large radio flare from the star was
observed at both 3.6 and 6 cm and is the most luminous example of a
gyrosynchrotron flare yet observed on a dMe flare star. The radio flare
can be explained as encompassing a large magnetic volume, comparable
to the stellar disk, and involving trapped electrons that decay over
timescales of hours. Flux enhancements at 6 cm accompanied by highly
negatively circularly polarized emission (π<SUB>c</SUB>-->-100%)
imply that a coherent emission mechanism is operating in the corona
of EV Lac. There are numerous optical white-light flares, and yet no
signature of emission-line response from the chromosphere appears. Two
small ultraviolet enhancements differ in the amount of nonthermal
broadening present. There are numerous X-ray flares occurring throughout
the observation, and an analysis of undispersed photons and grating
events reveals no evidence for abundance variations. Higher temperatures
are present during some flares; however, the maximum temperature
achieved varies from flare to flare. There is no evidence for density
variations during any flare intervals. In the multiwavelength context,
the start of the intense radio flare is coincident with an impulsive
optical U-band flare, to within 1 minute, and yet there is no signature
of an X-ray response. There are other intervals of time when optical
flaring and UV flaring is occurring, but these cannot be related to
the contemporaneous X-ray flaring: the time-integrated luminosities
do not match the instantaneous X-ray flare luminosity, as one would
expect for the Neupert effect. We investigate the probability of chance
occurrences of flares from disparate wavelength regions producing
temporal coincidences but find that not all the flare associations
can be explained by a superposition of flares due to a high flaring
rate. We caution against making causal associations of multiwavelength
flares based solely on temporal correlations for high flaring rate
stars such as EV Lac.
---------------------------------------------------------
Title: Radio observations of brown dwarfs
Authors: Osten, R. A.; Hawley, S. L.; Bastian, T. S.; Reid, I. N.
2005ESASP.560..857O Altcode: 2005csss...13..857O
No abstract at ADS
---------------------------------------------------------
Title: Long-Period Variables in the Large Magellanic Cloud: Results
from MACHO and 2MASS
Authors: Fraser, Oliver J.; Hawley, Suzanne L.; Cook, Kem H.; Keller,
Stefan C.
2005AJ....129..768F Altcode: 2004astro.ph.10398F
We use the 8 year light-curve database from the MAssive Compact Halo
Objects project together with infrared colors and magnitudes from the
Two Micron All Sky Survey to identify a sample of 22,000 long-period
variables in the Large Magellanic Cloud (referred to hereafter as
LMC LPVs). A period-luminosity diagram of these stars reveals six
well-defined sequences, in substantial agreement with previous analyses
of samples from the Optical Gravitational Lensing Experiment. In
our analysis we identify analogues to Galactic LPVs in the LMC LPV
sample. We find that carbon-dominated asymptotic giant branch (AGB)
stars populate only two of the sequences, one of which includes the
Mira variables. The high-luminosity end of the same two sequences
are also the location of the only stars with J-K<SUB>s</SUB>>2,
indicating that they are enshrouded in dust. The unknown mechanism
that drives the variability of stars in the longest period produces
different morphology in the period-luminosity diagram as compared
with the shortest period sequences, which are thought to be caused
by pulsation. In particular, the longest period sequence extends to
lower luminosity red giant branch stars, and the luminosity function
does not peak among the AGB stars. We point out several features that
will constrain new models of the period-luminosity sequences.
---------------------------------------------------------
Title: The Fall 2004 SDSS Supernova Survey
Authors: Sako, Masao; Romani, Roger; Frieman, Josh; Adelman-McCarthy,
Jen; Becker, Andrew; Dejongh, Fritz; Dilday, Ben; Estrada, Juan;
Hendry, John; Holtzman, Jon; Kaplan, Jared; Kessler, Rick; Lampeitl,
Hubert; Marriner, John; Miknaitis, Gajus; Riess, Adam; Tucker, Douglas;
Barentine, John; Blandford, Roger; Brewington, Howard; Dembicky, Jack;
Harvanek, Mike; Hawley, Suzanne; Hogan, Craig; Johnston, David; Kahn,
Steve; Ketzeback, Bill; Kleinman, Scot; Krzesinski, Jerzy; Lamenti,
Dennis; Long, Dan; McMillan, Russet; Newman, Peter; Nitta, Atsuko;
Nichol, Robert; Scranton, Ryan; Sheldon, Erin; Snedden, Stephanie;
Stoughton, Chris; York, Don; SDSS Collaboration
2005tsra.conf..415S Altcode: 2005astro.ph..4455S
In preparation for the Supernova Survey of the Sloan Digital Sky Survey
(SDSS) II, a proposed 3-year extension to the SDSS, we have conducted
an early engineering and science run during the fall of 2004, which
consisted of approximately 20 scheduled nights of repeated imaging of
half of the southern equatorial stripe. Transient supernova-like events
were detected in near real-time and photometric measurements were made
in the five SDSS filter bandpasses with a cadence of ~ 2 days. Candidate
type Ia supernovae (SNe) were pre-selected based on their colors,
light curve shape, and the properties of the host galaxy. Follow-up
spectroscopic observations were performed with the Astrophysical
Research Consortium 3.5m telescope and the 9.2m Hobby-Eberly Telescope
to confirm their types and measure the redshifts. The 2004 campaign
resulted in 22 spectroscopically confirmed SNe, which includes 16 type
Ia, 5 type II, and 1 type Ib/c. These SN Ia will help fill in the
sparsely sampled redshift interval of z = 0.05-0.35, the so-called
'redshift desert', in the Hubble diagram. Detailed investigation
of the spectral properties of these moderate-redshift SNe Ia will
also provide a bridge between local SNe and high-redshift objects,
and will help us understand the systematics for future cosmological
applications that require high photometric precision. Finally, the
large survey volume also provides the opportunity to select unusual
supernovae for spectroscopic study that are poorly sampled in other
surveys. We report on some of the early results from this program and
discuss potential future applications.
---------------------------------------------------------
Title: New light on dark stars : red dwarfs, low-mass stars,
brown dwarfs
Authors: Reid, I. Neill; Hawley, Suzanne L.
2005nlds.book.....R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Search for Magnetic White Dwarfs in Pre-Cataclysmic
Binaries from the SDSS
Authors: Lemagie, M. P.; Silvestri, N. M.; Hawley, S. L.; Schmidt,
G. D.; Liebert, J.; Wolfe, M. A.
2004AAS...20510305L Altcode: 2004BAAS...36Q1515L
We present the results of our investigation of white dwarfs in several
hundred close binary systems from the SDSS. The close binary systems
in this study are believed to be the progenitors of cataclysmic
variables. Since approximately 25% of the known cataclysmic variables
have magnetic white dwarfs, many of the white dwarfs in our large sample
of pre-cataclysmic binary systems should have a measurable magnetic
field. A cursory inspection of the composite spectra of these systems
however, reveals no obvious magnetic white dwarfs, possibly because
of the low signal-to-noise of the spectrum and/or the contamination
of the white dwarf spectrum by the low mass companion. To reduce
the contamination, we first subtract the low mass companion from
the composite SDSS spectrum. We then smooth and compare the Balmer
absorption features of the remaining DA white dwarf spectrum to magnetic
models at a variety of field strengths. Our search reveals only about
10 magnetic white dwarf stars in these systems. All of the candidate
magnetic white dwarfs have relatively low magnetic field strengths (<
10 MG), as expected. Our techniques for finding magnetic white dwarfs
in these systems, their physical properties, and the implications of
our results are discussed. <P />This work was supported in part by
NSF Grant AST02-05875.
---------------------------------------------------------
Title: First results from the SDSS Supernova Survey
Authors: Lampeitl, H.; Adelman-McCarthy, J.; Barentine, J.; Becker,
A.; Boroski, W.; Brewington, H.; Connolly, A.; DeJongh, F.; Dembicky,
J.; Dilday, B.; Doi, M.; Frieman, J.; Gunn, J.; Harvanek, M.; Hawley,
S.; Hendry, J.; Hoeflich, P.; Hogan, C.; Holtzman, J.; Inkmann, J.;
Johnston, D.; Kaplan, J.; Kessler, R.; Ketzeback, B.; Kilper, G.;
Kleinman, A.; Kleinman, S.; Kron, R. G.; Krughoff, S.; Krzesinski,
J.; Lamenti, D.; Long, D.; Marriner, J.; McMillan, R.; Miknaitis, G.;
Newman, P. R.; Nichol, R.; Riess, A.; Romani, R.; Sako, M.; Scranton,
R.; Snedden, S.; Stoughton, C.; Subbarao, M.; Tucker, D.; Wang, L.;
Yasuda, N.; Yocum, D. R.; York, D.; Sloan Digital Sky Survey
2004AAS...20511404L Altcode: 2005BAAS...37R.374L
The SDSS Supernova Survey is a proposed optical survey to discover
supernovae of type Ia (SN Ia) in the redshift range of z 0.1 to
z<0.3. Data acquisition is intended to take place in the fall
period of 2005, 2006 and 2007 and an additional feasibility study
already carried out in 2004. The final survey will cover a region of
approx. 200 sq. degrees along the celestial equator in imaging using
the well calibrated and understood SDSS 2.5m telescope. Dedicated
spectroscopic follow up observations will be carried out on the ARC
3.5m, the HET and various other telescopes to determine the type and the
redshift of the supernovae. The complete survey is projected to discover
approximately 200 SN Ia with well measured lightcurves. <P />The
feasibility study carried out in October and November 2004 resulted
in 11 useful nights of imaging data under various sky conditions and
covered a field of view of approx 100 sq. degrees. The imaging data
has been reduced and visually inspected usually within 48 hours to
allow for fast spectroscopic follow up observations. So far more than
10 SN Ia have been identified spectroscopically by using the ARC 3.5m
telescope and the HET. In addition several SN of various other types
have been discovered. The poster will give an outline of the search
strategy and will present preliminary lightcurves and spectra of the
newly discovered supernova. <P />Funding for the Sloan Digital Sky
Survey (SDSS) has been provided by the Alfred P. Sloan Foundation,
the Participating Institutions, the National Aeronautics and Space
Administration, the National Science Foundation, the U.S. Department
of Energy, the Japanese Monbukagakusho, and the Max Planck Society.
---------------------------------------------------------
Title: Radio Observations of Brown Dwarfs
Authors: Quick, L. C.; Osten, R.; Bastian, T.; Hawley, S.
2004AAS...205.1101Q Altcode: 2004BAAS...36.1351Q
Radio emission commonly signifies the presence of magnetic
activity in the coronae of late-type stars, while emission from
the H-alpha transition is a sign of magnetic activity in their
chromospheres. Surveys of H-alpha emission from ultracool dwarfs of
spectral types late M, L, and T have not shown this indicator of
magnetic activity. As a result, it was believed that all magnetic
activity declined in these cool bodies. Although sparse, the most
recent detections of radio emission contradict this behavior. As
part of a large VLA survey of nearby ultracool dwarfs out to 13pc,
the aim of my research was to determine how common radio emission is
in these late-type stars. Data from 9 L and T dwarfs was reduced, and
evidence for emission was detected from three of these objects. This
research was conducted as a part of the NRAO Summer Student program,
with partial funding from the National Science Foundation.
---------------------------------------------------------
Title: A Spectroscopic Survey of M Dwarfs within 100 Parsecs of
the Sun
Authors: Bochanski, J. J.; Hawley, S. L.; Reid, I. N.; Covey, K.;
Munn, J. A.; Tinney, C. G.
2004AAS...205.5506B Altcode: 2004BAAS...36S1431B
Low mass M dwarfs are the dominant stellar component in the
Universe. Their ubiquity and longevity make them ideal tracers of
galactic populations. Using 12 Schmidt plates from both northern and
southern galactic hemispheres, we constructed a sample of M dwarfs to
distances of about 100 pc, to investigate the dependence of magnetic
activity on location in the Galaxy. We have also investigated the
kinematics of active and non-active M dwarfs at various distances from
the Galactic plane. We find that there is no statistically significant
variation in activity for equidistant locations above and below the
plane. We also confirm that active stars are a younger dynamical
population. <P />We gratefully acknowledge the support of NSF grant
AST02-05875 and NASA ADP grant NAG5-13111.
---------------------------------------------------------
Title: The Quiescent Atmosphere of the dMe Flare Star EV Lacertae
Authors: Osten, R. A.; Hawley, S. L.; Johns-Krull, C. M.; Brown, A.;
Allred, J.
2004AAS...205.5507O Altcode: 2004BAAS...36.1431O
We report on multi-wavelength spectroscopic observations of the
M dwarf flare star, EV Lacertae, during quiescent intervals. The
study of extreme coronae, such as on M dwarf flare stars, allows an
investigation into regimes of temperature, density, and activity not
available from spatially detailed studies of our low-activity Sun. Our
investigation makes use of simultaneous Chandra HETGS and HST/STIS
high resolution spectra, along with non-contemporaneous FUSE and
EUVE spectra, to probe the characteristics of the outer atmospheric
plasma from the upper chromosphere to the corona. A detailed study of
the coronal spectrum finds evidence of the inverse First Ionization
Potential (FIP) effect, commonly seen in active stars. We examine the
structures producing this emission through the shape of the emission
measure distribution over a span of three decades in temperature,
and the variation of electron density with electron temperature over a
similar range. The correspondence of elements with ionic transitions in
both X-ray and UV spectral ranges allows us to investigate the region
in the atmosphere where the coronal abundance fractionation pattern
begins. <P />RAO acknowledges funding through a Jansky fellowship from
NRAO. RAO acknowledges funding through grants from SAO and STScI.
---------------------------------------------------------
Title: The Evolution of Low Mass Stars in Close Binary Systems
Authors: Silvestri, N. M.; Hawley, S. L.; Szkody, P.; Bochanski, J. J.;
West, A. A.; Fraser, O. J.; Covey, K. R.; Wolfe, M. A.; Vanlandingham,
K. M.; Dang, L. C.; SDSS Collaboration
2004AAS...20512005S Altcode: 2004BAAS...36.1549S
We report on our extensive investigation of the evolution of low mass
stars in close binary systems with white dwarfs. Cataclysmic variables
(CVs), which are the most numerous UV and X-ray sources in the Galaxy,
and Type Ia supernovae, which are standard candles for cosmology,
are believed to be the end products of these close binary systems,
but little is known about their evolution before they reach the CV
stage. In particular, we are studying the influence of the binary
environment on the evolution of the low mass secondary star (typically
an M dwarf), and investigating how the properties of the M dwarf
are impacted by the presence of the white dwarf primary. Using our
growing sample of over 700 M dwarf-white dwarf close binary systems
identified spectroscopically in the Sloan Digital Sky Survey, we
determine spectral types and magnetic activity properties of the M
dwarfs, and effective temperatures and gravities of the white dwarfs,
which allows us to determine their ages. Candidate systems with very
active secondaries are then observed using time-series spectroscopy
on the ARC 3.5m to find their orbital periods. Candidates are also
observed using photometric time-series on the MDM 2.4m to search for
variability (eclipses, rotational modulation). We have now compiled
a sample of systems with a wide range of orbital period and age, and
will discuss our results on the properties of the secondary stars, and
compare them to recent field M dwarf studies (e.g. West et al. 2004). <P
/>This work was supported in part by NSF Grant AST02-05875.
---------------------------------------------------------
Title: The SDSS Supernova Survey
Authors: Frieman, J.; Adelman-McCarthy, J.; Barentine, J.; Becker, A.;
Boroski, W.; Brewington, H.; Connolly, A.; DeJongh, F.; Dembicky, J.;
Dilday, B.; Doi, M.; Gunn, J.; Harvanek, M.; Hawley, S.; Hoeflich,
P.; Hogan, C.; Holtzman, J.; Johnston, D.; Kaplan, J.; Kessler, R.;
Ketzeback, B.; Kilper, G.; Kleinman, A.; Kleinman, S.; Kron, R. G.;
Krughoff, S.; Krzesinski, J.; Lamenti, D.; Lampeitl, H.; Long, D.;
Marriner, J.; McMillan, R.; Miknaitis, G.; Newman, P. R.; Nichol,
R.; Riess, A.; Romani, R.; Sako, M.; Scranton, R.; Snedden, S.;
Stoughton, C.; Subbarao, M.; Tucker, D.; Wang, L.; Yasuda, N.; York,
D.; SDSS Affiliation
2004AAS...20512001F Altcode: 2004BAAS...36.1548F
The proposed SDSS II includes a Supernova Survey that will encompass
three 3-month seasons, Sept.-Nov. 2005-7, with the aim of obtaining
well-sampled, well-calibrated, multi-band lightcurves for 200 Type Ia
supernovae in the redshift `desert' z = 0.1-0.35. This sample, with
photometric data over 250 square degrees imaged every other night from a
single instrument with well-understood wavelength response, will yield
improved constraints on the dark energy and enable detailed study of
the systematics of the Ia population as they affect the use of these
objects as standard candles for cosmology. The survey will include
spectroscopic follow-up on other telescopes for SN identification and
redshift determination, near-infrared imaging follow-up to constrain
host galaxy extinction, and multi-epoch spectrophotometry for a
subsample in order to obtain improved K corrections. In preparation for
SDSS II, the collaboration is carrying out 20 nights of repeat imaging
on the SDSS 2.5m telescope in Fall 2004, with follow-up planned on the
ARC 3.5m, HET, and other telescopes. This talk will describe the goals,
status, and early results from the SDSS Supernova Survey. It will also
briefly describe the sample of nearby supernovae discovered in SDSS
galaxy spectra. <P />Funding for the Sloan Digital Sky Survey (SDSS)
has been provided by the Alfred P. Sloan Foundation, the Participating
Institutions, the National Aeronautics and Space Administration,
the National Science Foundation, the U.S. Department of Energy, the
Japanese Monbukagakusho, and the Max Planck Society.
---------------------------------------------------------
Title: Thin Disk Dynamical Heating and the Activity of Low Mass Dwarfs
Authors: Silvestri, N. M.; West, A. A.; Hawley, S. L.; Cruz, K.;
Reid, I. N.; Liebert, J. W.
2004AAS...20511402S Altcode: 2004BAAS...36.1542S
We present a continuing analysis of the magnetic activity of thousands
of M-dwarfs from the Sloan Digital Sky Survey (SDSS) and 2MASS. We
confirm the trend described by West et al. (2004) that the fraction
of active stars decreases as a function of vertical distance from
the galactic plane. This result suggests that the older stars, which
have undergone more dynamical heating, are also less likely to remain
active, a further confirmation of an age-activity relation. We also
investigate a possible variation in the amount of activity (as measured
by L<SUB>H-alpha</SUB>/L<SUB>bol</SUB>) as a function of distance
from the plane and find that there is no statistically significant
trend. These data imply that older stars continue to have the same
distribution of activity until they cease being active.
---------------------------------------------------------
Title: A Second Stellar Color Locus: a Bridge from White Dwarfs to
M stars
Authors: Smolcic, V.; Ivezic, Z.; Knapp, G. R.; Lupton, R. H.;
Pavlovski, K.; Ilijic, S.; Schlegel, D.; Smith, J. A.; McGehee, P. M.;
Silvestri, N. M.; Hawley, S. L.; Rockosi, C.; Gunn, J. E.; Strauss,
M. A.
2004ASPC..318..396S Altcode: 2004ssrc.conf..396S
We report the discovery of a locus of stars in the SDSS g-r vs. u-g
color-color diagram that connects the colors of white dwarfs and M
dwarfs. While its contrast with respect to the main stellar locus
is only ∼1:2300, this previously unrecognized feature includes 863
stars from SDSS Data Release 1. The position and shape of the feature
is in good agreement with predictions of a simple binary star model
that consists of a white dwarf and an M dwarf, with the components'
luminosity ratio controlling the position along this binary system
locus. SDSS DR1 spectra for 47 of these objects strongly support
this model.
---------------------------------------------------------
Title: A Second Stellar Color Locus: a Bridge from White Dwarfs to
M stars
Authors: Smolčić, Vernesa; Ivezić, Željko; Knapp, Gillian R.;
Lupton, Robert H.; Pavlovski, Krešimir; Ilijić, Saša; Schlegel,
David; Smith, J. Allyn; McGehee, Peregrine M.; Silvestri, Nicole M.;
Hawley, Suzanne L.; Rockosi, Constance; Gunn, James E.; Strauss,
Michael A.; Fan, Xiaohui; Eisenstein, Daniel; Harris, Hugh
2004ApJ...615L.141S Altcode: 2004astro.ph..3218S
We report the discovery of a locus of binary stars in the Sloan Digital
Sky Survey (SDSS) g-r versus u-g color-color diagram that connects
the colors of white dwarfs and M dwarfs. While its contrast with
respect to the main stellar locus is only ~1:2300, this previously
unrecognized feature includes 863 stars from the SDSS Data Release 1
(DR1). The position and shape of the feature are in good agreement
with predictions of a simple binary star model that consists of a
white dwarf and an M dwarf, with the components' luminosity ratio
controlling the position along this binary system locus. SDSS DR1
spectra for 47 of these objects strongly support this model. The
absolute magnitude-color distribution inferred for the white dwarf
component is in good agreement with the models of Bergeron et al.
---------------------------------------------------------
Title: The χ Factor: Determining the Strength of Activity in
Low-Mass Dwarfs
Authors: Walkowicz, Lucianne M.; Hawley, Suzanne L.; West, Andrew A.
2004PASP..116.1105W Altcode: 2004astro.ph.10422W
We describe a new, distance-independent method for
calculating the magnetic activity strength in low-mass dwarfs,
L<SUB>Hα</SUB>/L<SUB>bol</SUB>. Using a well-observed sample of
nearby stars and cool standards spanning spectral type M0.5 to L0,
we compute χ, the ratio between the continuum flux near Hα and the
bolometric flux, f<SUB>λ6560</SUB>/f<SUB>bol</SUB>. This ratio can be
multiplied by the measured equivalent width of the Hα emission line
to yield L<SUB>Hα</SUB>/L<SUB>bol</SUB>. We provide χ values for
all objects in our sample, and also fits to χ as a function of color
and average values by spectral type. This method was used by West et
al. to examine trends in magnetic activity strength in low-mass stars.
---------------------------------------------------------
Title: Cataclysmic Variables from the Sloan Digital Sky
Survey. III. The Third Year
Authors: Szkody, Paula; Henden, Arne; Fraser, Oliver; Silvestri,
Nicole; Bochanski, John; Wolfe, Michael A.; Agüeros, Marcel; Warner,
Brian; Woudt, Patrick; Tramposch, Jonica; Homer, Lee; Schmidt, Gary;
Knapp, Gillian R.; Anderson, Scott F.; Covey, Kevin; Harris, Hugh;
Hawley, Suzanne; Schneider, Donald P.; Voges, Wolfgang; Brinkmann, J.
2004AJ....128.1882S Altcode:
This paper continues the series that identifies new cataclysmic
variables found in the Sloan Digital Sky Survey (SDSS). We present
36 cataclysmic variables and one possible symbiotic star from Sloan
spectra obtained during 2002, of which 34 are new discoveries, two are
known dwarf novae (BC UMa and KS UMa), and one is a known cataclysmic
variable identified from the Two-Degree Field survey. The positions,
colors, and spectra of all 37 systems are presented, along with
follow-up spectroscopic/photometric observations of 10 systems. As
in the past 2 yr of data, the new SDSS systems show a large variety
of characteristics based on their inclination and magnetic fields,
including three eclipsing systems, four with prominent He II emission,
and 15 systems showing features of the underlying stars. <P />Based
on observations obtained with the Sloan Digital Sky Survey and with
the Apache Point Observatory (APO) 3.5 m telescope, which are owned
and operated by the Astrophysical Research Consortium.
---------------------------------------------------------
Title: Chandra Observation of V426 Ophiuchi: Weighing the Evidence
for a Magnetic White Dwarf
Authors: Homer, Lee; Szkody, Paula; Raymond, John C.; Fried, Robert E.;
Hoard, D. W.; Hawley, S. L.; Wolfe, M.; Tramposch, J. N.; Yirak, K. T.
2004ApJ...610..991H Altcode: 2004astro.ph..4289H
We report the results of a 45 ks Chandra observation of the cataclysmic
variable (CV) V426 Ophiuchus. The high-resolution spectrum from the
high-energy transmission grating spectrometer is most consistent with a
cooling flow model, placing V426 Oph among the group of CVs including
U Gem and EX Hya. An uninterrupted light curve was also constructed,
in which we detect a significant 4.2 hr modulation together with its
first harmonic at 2.1 hr. Reanalysis of archival Ginga and ROSAT X-ray
light curves also reveals modulations at periods consistent with 4.2
and/or 2.1 hr. Furthermore, optical photometry in V, simultaneous with
the Chandra observation, indicates a modulation anticorrelated with
the X-ray, and later more extensive R-band photometry finds a signal at
~2.1 hr. The earlier reported X-ray periods at ~0.5 and 1 hr appear to
be only transient and quasi-periodic in nature. In contrast, the 4.2
hr period or its harmonic is stable and persistent in X-ray/optical
data from 1988 to 2003. This periodicity is clearly distinct from
the 6.85 hr orbit and could be due to the spin of the white dwarf. If
this is the case, V426 Oph would be the first long-period intermediate
polar with a ratio P<SUB>spin</SUB>/P<SUB>orb</SUB> of 0.6. However,
this interpretation requires unreasonable values of magnetic field
strength and mass accretion rate.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Catalog of white dwarfs in SDSS-DR1
(Kleinman+, 2004)
Authors: Kleinman, S. J.; Harris, H. C.; Eisenstein, D. J.; Liebert,
J.; Nitta, A.; Krzesinski, J.; Munn, J. A.; Dahn, C. C.; Hawley,
S. L.; Pier, J. R.; Schmidt, G.; Silvestri, N. M.; Smith, J. A.;
Szkody, P.; Strauss, M. A.; Knapp, G. R.; Collinge, M. J.; Mukadam,
A. S.; Koester, D.; Uomoto, A.; Schlegel, D. J.; Anderson, S. F.;
Brinkmann, J.; Lamb, D. Q.; Schneider, D. P.; York, D. G.
2004yCat..16070426K Altcode:
We present the full spectroscopic white dwarf and hot subdwarf sample
from the Sloan Digital Sky Survey (SDSS) First Data Release, DR1. We
find 2551 white dwarf stars of various types, 240 hot subdwarf stars,
and an additional 144 objects we have identified as uncertain white
dwarf stars. Of the white dwarf stars, 1888 are nonmagnetic DA types
and 171 are nonmagnetic DBs. The remaining (492) objects consist of all
different types of white dwarf stars: DO, DQ, DC, DH, DZ, hybrid stars
such as DAB, etc., and those with nondegenerate companions. We fit the
DA and DB spectra with a grid of models to determine the T<SUB>eff</SUB>
and logg for each object. For all objects, we provide coordinates,
proper motions, SDSS photometric magnitudes, and enough information
to retrieve the spectrum/image from the SDSS public database. This
catalog nearly doubles the known sample of spectroscopically identified
white dwarf stars. In the DR1 imaged area of the sky, we increase the
known sample of white dwarf stars by a factor of 8.5. We also comment
on several particularly interesting objects in this sample. <P />(6
data files).
---------------------------------------------------------
Title: Spectroscopic Properties of Cool Stars in the Sloan Digital Sky
Survey: An Analysis of Magnetic Activity and a Search for Subdwarfs
Authors: West, Andrew A.; Hawley, Suzanne L.; Walkowicz, Lucianne
M.; Covey, Kevin R.; Silvestri, Nicole M.; Raymond, Sean N.; Harris,
Hugh C.; Munn, Jeffrey A.; McGehee, Peregrine M.; Ivezić, Željko;
Brinkmann, J.
2004AJ....128..426W Altcode: 2004astro.ph..3486W
We present a spectroscopic analysis of nearly 8000 late-type dwarfs
in the Sloan Digital Sky Survey. Using the Hα emission line as an
activity indicator, we investigate the fraction of active stars as
a function of spectral type and find a peak near type M8, confirming
previous results. In contrast to past findings, we find that not all
M7-M8 stars are active. We show that this may be a selection effect
of the distance distributions of previous samples, since the active
stars appear to be concentrated near the Galactic plane. We also
examine the activity strength (ratio of the luminosity emitted in Hα
to the bolometric luminosity) for each star and find that the mean
activity strength is constant over the range M0-M5 and declines at
later types. The decline begins at a slightly earlier spectral type
than previously found. We explore the effect that activity has on
the broadband photometric colors and find no significant differences
between active and inactive stars. We also carry out a search for
subdwarfs using spectroscopic metallicity indicators and find 60
subdwarf candidates. Several of these candidates are near the extreme
subdwarf boundary. The spectroscopic subdwarf candidates are redder
by ~0.2 mag in g-r compared with disk dwarfs at the same r-i color.
---------------------------------------------------------
Title: Cataclysmic Variables from SDSS III. The Third Year
Authors: Szkody, Paula; Henden, Arne; Fraser, Oliver; Silvestri,
Nicole; Bochanski, John; Wolfe, Michael A.; Agüeros, Marcel; Warner,
Brian; Woudt, Patrick; Tramposch, Jonica; Homer, Lee; Schmidt, Gary;
Knapp, Gillian R.; Anderson, Scott F.; Covey, Kevin; Harris, Hugh;
Hawley, Suzanne; Schneider, Donald P.; Voges, Wolfgang; Brinkmann, J.
2004astro.ph..7071S Altcode:
This paper continues the series that identifies new cataclysmic
variables found in the Sloan Digital Sky Survey. We present 36
cataclysmic variables and one possible symbiotic star from Sloan
spectra obtained during 2002, of which 34 are new discoveries, 2 are
known dwarf novae (BC UMa, KS UMa) and one is a known CV identified from
the 2dF survey. The positions, colors and spectra of all 37 systems are
presented, along with follow-up spectroscopic/photometric observations
of 10 systems. As in the past 2 years of data, the new SDSS systems
show a large variety of characteristics based on their inclination
and magnetic fields, including 3 eclipsing systems, 4 with prominent
He II emission, and 15 systems showing features of the underlying stars.
---------------------------------------------------------
Title: Meeting the Cool Neighbors. VIII. A Preliminary 20 Parsec
Census from the NLTT Catalogue
Authors: Reid, I. Neill; Cruz, Kelle L.; Allen, Peter; Mungall, F.;
Kilkenny, D.; Liebert, James; Hawley, Suzanne L.; Fraser, Oliver J.;
Covey, Kevin R.; Lowrance, Patrick; Kirkpatrick, J. Davy; Burgasser,
Adam J.
2004AJ....128..463R Altcode: 2004astro.ph..4061R
Continuing our census of late-type dwarfs in the solar neighborhood,
we present BVRI photometry and optical spectroscopy of 800
mid-type M dwarfs drawn from the NLTT proper-motion catalog. The
targets are taken both from our own cross-referencing of the NLTT
Catalogue and the 2MASS Second Incremental Data Release, and from
the revised NLTT compiled recently by Salim & Gould. All are
identified as nearby-star candidates based on their location in the
(m<SUB>r</SUB>,m<SUB>r</SUB>-K<SUB>s</SUB>) diagram. Three hundred stars
discussed here have previous astrometric, photometric, or spectroscopic
observations. We present new BVRI photometry for 101 stars, together
with low-resolution spectroscopy of a further 400 dwarfs. In total,
we find that 241 stars are within 20 pc of the Sun, while a further 70
lie within 1 σ of our distance limit. Combining the present results
with previous analyses, we have quantitative observations for 1910 of
the 1913 candidates in our NLTT nearby-star samples. Eight hundred
fifteen of those stars have distance estimates of 20 pc or less,
including 312 additions to the local census. With our NLTT follow-up
observations essentially complete, we have searched the literature
for K and early-type M dwarfs within the sampling volume covered by
the 2MASS second release. Comparing the resultant 20 pc census against
predicted numbers, derived from the 8 pc luminosity function, shows an
overall deficit of ~20% for stellar systems and ~35% for individual
stars. Almost all are likely to be fainter than M<SUB>J</SUB>=7, and
at least half are probably as yet undiscovered companions of known
nearby stars. Our results suggest that there are relatively few missing
systems at the lowest luminosities, M<SUB>J</SUB>>8.5. We discuss
possible means of identifying the missing stars.
---------------------------------------------------------
Title: Investigation of M Dwarf Atmospheres Using Archival STIS Data
Authors: Hawley, Suzanne
2004hst..prop10312H Altcode: 2004hst..prop.6630H
We propose an archival study of the STIS/MAMA data from program
GO-8129. The data comprise the only high-resolution, near-ultraviolet
spectra in the HST archive, and indeed in existence, for an M dwarf. We
will analyze the six orbits of data to find periods of quiescence
{between obvious flares}, and will produce a high signal-to-noise
ratio summed quiescent spectrum for analysis. Using the CHIANTI
database together with detailed radiative hydrodynamic models,
we will investigate the outer atmospheric structure of active M
dwarfs. Employing hundreds of lines in the archival spectrum as
constraints, we will construct the first self-consistent model of an
M dwarf atmosphere.
---------------------------------------------------------
Title: Chandra X-ray results on V426 Ophiuchi
Authors: Homer, L.; Szkody, P.; Raymond, J. C.; Fried, R. E.; Hoard,
D. W.; Hawley, S. L.; Wolfe, M.; Tramposch, J. N.; Yirak, K. T.
2004RMxAC..20..176H Altcode: 2004IAUCo.194..176H
From a 45ks Chandra observation of V426 Oph we have obtained
high-resolution X-ray spectra at moderate signal-to-noise, and a good
quality, uninterrupted lightcurve. The spectra are reasonably fit with
a cooling flow model, similar to EX Hya and U Gem. Our analysis of the
Chandra and additional X-ray/optical lightcurves reveals a persistent
modulation at 4.2 hr from 1988 to 2003, likely the white dwarf spin
period indicating an intermediate polar nature for V426 Oph.
---------------------------------------------------------
Title: Radiative Hydrodynamic Simulations of Solar and Stellar Flares
Authors: Allred, J. C.; Hawley, S. L.; Abbett, W. P.
2004AAS...204.0305A Altcode: 2004BAAS...36..671A
We have constructed radiative hydrodynamic simulations of the effects
of flare heating on model solar and dMe stellar atmospheres. The
heating is assumed to be driven by a beam of non-thermal electrons
originating in the corona and impacting on the lower transition region
and chromosphere. We use thick target bremsstrahlung fits to RHESSI
hard X-ray observations of the July 23, 2002 and February 26, 2002
flares to model the electron beam. Our simulations include detailed
calculations of numerous bound-bound and bound-free transitions which
we compare with line profiles measured during flares on the Sun and on
the dMe star AD Leo. We also investigate the possibility that the 511
keV emission line is produced from a significant amount of material
at transition region temperatures.
---------------------------------------------------------
Title: A Strategy for Finding Near-Earth Objects with the SDSS
Telescope
Authors: Raymond, Sean N.; Miknaitis, Gajus; Fraser, Oliver J.; Garg,
Arti; Hawley, Suzanne L.; Jedicke, Robert; Quinn, Thomas; Rockosi,
Constance M.; Stubbs, Christopher W.; Anderson, Scott F.; Hogan,
Craig J.; Ivezić, Željko; Lupton, Robert H.; West, Andrew A.;
Brewington, Howard; Brinkmann, J.; Harvanek, Michael; Kleinman,
Scot J.; Krzesiński, Jurek; Long, Dan; Neilsen, Eric H.; Newman,
Peter R.; Nitta, Atsuko; Snedden, Stephanie A.
2004AJ....127.2978R Altcode: 2004astro.ph..1438R
We present a detailed observational strategy for finding near-Earth
objects (NEOs) with the Sloan Digital Sky Survey (SDSS) telescope. We
investigate strategies in normal, unbinned mode, as well as binning
the CCDs 2×2 or 3×3, which affects the sky coverage rate and the
limiting apparent magnitude. We present results from 1 month, 3 year,
and 10 year simulations of such surveys. For each cadence and binning
mode, we evaluate the possibility of achieving the Spaceguard goal of
detecting 90% of 1 km NEOs (absolute magnitude H<=18 for an albedo
of 0.1). We find that an unbinned survey is most effective at detecting
H<=20 NEOs in our sample. However, a 3×3 binned survey reaches
the Spaceguard goal after only 7 years of operation. As the proposed
large survey telescopes (Pan-STARRS, LSST) are at least 5-10 years from
operation, an SDSS NEO survey could make a significant contribution
to the detection and photometric characterization of the NEO population.
---------------------------------------------------------
Title: Spectroscopic Properties of Cool Stars in the SDSS
Authors: Hawley, S. L.; West, A. A.; Walkowicz, L. M.; Covey, K. R.
2004AAS...204.0307H Altcode: 2004BAAS...36..672H
We present a spectroscopic analysis of nearly 8000 late-type dwarfs
in the Sloan Digital Sky Survey. Using the H-alpha emission line as
an activity indicator, we investigate the fraction of active stars as
a function of spectral type and find a peak near type M8, confirming
previous results. In contrast to past findings, we find that not all
M7-M8 stars are active. We show that this may be a selection effect of
the distance distributions of previous samples, as the active stars
appear to be concentrated near the Galactic Plane. We also examine
the activity strength (ratio of the luminosity emitted in H-alpha
to the bolometric luminosity) for each star, and find that the mean
activity strength is constant over the range M0-M5 and declines at
later types. The decline begins at a slightly earlier spectral type
than previously found. We explore the effect that activity has on
the broadband photometric colors and find no significant differences
between active and inactive stars. We also carry out a search for
subdwarfs using spectroscopic metallicity indicators, and find 60
subdwarf candidates. Several of these candidates are near the extreme
subdwarf boundary. The spectroscopic subdwarf candidates are redder by
approx. 0.2 magnitudes in (g-r) compared to disk dwarfs at the same
(r-i) color. <P />A paper describing these results is scheduled for
the June 2004 issue of the Astronomical Journal. This work is supported
by NSF grant AST 02-05875.
---------------------------------------------------------
Title: A Catalog of Spectroscopically Identified White Dwarf Stars
in the First Data Release of the Sloan Digital Sky Survey
Authors: Kleinman, S. J.; Harris, Hugh C.; Eisenstein, Daniel J.;
Liebert, James; Nitta, Atsuko; Krzesiński, Jurek; Munn, Jeffrey A.;
Dahn, Conard C.; Hawley, Suzanne L.; Pier, Jeffrey R.; Schmidt, Gary;
Silvestri, Nicole M.; Smith, J. Allyn; Szkody, Paula; Strauss, Michael
A.; Knapp, G. R.; Collinge, Matthew J.; Mukadam, A. S.; Koester, D.;
Uomoto, Alan; Schlegel, D. J.; Anderson, Scott F.; Brinkmann, J.;
Lamb, D. Q.; Schneider, Donald P.; York, Donald G.
2004ApJ...607..426K Altcode: 2004astro.ph..2209K
We present the full spectroscopic white dwarf and hot subdwarf sample
from the Sloan Digital Sky Survey (SDSS) first data release, DR1. We
find 2551 white dwarf stars of various types, 240 hot subdwarf stars,
and an additional 144 objects we have identified as uncertain white
dwarf stars. Of the white dwarf stars, 1888 are nonmagnetic DA types
and 171 are nonmagnetic DBs. The remaining (492) objects consist of all
different types of white dwarf stars: DO, DQ, DC, DH, DZ, hybrid stars
such as DAB, etc., and those with nondegenerate companions. We fit the
DA and DB spectra with a grid of models to determine the T<SUB>eff</SUB>
and logg for each object. For all objects, we provide coordinates,
proper motions, SDSS photometric magnitudes, and enough information to
retrieve the spectrum/image from the SDSS public database. This catalog
nearly doubles the known sample of spectroscopically identified white
dwarf stars. In the DR1 imaged area of the sky, we increase the known
sample of white dwarf stars by a factor of 8.5. We also comment on
several particularly interesting objects in this sample.
---------------------------------------------------------
Title: Persistent Transition Region Emission in Very Low Mass Stars
Authors: Hawley, S. L.; Johns-Krull, C. M.
2004IAUS..219..306H Altcode: 2003IAUS..219E.216H
We present results from our cycle 10 HST program to search for
transition region emission in very low-mass main-sequence stars in the
spectral range M7-M9. flaring and quiescent origin for the emission. We
have obtained HST/STIS time series observations of three active very low
mass stars (VB 8 VB 10 and LHS 2065) which show persistent activity in
transition region lines including C IV Si IV and He II. The emission
in these transition region lines is variable between exposures but
is always observed. A strong flare was observed in one 10 minute
exposure on VB 10. Our results indicate that active very low-mass
stars maintain a persistent quiescent chromosphere and transition
region that is similar to those observed in active earlier type M
dwarfs in contrast to suggestions that these low-mass main-sequence
stars exhibit only flaring activity.
---------------------------------------------------------
Title: Magnetic Activity in Low Mass Stars: SDSS Results
Authors: West, A. A.; Hawley, S. L.; Walkowicz, L. M.; Covey, K. R.
2004IAUS..219..935W Altcode: 2003IAUS..219E.232W
We present a study of the magnetic activity properties of low-mass
stars in the Sloan Digital Sky Survey. Using the H-alpha emission line
as an activity indicator we examine the fraction of active stars as
a function of spectral type and find a peak near type M7 confirming
previous results. However contrary to past findings we find that not
all M7 stars are active. We investigate the ratio of the luminosity
emitted in H-alpha compared to the bolometric luminosity for each star
and find a roughly constant ratio (with large scatter) over the range
M0-M7. There appears to be a slight decrease in this ratio for types
M8-L0 in agreement with previous determinations. We also explore the
effect of metallicity on activity and examine whether activity is
correlated with changes in SDSS colors.
---------------------------------------------------------
Title: Multi-Wavelength Observations of EV Lacertae
Authors: Osten, R. A.; Hawley, S. L.; Allred, J.; Johns-Krull, C. M.;
Roark, C.; Ambruster, C.; Brown, A.; Ayres, T. R.; Linsky, J. L.
2004IAUS..219..249O Altcode: 2003IAUS..219E.207O
We present an analysis of simultaneous radio optical UV and
X-ray observations of the dMe flare star EV Lacertae taken in 2001
September. The analysis is time-resolved and concentrates on determining
flare-related changes in each spectral region. Temporal correlations
in different wavelength regions are examined. Numerous X-ray flares
were observed; two X-ray flares are accompanied by UV enhancements
in a pattern reminiscent of the Neupert effect seen in solar flares
where UV bursts are interpreted as a product of nonthermal heat input
to the lower atmosphere and soft X-ray emission occurs as a result of
the heating. An extemely large radio flare seen at two frequencies
and representing a factor of 100 increase in quiescent radio flux
density has an optical counterpart with an enhancement of about 3
magnitudes in the U filter. There is no corresponding increase in
soft X-ray flux. We investigate scenarios which could give rise to the
observed multi-wavelength correlations. The run of electron density with
temperature in the outer atmosphere (transition region through corona)
is investigated and implications for coronal structure are given.
---------------------------------------------------------
Title: HST, EUVE and Ground-Based Observations of Flares on AD Leo
Authors: Allred, J. C.; Hawley, S. L.; Johns-Krull, C. M.; Fisher,
G. H.; Abbett, W. P.; Avgoloupis, S. I.; Seiradakis, J. H.
2004IAUS..219..829A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: VizieR Online Data Catalog: Spectroscopy of faint red NLTT
dwarfs (Reid+, 2003)
Authors: Reid, I. N.; Cruz, K. L.; Allen, P.; Mungall, F.; Kilkenny,
D.; Liebert, J.; Hawley, S. L.; Fraser, O. J.; Covey, K. R.;
Lowrance, P.
2004yCat..51263007R Altcode:
We present low-resolution optical spectroscopy and BVRI
photometry of 453 candidate nearby stars drawn from the NLTT
(<I/98>) proper-motion catalog. The stars were selected based on
optical/near-infrared colors, derived by combining the NLTT photographic
data with photometry from the 2MASS Second Incremental Data Release
(<II/241>). Based on the derived photometric and spectroscopic
parallaxes, we identify 111 stars as lying within 20pc of the Sun,
including nine stars with formal distance estimates of less than
10pc. A further 53 stars have distance estimates within 1σ of our
20pc limit. Almost all of those stars are additions to the nearby-star
census. In total, our NLTT-based survey has so far identified 496 stars
likely to be within 20pc, of which 195 are additions to nearby-star
catalogs. Most of the newly identified nearby stars have spectral
types between M4 and M8. <P />(5 data files).
---------------------------------------------------------
Title: Recent Advances in Understanding Star and Planet Formation
Authors: Reid, I. N.; Hawley, S. L.
2004autt.book....1R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Meeting the Cool Neighbors. VII. Spectroscopy of Faint Red
NLTT Dwarfs
Authors: Reid, I. Neill; Cruz, Kelle L.; Allen, Peter; Mungall, F.;
Kilkenny, D.; Liebert, James; Hawley, Suzanne L.; Fraser, Oliver J.;
Covey, Kevin R.; Lowrance, Patrick
2003AJ....126.3007R Altcode: 2003astro.ph..8380R
We present low-resolution optical spectroscopy and BVRI photometry
of 453 candidate nearby stars drawn from the NLTT proper-motion
catalog. The stars were selected based on optical/near-infrared colors,
derived by combining the NLTT photographic data with photometry from the
2MASS Second Incremental Data Release. Based on the derived photometric
and spectroscopic parallaxes, we identify 111 stars as lying within 20
pc of the Sun, including nine stars with formal distance estimates of
less than 10 pc. A further 53 stars have distance estimates within
1 σ of our 20 pc limit. Almost all of those stars are additions
to the nearby-star census. In total, our NLTT-based survey has so
far identified 496 stars likely to be within 20 pc, of which 195 are
additions to nearby-star catalogs. Most of the newly identified nearby
stars have spectral types between M4 and M8.
---------------------------------------------------------
Title: Identification of Low Mass T Tauri Candidates at High Galactic
Latitudes
Authors: McGehee, P. M.; Hawley, S. L.; Ivezic, Z.
2003AAS...203.0510M Altcode: 2003BAAS...35Q1211M
We present an optical study of low mass stars at high galactic latitudes
(|b| > 30) using Sloan Digital Sky Survey (SDSS) imaging and
spectroscopy. We specifically target stars whose SDSS colors indicate a
M dwarf spectral type which, for objects having ages between 1 and 10
Myr, corresponds to masses less than 0.8 solar. Analysis of SDSS data
obtained in the Orion OB1b and Taurus Star Formation Regions shows
that actively accreting young stars have (u-g, g-r) colors distinct
from those of the white dwarf - M dwarf pairs that dominate the field
ultraviolet excess low mass star population. Furthermore, we find that
this separation can be drawn using the reddening-invariant index formed
by u-g and g-r, thus enabling selection of low mass Classical T Tauri
candidates without correction for extinction. The spatial distribution
of candidates is analyzed with emphasis on their relation to high
latitude molecular clouds.
---------------------------------------------------------
Title: Spectroscopic Calibrations for the SDSS/2MASS Low Mass
Luminosity Function
Authors: Covey, K. R.; Hawley, S. L.; Sloan Digital Sky Survey
Collaboration
2003AAS...203.4301C Altcode: 2003BAAS...35.1272C
The photometric precision and overwhelming size of the SDSS and 2MASS
databases lend themselves to large statistical studies of astronomical
objects. One such project is currently underway, correlating detections
of low mass stars in both databases and making use of photometric
parallax relations to construct a luminosity function for late type
stars. However, a sample constructed from photometric identifications
alone must be carefully corrected for bias, incompleteness, and
contamination. We describe an ongoing observational campaign to
calibrate the extent of these effects, and present early indications
of the reliability of the relationships with which low mass dwarfs
can be targeted from photometric detections in the SDSS and 2MASS
databases. <P />The authors gratefully acknowledge support of this
work from NASA ADP grant NAG5-13111.
---------------------------------------------------------
Title: Radiative Hydrodynamic Models of Solar White Light Flares
Authors: Allred, J. C.; Hawley, S. L.; Abbett, W. P.; Fisher, G. H.;
Hudson, H. S.; Metcalf, T. R.
2003AGUFMSH22A0175A Altcode:
We report on theoretical radiative hydrodynamic simulations of solar
white light flares. The solar atmosphere is modeled in detail from
the transition region to the photosphere. The coronal pressure and
X-ray backheating are included self-consistently. Flare heating is
assumed to be from an electron beam which is modeled for several
white light flares using data from RHESSI, TRACE and Yohkoh. We also
investigate the possibility that the 511 keV line width is produced
from a significant column depth of atmosphere at transition region
temperatures. We compare our new solar flare models to previous results,
and to models of M dwarf stellar flares.
---------------------------------------------------------
Title: Quasar Outburst in Mensa
Authors: Clocchiatti, A.; Minitti, D.; Aguilera, C.; Becker, A.; Cook,
K.; Covarrubias, R.; Hawley, S.; Hiriart, R.; Keller, S.; Miceli,
A.; Miknaitis, G.; Nikolaev, S.; Olsen, K.; Prieto, J.; Proctor, G.;
Rest, A.; Schmidt, B.; Smith, C.; Stubbs, C.; Suntzeff, N.; Welch, D.
2003IAUC.8258....1C Altcode: 2003IAUC.8258A...1C
A. Clocchiatti and D. Minitti, Pontificia Universidad Catolica de
Chile, on behalf of the SuperMACHO project (involving also C. Aguilera,
A. Becker, K. Cook, R. Covarrubias, S. Hawley, R. Hiriart, S. Keller,
A. Miceli, G. Miknaitis, S. Nikolaev, K. Olsen, J. Prieto, G. Proctor,
A. Rest, B. Schmidt, C. Smith, C. Stubbs, N. Suntzeff, and D. Welch),
report the discovery of a highly unusual outburst of a quasistellar
object (QSO) at z = 2.87. The object, located at R.A. = 5h13m03s.94,
Decl. = -70o22'50".5 (equinox 2000.0), had a quiescent broadband
magnitude of VR approximately 22.2. Multiple broadband-VR-filter
images taken at the Blanco 4-m telescope at Cerro Tololo reveal no
significant change in brightness from the beginning of observations
in 2001 Sept. until 2003 Sept. 27 UT, around the date that it began
to brighten linearly in flux with time. By Dec. 15, it had brightened
by a factor of 15 and has reached VR = 19.4 with no evidence of a
change in trend. Identified as a SuperMACHO microlensing candidate,
follow-up spectroscopy (456-s exposure) was obtained at the Magellan II
(Clay) 6.5-m telescope (+ LDSS2 spectrograph with medium-blue grism)
on Dec. 3.8. The spectrum reveals several prominent QSO lines with
strong P-Cyg profiles, indicative of an ejection velocity of 1600 km/s;
identified features include H (Lyman-alpha), N V, C IV 154.9-nm, Si
IV 139.3-nm, O IV, and [C III] 191.0-nm. The high redshift, extreme
current luminosity, evidence of outflow (from P-Cyg line profiles),
and continued brightening suggest that this is an object worthy of
intense monitoring.
---------------------------------------------------------
Title: White Dwarf-M Dwarf Close Binary Systems in the Sloan Digital
Sky Survey
Authors: Silvestri, N. M.; Hawley, S. L.; Szkody, P.; SDSS
Collaboration
2003AAS...203.4201S Altcode: 2003BAAS...35.1271S
Using photometric colors and spectra, we have identified over 400
white dwarf-M dwarf close binary systems in the SDSS database. We are
in the process of performing followup observations of systems with the
strongest Balmer emission on the ARC 3.5-m telescope as we suspect these
pairs may be in a pre-cataclysmic variable phase of evolution. There has
been much emphasis on the evolution of the white dwarf in these systems,
but it is not really known how the binary environment influences the
evolution of the M dwarf and whether the properties of the M dwarf are
impacted by the presence of a white dwarf companion. From the followup
spectroscopy, we have determined the physical properties of the M dwarf,
the temperature, spectral type and rough age estimate of the white
dwarf as well as the radial velocity and orbital period for several
of these close binary systems. The physical properties and activity of
the M dwarf and influence of the pre-CV system on M dwarf evolution are
discussed. <P />This work is supported in part by NSF Grant AST02-05875.
---------------------------------------------------------
Title: Multiwavelength Observations of Flares on AD Leonis
Authors: Hawley, Suzanne L.; Allred, Joel C.; Johns-Krull, Christopher
M.; Fisher, George H.; Abbett, William P.; Alekseev, Ilya; Avgoloupis,
Stavros I.; Deustua, Susana E.; Gunn, Alastair; Seiradakis, John H.;
Sirk, Martin M.; Valenti, Jeff A.
2003ApJ...597..535H Altcode:
We report results from a multiwavelength observing campaign conducted
during 2000 March on the flare star AD Leo. Simultaneous data were
obtained from several ground- and space-based observatories, including
observations of eight sizable flares. We discuss the correlation of
line and continuum emission in the optical and ultraviolet wavelength
regimes, as well as the flare energy budget, and we find that the
emission properties are remarkably similar even for flares of very
different evolutionary morphology. This suggests a common heating
mechanism and atmospheric structure that are independent of the detailed
evolution of individual flares. We also discuss the Neupert effect,
chromospheric line broadening, and velocity fields observed in several
transition region emission lines. The latter show significant downflows
during and shortly after the flare impulsive phase. Our observations are
broadly consistent with the solar model of chromospheric evaporation
and condensation following impulsive heating by a flux of nonthermal
electrons. These data place strong constraints on the next generation
of radiative hydrodynamic models of stellar flares.
---------------------------------------------------------
Title: SDSS White Dwarfs with Spectra Showing Atomic Oxygen and/or
Carbon Lines
Authors: Liebert, James; Harris, H. C.; Dahn, C. C.; Schmidt, Gary
D.; Kleinman, S. J.; Nitta, Atsuko; Krzesiński, Jurek; Eisenstein,
Daniel; Smith, J. Allyn; Szkody, Paula; Hawley, Suzanne; Anderson,
Scott F.; Brinkmann, J.; Collinge, Matthew J.; Fan, Xiaohui; Hall,
Patrick B.; Knapp, Gillian R.; Lamb, Don Q.; Margon, B.; Schneider,
Donald P.; Silvestri, Nicole
2003AJ....126.2521L Altcode:
We discuss 18 white dwarfs, one of which (G227-5) was previously
known, whose SDSS spectra show lines of neutral and/or singly ionized
carbon. At least two and perhaps four show lines of neutral or singly
ionized oxygen. Apart from the extremely hot “PG 1159” stars, these
are the first white dwarfs with photospheric oxygen detected in their
optical spectra. The photometry strongly suggests that these stars lie
in the 11,000-30,000 K temperature range of the helium-atmosphere DB
white dwarfs, though only one of them shows weak neutral helium lines in
the spectrum. Trigonometric parallaxes are known for G227-5 and another,
previously known white dwarf (G35-26) showing atomic carbon lines,
and they indicate that both are massive stars. Theoretical arguments
suggest that all members of this class of rare white dwarfs are massive
(~1 M<SUB>solar</SUB>), and this finding could explain the paucity of
massive DB white dwarfs.
---------------------------------------------------------
Title: An Insider's View of Brown Dwarfs
Authors: Hawley, S. L.
2003csss...12...97H Altcode:
This review seeks to provide the background material necessary to
understand the newest developments in the study of brown dwarfs. I
describe the physical and observational properties of low mass stars and
brown dwarfs, and discuss our ability to distinguish between them. Other
topics include atmospheric variability in the form of magnetic activity
and weather, and the mass function and local density of brown dwarfs in
the solar neighborhood. The connection between brown dwarfs and planets
will be covered in the companion review paper on extrasolar planets.
---------------------------------------------------------
Title: The First Data Release of the Sloan Digital Sky Survey
Authors: Abazajian, Kevork; Adelman-McCarthy, Jennifer K.; Agüeros,
Marcel A.; Allam, Sahar S.; Anderson, Scott F.; Annis, James; Bahcall,
Neta A.; Baldry, Ivan K.; Bastian, Steven; Berlind, Andreas; Bernardi,
Mariangela; Blanton, Michael R.; Blythe, Norman; Bochanski, John
J., Jr.; Boroski, William N.; Brewington, Howard; Briggs, John W.;
Brinkmann, J.; Brunner, Robert J.; Budavári, Tamás; Carey, Larry N.;
Carr, Michael A.; Castander, Francisco J.; Chiu, Kuenley; Collinge,
Matthew J.; Connolly, A. J.; Covey, Kevin R.; Csabai, István;
Dalcanton, Julianne J.; Dodelson, Scott; Doi, Mamoru; Dong, Feng;
Eisenstein, Daniel J.; Evans, Michael L.; Fan, Xiaohui; Feldman, Paul
D.; Finkbeiner, Douglas P.; Friedman, Scott D.; Frieman, Joshua A.;
Fukugita, Masataka; Gal, Roy R.; Gillespie, Bruce; Glazebrook, Karl;
Gonzalez, Carlos F.; Gray, Jim; Grebel, Eva K.; Grodnicki, Lauren;
Gunn, James E.; Gurbani, Vijay K.; Hall, Patrick B.; Hao, Lei;
Harbeck, Daniel; Harris, Frederick H.; Harris, Hugh C.; Harvanek,
Michael; Hawley, Suzanne L.; Heckman, Timothy M.; Helmboldt, J. F.;
Hendry, John S.; Hennessy, Gregory S.; Hindsley, Robert B.; Hogg,
David W.; Holmgren, Donald J.; Holtzman, Jon A.; Homer, Lee; Hui, Lam;
Ichikawa, Shin-ichi; Ichikawa, Takashi; Inkmann, John P.; Ivezić,
Željko; Jester, Sebastian; Johnston, David E.; Jordan, Beatrice;
Jordan, Wendell P.; Jorgensen, Anders M.; Jurić, Mario; Kauffmann,
Guinevere; Kent, Stephen M.; Kleinman, S. J.; Knapp, G. R.; Kniazev,
Alexei Y.; Kron, Richard G.; Krzesiński, Jurek; Kunszt, Peter Z.;
Kuropatkin, Nickolai; Lamb, Donald Q.; Lampeitl, Hubert; Laubscher,
Bryan E.; Lee, Brian C.; Leger, R. French; Li, Nolan; Lidz, Adam;
Lin, Huan; Loh, Yeong-Shang; Long, Daniel C.; Loveday, Jon; Lupton,
Robert H.; Malik, Tanu; Margon, Bruce; McGehee, Peregrine M.; McKay,
Timothy A.; Meiksin, Avery; Miknaitis, Gajus A.; Moorthy, Bhasker K.;
Munn, Jeffrey A.; Murphy, Tara; Nakajima, Reiko; Narayanan, Vijay K.;
Nash, Thomas; Neilsen, Eric H., Jr.; Newberg, Heidi Jo; Newman, Peter
R.; Nichol, Robert C.; Nicinski, Tom; Nieto-Santisteban, Maria; Nitta,
Atsuko; Odenkirchen, Michael; Okamura, Sadanori; Ostriker, Jeremiah P.;
Owen, Russell; Padmanabhan, Nikhil; Peoples, John; Pier, Jeffrey R.;
Pindor, Bartosz; Pope, Adrian C.; Quinn, Thomas R.; Rafikov, R. R.;
Raymond, Sean N.; Richards, Gordon T.; Richmond, Michael W.; Rix,
Hans-Walter; Rockosi, Constance M.; Schaye, Joop; Schlegel, David J.;
Schneider, Donald P.; Schroeder, Joshua; Scranton, Ryan; Sekiguchi,
Maki; Seljak, Uroš; Sergey, Gary; Sesar, Branimir; Sheldon, Erin;
Shimasaku, Kazu; Siegmund, Walter A.; Silvestri, Nicole M.; Sinisgalli,
Allan J.; Sirko, Edwin; Smith, J. Allyn; Smolčić, Vernesa; Snedden,
Stephanie A.; Stebbins, Albert; Steinhardt, Charles; Stinson, Gregory;
Stoughton, Chris; Strateva, Iskra V.; Strauss, Michael A.; SubbaRao,
Mark; Szalay, Alexander S.; Szapudi, István; Szkody, Paula; Tasca,
Lidia; Tegmark, Max; Thakar, Aniruddha R.; Tremonti, Christy; Tucker,
Douglas L.; Uomoto, Alan; Vanden Berk, Daniel E.; Vandenberg, Jan;
Vogeley, Michael S.; Voges, Wolfgang; Vogt, Nicole P.; Walkowicz,
Lucianne M.; Weinberg, David H.; West, Andrew A.; White, Simon D. M.;
Wilhite, Brian C.; Willman, Beth; Xu, Yongzhong; Yanny, Brian; Yarger,
Jean; Yasuda, Naoki; Yip, Ching-Wa; Yocum, D. R.; York, Donald G.;
Zakamska, Nadia L.; Zehavi, Idit; Zheng, Wei; Zibetti, Stefano;
Zucker, Daniel B.
2003AJ....126.2081A Altcode: 2003astro.ph..5492C; 2003astro.ph..5492T
The Sloan Digital Sky Survey (SDSS) has validated and made publicly
available its First Data Release. This consists of 2099 deg<SUP>2</SUP>
of five-band (u,g,r,i,z) imaging data, 186,240 spectra of galaxies,
quasars, stars and calibrating blank sky patches selected over 1360
deg<SUP>2</SUP> of this area, and tables of measured parameters
from these data. The imaging data go to a depth of r~22.6 and are
photometrically and astrometrically calibrated to 2% rms and 100
mas rms per coordinate, respectively. The spectra cover the range
3800-9200 Å, with a resolution of 1800-2100. This paper describes
the characteristics of the data with emphasis on improvements since
the release of commissioning data (the SDSS Early Data Release) and
serves as a pointer to extensive published and on-line documentation
of the survey.
---------------------------------------------------------
Title: An Outsiders View of Extrasolar Planets
Authors: Hawley, S. L.; Reid, I. N.
2003csss...12..128H Altcode:
We summarize the current state of extrasolar planet research, including
the newest discoveries, properties of planetary systems, the current
census, the mass function, and some thoughts on the formation and
evolution of planetary disks.
---------------------------------------------------------
Title: The March 2000 AD Leo Flare Campaign
Authors: Hawley, S. L.; Johns-Krull, C. M.; Fisher, G. H.; Abbett,
W. P.; Seiradakis, J. H.; Avgoloupis, S. I.
2003csss...12..975H Altcode:
Flares are by their nature random and unpredictable events and flare
observations are often the serendipitous result of programs designed for
other scientific endeavors. Thus, few observations of flares covering
multiple wavelength regimes, with both spectroscopic and photometric
information, are available to test stellar flare models. Occasionally,
a bold and reckless team will put together a flare campaign, employing
suitable statistical arguments to convince the relevant telescope
allocation committees that such a campaign will prove fruitful, while
hoping desperately for the combination of clear weather, working
instruments and cooperative star necessary to warrant the herculean
organizational effort. We report here on one such campaign, conducted
during March, 2000 on the dM3e flare star AD Leo.
---------------------------------------------------------
Title: White Dwarf - M Dwarf Pairs in the Sloan Digital Sky Survey
(SDSS)
Authors: Raymond, S. N.; Szkody, P.; Hawley, S. L.
2003csss...12..992R Altcode:
Using spectra and color cuts in the Sloan filter system, we have
identified 83 White Dwarf - M dwarf pairs in the Sloan Digital Sky
Survey (SDSS). The blue portion of the spectrum is fit with white dwarf
models as a function of temperature. The best fit is then subtracted
off to extract the M-dwarf spectrum. Many of these objects show strong
Hα emission, an indicator of M-dwarf chromospheric activity. We have
extracted a list of white dwarf temperatures, M-dwarf spectral types,
and Hα equivalent widths, and we compare the activity level of these
irradiated systems with the field M star population. If a portion of
this activity is due to irradiation from the white dwarf companion,
then we are studying binaries at a wide range in separations, from
loosely bound systems to close binary pre-CVs. This hypothesis is being
tested with a spectroscopic follow-up of SDSS objects by looking for
(orbital) periodicity in the systems with the highest activity levels,
using the ARC 3.5m telescope at Apache Point Observatory (APO).
---------------------------------------------------------
Title: New M and L Dwarfs Identified in the Sloan Digital Sky Survey
Early Data Release
Authors: Covey, K. R.; Hawley, S. L.; Knapp, G. R.; Anderson, S. F.
2003csss...12..658C Altcode:
Spectra from the Sloan Digital Sky Survey (SDSS) Early Data Release
(EDR) reveal 645 late-type (spectral type M and L) dwarfs. Additional
SDSS spectra have been obtained of 34 L dwarfs from SDSS data not
contained within the EDR. Stars were assigned spectral types from the
spectral sequence of Kirkpatrick et al. (1999) using measurements of
spectral indices and least squares fits to templates. Correlations
between spectral type, optical (SDSS) and infrared (2MASS) colors
are investigated.
---------------------------------------------------------
Title: Magnetic White Dwarfs from the Sloan Digital Sky Survey:
The First Data Release
Authors: Schmidt, Gary D.; Harris, Hugh C.; Liebert, James; Eisenstein,
Daniel J.; Anderson, Scott F.; Brinkmann, J.; Hall, Patrick B.;
Harvanek, Michael; Hawley, Suzanne; Kleinman, S. J.; Knapp, Gillian
R.; Krzesinski, Jurek; Lamb, Don Q.; Long, Dan; Munn, Jeffrey A.;
Neilsen, Eric H.; Newman, Peter R.; Nitta, Atsuko; Schlegel, David J.;
Schneider, Donald P.; Silvestri, Nicole M.; Smith, J. Allyn; Snedden,
Stephanie A.; Szkody, Paula; Vanden Berk, Dan
2003ApJ...595.1101S Altcode: 2003astro.ph..7121S
Beyond its goals related to the extragalactic universe, the Sloan
Digital Sky Survey (SDSS) is an effective tool for identifying stellar
objects with unusual spectral energy distributions. Here we report
on the 53 new magnetic white dwarfs discovered during the first two
years of the survey, including 38 whose data are made public in the
1500 deg<SUP>2</SUP> First Data Release. Discoveries span the magnitude
range 16.3<=g<=20.5, and based on the recovery rate for previously
known magnetic white dwarfs, the completeness of the SDSS appears to
be high for reasonably hot stars with B>~3 MG and g>~15. The new
objects nearly double the total number of known magnetic white dwarfs
and include examples with polar field strengths B<SUB>p</SUB>>500 MG,
as well as several with exotic atmospheric compositions. The improved
sample statistics and uniformity indicate that the distribution of
magnetic white dwarfs has a broad peak in the range ~5-30 MG and a
tail extending to nearly 10<SUP>9</SUP> G. Degenerates with polar
fields B<SUB>p</SUB>>~50 MG are consistent with being descendents
of magnetic Ap/Bp main-sequence stars, but low- and moderate-field
magnetic white dwarfs appear to imply another origin. Yet-undetected
magnetic F-type stars with convective envelopes that destroy the
ordered underlying field are attractive candidates. <P />A portion of
the results presented here were obtained with the MMT Observatory,
a facility operated jointly by the University of Arizona and the
Smithsonian Institution.
---------------------------------------------------------
Title: Cataclysmic Variables from the Sloan Digital Sky
Survey. II. The Second Year
Authors: Szkody, Paula; Fraser, Oliver; Silvestri, Nicole; Henden,
Arne; Anderson, Scott F.; Frith, James; Lawton, Brandon; Owens, Ethan;
Raymond, Sean; Schmidt, Gary; Wolfe, Michael; Bochanski, John; Covey,
Kevin; Harris, Hugh; Hawley, Suzanne; Knapp, Gillian R.; Margon,
Bruce; Voges, Wolfgang; Walkowicz, Lucianne; Brinkmann, J.; Lamb, D. Q.
2003AJ....126.1499S Altcode: 2003astro.ph..6269S
The first full year of operation following the commissioning year of
the Sloan Digital Sky Survey (SDSS) has revealed a wide variety of
newly discovered cataclysmic variables (CVs). We show the SDSS spectra
of 42 CVs observed in 2002, of which 35 are new classifications,
four are known dwarf novae (CT Hya, RZ Leo, T Leo, and BZ UMa), one
is a known CV identified from a previous quasar survey (Aqr1), and
two are known ROSAT or FIRST discovered CVs (RX J09445+0357, FIRST
J102347.6+003841). The SDSS positions, colors, and spectra of all 42
systems are presented. In addition, the results of follow-up studies
of several of these objects identify the orbital periods, velocity
curves, and polarization that provide the system geometry and accretion
properties. While most of the SDSS discovered systems are faint (greater
than 18th magnitude) with low accretion rates (as implied from their
spectral characteristics), there are also a few bright objects that
may have escaped previous surveys due to changes in the mass transfer
rate. <P />Based on observations obtained with the Sloan Digital Sky
Survey and with the Apache Point Observatory 3.5 m telescope, which
are owned and operated by the Astrophysical Research Consortium (ARC).
---------------------------------------------------------
Title: An Initial Survey of White Dwarfs in the Sloan Digital
Sky Survey
Authors: Harris, Hugh C.; Liebert, James; Kleinman, S. J.; Nitta,
Atsuko; Anderson, Scott F.; Knapp, Gillian R.; Krzesiński, Jurek;
Schmidt, Gary; Strauss, Michael A.; Vanden Berk, Dan; Eisenstein,
Daniel; Hawley, Suzanne; Margon, Bruce; Munn, Jeffrey A.; Silvestri,
Nicole M.; Smith, J. Allyn; Szkody, Paula; Collinge, Matthew J.;
Dahn, Conard C.; Fan, Xiaohui; Hall, Patrick B.; Schneider, Donald P.;
Brinkmann, J.; Burles, Scott; Gunn, James E.; Hennessy, Gregory S.;
Hindsley, Robert; Ivezić, Zeljko; Kent, Stephen; Lamb, Donald Q.;
Lupton, Robert H.; Nichol, R. C.; Pier, Jeffrey R.; Schlegel, David
J.; SubbaRao, Mark; Uomoto, Alan; Yanny, Brian; York, Donald G.
2003AJ....126.1023H Altcode: 2003astro.ph..5347H
An initial assessment is made of white dwarf and hot subdwarf stars
observed in the Sloan Digital Sky Survey. In a small area of sky
(190 square degrees), observed much like the full survey will
be, 269 white dwarfs (WDs) and 56 hot subdwarfs are identified
spectroscopically where only 44 white dwarfs and five hot subdwarfs
were known previously. Most are ordinary DA (hydrogen atmosphere) and
DB (helium) types. In addition, in the full survey to date, a number
of WDs have been found with uncommon spectral types. Among these are
blue DQ stars displaying lines of atomic carbon; red DQ stars showing
molecular bands of C<SUB>2</SUB> with a wide variety of strengths; DZ
stars where Ca and occasionally Mg, Na, and/or Fe lines are detected;
and magnetic WDs with a wide range of magnetic field strengths in DA,
DB, DQ, and (probably) DZ spectral types. Photometry alone allows
identification of stars hotter than 12,000 K, and the density of
these stars for 15<g<20 is found to be ~2.2 deg<SUP>-2</SUP>
at Galactic latitudes of 29°-62°. Spectra are obtained for roughly
half of these hot stars. The spectra show that for 15<g<17,
40% of hot stars are WDs, and the fraction of WDs rises to ~90% at
g=20. The remainder are hot sdB and sdO stars.
---------------------------------------------------------
Title: Looking for Very Low-Mass Pre-Main Sequence Objects with SDSS
Authors: McGehee, Peregrine M.; Hawley, Suzanne L.; Covey, Kevin R.
2003IAUS..211..525M Altcode:
Determining the process(es) by which brown dwarfs form is key to
understanding their intrinsic nature. If their origins are within
circumstellar disks they are akin to giant planets. If, on the other
hand, they coalesce from molecular cloud cores, then they share a common
lineage with low mass stars. These two mechanisms can be distinguished
by investigation of young (< 10 Myr) substellar objects. If
brown dwarfs are small failed stars, we expect to find very low mass
analogs of the Classical T Tauris, with primordial magnetic fields
from the molecular cloud collapse. Accretion onto these objects leads
to characteristic magnetic activity signatures such as chromospheric
and coronal emission resulting in an ultraviolet excess continuum. The
Orion OB1b association (m-M = 7.9, 2 Myr) provides a laboratory for
following the strength and occurrence of the accretion process as a
function of mass. Studies of the substellar mass function within the
sigma Orionis cluster at the southern end of the association indicate
that brown dwarfs are common. Based on model isochrones and the SDSS
M dwarf sequence we expect the 95% completeness limit of the "Orion"
scans to correspond to 0.1 and 0.03 solar masses for the u and g bands.
---------------------------------------------------------
Title: A First Look at White Dwarf-M Dwarf Pairs in the Sloan Digital
Sky Survey
Authors: Raymond, Sean N.; Szkody, Paula; Hawley, Suzanne L.; Anderson,
Scott F.; Brinkmann, J.; Covey, Kevin R.; McGehee, P. M.; Schneider,
D. P.; West, Andrew A.; York, D. G.
2003AJ....125.2621R Altcode: 2003astro.ph..2405R
We have identified 109 white dwarf (WD)-M dwarf pairs in the Sloan
Digital Sky Survey (SDSS) with g<20th magnitude. For each system
we determined the temperature of the WD primary and the spectral
type of the M dwarf secondary. Using Hα emission as a proxy for
the chromospheric activity level of the M dwarf, we investigated
correlations between the activity level and properties of the
system. Compared with field M dwarfs previously observed in the
Palomar/MSU Survey, we see a slightly higher active fraction of
early-type stars, with activity levels similar to the field. We have
conducted follow-up observations at the ARC 3.5 m telescope to obtain
radial velocity information and to search for short-period binaries
that may be on the verge of interacting. We report on one system
with a 4.1 hr period and several additional systems with significant
velocity variations.
---------------------------------------------------------
Title: Transition Region Emission from Very Low Mass Stars
Authors: Hawley, Suzanne L.; Johns-Krull, Christopher M.
2003ApJ...588L.109H Altcode: 2003astro.ph..4542H
We present results from our Cycle 10 Hubble Space Telescope (HST)
program to search for transition region emission in very low mass
main-sequence stars in the spectral range M7-M9. Our program is aimed
at (1) detecting emission and (2) distinguishing between flaring and
quiescent origin for the emission. We have obtained HST/Space Telescope
Imaging Spectrograph time series observations of three active, very low
mass stars (VB 8, VB 10, and LHS 2065), which show persistent activity
in transition region lines including Si IV, C IV, and He II. Emission
in transition region lines appears to be variable between exposures
but is always observed. A strong flare was also observed in one 10
minute exposure on VB 10. Our results indicate that active, very low
mass stars maintain a persistent quiescent chromosphere and transition
region that is similar to those observed in active earlier type M
dwarfs, in contrast to suggestions that these low-mass main-sequence
stars exhibit only relatively strong flares and no quiescent emission.
---------------------------------------------------------
Title: Discovery of a New Nearby Star
Authors: Teegarden, B. J.; Pravdo, S. H.; Hicks, M.; Lawrence, K.;
Shaklan, S. B.; Covey, K.; Fraser, O.; Hawley, S. L.; McGlynn, T.;
Reid, I. N.
2003ApJ...589L..51T Altcode: 2003astro.ph..2206T
We report the discovery of a nearby star with a very large proper
motion of 5.05"+/-0.03" yr<SUP>-1</SUP>. The star is called SO
025300.5+165258 and referred to herein as a high proper motion star
(HPMS). The discovery came as a result of a search of the SkyMorph
database, a sensitive and persistent survey that is well suited for
finding stars with high proper motions. There are currently only seven
known stars with proper motions greater than 5" yr<SUP>-1</SUP>. The
spectrum and measured tangential velocity indicate that the HPMS
is a main-sequence star with spectral type M6.5. Trigonometric and
photometric parallaxes have been determined, yielding distance estimates
of 2.4<SUP>+0.7</SUP><SUB>-0.4</SUB> pc (lower limit) and 3.6+/-0.4
pc, respectively. If the former is correct, the HPMS ranks third in
the list of nearest stellar systems. If the latter is correct, it is
17th. A more precise trigonometric parallax measurement is expected
to be completed near the end of the year.
---------------------------------------------------------
Title: Two Rare Magnetic Cataclysmic Variables with Extreme Cyclotron
Features Identified in the Sloan Digital Sky Survey
Authors: Szkody, Paula; Anderson, Scott F.; Schmidt, Gary; Hall,
Patrick B.; Margon, Bruce; Miceli, Antonino; SubbaRao, Mark; Frith,
James; Harris, Hugh; Hawley, Suzanne; Lawton, Brandon; Covarrubias,
Ricardo; Covey, Kevin; Fan, Xiaohui; Murphy, Thomas; Narayanan, Vijay;
Raymond, Sean; Rest, Armin; Strauss, Michael A.; Stubbs, Christopher;
Turner, Edwin; Voges, Wolfgang; Bauer, Amanda; Brinkmann, J.; Knapp,
Gillian R.; Schneider, Donald P.
2003ApJ...583..902S Altcode: 2002astro.ph..8241S
Two newly identified magnetic cataclysmic variables discovered in
the Sloan Digital Sky Survey (SDSS), SDSS J155331.12+551614.5 and
SDSS J132411.57+032050.5, have spectra showing highly prominent,
narrow, strongly polarized cyclotron humps with amplitudes that vary
on orbital periods of 4.39 and 2.6 hr, respectively. In the former,
the spacing of the humps indicates the third and fourth harmonics in
a magnetic field of ~60 MG. The narrowness of the cyclotron features
and the lack of strong emission lines imply very low temperature
plasmas and very low accretion rates, so that the accreting area
is heated by particle collisions rather than accretion shocks. The
detection of rare systems like these exemplifies the ability of the
SDSS to find the lowest accretion rate close binaries. <P />Based
in part on observations obtained with the Sloan Digital Sky Survey
(SDSS) and with the Apache Point Observatory (APO) 3.5 m telescope,
which are owned and operated by the Astrophysical Research Consortium
(ARC). A portion of the observations reported here were obtained at
the MMT Observatory, a joint facility of the University of Arizona
and the Smithsonian Institution.
---------------------------------------------------------
Title: White Dwarfs in Cataclysmic Variables: HST Results on GW LIB
and Gleanings from SDSS Provide Insight on the Effects of Accretion
Authors: Szkody, P.; Gänsicke, B. T.; Sion, E. M.; Howell, S. B.;
Raymond, S.; Hawley, S. L.
2003ASIB..105..309S Altcode: 2003whsw.conf..309S; 2003whdw.conf..309S
Cataclysmic variables (CVs) provide a rich laboratory to study
the effects of mass transfer and accretion on the properties and
evolution of white dwarfs. One interesting aspect is the effect of
accretion on the instability strip. So far, there is only one ZZ Cet
pulsator known to be a CV - GW Lib. Our UV spectra obtained with HST
provide interesting results. The UV light curve of GW Lib reveals
large amplitude pulsations at 3 periods while the spectrum shows a
temperature hotter than single DAVs. However, our UV data on systems
with WD temperatures in the DAV zone show no pulsation. The emerging
SDSS database provides a rich resource for studies of many other
aspects of accretion. So far, there are more than 60 new CVs and more
than 100 WD+M pairs that have been found. A few of the unusual systems
and some of the results on the pairs are highlighted. <P />The SDSS
Web site is <A href="http://www.sdss.org/">SDSS</A>.
---------------------------------------------------------
Title: The Nature of High Velocity White Dwarfs
Authors: Silvestri, Nicole M.; Oswalt, Terry D.; Hawley, Suzanne L.
2003ASIB..105..395S Altcode: 2003whsw.conf..395S; 2003whdw.conf..395S
No abstract at ADS
---------------------------------------------------------
Title: The Quiescent and Flaring Atmosphere of the dMe Flare Star
EV Lacertae
Authors: Osten, R. A.; Hawley, S. L.; Johns-Krull, C. M.; Brown, A.;
Ayres, T. R.; Ambruster, C.
2002AAS...201.1207O Altcode: 2002BAAS...34.1113O
We report on a multi-wavelength campaign to observe flares on the dM4.5e
flare star, EV Lac, in 2001 September. The campaign utilized the Chandra
ACIS-HETGS, HST-STIS, VLA, and optical photometry and spectroscopy
with the McDonald Observatory's 2.1 and 2.7m telescopes. The goal of
the campaign was to characterize EV Lac's dynamic outer atmosphere
and study the characteristics of magnetic energy release processes in
a completely convective star. X-ray grating observations confirm the
quiescent underabundance of iron deduced from previous low spectral
resolution observations and show evidence of enhanced and variable
Ne/Fe abundance ratios. Numerous flares were observed in the 100
ksec X-ray pointing; UV observations overlap one impulsive event,
while radio and optical observations reveal impulsive flare signatures
during a moderate X-ray flare. Preliminary results from a time-resolved
spectroscopic analysis of the X-ray data will be presented, including
determination of changing abundances, density, and temperature structure
of the coronal plasma in EV Lac. The timing of flares in radio, UV,
and optical will be compared against X-ray variations. A discussion
of the observed multi-wavelength temporal trends will be given, and
comparison made to solar flares. RAO acknowledges support from Chandra
grant G01-2014A and HST grant GO-08880.04-A, as well as support from
NRAO through a Jansky fellowship.
---------------------------------------------------------
Title: White Dwarf - M Dwarf Pairs in the Sloan Digital Sky Survey
Authors: Bochanski, J.; Raymond, S.; Hawley, S.; Szkody, P.; Sloan
Digtial Sky Survey Collaboration
2002AAS...201.1606B Altcode: 2002BAAS...34.1125B
We present intial analysis of 109 White Dwarf (WD) - M dwarf
pairs observed with the Sloan Digital Sky Survey (SDSS). For each
of these pairs, the temperature of the WD primary and spectral
type of the M dwarf were determined. Further examination of the M
dwarfs was conducted, using Hα emission as a marker of chromospheric
activity. Comparing this new data set to that of Hawley et al. (1996),
we observe a somewhat higher active fraction of early-type M dwarfs
in these pairs. Followup radial velocity observations at the ARC 3.5m
telescope are being used to confirm any short period binaries with
substantial velocity variations. These observations, which already
span over 5 nights, have already detected a short period binary (P=4.1
hr). We have also produced a catalog of the WD - M dwarf pairs in the
DR1 of the SDSS. We report on the status of this project. We gratefully
acknoledge the support of NSF grant AST-0205875.
---------------------------------------------------------
Title: T Tauri and Chromospherically Active Stars in the SDSS II:
Variability
Authors: McGehee, P. M.; Ivezić, Ž.; Hawley, S. L.
2002AAS...201.1605M Altcode: 2002BAAS...34.1125M
The detection of pre-main sequence and magnetically active low
mass stars in the field via ultraviolet excess is complicated by
the presence of white dwarf - M dwarf pairs (WD+M) in which the
white dwarf signature mimics the excess continuum due to accretion
or chromospheric activity. However, the use of synoptic survey data
permits a clean separation between the WD+M and candidate T Tauris
and dMe on the grounds of near-UV and blue variability. We utilize
multi-epoch photometry obtained by the Sloan Digital Sky Survey to
identify possible PMS and magnetically active M stars using changes
in the SDSS u<SUP>*</SUP> and g<SUP>*</SUP> magnitudes. The spatial
location of the resulting candidates are studied in relation to that
of high-latitude molecular clouds.
---------------------------------------------------------
Title: Transition Region Emission From Very Low Mass Stars
Authors: Johns-Krull, C. M.; Hawley, S. L.
2002AAS...201.1208J Altcode: 2002BAAS...34.1113J
We present results from our cycle 10 HST program to search for
transition region emission in very low mass stars in the spectral
range M7-M9. Our program is aimed at 1) detecting emission;
and 2) distinguishing between flaring and persistent origin for
the emission. We have obtained time series observations of HST/STIS
spectra of three active, very low mass stars (VB8, VB10, and LHS 2065)
which reveal persistent emission in transition region lines including
Si IV, C IV, and He II. This emission does show variability from one
exposure to the next, but is always observed. A strong flare was also
observed in one 10 minute exposure on VB10. Our preliminary analysis
indicates that active, very low mass stars maintain a chromosphere
and transition region that is similar to those observed in active,
earlier type M dwarfs, in contrast to suggestions that these low mass
stars exhibit only flaring activity. This research was made possible
by grant HST-GO-9090 from the Space Telescope Science Institute,
operated by AURA for NASA.
---------------------------------------------------------
Title: Multiwavelength Observations of Flares on AD Leo
Authors: Allred, J. C.; Hawley, S. L.; Johns-Krull, C. M.; Fisher,
G. H.
2002AAS...201.1205A Altcode: 2002BAAS...34R1113A
In March 2000, a campaign was conducted to observe flares on the
dM3e flare star AD Leo over a large range of wavelengths, using
both ground and space-based observatories. Eight sizable flares and
numerous smaller ones were observed over the four day duration of
the campaign. We compare and contrast the behavior of the optical and
ultraviolet continuum and emission lines during the large flares. We
also investigate line broadening, velocity evolution and evidence for
the Neupert effect.
---------------------------------------------------------
Title: Magnetic Activity in Low Mass Stars: SDSS Results
Authors: Hawley, S. L.; West, A. A.; Covey, K. R.; Raymond, S. N.;
Walkowicz, L. M.
2002AAS...201.1604H Altcode: 2002BAAS...34.1125H
We present a study of the magnetic activity properties of low-mass
stars in the Sloan Digital Sky Survey. Using the Hα emission line
as an activity indicator, we examine the fraction of active stars as
a function of spectral type and find a peak near type M7, confirming
previous results. We investigate the ratio of the luminosity emitted
in Hα compared to the bolometric luminosity for each star, and find a
roughly constant ratio (with large scatter) over the range M0-M9. There
does not appear to be a decrease in the ratio for types M8-M9, in
contrast to previous determinations. We also explore the effect of
metallicity on activity, and examine whether activity is correlated
with changes in the SDSS colors.
---------------------------------------------------------
Title: The Space Density of Field Methane (“T") Dwarfs
Authors: Collinge, M. J.; Knapp, G. R.; Fan, X.; Lupton, R. H.;
Narayanan, V.; Strauss, M. A.; Gunn, J. E.; Schlegel, D. J.; Ivezić,
Ž.; Rockosi, C. M.; Geballe, T. R.; Leggett, S. K.; Golimowski, D.;
Hawley, S. L.
2002AAS...201.1603C Altcode: 2002BAAS...34.1125C
We describe a complete magnitude-limited sample of 11 field methane
(T) dwarfs brighter than z ≈ 20.2 selected from the imaging data
of the Sloan Digital Sky Survey (SDSS). We discuss the optical and
near-infrared colors of these and other extremely red objects and show
that T dwarfs occupy a unique region in optical color-color space. The
area density of methane dwarfs in this sample is one per 140 square
degrees, and the space density is about one per 160 pc<SUP>3</SUP>. We
use simulations to show that this is consistent with an IMF that is
slowly rising toward lower mass through the substellar regime (dn/dm
m<SUP>-α </SUP>, where α < 1), in reasonable agreement with the
results of many open cluster studies. The inferred mass density in
substellar objects is about 10% of that in stars. Funding for the
SDSS is provided by the Alfred P. Sloan Foundation, NASA, NSF, DoE,
Monbukagakusho, the Max Planck Society and the member institutions. The
SDSS web site is http://www.sdss.org/.
---------------------------------------------------------
Title: Well Defined Areas of Doubt and Uncertainty in M Dwarf
Astrophysics
Authors: Hawley, S. L.
2002AAS...201.0201H Altcode: 2002AAS...201..201H; 2002BAAS...34.1094H
Although M dwarfs comprise some 80% of the stars in the Galaxy, many
of their properties remain unexplained. I will concentrate on three
well-defined, unsolved problems in these stars, to wit: 1) the response
of the M dwarf atmosphere to flare heating, a classic problem in stellar
atmospheric physics; 2) the appearance of a break in the HR diagram
in the mid-M dwarfs; and 3) the changes in surface magnetic activity
through the M dwarf temperature sequence. I will show conclusively
that, while our understanding of this ubiquitous population is far from
complete, M dwarfs are an excellent testbed for stellar astrophysics.
---------------------------------------------------------
Title: The Sloan Digital Sky Survey low mass star & brown
dwarf sample
Authors: Covey, K. R.; Hawley, S. L.; Walkowicz, L. M.; SDSS
Collaboration
2002AAS...201.1601C Altcode: 2002BAAS...34R1124C
The large numbers of late type stars and brown dwarf candidates
identified in the Sloan Digital Sky Survey's photometric and
spectrscopic databases have laid the foundation for a study of the
stellar population in the solar neighborhood, as well as at different
heights within the Galactic disk. We characterize the photometric
properties of these objects as a function of spectral type and present
derived spectroscopic and photometric parallax relations. We describe
the status of efforts to identify new candidates within the newly
public Data Release 1, and discuss topics of stellar astrophysics and
galactic structure for which this sample could hold promise.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Radial velocities of high-velocity
white dwarfs (Silvestri+, 2002)
Authors: Silvestri, N. M.; Oswalt, T. D.; Hawley, S. L.
2002yCat..51241118S Altcode:
Radial velocities and complete space motions were measured for 116
white dwarf stars with M dwarf companions (WD+M), including thirteen
pairs having "halo-like" velocities. These 116 WD+dM binaries were
observed on the 3.5 m telescope at the Apache Point Observatory (APO)
on nearly 30 half-nights between 2000 September 4 and 2001 October
20. The APO Double Imaging Spectrograph was used with a 15" slit,
yielding a resolution of approximately 2arcsrc/pixel. <P />>From
the near-solar abundance levels of the M dwarf companions, only one
potential stellar halo white dwarf (LP 164-52) was found in the sample,
12 of the 13 high-velocity white dwarfs being actually part of the
high-velocity tail of the thick disk rather than the dark matter halo
of the Galaxy. <P />(1 data file).
---------------------------------------------------------
Title: The Palomar/MSU Nearby Star Spectroscopic Survey. IV. The
Luminosity Function in the Solar Neighborhood and M Dwarf Kinematics
Authors: Reid, I. Neill; Gizis, John E.; Hawley, Suzanne L.
2002AJ....124.2721R Altcode:
We have used new astrometric and spectroscopic observations to
refine the volume-complete sample of M dwarfs defined in previous
papers in this series. With the addition of Hipparcos astrometry,
our revised VC<SUP>2</SUP> sample includes 558 main-sequence
stars in 448 systems. Analysis of that data set shows no evidence
of any systematic kinematic bias. Combining those data with a
Hipparcos-based sample of AFGK dwarfs within 25 pc of the Sun,
we have derived the solar neighborhood luminosity function,
Φ(M<SUB>V</SUB>), for stars with absolute magnitudes between -1 and
+17. Using empirical and semiempirical mass-M<SUB>V</SUB> relations,
we transform Φ(M<SUB>V</SUB>) to the present-day mass function, ψ(M)
(=dN/dM). Depending on the mass-luminosity calibration adopted, ψ(M)
can be represented by either a two-component or a three-component power
law. In either case, the power-law index α has a value of ~1.3 at low
masses (0.1 M<SUB>solar</SUB><M<0.7 M<SUB>solar</SUB>), and the
local mass density of main-sequence stars is ~0.031 M<SUB>solar</SUB>
pc<SUP>-3</SUP>. We have converted ψ(M) to an estimate of the
initial mass function, Ψ(M), by allowing for stellar evolution, the
density law perpendicular to the plane, and the local mix of stellar
populations. The results give α=1.1-1.3 at low masses and α=2.5-2.8
at high masses, with the change in slope lying between 0.7 and 1.1
M<SUB>solar</SUB>. Finally, the (U,W) velocity distributions of both
the VC<SUP>2</SUP> sample and the fainter (M<SUB>V</SUB>>4) stars
in the Hipparcos 25 pc sample are well represented by two-component
Gaussian distributions, with ~10% of the stars in the higher velocity
dispersion component. We suggest that the latter component is the
thick disk, and we offer a possible explanation for the relatively low
velocity dispersions shown by ultracool dwarfs. <P />Based partly on
observations made at the 60 inch (1.5 m) telescope at Palomar Mountain,
which is jointly owned by the California Institute of Technology and
the Carnegie Institution of Washington.
---------------------------------------------------------
Title: Wide Binary Systems and the Nature of High-Velocity White
Dwarfs
Authors: Silvestri, Nicole M.; Oswalt, Terry D.; Hawley, Suzanne L.
2002AJ....124.1118S Altcode:
We present measured radial velocities and complete space motions for
116 white dwarf stars with M dwarf companions. Thirteen pairs have
“halo-like” velocities. According to a recent study by Oppenheimer
et al., all these high-velocity white dwarfs should be considered
part of the dark matter heavy halo of the Galaxy, based on their
kinematics. Based on the near-solar abundance levels of the M
dwarf companions, we conclude that 12 of our 13 high-velocity white
dwarfs are actually part of the high-velocity tail of the thick disk,
rather than the dark matter halo of the Galaxy, in agreement with the
results of a recent study of 514 M dwarfs performed by Reid, Sahu,
& Hawley. We find only one potential stellar halo white dwarf
(LP 164-52) in our sample. The M dwarf companion of LP 164-52 is
a metal-poor, intermediate subdwarf with high-velocity UVW-space
motions. In view of the similarity to our sample, we conclude that
the majority of the dark matter halo white dwarfs identified by
Oppenheimer et al. are most likely to be members of the thick disk,
and hence their contribution to the dark matter content of the halo
is very much overestimated. Our results suggest that the assignment
of population membership solely on incomplete kinematical information
is not definitive and that a more robust examination of suspected halo
white dwarfs must be performed. Based on observations obtained with the
Apache Point Observatory 3.5 m telescope, which is owned and operated
by the Astrophysical Research Consortium, and the SARA Observatory at
Kitt Peak, which is owned and operated by the Southeastern Association
for Research in Astronomy.
---------------------------------------------------------
Title: The MACHO Project Large Magellanic Cloud Variable Star
Inventory. XII. Three Cepheid Variables in Eclipsing Binaries
Authors: Alcock, C.; Allsman, R. A.; Alves, D. R.; Becker, A. C.;
Bennett, D. P.; Cook, K. H.; Drake, A. J.; Freeman, K. C.; Griest, K.;
Hawley, S. L.; Keller, S.; Lehner, M. J.; Lepischak, D.; Marshall,
S. L.; Minniti, D.; Nelson, C. A.; Peterson, B. A.; Popowski, P.;
Pratt, M. R.; Quinn, P. J.; Rodgers, A. W.; Suntzeff, N.; Sutherland,
W.; Vandehei, T.; Welch, D. L.
2002ApJ...573..338A Altcode: 2002astro.ph..1481A
We present a method for solving the light curve of an eclipsing binary
system that contains a Cepheid variable as one of its components
as well as the solutions for three eclipsing Cepheids in the Large
Magellanic Cloud (LMC). A geometric model is constructed in which
the component stars are assumed to be spherical and on circular
orbits. The emergent system flux is computed as a function of time,
with the intrinsic variations in temperature and radius of the Cepheid
treated self-consistently. Fitting the adopted model to photometric
observations, incorporating data from multiple bandpasses, yields
a single parameter set best describing the system. This method is
applied to three eclipsing Cepheid systems from the MACHO project
LMC database: MACHO 6.6454.5, 78.6338.24, and 81.8997.87. A best-fit
value is obtained for each system's orbital period and inclination
and for the relative radius, color, and limb-darkening coefficients
of each star. Pulsation periods and parameterizations of the intrinsic
color variations of the Cepheids are also obtained, and the amplitude
of the radial pulsation of each Cepheid is measured directly. The
system 6.6454.5 is found to contain a 4.97 day Cepheid, which cannot
be definitely classified as type I or type II, with an unexpectedly
brighter companion. The system 78.6338.24 consists of a 17.7 day, W
Virginis class type II Cepheid with a smaller, dimmer companion. The
system 81.8997.87 contains an intermediate-mass, 2.03 day overtone
Cepheid with a dimmer, red giant secondary.
---------------------------------------------------------
Title: The Palomar/MSU Nearby Star Spectroscopic
Survey. III. Chromospheric Activity, M Dwarf Ages, and the Local
Star Formation History
Authors: Gizis, John E.; Reid, I. Neill; Hawley, Suzanne L.
2002AJ....123.3356G Altcode: 2002astro.ph..3499G
We present high-resolution echelle spectroscopy of 676 nearby M
dwarfs. Our measurements include radial velocities, equivalent widths of
important chromospheric emission lines, and rotational velocities for
rapidly rotating stars. We identify several distinct groups by their
Hα properties and investigate variations in chromospheric activity
among early (M0-M2.5) and mid (M3-M6) dwarfs. Using a volume-limited
sample together with a relationship between age and chromospheric
activity, we show that the rate of star formation in the immediate
solar neighborhood has been relatively constant over the last 4 Gyr. In
particular, our results are inconsistent with recent large bursts of
star formation. We use the correlation between Hα activity and age as a
function of color to set constraints on the properties of L and T dwarf
secondary components in binary systems. We also identify a number of
interesting stars, including rapid rotators, radial velocity variables,
and spectroscopic binaries. Observations were made at the 60 inch
telescope at Palomar Mountain, which is jointly owned by the California
Institute of Technology and the Carnegie Institution of Washington.
---------------------------------------------------------
Title: Characterization of M, L, and T Dwarfs in the Sloan Digital
Sky Survey
Authors: Hawley, Suzanne L.; Covey, Kevin R.; Knapp, Gillian R.;
Golimowski, David A.; Fan, Xiaohui; Anderson, Scott F.; Gunn, James E.;
Harris, Hugh C.; Ivezić, Željko; Long, Gary M.; Lupton, Robert H.;
McGehee, Peregrine M.; Narayanan, Vijay; Peng, Eric; Schlegel, David;
Schneider, Donald P.; Spahn, Emily Y.; Strauss, Michael A.; Szkody,
Paula; Tsvetanov, Zlatan; Walkowicz, Lucianne M.; Brinkmann, J.;
Harvanek, Michael; Hennessy, Gregory S.; Kleinman, S. J.; Krzesinski,
Jurek; Long, Dan; Neilsen, Eric H.; Newman, Peter R.; Nitta, Atsuko;
Snedden, Stephanie A.; York, Donald G.
2002AJ....123.3409H Altcode: 2002astro.ph..4065H
An extensive sample of M, L, and T dwarfs identified in the Sloan
Digital Sky Survey (SDSS) has been compiled. The sample of 718 dwarfs
includes 677 new objects (629 M dwarfs and 48 L dwarfs), together with
41 that have been previously published. All new objects and some of
the previously published ones have new optical spectra obtained either
with the SDSS spectrographs or with the Apache Point Observatory 3.5
m ARC telescope. Spectral types and SDSS colors are available for all
objects; approximately 35% also have near-infrared magnitudes measured
by 2MASS (Two Micron All Sky Survey) or on the Mauna Kea system. We use
this sample to characterize the color-spectral type and color-color
relations of late-type dwarfs in the SDSS filters and to derive
spectroscopic and photometric parallax relations for use in future
studies of the luminosity and mass functions based on SDSS data. We
find that the i<SUP>*</SUP>-z<SUP>*</SUP> and i<SUP>*</SUP>-J colors
provide good spectral type and absolute magnitude (M<SUB>i*</SUB>)
estimates for M and L dwarfs. Our distance estimates for the current
sample indicate that SDSS is finding early M dwarfs out to ~1.5 kpc, L
dwarfs to ~100 pc, and T dwarfs to ~20 pc. The T dwarf photometric data
show large scatter and are therefore less reliable for spectral type
and distance estimation. Based on observations obtained with the Sloan
Digital Sky Survey and the Apache Point Observatory 3.5 m telescope,
which are owned and operated by the Astrophysical Research Consortium.
---------------------------------------------------------
Title: Multiwavelength Flares on AD Leo
Authors: Allred, J. C.; Hawley, S. L.; Johns-Krull, C. M.; Fisher,
G. H.
2002AAS...200.7408A Altcode: 2002BAAS...34..771A
We report on a multiwavelength flare campaign conducted during March,
2000 on the dM3e flare star AD Leo. Participating observatories included
HST, EUVE, McDonald, DAO, Stephanion, CrAO, and Jodrell Bank. We present
a preliminary analysis of the optical and ultraviolet photometry and
spectrosocpy obtained during several flares observed with multiple
instruments. The CIV light curves and velocity evolution are consistent
with models of chromospheric evaporation and condensation which are
commonly applied to solar flares.
---------------------------------------------------------
Title: Transition Region Emission Observed During a Flare on VB8
Authors: Hawley, S. L.; Johns-Krull, C. M.
2002AAS...200.7416H Altcode: 2002BAAS...34..772H
We present results from our cycle 10 HST program to search for
transition region emission in very low mass stars. Our program is aimed
at 1) detecting emission; and 2) distinguishing between flaring and
persistent origin for the emission. Observations of our first target,
VB8 (dM7e), comprise a sequence of 15 exposures with STIS, each of 5
minute duration. Our preliminary analysis indicates that we detect C
IV and He I emission during only one of the exposures. This supports
the hypothesis that transition region emission occurs as the result
of transient flare activity in very low mass stars. This research was
made possible by grant HST-GO-9090 from the Space Telescope Science
Institute, operated by AURA for NASA.
---------------------------------------------------------
Title: Is There an Empirical Connection Between Rotation and Activity
in Low Mass Stars?
Authors: Hawley, Suzanne
2002smra.progE...9H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Sloan Digital Sky Survey: Early Data Release
Authors: Stoughton, Chris; Lupton, Robert H.; Bernardi, Mariangela;
Blanton, Michael R.; Burles, Scott; Castander, Francisco J.; Connolly,
A. J.; Eisenstein, Daniel J.; Frieman, Joshua A.; Hennessy, G. S.;
Hindsley, Robert B.; Ivezić, Željko; Kent, Stephen; Kunszt,
Peter Z.; Lee, Brian C.; Meiksin, Avery; Munn, Jeffrey A.; Newberg,
Heidi Jo; Nichol, R. C.; Nicinski, Tom; Pier, Jeffrey R.; Richards,
Gordon T.; Richmond, Michael W.; Schlegel, David J.; Smith, J. Allyn;
Strauss, Michael A.; SubbaRao, Mark; Szalay, Alexander S.; Thakar,
Aniruddha R.; Tucker, Douglas L.; Vanden Berk, Daniel E.; Yanny,
Brian; Adelman, Jennifer K.; Anderson, John E., Jr.; Anderson,
Scott F.; Annis, James; Bahcall, Neta A.; Bakken, J. A.; Bartelmann,
Matthias; Bastian, Steven; Bauer, Amanda; Berman, Eileen; Böhringer,
Hans; Boroski, William N.; Bracker, Steve; Briegel, Charlie; Briggs,
John W.; Brinkmann, J.; Brunner, Robert; Carey, Larry; Carr, Michael
A.; Chen, Bing; Christian, Damian; Colestock, Patrick L.; Crocker,
J. H.; Csabai, István; Czarapata, Paul C.; Dalcanton, Julianne;
Davidsen, Arthur F.; Davis, John Eric; Dehnen, Walter; Dodelson,
Scott; Doi, Mamoru; Dombeck, Tom; Donahue, Megan; Ellman, Nancy; Elms,
Brian R.; Evans, Michael L.; Eyer, Laurent; Fan, Xiaohui; Federwitz,
Glenn R.; Friedman, Scott; Fukugita, Masataka; Gal, Roy; Gillespie,
Bruce; Glazebrook, Karl; Gray, Jim; Grebel, Eva K.; Greenawalt,
Bruce; Greene, Gretchen; Gunn, James E.; de Haas, Ernst; Haiman,
Zoltán; Haldeman, Merle; Hall, Patrick B.; Hamabe, Masaru; Hansen,
Brad; Harris, Frederick H.; Harris, Hugh; Harvanek, Michael; Hawley,
Suzanne L.; Hayes, J. J. E.; Heckman, Timothy M.; Helmi, Amina; Henden,
Arne; Hogan, Craig J.; Hogg, David W.; Holmgren, Donald J.; Holtzman,
Jon; Huang, Chih-Hao; Hull, Charles; Ichikawa, Shin-Ichi; Ichikawa,
Takashi; Johnston, David E.; Kauffmann, Guinevere; Kim, Rita S. J.;
Kimball, Tim; Kinney, E.; Klaene, Mark; Kleinman, S. J.; Klypin,
Anatoly; Knapp, G. R.; Korienek, John; Krolik, Julian; Kron, Richard
G.; Krzesiński, Jurek; Lamb, D. Q.; Leger, R. French; Limmongkol,
Siriluk; Lindenmeyer, Carl; Long, Daniel C.; Loomis, Craig; Loveday,
Jon; MacKinnon, Bryan; Mannery, Edward J.; Mantsch, P. M.; Margon,
Bruce; McGehee, Peregrine; McKay, Timothy A.; McLean, Brian; Menou,
Kristen; Merelli, Aronne; Mo, H. J.; Monet, David G.; Nakamura, Osamu;
Narayanan, Vijay K.; Nash, Thomas; Neilsen, Eric H., Jr.; Newman,
Peter R.; Nitta, Atsuko; Odenkirchen, Michael; Okada, Norio; Okamura,
Sadanori; Ostriker, Jeremiah P.; Owen, Russell; Pauls, A. George;
Peoples, John; Peterson, R. S.; Petravick, Donald; Pope, Adrian;
Pordes, Ruth; Postman, Marc; Prosapio, Angela; Quinn, Thomas R.;
Rechenmacher, Ron; Rivetta, Claudio H.; Rix, Hans-Walter; Rockosi,
Constance M.; Rosner, Robert; Ruthmansdorfer, Kurt; Sandford, Dale;
Schneider, Donald P.; Scranton, Ryan; Sekiguchi, Maki; Sergey, Gary;
Sheth, Ravi; Shimasaku, Kazuhiro; Smee, Stephen; Snedden, Stephanie A.;
Stebbins, Albert; Stubbs, Christopher; Szapudi, István; Szkody, Paula;
Szokoly, Gyula P.; Tabachnik, Serge; Tsvetanov, Zlatan; Uomoto, Alan;
Vogeley, Michael S.; Voges, Wolfgang; Waddell, Patrick; Walterbos,
René; Wang, Shu-i.; Watanabe, Masaru; Weinberg, David H.; White,
Richard L.; White, Simon D. M.; Wilhite, Brian; Wolfe, David; Yasuda,
Naoki; York, Donald G.; Zehavi, Idit; Zheng, Wei
2002AJ....123..485S Altcode:
The Sloan Digital Sky Survey (SDSS) is an imaging and spectroscopic
survey that will eventually cover approximately one-quarter of the
celestial sphere and collect spectra of ~10<SUP>6</SUP> galaxies,
100,000 quasars, 30,000 stars, and 30,000 serendipity targets. In 2001
June, the SDSS released to the general astronomical community its early
data release, roughly 462 deg<SUP>2</SUP> of imaging data including
almost 14 million detected objects and 54,008 follow-up spectra. The
imaging data were collected in drift-scan mode in five bandpasses (u,
g, r, i, and z); our 95% completeness limits for stars are 22.0, 22.2,
22.2, 21.3, and 20.5, respectively. The photometric calibration is
reproducible to 5%, 3%, 3%, 3%, and 5%, respectively. The spectra are
flux- and wavelength-calibrated, with 4096 pixels from 3800 to 9200 Å
at R~1800. We present the means by which these data are distributed
to the astronomical community, descriptions of the hardware used
to obtain the data, the software used for processing the data, the
measured quantities for each observed object, and an overview of the
properties of this data set.
---------------------------------------------------------
Title: Toward Spectral Classification of L and T Dwarfs: Infrared
and Optical Spectroscopy and Analysis
Authors: Geballe, T. R.; Knapp, G. R.; Leggett, S. K.; Fan, X.;
Golimowski, D. A.; Anderson, S.; Brinkmann, J.; Csabai, I.; Gunn,
J. E.; Hawley, S. L.; Hennessy, G.; Henry, T. J.; Hill, G. J.;
Hindsley, R. B.; Ivezić, Ž.; Lupton, R. H.; McDaniel, A.; Munn,
J. A.; Narayanan, V. K.; Peng, E.; Pier, J. R.; Rockosi, C. M.;
Schneider, D. P.; Smith, J. Allyn; Strauss, M. A.; Tsvetanov, Z. I.;
Uomoto, A.; York, D. G.; Zheng, W.
2002ApJ...564..466G Altcode: 2001astro.ph..8443G
We present 0.6-2.5 μm, R>~400 spectra of 27 cool, low-luminosity
stars and substellar objects. Based on these and previously published
spectra, we develop a preliminary spectral classification system for L
and T dwarfs. For late L and T types the classification system is based
entirely on four spectral indices in the 1-2.5 μm interval. Two of
these indices are derived from water absorption bands at 1.15 and 1.4
μm, the latter of which shows a smooth increase in depth through the
L and T sequences and can be used to classify both spectral types. The
other two indices make use of methane absorption features in the H
and K bands, with the K-band index also applicable to mid-to-late
L dwarfs. Continuum indices shortward of 1 μm used by previous
authors to classify L dwarfs are found to be useful only through
mid-L subclasses. We employ the 1.5 μm water index and the 2.2 μm
methane index to complete the L classification through L9.5 and to
link the new system with a modified version of the 2MASS “color-d”
index. By correlating the depths of the methane and water absorption
features, we establish a T spectral sequence from T0 to T8, based on
all four indices, that is a smooth continuation of the L sequence. We
reclassify two 2MASS L8 dwarfs as L9 and L9.5 and identify one SDSS
object as L9. In the proposed system methane absorption appears in the
K band approximately at L8, two subclasses earlier than its appearance
in the H band. The L and T spectral classes are distinguished by the
absence and presence, respectively, of H-band methane absorption.
---------------------------------------------------------
Title: L Dwarfs Found in Sloan Digital Sky Survey Commissioning
Data. II. Hobby-Eberly Telescope Observations
Authors: Schneider, Donald P.; Knapp, Gillian R.; Hawley, Suzanne L.;
Covey, Kevin R.; Fan, Xiaohui; Ramsey, Lawrence W.; Richards, Gordon
T.; Strauss, Michael A.; Gunn, James E.; Hill, Gary J.; MacQueen,
Phillip J.; Adams, Mark T.; Hill, Grant M.; Ivezić, Željko; Lupton,
Robert H.; Pier, Jeffrey R.; Saxe, David H.; Shetrone, Matthew; Tufts,
Joseph R.; Wolf, Marsha J.; Brinkmann, J.; Csabai, István; Hennessy,
G. S.; York, Donald G.
2002AJ....123..458S Altcode: 2001astro.ph.10273S
Low-dispersion optical spectra have been obtained with the Hobby-Eberly
Telescope of 22 very red objects found in early imaging data from the
Sloan Digital Sky Survey (SDSS). The objects are assigned spectral types
on the Two Micron All Sky Survey (2MASS) system and are found to range
from late M to late L. The red and near-infrared colors from SDSS and
2MASS correlate closely with each other, and most of the colors are
closely related to spectral type in this range; the exception is the
i*-z* color, which appears to be independent of spectral type between
about M7 and L4. The spectra suggest that this independence is due
to the disappearance of the TiO and VO absorption in the i band for
later spectral types, the presence of strong Na I and K I absorption
in the i band, and the gradual disappearance of the 8400 Å absorption
of TiO and FeH in the z band. Based on observations obtained with
the Sloan Digital Sky Survey, which is owned and operated by the
Astrophysical Research Consortium, and on observations obtained with
the Hobby-Eberly Telescope, which is a joint project of the University
of Texas at Austin, Pennsylvania State University, Stanford University,
Ludwig-Maximillians-Universität München, and Georg-August-Universität
Göttingen.
---------------------------------------------------------
Title: EUVE and Multiwavelength Studies of Stellar Flares
Authors: Hawley, S. L.
2002ASPC..264..123H Altcode: 2002ccea.conf..123H
No abstract at ADS
---------------------------------------------------------
Title: Cataclysmic Variables from The Sloan Digital Sky Survey. I. The
First Results
Authors: Szkody, Paula; Anderson, Scott F.; Agüeros, Marcel;
Covarrubias, Ricardo; Bentz, Misty; Hawley, Suzanne; Margon, Bruce;
Voges, Wolfgang; Henden, Arne; Knapp, Gillian R.; Vanden Berk, Daniel
E.; Rest, Armin; Miknaitis, Gajus; Magnier, Eugene; Brinkmann, J.;
Csabai, I.; Harvanek, M.; Hindsley, R.; Hennessy, G.; Ivezic, Z.;
Kleinman, S. J.; Lamb, D. Q.; Long, D.; Newman, P. R.; Neilsen, E. H.;
Nichol, R. C.; Nitta, A.; Schneider, D. P.; Snedden, S. A.; York, D. G.
2002AJ....123..430S Altcode: 2001astro.ph.10291S
The commissioning year of the Sloan Digital Sky Survey (SDSS) has
demonstrated that many cataclysmic variables (CVs) have been missed in
previous surveys with brighter limits. We report the identification of
22 CVs, of which 19 are new discoveries and three are known systems
(SW UMa, BH Lyn, and OU Vir). A compendium of positions, colors, and
characteristics of these systems obtained from the SDSS photometry
and spectroscopy is presented, along with data obtained during
follow-up studies with the Apache Point Observatory and Manastash
Ridge Observatory telescopes. We have determined orbital periods
for three of the new systems, two show dwarf nova outbursts, and
the third is a likely magnetic system with eclipses of its region of
line emission. Based on these results, we expect the completed survey
to locate at least 400 new CVs. Most of these will be faint systems
with low accretion rates that will provide new constraints on binary
evolution models. Based on observations obtained with the Sloan Digital
Sky Survey and with the Apache Point Observatory 3.5 m telescope,
which are owned and operated by the Astrophysical Research Consortium.
---------------------------------------------------------
Title: Infrared Photometry of Late-M, L, and T Dwarfs
Authors: Leggett, S. K.; Golimowski, David A.; Fan, Xiaohui; Geballe,
T. R.; Knapp, G. R.; Brinkmann, J.; Csabai, István; Gunn, James
E.; Hawley, Suzanne L.; Henry, Todd J.; Hindsley, Robert; Ivezić,
Željko; Lupton, Robert H.; Pier, Jeffrey R.; Schneider, Donald P.;
Smith, J. Allyn; Strauss, Michael A.; Uomoto, Alan; York, D. G.
2002ApJ...564..452L Altcode: 2001astro.ph..8435L
We present ZJHKL<SUP>'</SUP>M<SUP>'</SUP> photometry of a sample of 58
late M, L, and T dwarfs, most of which are identified from the Sloan
Digital Sky Survey and the Two Micron All-Sky Survey. Near-infrared
spectra and spectral classifications for most of this sample
are presented in a companion paper by Geballe et al. We derive
the luminosities of 18 dwarfs in the sample with known parallaxes,
and the results imply that the effective temperature range for the L
dwarfs in our sample is approximately 2200-1300 K and for the T dwarfs
1300-800 K. We obtained new photometric data at the United Kingdom
Infrared Telescope for: 42 dwarfs at Z, 34 dwarfs at JHK, 21 dwarfs
at L', as well as M' data for two L dwarfs and two T dwarfs. The M'
data provide the first accurate photometry for L and T dwarfs in
this bandpass-for a T2 and a T5 dwarf, we find K-M<SUP>'</SUP>=1.2
and 1.6, respectively. These colors are much bluer than predicted by
published models, suggesting that CO may be more abundant in these
objects than expected, as has been found for the T6 dwarf Gl 229B. We
also find that K-L' increases monotonically through most of the M,
L, and T subclasses, but it is approximately constant between types
L6 and T5, restricting its usefulness as a temperature indicator. The
degeneracy is probably due to the onset of CH<SUB>4</SUB> absorption
at the blue edge of the L' bandpass. The JHK colors of L dwarfs show
significant scatter, suggesting that the fluxes in these bandpasses
are sensitive to variations in photospheric dust properties. The H-K
colors of the later T dwarfs also show some scatter, which we suggest
is due to variations in pressure-induced H<SUB>2</SUB> opacity, which
is sensitive to gravity and metallicity.
---------------------------------------------------------
Title: LONEOS RR Lyrae Survey: Early Results
Authors: Miceli, A.; Rest, A.; Miknaitis, G. A.; Covarrubias, R.;
Stubbs, C. W.; Hawley, S.; Magnier, G.; Koehn, B.; Bowell, T.; Cook, K.
2001AAS...19910111M Altcode: 2001BAAS...33.1463M
We have investigated 6000 sq. deg. of data from the Lowell Observatory
Near Earth Object Survey (LONEOS) with more than 20 epochs down to a
limiting magnitude of 19 in R (see Rest, et.al these proceedings). From
this dataset, thousands of candidate RR Lyrae stars have been
extracted. RR Lyrae stars are excellent standard candles for two
reasons: they have characteristic lightcurves which make them easily
identifiable, and they also have small scatter in their intrinsic
brightness. Thus, a sufficiently large sample of Galactic RR Lyrae
stars can probe the structure of the Galaxy. We present lightcurves of
several newly discovered RR Lyrae. We also present follow-up photometry
with the 3.5-m Apache Point Observatory (APO) and 0.76-m Manastash
Ridge Observatory (MRO) to determine the degree of contamination and
for the refinement of selection criteria. Finally, we present radial
velocity measurements taken at APO for a small sample of RR Lyrae
stars identified in LONEOS.
---------------------------------------------------------
Title: T Tauri and Chromospherically Active Stars in the SDSS I:
Photometric Selection and First Results
Authors: McGehee, P. M.; Hawley, S. L.; Ivezic, Z.
2001AAS...199.8901M Altcode: 2001BAAS...33.1434M
We present first results from the Sloan Digital Sky Survey T Tauri and
flare star program including new Classical T Tauris and related emission
line stars selected on the basis of SDSS u<SUP>*g^*r^*i^*z^*</SUP>
photometry and spectroscopically verified using the facilities at
Apache Point Observatory (APO) and Calar Alto Observatory (CAHA). The
photometric search criteria make use of reddening invariant combinations
of the SDSS passbands to select for late spectral type stars exhibiting
an ultraviolet excess. The depth of the SDSS UV-excess technique is
compared with other wide-field surveys including IRAS, RASS, and,
in detail, 2MASS, where it is evident that the SDSS will excel in the
detection of dMe and the post-circumstellar disk Weak-lined T Tauris
that are expected to comprise the bulk of the high galactic latitude
pre-main-sequence star population.
---------------------------------------------------------
Title: High-Velocity White Dwarfs: Thick Disk, Not Dark Matter
Authors: Reid, I. Neill; Sahu, Kailash C.; Hawley, Suzanne L.
2001ApJ...559..942R Altcode: 2001astro.ph..4110R
We present an alternative interpretation of the nature of the extremely
cool, high-velocity white dwarfs identified by Oppenheimer et al. in
a high-latitude astrometric survey. We argue that the velocities of
the majority of the sample are more consistent with the high-velocity
tail of a rotating population, probably the thick disk, rather than
with a pressure-supported halo system. Indeed, the observed numbers
are well matched by predictions based on the kinematics of a complete
sample of nearby M dwarfs. Analyzing only stars showing retrograde
motion gives a local density close to that expected for white dwarfs
in the stellar (R<SUP>-3.5</SUP>) halo. Under our interpretation,
none of the white dwarfs need be assigned to the dark matter heavy
halo. However, luminosity functions derived from observations of these
stars can set important constraints on the age of the oldest stars in
the Galactic disk.
---------------------------------------------------------
Title: The Chromospheric Activity-Age Relation for M Dwarf Stars
Authors: Silvestri, Nicole M.; Oswalt, Terry D.; Hawley, Suzanne L.
2001noao.prop..254S Altcode:
We propose to complete our study of M dwarf/white dwarf binary
systems with the goal of determining the correlation between the
chromospheric activity and ages of M dwarf stars for ages up to the
age of the galactic disk (~M7-8; ~10 Gyr). This project is unique in
that it uses the well determined age of the white dwarf to establish
the age of the M dwarf in the binary system. Previous studies used
open clusters for age determination, and were confined to ages <
5 Gyr. These indicated the surprising result that the age at which
activity ceased depended on the mass (temperature, color) of the M
dwarf, in contrast to the well known Skumanich relation for early type
F-G-K stars where the age-activity relation is a manifestation of the
rotational velocity evolution. Such a different age-activity relation
has important consequences for understanding the dynamo generation
of the magnetic fields in the lowest mass stars and brown dwarfs,
and the different manifestations of the magnetic activity compared to
solar-type stars.
---------------------------------------------------------
Title: A Next Generation Microlensing Survey of the LMC
Authors: Stubbs, Christopher W.; Cook, Kem; Hawley, Suzanne; Welch,
Doug; Alcock, Charles; Mighell, Ken; Becker, Andrew; Nelson, Cailin;
Drake, Andrew; Rest, Armin; Miknaitis, Gajus; Keller, Stefan
2001noao.prop...37S Altcode:
One of the foremost outstanding problems in the physical sciences
is the nature and distribution of the “dark matter” that is the
gravitationally dominant component of mass in all galaxies, including
the Milky Way. One way to search for astrophysical dark matter objects
(often called MAssive Compact Halo Objects, or MACHOs) is to search for
the transient brightening of background stars due to the gravitational
lensing by foreground MACHOs. A previous experiment has produced a
peculiar result: While the detected rate of gravitational lensing
events indicates that MACHOs comprise at most perhaps 20% of the
dark matter halo, the number of events far exceeds that expected from
known stellar populations. The nature of these excess lensing objects
remains a mystery. We intend to determine the nature of this lensing
population, which may outweigh all other known components of the Galaxy,
by conducting a search with at least a tenfold improvement in the event
detection rate. This will be one of the deepest time-domain surveys
to date. The survey will have no proprietary data period, and we can
draw heavily upon existing tools to provide useful access to the data.
---------------------------------------------------------
Title: Transition Region Emission in Very Low Mass Stars
Authors: Hawley, Suzanne
2001hst..prop.9090H Altcode: 2001hst..prop.5438H
The origin of the magnetic heating which produces hot outer atmospheres
in late-type stars is one of the most interesting, and elusive,
problems in stellar astrophysics. Our poor understanding is due in part
to the lack of data for a large and varied sample of stars, which are
needed to provide the basis for a general theory. Observationally, our
knowledge is particularly sparse for the very low mass stars. In fact,
diametrically opposed conclusions have been reached in this field:
the available data has been interpreted 1.} to indicate that magnetic
heating of the hot transition region and corona becomes relatively more
important in stars of later spectral type {lower mass} - the pre-1999
position; and 2.} to claim that the magnetic heating is insufficient
to produce these regions at all, except during flares, in very low mass
objects - the current widely held view. The manifestations of magnetic
activity at the stellar/brown dwarf boundary have yet to be probed in
transition region diagnostics; previous IUE and HST/GHRS observations
were not sensitive enough to provide constraining data. Our proposed
HST/STIS observations of three very low mass stars will conclusively
show if quiescent magnetic heating sufficient to produce a hot
outer atmosphere still exists in these objects, or whether they are
categorically different than higher mass M dwarfs.
---------------------------------------------------------
Title: SDSS Stellar Spectroscopy
Authors: Pier, J. R.; Harris, H. C.; Vanden Berk, D. E.; Bauer, A.;
Anderson, S. F.; Hawley, S. L.; Margon, B.; Szkody, P.; Knapp, G. R.;
Schlegel, D.; Strauss, M. A.; SDSS Collaboration
2000AAS...197.1310P Altcode: 2000BAAS...32.1424P
While the SDSS spectroscopic survey is intended primarily to obtain
redshifts of galaxies and quasars, spectra of thousands of stars are
also being obtained. Some of these stars are intended spectroscopic
targets: there are standards of various kinds, stars targeted for
stellar science and/or Galactic structure science, and objects that are
assigned spectroscopic fibers due to their unusual location in 5-color
space. We present a number of spectra showing the spectral sequence
of early through late stellar types. This sequence demonstrates the
coverage, resolution, and spectral classification capabilities of
the SDSS spectrographs and shows the promise of a stellar spectral
atlas of SDSS spectra, currently under construction. We also show
spectra of unusual objects. Many of these are of relatively rare,
though previously classified, stellar types or binary systems. But
some of the more unusual spectra show stellar features that have defied
classification to date.
---------------------------------------------------------
Title: The Chromospheric Activity-Age Relation for M Dwarf Stars
Authors: Silvestri, N. M.; Oswalt, T. D.; Hawley, S. L.
2000AAS...197.4416S Altcode: 2000BAAS...32.1474S
We present preliminary results from our study in which we use
moderate resolution spectroscopy to determine the correlation
between the chromospheric activity and age of M dwarf stars in wide
binary systems. We have observed ~50 M dwarf stars from our sample
with the Apache Point Observatory 3.5-m telescope. We measure the
ratio of Hα luminosity to the bolometric luminosity (L<SUB>Hα
</SUB>/L<SUB>bol</SUB>) of the M dwarf---a measure of activity that is
proven to correlate well with age. This project is unique in that it
will extend the chromospheric activity-age relation of low-mass main
sequence stars beyond the ages provided by cluster methods. The ages
so determined are also independent of the uncertainties in cluster
age determinations. The technique has the potential to improve by at
least a factor of two the precision and the range over which ages can
currently be determined for main sequence stars. Work on this project
is supported by the NASA Graduate Student Researchers Program grant
NGT-50290 (N.M.S.).
---------------------------------------------------------
Title: Optical Spectroscopy of Supernova 1993J During Its First
2500 Days
Authors: Matheson, Thomas; Filippenko, Alexei V.; Barth, Aaron J.;
Ho, Luis C.; Leonard, Douglas C.; Bershady, Matthew A.; Davis, Marc;
Finley, David S.; Fisher, David; González, Rosa A.; Hawley, Suzanne
L.; Koo, David C.; Li, Weidong; Lonsdale, Carol J.; Schlegel, David;
Smith, Harding E.; Spinrad, Hyron; Wirth, Gregory D.
2000AJ....120.1487M Altcode: 2000astro.ph..6263M
We present 42 low-resolution spectra of supernova (SN) 1993J, our
complete collection from the Lick and Keck observatories, from day
3 after explosion to day 2454, as well as one Keck high-dispersion
spectrum from day 383. SN 1993J began as an apparent SN II, albeit
an unusual one. After a few weeks, a dramatic transition took place,
as prominent helium lines emerged in the spectrum. SN 1993J had
metamorphosed from a SN II to a SN IIb. Nebular spectra of SN 1993J
closely resemble those of SNe Ib and Ic, but with a persistent
Hα line. At very late times, the Hα emission line dominated the
spectrum, but with an unusual, boxlike profile. This is interpreted
as an indication of circumstellar interaction.
---------------------------------------------------------
Title: Coordinated Observations of Stellar Flares on AD Leo
Authors: Hawley, Suzanne
2000hst..prop.8613H Altcode: 2000hst..prop.4949H
We will obtain high resolution HST/STIS spectra of the dMe star AD Leo
during periods of quiescence and during flares to study the physics
of atmospheric heating in flare stars. The HST observations will
form an essential part of a large, coordinated observing campaign
including FUSE, EUVE, and ground-based observations {both multicolor
photometry and high resolution optical spectroscopy}. The STIS spectra,
in combination with data from the other satellites, will allow us to
determine the structure {during quiescence} and evolution {during
flares} of the temperature and density in the corona, transition
region, and chromosphere. These data will provide strong empirical
constraints on our current generation of flare evolution models. The
uniquely high spectral resolution of the STIS data will also allow us
to directly observe the dynamic effects of the chromospheric shocks
that are predicted by the models. In addition, we will search for
significant red-shifted emission in the hydrogen Lyman-Alpha line
during the flare rise phase, which is a signature of an energetic
proton beam. The existence and role of proton beams in both solar and
stellar flares is currently a subject of considerable debate.
---------------------------------------------------------
Title: CCD photometry and proper motions of late-type stars in the
young open cluster Stock 2
Authors: Foster, D. C.; Theissen, A.; Butler, C. J.; Rolleston,
W. R. J.; Byrne, P. B.; Hawley, S. L.
2000A&AS..143..409F Altcode:
We present the results of the first CCD BVRI photometric and proper
motion study of late-type stars in the young open cluster Stock
2. Twenty-one fields of approximately 5'x 5' size have been observed
photometrically, from which we have identified 118 candidate members
based on their positions on colour-magnitude diagrams relative to
theoretical isochrones. From a comparison of the known star density
of the Pleiades, we estimate the contamination of this selection
process due to background stars to be as large as ~ 50%. However,
only 22 of those 118 candidate members have proper motions consistent
with membership, suggesting that the contamination is of the order
of 80%. Additional candidate members were found by means of a proper
motion analysis of Schmidt plate material for a 3<SUP>deg</SUP>x
3<SUP>deg</SUP> field containing the cluster. The cluster proper motion
allows us to separate members from background and foreground stars. We
have found 634 stars with a membership probability >= 50% down to
a limiting magnitude of B ~ 20, corresponding to late-M dwarfs at the
distance of Stock 2. Table 5 and the Table Appendix are only 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/Abstract.html.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Stock 2 CCD photometry and proper
motions (Foster+, 2000)
Authors: Foster, D. C.; Theissen, A.; Butler, C. J.; Rolleston,
W. R. J.; Byrne, P. B.; Hawley, S. L.
2000yCat..41430409F Altcode:
We present the results of the first CCD BVRI photometric and proper
motion study of late-type stars in the young open cluster Stock
2. Twenty-one fields of approximately 5'x5' size have been observed
photometrically, from which we have identified 118 candidate members
based on their positions on colour-magnitude diagrams relative to
theoretical isochrones. From a comparison of the known star density
of the Pleiades, we estimate the contamination of this selection
process due to background stars to be as large as ~50%. However,
only 22 of those 118 candidate members have proper motions consistent
with membership, suggesting that the contamination is of the order
of 80%. Additional candidate members were found by means of a proper
motion analysis of Schmidt plate material for a 3°x3° field containing
the cluster. The cluster proper motion allows us to separate members
from background and foreground stars. We have found 634 stars with
a membership probability >=50% down to a limiting magnitude of
B=~20, corresponding to late-M dwarfs at the distance of Stock 2. (2
data files).
---------------------------------------------------------
Title: Understanding The Secondary in AL Com
Authors: Szkody, Paula; Hawley, Suzanne; Harrison, Thomas; Howell,
Steve; Laws, Chris
2000noao.prop..362S Altcode:
We will use the MMT Spectrograph at moderate resolution to explore
the secondary in the faint (20th mag), ultrashort period (81 min)
cataclysmic variable AL Com. WHT optical spectra obtained during
our HST UV spectral program in 1996 indicated broad band features
consistent with MgH and CaH. The corresponding lack of TiO implies
a metal defficiency in the secondary. Confirmation and further
exploration of these features will provide important insight into
abundance peculiarities related to the evolution of close binaries,
as AL Com sits at the critical juncture of the orbital period minimum
in evolution. Theoretical models predict systems that start at high
mass should ultimately evolve to the period minimum, after which the
secondary becomes a degenerate low mass (brown dwarf-like) star. The
low mass transfer rate in AL Com allows us a rare glimpse into the
stellar properties that are affected by mass transfer scenarios in
comparison to normal field M dwarfs and brown dwarfs.
---------------------------------------------------------
Title: Magnetic Activity in Low Mass Stars and Brown Dwarfs
Authors: Hawley, S.; Reid, I. N.; Gizis, J.
2000ASPC..212..252H Altcode: 2000fgpc.conf..252H
No abstract at ADS
---------------------------------------------------------
Title: New light on dark stars. Red dwarfs, low-mass stars, brown
dwarfs.
Authors: Reid, I. N.; Hawley, S. L.
2000nlod.book.....R Altcode:
This book presents a comprehensive discussion of both the astrophysical
structure of individual M dwarf and brown dwarf star, and their
collective statistical properties as a Galactic stellar population. The
first section of the book discusses M dwarfs and brown dwarfs as
individual objects - their observational properties, formation,
internal structure and atmospheres. The second section deals with
M dwarfs from the Galactic perspective - the number of stars, their
possible contribution to dark matter and the missing mass and their use
as probes of the stellar populations that make up our Galaxy. Contents:
(1) Astronomical concepts. (2) Basic observational properties of
low-mass dwarfs. (3) The structure, formation and evolution of low-mass
stars and brown dwarfs. (4) The photosphere. (5) Stellar activity. (6)
A Galactic structure primer. (7) The stellar luminosity function. (8)
The mass function. (9) Brown dwarfs: new light on dark stars. (10)
Extrasolar planets. (11) M dwarfs in the Galactic halo. Appendix:
The 8 parsec sample.
---------------------------------------------------------
Title: New light on dark stars : red dwarfs, low mass stars,
brown dwarfs
Authors: Reid, Neill; Hawley, Suzanne L.
2000nlds.conf.....R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Properties of M Dwarfs in Clusters and the Field
Authors: Hawley, S. L.; Reid, I. N.; Tourtellot, J. G.
2000vlms.conf..109H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Dynamic Models of Optical Emission in Impulsive Solar Flares
Authors: Abbett, William P.; Hawley, Suzanne L.
1999ApJ...521..906A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Some Astronomical Performance Advantages of Off-Axis Telescopes
Authors: Kuhn, J. R.; Hawley, S. L.
1999PASP..111..601K Altcode:
Measurements requiring very high photometric dynamic range, like
astronomical observations of faint objects near bright sources (e.g.,
extrasolar planet detection), are often limited by the scattered
light characteristics of the telescope. Although the light-gathering
power of recently built telescopes has increased dramatically,
their scattered light performance has not. We compare models and
measurements of telescope scattered light and discuss some of the
scientific and technical issues that suggest how a low scattered
light design could extend the scientific capabilities of moderate
(4 m aperture) telescopes.
---------------------------------------------------------
Title: Low-Mass Stars in Open Clusters. I. NGC 2516 and NGC 3680
Authors: Hawley, Suzanne L.; Tourtellot, Jonathan G.; Reid, I. Neill
1999AJ....117.1341H Altcode:
We have obtained photometric and spectroscopic observations of
low-mass stars in the young cluster NGC 2516 and the older cluster NGC
3680. Our observations extend the membership surveys approximately 6
mag fainter than previous studies in these clusters. Using fiducial
main sequences representative of the cluster metallicities, we present
candidate membership lists and use these to investigate the magnetic
activity and luminosity functions in the clusters. NGC 2516 has many
active M dwarfs and their properties are similar to those in other
young clusters. The dMe stars tend to lie above/red of the fiducial
main sequence in an M_V versus V-I color-magnitude diagram. Using
spectroscopic observations of the CaOH band at 6230 Å, we show
that CaOH is shallower in dMe stars compared with dM stars at the
same color. The absolute magnitudes of the dMe stars and dM stars
can be brought into agreement when CaOH is used as the temperature
indicator, which indicates that the magnetic activity is affecting
the V-I color in these stars. The activity strength, measured by log
(L_Hα/L_bol), increases toward lower mass stars, in agreement with
X-ray and chromospheric results in other young clusters. A few anomalous
stars with low activity strength were found, in contrast to other young
clusters. Comparison with a recent X-ray survey of NGC 2516 revealed
very few low-mass stars with X-ray emission, indicating that low-mass
cluster stars probably cannot explain the many X-ray sources without
optical counterparts in the survey. The luminosity function for NGC
2516 shows that the cluster is quite extended on the sky, and mass
segregation and preferential evaporation of certain low-mass stars
are probably occurring. The NGC 3680 observations are consistent with
a truncation of the cluster at ~1 M_solar (M_V<~5-6) stars. The
absence of low-mass members indicates extensive dynamical evolution
or a deviation from a typical initial mass function for this cluster.
---------------------------------------------------------
Title: Mass Segregation and the Initial Mass Function of Low Mass
Stars in Open Clusters
Authors: Tourtellot, Jonathan; Hawley, Suzanne L.; Reid, I. Neill
1999noao.prop..368T Altcode:
The observed luminosity function of low mass stars in an open cluster
provides information about the initial mass function (IMF) and the
dynamical evolution of that cluster. Our previous survey of open
clusters has revealed three clusters with interesting low mass star
luminosity functions. We propose to observe these clusters over a
much greater spatial extent, and to deeper magnitude limits, than has
previously been possible. These data will provide us with complete
samples of candidate members out to a large radius from the cluster
center. We will use the samples to investigate the mass segregation,
dynamical evolution and initial mass functions of the clusters.
---------------------------------------------------------
Title: CCDPHOT Photometry of Extremely Metal-Poor Stars
Authors: Anthony-Twarog, B. J.; Beers, T. C.; Hawley, S. L.;
Sarajedini, A.; Twarog, B. A.
1999ASPC..189..192A Altcode: 1999pcp..conf..192A
No abstract at ADS
---------------------------------------------------------
Title: Chromospheric Activity in Low Mass Stars: Observational
Results from Clusters and the Field
Authors: Hawley, S. L.; Reid, I. N.; Gizis, J. E.; Byrne, P. B.
1999ASPC..158...63H Altcode: 1999ssa..conf...63H
No abstract at ADS
---------------------------------------------------------
Title: Brown Dwarfs in the Hyades and Beyond?
Authors: Reid, I. Neill; Hawley, Suzanne L.
1999AJ....117..343R Altcode: 1998astro.ph.11347R
We have used both the Low-Resolution Imaging Spectrograph and the High
Resolution Echelle Spectrograph on the Keck telescopes to obtain spectra
of 12 candidate members of the Hyades identified by Leggett &
Hawkins. All of the objects are chromospherically active, late-type
M dwarfs, with Hα equivalent widths varying from 1 to 30 Å. Based
on our measured radial velocities, the level of stellar activity, and
other spectroscopic features, only one of the 12 stars has properties
consistent with cluster membership. We consider how this result affects
estimates of the luminosity and mass function of the Hyades. Five
of the 11 field stars have weak K I lambdalambda7665, 7699 and CaH
absorption as compared with M dwarf standards of the same spectral type,
suggesting a lower surface gravity. Two of these sources, LH 0416+14 and
LH 0419+15, exhibit significant lithium 6708 Å absorption. Based partly
on parallax measurements by the US Naval Observatory (Harris et al.),
we identify all five as likely to be young, pre-main-sequence objects
in or near the Taurus-Auriga association at distances of between 150
and 250 pc. A comparison with theoretical models of pre-main-sequence
stars indicates masses of less than 0.05 M_solar.
---------------------------------------------------------
Title: Dynamical Solar Flare Model Atmospheres
Authors: Abbett, W. P.; Hawley, S. L.
1999ASPC..158..212A Altcode: 1999ssa..conf..212A
No abstract at ADS
---------------------------------------------------------
Title: The absolute magnitudes of RR Lyraes from HIPPARCOS parallaxes
and proper motions
Authors: Fernley, J.; Barnes, T. G.; Skillen, I.; Hawley, S. L.;
Hanley, C. J.; Evans, D. W.; Solano, E.; Garrido, R.
1998A&A...330..515F Altcode:
We have used HIPPARCOS proper motions and the method of Statistical
Parallax to estimate the absolute magnitude of RR Lyrae stars. In
addition we used the HIPPARCOS parallax of RR Lyrae itself to determine
it's absolute magnitude. These two results are in excellent agreement
with each other and give a zero-point for the RR Lyrae M_v,[Fe/H]
relation of 0.77+/-0.15 at [Fe/H]=-1.53. This zero-point is in
good agreement with that obtained recently by several groups using
Baade-Wesselink methods which, averaged over the results from the
different groups, gives M_v = 0.73+/-0.14 at [Fe/H]=-1.53. Taking the
HIPPARCOS based zero-point and a value of 0.18+/-0.03 for the slope
of the M_v,[Fe/H] relation from the literature we find firstly, the
distance modulus of the LMC is 18.26+/-0.15 and secondly, the mean age
of the Globular Clusters is 17.4+/-3.0 GYrs. These values are compared
with recent estimates based on other "standard candles" that have also
been calibrated with HIPPARCOS data. It is clear that, in addition to
astrophysical problems, there are also problems in the application
of HIPPARCOS data that are not yet fully understood. Table 1, which
contains the basic data for the RR Lyraes, is available only at CDS. It
may be retrieved via anonymous FTP at cdsarc.u-strasbg.fr (130.79.128.5)
or via the Web at http://cdsweb.u-strasbg.fr/Abstract.html
---------------------------------------------------------
Title: Coordinated Observations of Stellar Flares on AD Leo
Authors: Hawley, Suzanne L.
1998euve.prop....4H Altcode:
We will obtain EUVE observations of the dMe star AD Leo during periods
of quiescence and during flares to study the physics of atmospheric
heating in flare stars. These observations will be coordinated with
our approved FUSE Guest Observer program and with ground-based
observations including multicolor photometry and high resolution
optical spectroscopy. The EUVE and optical light curves obtained
during flares will allow us to determine the coronal loop length and
flare coverage area on the stellar surface. The combination of EUVE,
FUSE and optical spectra will allow us to determine the structure
and evolution of temperature and density in the corona, transition
region, and chromosphere, providing unique constraints on our detailed
theoretical and numerical models of flare evolution corresponding to
various heating mechanisms.
---------------------------------------------------------
Title: The Absolute Magnitudes of RR Lyrae Stars
Authors: Fernley, J. D.; Barnes, T. G.; Skillen, I.; Hawley, S. L.;
Hanley, C. J.; Evans, D. W.; Solano, E.; Garrido, R.
1998ASPC..135..385F Altcode: 1998hcsp.conf..385F
We estimate the absolute magnitude of RR Lyrae stars using the recently
published HIPPARCOS data. Comparisons are made with previous work
on RR Lyrae absolute magnitudes and the impact on the distance scale
is discussed.
---------------------------------------------------------
Title: Extreme Ultraviolet Explorer Spectra of the 1993 March Flares
on AD Leonis: The Differential Emission Measure and Implications
for Coronal Structure
Authors: Cully, Scott L.; Fisher, George H.; Hawley, Suzanne L.;
Simon, Theodore
1997ApJ...491..910C Altcode:
The flare star AD Leonis was observed by the Extreme Ultraviolet
Explorer (EUVE) from 1993 March 1 to 3 UT. Two flares were detected by
the EUVE Deep Survey detector and spectrometer and also seen in optical
photometry on 1993 March 2 UT. The DS Lexan/boron-band and optical
results have been discussed in the previous paper by Hawley et al. In
this paper, we describe the spectra observed by EUVE during quiescence,
the peaks of the flares, and the decay phase following the first flare
and analyze the spectra to investigate the stellar atmospheric structure
during these time periods. <P />The spectra show that the observed EUV
emission from AD Leo is dominated by iron lines from a hot coronal
plasma. Two methods were used to estimate the differential emission
measure distribution (DEM) of the stellar corona. In the “Pottasch”
method, we fitted Gaussian line profiles to the strongest lines
in the spectra and estimated the DEM at the formation temperature
of those lines. Upper limits to the DEM were obtained in the case
of no detection. We also used a regularized inversion technique,
together with a weighting scheme based on information contained in the
plasma-emission model and on the signal-to-noise ratio of the data,
to find the DEM. The weighting was designed to prevent the noisy pixels
in our low-signal-to-noise ratio data from dominating the solution. The
results produced by the two methods are consistent in the temperature
regimes where strong lines are present. The inversion method provides
additional information where no strong single lines dominate the
spectra. The ability to use lines from the entire wavelength region
covered by the spectra allowed us to investigate the hydrogen column
N<SUB>H</SUB> and iron abundance [Fe/H]. <P />We found that [Fe/H]
in the corona of AD Leo was essentially unconstrained by our data, but
N<SUB>H</SUB> was well determined, yielding N<SUB>H</SUB> ~ (3 +/- 1)
× 10<SUP>18</SUP> cm<SUP>-2</SUP>. We assumed both a solar-coronal
value of [Fe/H] and a value one tenth of this and computed the DEM
distribution of the stellar corona for both cases. <P />The DEM of the
quiescent corona is dominated by a broad plateau of emission ranging
from 10<SUP>6.8</SUP> to 10<SUP>7.2</SUP> K, with the DEM of plasma
near 10<SUP>6.2</SUP> K about an order of magnitude less. We interpret
the plateau of the DEM in terms of a broad distribution of loops with
differing peak temperatures. We discuss and compare these results with
those of Giampapa et al., who analyzed ROSAT soft X-ray data from AD
Leo taken during a different time period. <P />The DEM of the flare
plasma is strongly peaked at temperatures greater than 10<SUP>7</SUP> K,
indicative of hot flare loops, while that of the decay phase consists of
a smaller peak at temperatures less than 10<SUP>7</SUP> K, as might be
expected from the cooling and condensation of previously heated flare
loops. These results are consistent with a flare model that includes
strong evaporation and condensation as in our previous paper. The EUVE
spectral analysis leads to lower peak flare temperatures than those
used in our previous paper, but the basic conclusion reached--that
the dominant flaring emission originates from long loops with L ~
R<SUB>*</SUB> and with peak flare densities ranging from 10<SUP>9</SUP>
to 10<SUP>11</SUP> cm<SUP>-3</SUP>--remains unchanged. This conclusion
is not qualitatively affected by the value of [Fe/H] used in our
DEM analysis.
---------------------------------------------------------
Title: CCD photometry of late-type stars in the young open cluster
IC 2602
Authors: Foster, D. C.; Byrne, P. B.; Hawley, S. L.; Rolleston,
W. R. J.
1997A&AS..126...81F Altcode:
We present the results of VRI photometry of the young open cluster IC
2602. Two 15 arcmin times 15 arcmin fields were observed in February
and May 1991 using the 1-m Swope telescope at Las Campanas. Using
theoretical isochrones obtained from \cite[D'Antona & Mazzitelli
(1994)]{dam94}, and allowing for observational and other uncertainties,
we identify 78 primary candidate members with 12<V<18.5 from
their positions on colour-magnitude diagrams. We compare the cluster
field with an offset field of similar galactic latitude and estimate
the contamination due to background stars to be large, >= 50%, as
might be expected given its low galactic latitude. We also compare our
photometry with that given for the X-ray detected stars of \cite[Randich
et al. (1995)]{ran95}. We present complimentary narrow band H alpha
photometry for a subset of the stars.
---------------------------------------------------------
Title: VizieR Online Data Catalog: RR Lyrae parallaxes & proper
motions (Fernley+ 1998)
Authors: Fernley, J.; Barnes, T. G.; Skillen, I.; Hawley, S. L.;
Hanley, C. J.; Evans, D. W.; Solano, E.; Garrido, R.
1997yCat..33300515F Altcode:
We have used HIPPARCOS proper motions and the method of Statistical
Parallax to estimate the absolute magnitude of RR Lyrae stars. In
addition we used the HIPPARCOS parallax of RR Lyrae itself to
determine it's absolute magnitude. These two results are in excellent
agreement with each other and give a zero-point for the RR Lyrae
M<SUB>v</SUB>,[Fe/H] relation of 0.77+/-0.15 at [Fe/H]=-1.53. This
zero-point is in good agreement with that obtained recently by
several groups using Baade-Wesselink methods which, averaged over the
results from the different groups, gives M<SUB>v</SUB>=0.73+/-0.14 at
[Fe/H]=-1.53. Taking the HIPPARCOS based zero-point and a value of
0.18+/-0.03 for the slope of the M<SUB>v</SUB>,[Fe/H] relation from
the literature we find firstly, the distance modulus of the LMC is
18.26+/-0.15 and secondly, the mean age of the Globular Clusters
is 17.4+/-3.0 GYrs. These values are compared with recent estimates
based on other "standard candles" that have also been calibrated with
HIPPARCOS data. It is clear that, in addition to astrophysical problems,
there are also problems in the application of HIPPARCOS data that are
not yet fully understood. <P />(2 data files).
---------------------------------------------------------
Title: Hamilton Echelle Spectroscopy of the 1993 March 6 Solar Flare
Authors: Johns-Krull, Christopher M.; Hawley, Suzanne L.; Basri,
Gibor; Valenti, Jeff A.
1997ApJS..112..221J Altcode:
We report on a successful program that used the Hamilton echelle
spectrograph and the coudé auxiliary telescope at Lick Observatory
to take spectra of solar flares. Our observations consist of
high-resolution (λ/δλ ~ 48,000) spectra covering the entire optical
region from approximately 3800 to 9000 Å in each exposure. These
are the first time-resolved high-resolution optical spectra of this
type obtained for a solar flare. <P />On 1993 March 6 we observed a
relatively large (GOES class M7.7) solar flare event. Our sequence of
observations began before flare maximum and continued for more than 1
hr. We present our high signal-to-noise spectra and compare them with
similar stellar flare observations. We find that the hydrogen-emitting
layers in flares on the Sun differ markedly from those in flares on dMe
stars, though the total energy emitted in various emission lines can be
rather similar. We also find that the amount of energy released in the
optical emission lines is similar to that emitted in soft X-rays. We
find evidence for Stark broadening in the Balmer lines for members
lower in the series than reported in earlier studies. This appears to
have occurred because the optical depth in the Balmer lines is lower
than in previously reported flares. Early in the flare, the Hα and
Hβ line profiles appear to be asymmetric as a result of absorption
by chromospheric material expanding upward into the corona. We also
examine solar flare model atmospheres synthesized with the non-LTE
code MULTI and find that our observations can be generally understood
in terms of equilibrium models of electron-beam- and X-ray-heated
chromospheres in equilibrium with coronal loops in which the pressure
is rather high; however, there remain marked differences between
the theoretical predictions and our observations, implying that
substantial refinement of the models is in order. Several photospheric
lines show flare enhancements as well. The temporal behavior of these
line enhancements is identical to that of the chromospheric lines,
but there is no indication that significant flare heating penetrates
to continuum formation depths. <P />Based on observations obtained at
Lick Observatory, which is operated by the University of California.
---------------------------------------------------------
Title: Non-LTE Radiative-hydrodynamic Models of Solar Flares
Authors: Abbett, William P.; Hawley, Suzanne L.
1997BAAS...29Q1120A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Absolute Magnitudes of RR Lyrae Stars
Authors: Fernley, J.; Barnes, T. G.; Skillen, I.; Hawley, S. L.;
Hanley, C.; Evans, D. W.; Solano, E.; Garrido, R.
1997ESASP.402..635F Altcode: 1997hipp.conf..635F
Using firstly, the Hipparcos proper motions and the method of
Statistical Parallax and secondly, the Hipparcos parallax of RR Lyrae
itself and thirdly, the Baade-Wesselink results from the literature we
find the zero-point of the RR Lyrae absolute magnitude - metallicity
relation to be M_v = 0.72 +/- 0.10 at [Fe/H] = -1.52. The small error
on this zero-point reflects the remarkably good agreement between the
three (independent) methods. Taking a value of 0.18 +/- 0.03 for the
slope of the relation from the literature we obtain a distance modulus
of the LMC of 18.31. This is compared to other recent determinations
of the distance to the LMC.
---------------------------------------------------------
Title: Erratum: Evaporation, Tidal Disruption, and Orbital Decay of
Star Clusters in a Galactic Halo
Authors: Capriotti, E. R.; Hawley, S. L.
1997ApJ...483..984C Altcode:
In § 2 of the recent paper “Evaporation, Tidal Disruption,
and Orbital Decay of Star Clusters in a Galactic Halo”
by E. R. Capriotti and S. L. Hawley (ApJ, 464, 765 [1996]),
equation (1) contains a misprint. It should read r<SUB>t</SUB>=2r/3
[(M<SUB>c</SUB>)/(AM<SUB>H</SUB>(r))]<SUP>1/3</SUP>/[1-r/(AM<SUB>H</SUB>(r))
(dM<SUB>H</SUB>(r))/dr]<SUP>1/3</SUP> , (1)where the difference from
the published version is that an A replaces the 3 in the denominator
of the last term. The authors regret the error.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Palomar/MSU nearby star
spectroscopic survey (Hawley+ 1997)
Authors: Reid, I. N.; Hawley, S. L.; Gizis, J. E.
1997yCat.3198....0R Altcode:
The Third Catalogue of Nearby Stars (Gliese & Jahreiss, "Preliminary
Version of the third Catalogue of Nearby Stars" (CNS3), 1991, catalog
<V/70>) includes over 1850 stars which lie north of Dec.= -30°
and are either identified as spectral type M, or are unclassified
but with an absolute visual magnitude estimate M<SUB>V</SUB> >
+8.0. Although there is no uniformity in selection criteria, and many
of the stars lack basic data (radial velocities, spectral types,
accurate photometry), the observational properties of these stars
underlie most estimates of the fundamental characteristics of the
Galactic Disk. We have obtained optical spectroscopy of 1746 of the
1876 stars -- the remaining 130 are binary companions of brighter
stars and inaccessible to our observations. These spectra allow us,
first, to exclude 61 stars as either degenerates or as misclassified
earlier-type (B-K) stars lying beyond the 25 pc limit; to establish
radial velocities accurate to ±10km/s for all stars confirmed as
late-type dwarfs; to determine spectral types and absolute magnitudes
from the TiO bandstrength, allowing more accurate distance estimates
for stars with inaccurate (or no) trigonometric parallax measurements;
and to identify stars with Hα emission (chromospherically active stars)
and with strong CaH absorption (perhaps including some metal-poor disk
subdwarfs). We have determined the nearby-star luminosity function from
complete samples derived by applying both the distance limits defined
by Wielen (1974, Highlights of Astron. 3, 395) and by using limits
derived from our own analysis. Spectroscopic data for the southern
stars (Dec.<-30°) in the PMSU survey are also presented. The data
were combined with the data from paper I to obtain a list of all the
magnetically active dMe stars in the survey. <P />(11 data files).
---------------------------------------------------------
Title: The Palomar/MSU Nearby Star Spectroscopic Survey.II.The
Southern M Dwarfs and Investigation of Magnetic Activity
Authors: Hawley, Suzanne L.; Gizis, John E.; Reid, Neill I.
1997AJ....113.1458H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: VizieR Online Data Catalog: IC 2602 VRI photometry (Foster+
1997)
Authors: Foster, D. C.; Byrne, P. B.; Hawley, S. L.; Rolleston,
W. R. J.
1997yCat..41260081F Altcode:
We present the results of VRI photometry of the young open cluster IC
2602. Two 15x15arcmin<SUP>2</SUP> fields were observed in February
and May 1991 using the 1-m Swope telescope at Las Campanas. Using
theoretical isochrones obtained from D'Antona & Mazzitelli
(1994ApJS...90..467D), and allowing for observational and other
uncertainties, we identify 78 primary candidate members with
12<V<18.5 from their positions on colour-magnitude diagrams. We
compare the cluster field with an offset field of similar galactic
latitude and estimate the contamination due to background stars to
be large, >=50%, as might be expected given its low galactic
latitude. We also compare our photometry with that given for the
X-ray detected stars of Randich et al. (1995A&A...300..134R)
present complimentary narrow band Hα photometry for a subset of the
stars. (1 data file).
---------------------------------------------------------
Title: Tidal Streams from the Carina and Draco Dwarf Galaxies
Authors: Smith, H. A.; Kuhn, J. R.; Hawley, S. L.
1997ASPC..127..163S Altcode: 1997pmga.conf..163S
No abstract at ADS
---------------------------------------------------------
Title: The Palomar/MSU Nearby Star Spectroscopic Survey.II.The
Southern M Dwarfs and Investigation of Magnetic Activity
Authors: Hawley, Suzanne L.; Gizis, John E.; Reid, I. Neill
1996AJ....112.2799H Altcode:
Spectroscopic data for the southern stars (δ<-30) in the PMSU survey
are presented. The data were combined with the data from Paper I [Reid,
Hawley & Gizis, AJ, 110, 1838 (1995)] to obtain a list of all the
magnetically active dMe stars in the survey. The incidence of activity
increases monotonically toward later spectral type, reaching a level
of 60% at spectral types >M5. This is not a selection effect, since
the chromospheric activity level (L<SUB>Hα</SUB>/L<SUB>bol</SUB>)
remains high throughout the spectral type range where the incidence
is increasing. At very late types, there is evidence that the mean
activity level drops in both chromospheric and coronal emission. The
ratio between the chromospheric and coronal emission levels remains
constant, indicating that the heating mechanism is not changing. There
is little or no dependence of the chromospheric activity level on
rotational velocity (υ sin i). The color-magnitude diagrams in both
M<SUB>V</SUB> and M<SUB>K</SUB> show strong evidence for a break between
spectral types M3-MS, in both the dMe and dM stars. The dMe stars at
earlier types than M3 are about 0.5 magnitudes brighter than dM stars
of the same spectral type in both M<SUP>V</SUP> and M<SUP>K</SUP>. They
also are slightly (≤0. 1 magnitude) redder. Both the Hyades and IC
2602 clusters show the same absolute magnitude effect for the early
type dMe stars. The Balmer decrement varies widely among the dMe field
stars, in contrast to the Hyades stars. The photospheric TiO bands
show detailed structure which depends on the chromospheric activity
level of the star. These spectroscopic signatures will provide useful
constraints on atmospheric models. A rigorous maximum likelihood
analysis of the kinematic properties of a complete subs ample of the
survey shows that the dMe stars are, as a whole, kinematically younger
than the dM stars. Subsets of the dM sample also show that the early
type dM stars are younger than the late dM stars, suggesting that
the dMe phenomenon lasts longer in later type stars. This provides
a natural explanation for the increase in the incidence of activity
toward later spectral types.
---------------------------------------------------------
Title: The Absolute Magnitude and Kinematics of RR Lyrae Stars Via
Statistical Parallax
Authors: Layden, Andrew C.; Hanson, Robert B.; Hawley, Suzanne L.;
Klemola, Arnold R.; Hanley, Christopher J.
1996AJ....112.2110L Altcode: 1996astro.ph..8108L
We present new statistical parallax solutions for the absolute
magnitude and kinematics of RR Lyrae stars. We have combined
new proper motions from the Lick Northern Proper Motion program
with new radial velocity and abundance measures to produce a data
set that is 50% larger, and of higher quality, than the data sets
employed by previous analyses. Based on an a priori kinematic study,
we separated the stars into halo and thick disk sub-populations. We
performed statistical parallax solutions on these sub-samples, and found
M<SUB>v</SUB>(RR)=+0.71±0.12 at <[Fe/H]>=-1.61 for the halo (162
stars), and M<SUB>v</SUB>(RR)=+0.79±0.30 at <[Fe/H]>=-0.76
for the thick disk (51 stars). The solutions yielded a solar
motion <V>=-2l0±12 km s<SUP>-1</SUP> and velocity ellipsoid
(σ<SUB>U</SUB>,σ<SUB>V</SUB>,σ<SUB>W</SUB>) = (168±13, l02±8,
97±7)km s<SUP>-1</SUP> for the halo. The values were <V>=-48±9km
s<SUP>-1</SUP> and (σ<SUB>U</SUB>,σ<SUB>V</SUB>,σ<SUB>W</SUB>) =
(56±8,51±8,31±5) km s<SUP>-1</SUP> for the thick disk. Both are in
good agreement with estimates of the halo and thick disk kinematics
derived from both RR Lyrae stars and other stellar tracers. Monte
Carlo simulations indicated that the solutions are accurate, and that
the errors may be smaller than the estimates above. The simulations
revealed a small bias in the disk solutions, and appropriate corrections
were derived. The large uncertainty in the disk M<SUB>v</SUB>(RR)
prevents ascertaining the slope of the M<SUB>v</SUB>(RR)-[Fe/H]
relation. Using a zero point defined by our halo solution and adopting
a slope of 0.15 mag dex<SUP>-1</SUP>, we find that (1) the distance
to the Galactic Center is 7.6±0.4 kpc; (2) the mean age of the 17
oldest Galactic globular clusters is 16.52<SUP>2.1/11.9</SUP> Gyr;
and (3) the distance modulus of the LMC is 18.28t 0.13 mag. Estimates
of H<SUB>0</SUB> which are based on an LMC distance modulus of 18.50
(e.g., Cepheid studies) increase by 10% if they are recalibrated to
match, our LMC distance modulus.
---------------------------------------------------------
Title: Tidal Disruption and Tails from the Carina Dwarf Spheroidal
Galaxy
Authors: Kuhn, J. R.; Smith, Horace A.; Hawley, Suzanne L.
1996ApJ...469L..93K Altcode:
New photometry of regions beyond the classical tidal radius of Carina
exposes a Carina-like stellar distribution that is about 1% of the
central surface density and which extends at least as far as 2 deg (3.5
kpc) from Carina's center. The detections of a spatially extended RR
Lyrae distribution, and a significant Carina-like stellar population at
large central distances confirm predictions of the time-dependent tidal
interaction model and suggest that Carina is not in virial equilibrium.
---------------------------------------------------------
Title: Teaching materials: stellar atmospheres/radiative transfer.
Authors: Hawley, S. L.; Ayres, T. R.
1996BAAS...28Q.883H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Evaporation, Tidal Disruption, and Orbital Decay of Star
Clusters in a Galactic Halo
Authors: Capriotti, Eugene R.; Hawley, Suzanne L.
1996ApJ...464..765C Altcode:
We consider the orbital evolution and tidal evaporation and disruption
of globular clusters and dwarf spheroidal galaxies in the gravitational
potential of an isothermal dark matter halo, consistent with that
predicted by current observations of flat rotation curves in spiral
galaxies. The rate of orbital decay due to dynamical friction and mass-
loss rates including halo-induced tidal effects are computed self
consistently using a semi-analytical model. A wide range of cluster
masses and central mass concentrations for both circular and radial
orbits was considered. We find that the high-mass clusters (M_c_
~> 10^7^ M_sun_) suffer substantial to complete orbital decay due
to dynamical friction, while the low-mass clusters (M_c_ <~ 10^5^
M_sun_) suffer substantial to complete evaporation or disruption. The
mass contribution to the halo, per cluster, is small in both
cases. Intermediate-mass clusters of high central mass concentration
survive for a Hubble time, while intermediate and high-mass clusters
of low central mass concentration evaporate or disrupt and may have
contributed a large fraction of the mass in the halo. For all initial
orbital sizes and cluster concentrations the mass range for surviving
clusters is narrower for radial orbits, and the halo stars contributed
by these clusters should have highly eccentric orbits. Our results show
that the current globular cluster population is, to a large extent,
consistent with that determined from our simple approximation, which
considers only the gravitational effects of an isothermal halo.
---------------------------------------------------------
Title: The Palomar/MSU Nearby-Star Spectroscopic Survey. I. The
Northern M Dwarfs-Bandstrengths and Kinematics
Authors: Reid, I. Neill; Hawley, Suzanne L.; Gizis, John E.
1996AJ....111.2469R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Teaching Materials: Stellar Atmospheres/Radiative Transfer
Authors: Hawley, S. L.; Ayres, T. R.
1996AAS...188.3905H Altcode: 1996BAAS...28..883H
We will present a selection of modern teaching materials for courses
in Stellar Atmospheres and Radiative Transfer that have been collected
from a wide variety of sources. We will provide brief synopses of each
book, or set of of notes, and endeavor to compare and contrast the
different presentations of the material. One of the newer additions
to the literature is “Radiative Transfer in Stellar Atmospheres,”
lecture notes from R.J. Rutten based on courses taught at Utrecht
University. In addition, I. Hubeny and D. Mihalas presently are writing
a new edition of Mihalas' famous “Stellar Atmospheres.” Other books
we are aware of range from the planning stages to near completion. We
will emphasize the diversity of styles and presentation techniques, but
will try to make clear the central themes around which any successful
Stellar Atmospheres/Radiative Transfer course must be built.
---------------------------------------------------------
Title: Observations of Tidal Disruption of the Carina Dwarf Spheroidal
Galaxy
Authors: Kuhn, J. R.; Smith, H. A.; Hawley, S. L.
1996AAS...188.7705K Altcode: 1996BAAS...28S.954K
New observations of the Carina dwarf spheroidal galaxy have been
obtained at angular distances as far as 2 degrees from its center. Along
the Carina major axis we detect RR Lyraes at Carina's MW distance, but
well beyond its classical tidal radius. Color-magnitude observations
show the existence of a surface density of Carina-population stars which
is a few percent of the central density as far as 3.5kpc away from the
dS center along its major axis. These measurements support the model
of Carina as a tidally disrupting galaxy with no excess dark matter.
---------------------------------------------------------
Title: Observations of tidal disruption of the Carina dwarf spheroidal
galaxy.
Authors: Kuhn, J. R.; Smith, H. A.; Hawley, S. L.
1996BAAS...28..954K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Moving Groups, Stellar Streams and Phase Space Substructure
in the Galactic Halo
Authors: Majewski, S. R.; Hawley, S. L.; Munn, J. A.
1996ASPC...92..119M Altcode: 1996fogh.conf..119M
We have been exploring the phase space and metallicity distributions
of stars in the North Galactic Pole field SA 57. The data are deep
(B ~ 22.5) proper motions and photometry, combined with Mayall 4-m
spectroscopy using the HYDRA multifiber system to brighter (B ~ 19.5)
limits. Our early spectroscopic results confirmed the existence of
a retrograde rotating, halo moving group in this field. We have
since obtained many more spectra, and we find the halo stars in
our survey to show a high degree of clumping in their U- V-W-[Fe/H]
distributions. From our data we conclude that (1) the halo is not
a dynamically relaxed system, (2) phase space substructure could
account for differences in halo kinematics derived from surveys along
different lines of sight, and (3) the halo field star population may
be derived predominantly from the accretion of stellar agglomerations,
most likely dwarf galaxies. The latter conclusion agrees with that of
Preston et al. (1994) from their work on blue, metal-poor stars.
---------------------------------------------------------
Title: Statistical Parallax Analysis of RR Lyrae Stars
Authors: Hawley, Suzanne L.; Hanley, Christopher; Layden, Andrew C.;
Hanson, Robert B.
1996ASPC...92..188H Altcode: 1996fogh.conf..188H
We present results from a new statistical parallax analysis of the
field RR Lyrae stars. New and improved data, together with a careful
population separation, allow us to investigate the dependence of the
RR Lyrae absolute magnitude on metallicity.
---------------------------------------------------------
Title: Evaporation, Tidal Disruption, and Orbital Decay of Star
Clusters in a Galactic Halo
Authors: Capriotti, Eugene R.; Hawley, Suzanne L.; Hamlin, Michael
1996ASPC...92..487C Altcode: 1996fogh.conf..487C
We consider the orbital evolution and tidal evaporation and disruption
of globular clusters in the gravitational potential of an isothermal
dark matter halo using a semi-analytic model. Our results show that
intermediate mass clusters of high central concentration survive for a
Hubble time, while low mass clusters tend to evaporate or disrupt, and
high mass clusters suffer orbital decay due to dynamical friction. The
current globular cluster population is, to a large extent, consistent
with that determined from our simple model.
---------------------------------------------------------
Title: Absolute Proper Motions to B approximately 22.5: Large-Scale
Streaming Motions and the Structure and Origin of the Galactic Halo
Authors: Majewski, Steven R.; Munn, Jeffrey A.; Hawley, Suzanne L.
1996ApJ...459L..73M Altcode:
With an enlarged sample of radial velocities, we explore the phase-space
and metallicity distributions for a sample of dwarf stars with distances
up to 8 kpc in a deep north Galactic pole proper motion survey. We
find that the halo stars in the sample are concentrated into clumps in
the combined phase-space and metallicity distribution, one of the most
prominent clumps representing a retrograde, predominantly metal-poor
([Fe/H] < -0.8) stream moving toward the Galactic plane. These new
data reveal that (1) the halo is not dynamically mixed but presently
contains a significant fraction of stars with membership in correlated
stellar streams, (2) phase-space substructure might account for
differences in halo kinematics derived among surveys along different
lines of sight, and (3) a significant fraction of the halo field star
population may be derived from the accretion of stellar agglomerations
(e.g., star clusters, satellite galaxies, or Searle & Zinn
"fragments").
---------------------------------------------------------
Title: All telescopes great and small.
Authors: Hawley, S. L.
1996Mercu..25a..13H Altcode:
The 1990s have been the era of the super-telescope, of 8- to 10-meter
mirrors that see to the edge of the observable universe. To some
astronomers and their benefactors, the 1- or 2-meter instruments are
now expendable. They are not.
---------------------------------------------------------
Title: Low-mass stars in old open clusters
Authors: Reid, I. N.; Hawley, S. L.
1996ASPC..109..383R Altcode: 1996csss....9..383R
No abstract at ADS
---------------------------------------------------------
Title: Large classes and quality instruction: the "interrupted
lecture".
Authors: Hufnagel, B.; Hawley, S. L.; Stein, R.; Wilhelm, R.
1996BAAS...28.1203H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Continued analysis of EUVE and optical observations of a
flare on AD Leonis.
Authors: Cully, S. L.; Fisher, G. H.; Hawley, S. L.; Simon, T.
1996aeu..conf..153C Altcode:
The flare star AD Leo was observed by EUVE from 1993 March 1 - March 3
UT. A flare was detected by the EUVE DS/S and seen in optical photometry
on 1993 March 2 UT. The authors summarize an analysis of the flare's
physical parameters, and present differential emission measure (DEM)
curves calculated for the quiescent, flare peak and flare decay phases
of the observation.
---------------------------------------------------------
Title: Continued Analysis of EUVE and Optical Observations of a
Flare on AD Leonis
Authors: Gully, S. L.; Fisher, G. H.; Hawley, S. L.; Simon, T.
1996aeu..conf..153G Altcode: 1996IAUCo.152..153G
No abstract at ADS
---------------------------------------------------------
Title: VRI photometry of the young open cluster IC 2602
Authors: Foster, D. C.; Byrne, P. B.; Rolleston, W. R. J.; Hawley,
S. L.
1996ASPC..109..357F Altcode: 1996csss....9..357F
No abstract at ADS
---------------------------------------------------------
Title: Simultaneous Extreme-Ultraviolet Explorer and Optical
Observations of AD Leonis: Evidence for Large Coronal Loops and the
Neupert Effect in Stellar Flares
Authors: Hawley, Suzanne L.; Fisher, George H.; Simon, Theodore;
Cully, Scott L.; Deustua, Susana E.; Jablonski, Marek; Johns-Krull,
Christopher M.; Pettersen, Bjorn R.; Smith, Verne; Spiesman, William
J.; Valenti, Jeffrey
1995ApJ...453..464H Altcode:
We report on the first simultaneous Extreme-Ultraviolet Explorer
(EUVE) and optical observations of flares on the dMe flare star AD
Leonis. The data show the following features: <P />1. Two flares
(one large and one of moderate size) of several hours duration were
observed in the EUV wavelength range; <P />2. Flare emission observed
in the optical precedes the emission seen with EUVE; <P />3. Several
diminutions (DIMs) in the optical continuum were observed during
the period of optical flare activity. <P />To interpret these data,
we develop a technique for deriving the coronal loop length from the
observed rise and decay behavior of the EUV flare. The technique is
generally applicable to existing and future coronal observations of
stellar flares. We also determine the pressure, column depth, emission
measure, loop cross- sectional area, and peak thermal energy during the
two EUV flares, and the temperature, area coverage, and energy of the
optical continuum emission. <P />When the optical and coronal data are
combined, we find convincing evidence of a stellar "Neupert effect"
which is a strong signature of chromospheric evaporation models. We
then argue that the known spatial correlation of white-light emission
with hard X-ray emission in solar flares, and the identification of
the hard X-ray emission with nonthermal bremsstrahlung produced by
accelerated electrons, provides evidence that flare heating on dMe
stars is produced by the same electron precipitation mechanism that
is inferred to occur on the Sun. <P />We provide a thorough picture of
the physical processes that are operative during the largest EUV flare,
compare and contrast this picture with the canonical solar flare model,
and conclude that the coronal loop length may be the most important
factor in determining the flare rise time and energetics.
---------------------------------------------------------
Title: The Palomar/MSU Nearby-Star Spectroscopic Survey. I. The
Northern M Dwarfs -Bandstrengths and Kinematics
Authors: Reid, I. Neill; Hawley, Suzanne L.; Gizis, John E.
1995AJ....110.1838R Altcode:
The Third Catalogue of Nearby Stars (Gliese & Jahreiss Preliminary
Version of the third Catalogue of Nearby Stars, 1991) includes over
1850 stars which lie north of δ 30° and are either identified as
spectral type M, or are unclassified but with an absolute visual
magnitude estimate M<SUB>V</SUB>>+8.O. Although there is no
uniformity in selection criteria, and many of the stars lack basic
data (radial velocities, spectral types, accurate photometry), the
observational properties of these stars underlie most estimates
of the fundamental characteristics of the Galactic Disk. We have
obtained optical spectroscopy of 1746 of the 1876 stars-the remaining
130 are binary companions of brighter stars and inaccessible to our
observations. These spectra allow us, first, to exclude 61 stars as
either degenerates or as misclassified earlier-type (B - K) stars lying
beyond the 25 pc limit; to establish radial velocities accurate to
±10 km s<SUP>-1</SUP> for all stars confirmed as late-type dwarfs;
to determine spectral types and absolute magnitudes from the TiO
bandstrength, allowing more accurate distance estimates for stars
with inaccurate (or no) trigonometric parallax measurements; and to
identify stars with Ha emission (chromospherically active stars)
and with strong CaH absorption (perhaps including some metal-poor
disk subdwarfs). We have determined the nearby-star luminosity
function from complete samples derived by applying both the distance
limits defined by Wielen (1974) and by using limits derived from our
own analysis. In both cases, we find good agreement with Wielen's
results to M<SUB>V</SUB> ∼+11, but lower densities at the maximum
(M<SUB>V</SUB>∼+12). The latter analysis results in a luminosity
function, Φ<SUB>CNS</SUB>, which closely matches photometric parallax
analyses for M<SUB>V</SUB><+11 and M<SUB>V</SUB>>+14 -- we do
not recover the apparent excess of low-luminosity stars inferred
from analysis of the 5 pc sample. However, Φ<SUB>CNS</SUB> does
lie below Φ<SUB>phot</SUB> at the peak (M<SUB>V</SUB>∼12), and we
suggest that this offset is caused by the inclusion of unrecognized
binaries in the photometric surveys. We have also reanalyzed the
local stellar kinematics using the complete sample and find that the
velocity distributions show significant departures from single Gaussian
velocity dispersions.
---------------------------------------------------------
Title: Tidal Evaporation and Orbital Decay of Star Clusters in a
Galactic Halo
Authors: Capriotti, E.; Hawley, S. L.
1995AAS...186.4907C Altcode: 1995BAAS...27..882C
We consider the evolution of globular clusters and dwarf galaxies under
the gravitational influence of an isothermal halo. Evaporation rates are
compared to orbital decay rates for a variety of initial cluster masses,
central concentrations, and orbital sizes and eccentricities. Clusters
which survive for a Hubble time fall into a mass range which depends
most crucially on the original orbital parameters.
---------------------------------------------------------
Title: Chromospheric and coronal activity in low-mass Hyades dwarfs
Authors: Reid, Neill; Hawley, Suzanne L.; Mateo, Mario
1995MNRAS.272..828R Altcode:
We present an extensive survey of the chromospheric and coronal
activity among low-mass members of the Hyades open cluster. We
have obtained H alpha spectroscopy of 91 probable cluster members,
including 23 that lie within three fields for which we have deep
ROSAT X-ray observations. 20 of the 23 stars are detected in X-rays;
the non-detections are probably not Hyades members. Combining these
observations with data from the literature, we find that the mean H
alpha to bolometric luminosity ratio log (L_H alpha/L_bol) is constant
at a value of ~-3.9 for M_bol>8, with a substantial dispersion and
an upper limit of -3.5. The X-ray to bolometric luminosity ratio log
(L_x/L_bol) first increases with increasing M_bol, then flattens at
a value of ~-3.3 for M_bol>8. Comparing this behaviour with stars
in the Pleiades cluster, there are significant differences: first,
the log (L_H alpha/L_bol) ratio increases with increasing M_bol while
M_bol<10, but appears to turn over sharply at fainter magnitudes,
with the lower luminosity stars being nearly an order of magnitude
lower in the ratio; secondly, we find no evidence for saturation in
the log (L_x/L_bol) ratio; L_x increases monotonically with M_bol,
reaching a value of ~-2.5 at M_bol~10. Lower luminosity stars have
not yet been detected in X-ray observations. The nearly constant H
alpha to H beta ratio in the Hyades stars, coupled with the small
range in coronal temperature seen in the X-ray data, suggest that the
(presumably magnetically generated) heating rate is nearly constant
in the outer atmospheres of these stars. Differences in the relative
activity levels are then ascribed to differences in the filling factor
of active regions, and in the sizes of the coronal structures.
---------------------------------------------------------
Title: The Frequency of Magnetic Activity in Field M Dwarfs
Authors: Hawley, S. L.
1995bmsb.conf..224H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectroscopic Survey of Nearby M Dwarfs
Authors: Gizis, J.; Reid, N.; Hawley, S.
1994AAS...185.2205G Altcode: 1994BAAS...26.1347G
The preliminary version of the Third Catalog of Nearby Stars lists
1736 M-dwarfs within 25 parsecs and another 470 stars of color
class 'k-m' or M_v > 8. We have obtained obtained ~ 2 Angstroms
resolution spectra of those stars north of declination -30(deg)
using the Palomar 60 ” and 200 ” telescopes over the wavelength
range lambda lambda 6180-7550. Stars are classified on the basis of
the TiO and CaH bands. H alpha emission stars are identified (EW >
1 Angstroms). We have defined volume complete samples on the basis of
our distance estimates. Radial velocities (sigma ~ 15 km s(-1) ) and the
catalog proper motions provide the full space velocity for the sample.
---------------------------------------------------------
Title: Absolute Proper Motions to B approximately 22.5: Evidence
for Kinematical Substructure in Halo Field Stars
Authors: Majewski, Steven R.; Munn, Jeffrey A.; Hawley, Suzanne L.
1994ApJ...427L..37M Altcode:
Radial velocities have been obtained for six of nine stars identified on
the basis of similar distances and common, extreme transverse velocities
in the proper motion survey of Majewski (1992) as a candidate halo
moving group at the north Galactic pole. These radial velocities
correspond to velocities perpendicular to the Galactic plane which
span the range -48 +/- 21 to -128 +/- 9 km/sec (but a smaller range,
-48 +/- 21 to -86 +/- 19 km/sec, when only our own measurements are
considered), significantly different than the expected distribution,
with mean 0 km/sec, for a random sample of either halo or thick disk
stars. The probability of picking such a set of radial velocities
at random is less than 1%. Thus the radial velocity data support the
hypothesis that these stars constitute part of a halo moving group or
star stream at a distance of approximately 4-5 kpc above the Galactic
plane. If real, this moving group is evidence for halo phase space
substructure which may be the fossil remains of a destroyed globular
cluster, Galactic satellite, or Searle & Zinn (1978) 'fragment.'
---------------------------------------------------------
Title: Comparison of Chromospheric and Coronal Activity in the Hyades
and Pleiades
Authors: Hawley, S. L.; Reid, I. N.
1994AAS...184.4305H Altcode: 1994BAAS...26..930H
We present results from our extensive survey of chromospheric and
coronal activity in lower main-sequence members of the Hyades open
cluster. We have obtained H alpha spectroscopy of ninety-one probable
cluster members, twenty-three of which lie within three fields for
which we have deep ROSAT X-ray observations. Twenty of the twenty-three
stars are detected. Combining these observations with data from the
literature, we find that the mean ratio log (L_alpha / L<SUB>bol</SUB>)
is roughly constant for M<SUB>bol</SUB> > 8, with a substantial
dispersion. The X-ray-to-bolometric luminosity ratio increases with
decreasing M<SUB>bol</SUB>, although the relation may flatten for
M<SUB>bol</SUB> > 9. Comparing this behaviour with stars in the
Pleiades cluster, there are significant differences: first, the log
(L_alpha / L<SUB>bol</SUB>) relation in the Pleiades increases for
M<SUB>bol</SUB> < 10, but appears to turn over sharply at fainter
magnitudes, with the lower luminosity stars having nearly an order of
magnitude lower H alpha luminosity; second, we find no evidence for
saturation in the log (L_X / L<SUB>bol</SUB>) ratio. However, none of
the lower luminosity Pleiades stars with low H alpha luminosity have
X-ray observations.
---------------------------------------------------------
Title: Solar Flare Model Atmospheres
Authors: Hawley, Suzanne L.; Fisher, George H.
1994ApJ...426..387H Altcode:
Solar flare model atmospheres computed under the assumption of energetic
equilibrium in the chromosphere are presented. The models use a static,
one-dimensional plane-parallel geometry and are designed within
a physically self-consistent coronal loop. Assumed flare heating
mechanisms include collisions from a flux of nonthermal electrons
and X-ray heating of the chromosphere by the corona. The heating by
energetic electrons accounts explicitly for variations of the ionized
fraction with depth in the atmosphere. X-ray heating of the chromosphere
by the corona incorporates a flare loop geometry by approximating
distant portions of the loop with a series of point sources, while
treating the loop leg closest to the chromospheric footpoint in the
plane-parallel approximation. Coronal flare heating leads to increased
heat conduction, chromospheric evaporation and subsequent changes
in coronal pressure; these effects are included self-consistently
in the models. Cooling in the chromosphere is computed in detail for
the important optically thick H I, Ca II and Mg II transitions using
the non-local thermodynamic equilibrium (non-LTE) prescription in the
program MULTI. Hydrogen ionization rates from X-ray photoionization and
collisional ionization by nonthermal electrons are included explicitly
in the rate equations. The models are computed in the 'impulsive'
and 'equilibrium' limits, and in a set of intermediate 'evolving'
states. The impulsive atmospheres have the density distribution frozen
in the pre-flare configuration, while the equilibrium models assume
the entire atmosphere is in hydrostatic and energetic equilibrium. The
evolving atmospheres represent intermediate stages where hydrostatic
equilibrium has been established in the chromosphere and corona, but
the corona is not yet in energetic equilibrium with the flare heating
source. Thus, for example, chromospheric evaporation is still in the
process of occurring. We have computed the chromospheric radiation
that results from a range of coronal heating rates, with particular
emphasis on the widely observed diagnostic H(alpha). Our conclusion is
that the H(alpha) fluxes and profiles actually observed in flares can
only be produced under conditions of a low-pressure corona with strong
beam heating. Therefore we suggest that H(alpha) in flares is produced
primarily at the footprints of newly heated loops where significant
evaporation has not yet occurred. As a single loop evolves in time,
no matter how strong the heating rate may become, the H(alpha) flux
will diminish as the corona becomes denser and hence more effective
at stopping the beam. This prediction leads to several observable
consequences regarding the spatial and temporal signatures of the
X-ray and H(alpha) radiation during flares.
---------------------------------------------------------
Title: EUVE Spectral Observations of a Flare on AD Leonis
Authors: Cully, S. L.; Fisher, G. H.; Hawley, S. L.; Simon, T.
1994AAS...184.4507C Altcode: 1994BAAS...26..935C
The flare star AD Leo (dM3.5e, 4.9 parsecs) was observed by the EUVE
DS/S from 1993 March 1 - March 3 UT. A flare was detected in the
Lexan/Boron (65 - 190 Angstroms) band of the Deep Survey Instrument
on March 2 UT. The flare was also observed with optical photometry
at several locations and with both high and low resolution optical
spectroscopy. The 0.3 magnitude optical U band (3000 - 4300 Angstroms)
flare had a peak DS Lex/B count rate of about 1.0 cps and was visible
for 7 hours. The total EUV energy released in the flare is estimated
to be 1 x 10(33) ergs. The above results were given by Hawley et al
(1994). In this work, we present the EUVE spectra (70 - 760 Angstroms)
for the quiescent and flaring times of the observation and differential
emission measure analysis of the strong emission lines visible in
each spectrum.
---------------------------------------------------------
Title: Absolute Magnitudes and Kinematics of RR Lyrae Stars via
Statistical Parallax
Authors: Layden, A. C.; Hanson, R. B.; Hawley, S. L.
1994AAS...184.3202L Altcode: 1994BAAS...26..911L
The absolute magnitude of the RR Lyrae stars is integral in determining
the distances to the old stellar systems in our Galaxy and to other
Local Group galaxies, and in determining the ages of the Galactic
globular clusters. We present new estimates of the RR Lyrae star
absolute magnitude as a function of metal abundance, based on a new
set of statistical parallax solutions. This analysis is an improvement
over previous works for several reasons: (1) it relies mainly on new
absolute proper motions from the Lick Northern Proper Motion Survey,
which are of uniformly high quality. (2) new metal abundances and
radial velocities are employed; the former are of particularly high
quality and uniformity. (3) the improved metallicities, combined with
kinematic analyses, allow us for the first time to properly separate
thick--disk and halo stars; these populations must be treated separately
for the solutions to be valid, and (4) over 200 stars are used in this
analysis (>20% have thick disk kinematics), significantly more than
in previous solutions. We discuss the kinematic properties of the local
RR Lyrae stars, and briefly discuss our absolute magnitude results with
regard to the distances and ages of some RR Lyrae-bearing populations.
---------------------------------------------------------
Title: X-Ray Emission from Halo M Dwarfs
Authors: Hawley, Suzanne L.; Feigelson, Eric D.
1994ASPC...64...89H Altcode: 1994csss....8...89H
No abstract at ADS
---------------------------------------------------------
Title: Solar flare model atmospheres
Authors: Hawley, Suzanne L.; Fisher, George H.
1993STIN...9519034H Altcode:
Solar flare model atmospheres computed under the assumption of
energetic equilibrium in the chromosphere are presented. The models
use a static, one-dimensional plane parallel geometry and are designed
within a physically self-consistent coronal loop. Assumed flare heating
mechanisms include collisions from a flux of non-thermal electrons
and x-ray heating of the chromosphere by the corona. The heating by
energetic electrons accounts explicitly for variations of the ionized
fraction with depth in the atmosphere. X-ray heating of the chromosphere
by the corona incorporates a flare loop geometry by approximating
distant portions of the loop with a series of point sources, while
treating the loop leg closest to the chromospheric footpoint in the
plane-parallel approximation. Coronal flare heating leads to increased
heat conduction, chromospheric evaporation and subsequent changes
in coronal pressure; these effects are included self-consistently
in the models. Cooling in the chromosphere is computed in detail for
the important optically thick HI, CaII and MgII transitions using the
non-LTE prescription in the program MULTI. Hydrogen ionization rates
from x-ray photo-ionization and collisional ionization by non-thermal
electrons are included explicitly in the rate equations. The models
are computed in the 'impulsive' and 'equilibrium' limits, and in a
set of intermediate 'evolving' states. The impulsive atmospheres
have the density distribution frozen in pre-flare configuration,
while the equilibrium models assume the entire atmosphere is in
hydrostatic and energetic equilibrium. The evolving atmospheres
represent intermediate stages where hydrostatic equilibrium has been
established in the chromosphere and corona, but the corona is not yet in
energetic equilibrium with the flare heating source. Thus, for example,
chromospheric evaporation is still in the process of occurring.
---------------------------------------------------------
Title: Magnetic Activity in Low-Mass Stars
Authors: Hawley, Suzanne L.
1993PASP..105..955H Altcode:
The manifestations of magnetic activity in low mass stars, particularly
M dwarfs, can be used as a tool to study their evolution, the
operation of the interior dynamo with changing interior conditions,
and the structure of their outer atmospheres. Extensive background
material on the current understanding of low mass stellar activity is
presented. Two new surveys are described which will greatly increase
the number of active low mass stars known in the field and in nearby
open clusters. These surveys will define the characteristics of the
activity on low mass stars, and how the activity changes with a number
of parameters of interest, including mass, effective temperature, and
age. The data will also allow a rigorous determination of a possible
age-activity relation among the low mass M dwarfs. Theoretical models
of M dwarf atmospheres, and their connection to the understanding
of the observations, are also discussed. (SECTION: The Second Hubble
Fellows Symposium)
---------------------------------------------------------
Title: Echelle Spectra of the 6 March 1993 Solar Flare
Authors: Johns, C. M.; Basri, G. S.; Hawley, S. L.
1993BAAS...25.1189J Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Flare Model Atmospheres
Authors: Hawley, S. L.; Fisher, G. H.
1993BAAS...25R1190H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Simultaneous Optical and EUVE Observations of a Flare on AD Leo
Authors: Hawley, S. L.; Deustua, S. E.; Cully, S. L.; Fisher, G. H.;
Johns, C. M.; Simon, T.; Smith, V. V.; Spiesman, W. J.
1993AAS...182.3808H Altcode: 1993BAAS...25..856H
An 80,000 second pointed observation of the flare star AD Leo was
carried out during 1-3 March 1993 (UT) by EUVE. Concurrent optical
monitoring observations were made using three telescopes at Lick
Observatory and two telescopes at McDonald Observatory. On 2 March 1993
(UT), the first simultaneous optical and EUV observations of a stellar
flare were obtained. The optical data include multi-color photometry,
and low and high resolution spectroscopy. We present the data for this
flare and compare it to previously observed stellar flares.
---------------------------------------------------------
Title: EUVE Deep Survey Observations of a Flare on AD Leo
Authors: Cully, S. L.; Siegmund, O. H. W.; Fisher, G. H.; Johns,
C. M.; Hawley, S. L.; Duestra, S.; Simon, T.
1993AAS...182.4104C Altcode: 1993BAAS...25R.860C
The flare star AD Leo was observed by the EUVE Deep Survey instrument
from 1993 March 1 through March 3 UT. A flare was detected in the
Lexan/boron (65-190 Angstroms) band on March 2 UT. This flare was also
observed in the optical U band and with both high and low resolution
spectroscopy. We compare this flare with solar observations and discuss
the implications for EUV stellar flare statistics. This work has
been supported by NASA grant NAGW-1290 and NASA contracts NAS5-29298
and -30180.
---------------------------------------------------------
Title: An Initial Search for Low Mass Stars with the 2MASS Prototype
Camera
Authors: Chester, T.; Beichman, C.; Evans, T.; Kopan, G.; Schombert,
J.; Kleinmann, S.; Lysaght, M.; Skrutksie, M.; Armus, L.; Matthews,
K.; Neugebauer, G.; Reid, N.; Soifer, T.; Tinney, C.; Hawley, S. L.
1992AAS...181.6809C Altcode: 1992BAAS...24.1229C
The Two Micron All Sky Survey (2MASS) is a ground-based, all-sky survey
at 1.2, 1.6 and 2.2 microns (J, H and K(') ) to a uniform limiting K(')
magnitude of 14 (10 sigma ) for point sources. A prototype camera has
been built to test many aspects of the survey. The camera was used
to obtain multiple (10) scans of a selected 1 square degree region
at intermediate galactic latitude, to investigate the completeness,
reliability, and positional accuracy that could be achieved in the
survey. Results from the processing of these data, presented here,
demonstrate that we currently exceed all the goals in these areas. To
understand the classes of sources that were detected, we have compared
all detected sources with m_{K('}) < 14 to optical sources extracted
from digitized POSS I plates. The infrared sources are highly reliable,
having been confirmed on 10 separate repeated scans. The distribution of
R - K(') colors is consistent with those expected from normal stellar
populations, except for one source with m_{K('}) = 13.1 which has no
counterpart on the POSS I. Follow-up observations show that the source
is actually double with a separation of about 0.5", with both components
having roughly equal magnitudes at I, J, H, K(') , and L(') . Each of
the components have the color of M6--7 stars, with a total R magnitude
of 18.9, consistent with the combined spectrum. The lack of a detection
on the POSS I plates is probably due to the extreme red color of this
object, but a high proper motion cannot yet be ruled out. These stars
are at an inferred distance of about 30--70 pc. If they represent a
binary system, the stars are separated by only 15--35 AU. Since this
object was found from a survey of only one square degree, and fewer
than 100 stars are known with spectral types later than M5, it is clear
that 2MASS will be valuable in deriving a complete census of nearby
low-mass stars that is not biased by proper motion selection effects.
---------------------------------------------------------
Title: Magnetic activity in low mass stars
Authors: Hawley, S. L.
1992STIN...9328547H Altcode:
The manifestations of magnetic activity in low mass stars, particularly
M dwarfs, can be used as a tool to study their evolution, the
operation of the interior dynamo with changing interior conditions,
and the structure of their outer atmospheres. Extensive background
material on the current understanding of low mass stellar activity is
presented. Two new surveys are described which will greatly increase
the number of active low mass stars known in the field and in nearby
open clusters. These surveys will define the characteristics of the
activity on low mass stars, and how the activity changes with a number
of parameters of interest, including mass, effective temperature, and
age. The data will also allow a rigorous determination of a possible
age-activity relation among the low mass M dwarfs. Theoretical models
of M dwarf atmospheres, and their connection to the understanding of
the observations, are also discussed.
---------------------------------------------------------
Title: Starspots - the ZEBRA Effect
Authors: Pettersen, Bjorn R.; Hawley, Suzanne L.; Fisher, George H.
1992SoPh..142..197P Altcode:
Recent observations of brightness variations on the Sun during the
solar cycle have motivated us to re-examine the widely held view that
cool, dark starspots, covering a significant fraction of the star,
are the centers of magnetic activity on BY Dra stars. We propose that
the magnetic regions are better described by a bright facular network,
and that the dark areas which give rise to photometric rotational
modulation are actually regions where the underlying quiet photosphere
is seen. This interpretation is consistent with recent observations
of late-type stars that show that bright areas covering much of the
star have magnetic fields with strengths of several thousand gauss. It
resolves several problems with the current model, including the size,
location, and stability of the starspots required to match photometric
and Doppler-imaging observations. It also has interesting observational
implications for the correlation of photometric rotational modulation
and long term brightness variations with other surface activity,
and for the positions of magnetically active stars in the H-R diagram.
---------------------------------------------------------
Title: New Cepheid Distances to Nearby Galaxies Based on BVRI CCD
Photometry. III. NGC 300
Authors: Freedman, Wendy L.; Madore, Barry F.; Hawley, S. L.; Horowitz,
Irwin K.; Mould, Jeremy; Navarrete, Mauricio; Sallmen, Shauna
1992ApJ...396...80F Altcode:
A true distance modulus of (m - M)_0_ = 26.66 +/- 0.10 mag
(corresponding to 2.1 +/- 0.1 Mpc) has been determined for the Sculptor
Group spiral galaxy NGC 300. New CCD data have been obtained for a
sample of known Cepheids in this galaxy from which apparent distance
moduli at B, V, R, and I wavelengths are determined. Combining the
data available at different wavelengths, and assuming a true distance
modulus to the LMC of 18.5 mag, a true distance modulus is obtained
for NGC 300, corrected for the effects of interstellar reddening. The
availability of a new distance to NGC 300 brings to five the total
number of galaxies with new CCD photometry of Cepheids, useful for
calibration of the Hubble constant.
---------------------------------------------------------
Title: X-Ray-heated Models of Stellar Flare Atmospheres: Theory and
Comparison with Observations: Erratum
Authors: Hawley, Suzanne L.; Fisher, George H.
1992ApJS...81..885H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Flare Model Atmospheres
Authors: Fisher, G. H.; Hawley, S. L.
1992AAS...180.4101F Altcode: 1992BAAS...24..794F
We present 3 sets of solar flare atmospheric models, computed in 3
different limits. In all of the models, energy balance is assumed,
with radiative losses from the optically thick transitions of HI,
CaII, and MgII balancing flare heating from nonthermal electrons
and X-rays from the flaring corona. In the “Hydrostatic” models,
we have assumed that flare heating by Coulomb collisions from a flux
of nonthermal electrons has been occurring for an infinitely long
time, and the corona and chromosphere have achieved both energetic and
hydrostatic equilibrium. In the “Impulsive” models, we have assumed
that the atmospheric density remains frozen in its preflare state,
but that the atmosphere rapidly achieves a temperature structure
consistent with energy balance. In the “Evolving” models, we have
assumed a temporal variation of the nonthermal electron heating
rate consistent with flare heating for timescales of 5-10 minutes,
corresponding to a long lived and intense flare, continually undergoing
chromospheric evaporation. In this case, the chromospheric model is
in hydrostatic equilibrium, but the flare transition region is at
depths that are much less than those in the “Hydrostatic” models. We
present temperature and density structures in these model atmospheres,
line and continuum fluxes from each model, and a few selected line
profiles. G.H.F. is supported by AFOSR grant AFOSR-91-116, NASA grant
NAGW-2969, and NSF grant ATM91-06052. S.L.H. is supported in part by a
Hubble Fellowship from STSI, and in part by Lawrence Livermore National
Laboratory. Lawrence Livermore is supported by the US Department of
Energy under contract number W-7405-ENG-48.
---------------------------------------------------------
Title: X-Ray--heated Models of Stellar Flare Atmospheres: Theory
and Comparison with Observations
Authors: Hawley, Suzanne L.; Fisher, George H.
1992ApJS...78..565H Altcode:
A sequence of five model atmospheres consisting of the photosphere,
chromosphere, and transition region is computed. The models represent
the response of the gas in a magnetically confined loop to intense
flare energy release. It is concluded that the structure of the
flare transition region is consistent with the conductive heating
balancing optically thin cooling; some UV line fluxes can be used
as a transition-region 'pressure gauge' and can provide a constraint
on the flare area. These models predict ratios of Ca II to hydrogen
emission which are much greater than those observed; they also
predict Balmer line profiles which are much narrower than those
observed. It is inferred that additional heating is taking place in
the upper chromosphere beyond that assumed in the models. The observed
flare continuum is much bluer than that computed from the models;
the observations fit a blackbody spectrum with T approximately equal
to 8500-9500 K. It is proposed that the flare continuum is formed by
photospheric reprocessing of intense UV to the EUV line emission from
the upper chromosphere.
---------------------------------------------------------
Title: Energy Balance Models of Solar Flare Atmospheres
Authors: Hawley, S. L.; Fisher, G. H.
1992ASPC...26..534H Altcode: 1992csss....7..534H
No abstract at ADS
---------------------------------------------------------
Title: A ZEBRA Interpretation of BY DRA Stars
Authors: Pettersen, B. R.; Hawley, S. L.; Fisher, G. H.
1992ASPC...26..285P Altcode: 1992csss....7..285P
No abstract at ADS
---------------------------------------------------------
Title: The Great Flare of 1985 April 12 on AD Leonis
Authors: Hawley, Suzanne L.; Pettersen, Bjorn R.
1991ApJ...378..725H Altcode:
A giant flare on the M dwarf star AD Leo is examined on the basis of
photometric and spectroscopic observations covering the wavelength
range 1200-1800 A. A flare energy budget over the entire optical and
ultraviolet wavelength region is constructed as a function of time
during the flare. The continuum radiation is shown to be the dominant
source of energy loss during both the initial 'impulsive' phase and
the later 'gradual' phase. The emission lines contribute less than
10 percent of the total flare energy in this wavelength region but
are about four times more important during the gradual phase than
in the impulsive phase. The energy budget is compared with another,
less energetic, flare on AD Leo and found to be quite similar. The
relationships between the integrated properties of several flare
emission features are investigated. Good correlation between H-gamma
and Ca II K emission, and H-gamma and U filter emission is found. It is
inferred from these correlations that the observed emission features
are produced under similar atmospheric conditions regardless of the
total flare energy emitted.
---------------------------------------------------------
Title: Absolute Magnitudes and Kinematic Properties of Cepheids
Authors: Wilson, Teresa D.; Barnes, Thomas G., III; Hawley, Suzanne
L.; Jefferys, William H.
1991ApJ...378..708W Altcode:
The relative solar motions, Oort constants, velocity ellipsoid
parameters, and zero points of the PL and PLC relations are determined
by performing a maximum likelihood statistical parallax analysis of
classical Cepheids. The analysis is based on 90 proper motions drawn
from the list of Karimova and Pavlovskaya (1981) and on the analytical
approach of Hawley et al. (1986). The results give a best estimate
for the mean absolute magnitude of Cepheids which, for the Cepheid
absolute magnitude zero point, is highly stable against refinements
in the mathematical technique and against additional Cepheid proper
motion data of quality similar to the existing proper motions. The
solar motion components along the axes of uncertainties less than +
or - 2 km/s are also determined.
---------------------------------------------------------
Title: Absolute Magnitudes and Kinematic Properties of Cepheids
Authors: Barnes, T. G., III; Wilson, T. D.; Hawley, S. L.; Jefferys,
W. H.
1991BAAS...23Q.877B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: What Do Stellar Flares Tell Us About Solar White Light Flares?
Authors: Fisher, G. H.; Hawley, S. L.
1991BAAS...23R1067F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The response of the chromosphere during a stellar flare.
Authors: Hawley, Suzanne L.
1991MmSAI..62..271H Altcode:
A set of chromospheric models was developed, having a coronal loop
geometry, energy balance through the entire loop from photosphere
to corona, and a rigorous treatment of the radiative transfer in the
important, optically thick, chromospheric emission lines. The models
show that the soft X-ray emission and thermal conduction from a long
lived hot corona are effective heating agents in the lower atmosphere
during the gradual phase of stellar flares. The model predictions show
the correct order of magnitude for the emission lines produced during
the gradual phase of the flare with a reasonable coronal temperature
evolution.
---------------------------------------------------------
Title: Absolute magnitudes and kinematic properties of Cepheids.
Authors: Wilson, T. D.; Jefferys, W. H.; Barnes, T. G., III; Hawley,
S. L.
1991amkp.book.....W Altcode:
A maximum-likelihood statistical parallax analysis of classical
Cepheids has been performed to determine the relative solar motion,
Oort constants, velocity ellipsoid parameters, and zero points of the
PL and PLC relations. The analysis is based upon 90 proper motions
drawn from the list of Karimova and Pavlovskaya 1981 and upon the
analytical approach of Hawley et al. 1986. The authors' results give
a best estimate for the mean absolute magnitude of Cepheids at log P
= 0.8 of <M<SUB>v</SUB>> = -3.46±0.33 mag. This estimate for
the Cepheid absolute magnitude zero point is highly stable against
refinements in the mathematical technique and against additional
Cepheid proper motion data of quality similar to the existing proper
motions. Improvement in this value will likely come only from a marked
improvement in the quality of the Cepheid proper motions.
---------------------------------------------------------
Title: Starspots: The Zebra Effect
Authors: Pettersen, B. R.; Hawley, S. L.
1990BAAS...22.1202P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The 12 April 1985 Flare on AD Leo
Authors: Hawley, S. L.; Pettersen, B. R.
1990BAAS...22.1202H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: An Equation for the Evolution of Solar and Stellar Flare Loops
Authors: Fisher, George H.; Hawley, Suzanne L.
1990ApJ...357..243F Altcode:
An ordinary differential equation describing the evolution of a coronal
loop subjected to a spatially uniform but time-varying heating rate is
discussed. It is assumed that the duration of heating is long compared
to the sound transit time through the loop, which is assumed to have
uniform cross section area. The form of the equation changes as the
loop evolves through three states: 'strong evaporation', 'scaling law
behavior', and 'strong condensation'. Solutions to the equation may be
used to compute the time dependence of the average coronal temperature
and emission measure for an assumed temporal variation of the flare
heating rate. The results computed from the model agree reasonably
well with recent published numerical simulations and may be obtained
with far less computational effort. The model is then used to study
the May 21, 1980, solar flare observed by SMM and the giant April 12,
1985, flare observed on the star AD Leo.
---------------------------------------------------------
Title: The Metallicity Sensitivity of the Cepheid Period-Luminosity
Relation: Implications for the Extragalactic Distance Scale
Authors: Madore, B. F.; Freedman, W. L.; Hawley, S. L.
1990BAAS...22..841M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: An Equation for the Evolution of Solar and Stellar Flare Loops
Authors: Hawley, S. L.; Fisher, G. H.
1990BAAS...22..826H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Flare Activity of the Uv-Ceti System 1966-1988
Authors: Pettersen, B. R.; Sundland, S. R.; Hawley, S. L.; Coleman,
L. A.
1990ASPC....9..177P Altcode: 1990csss....6..177P
No abstract at ADS
---------------------------------------------------------
Title: The flare activity of the red dwarf binary Gliese 277AB.
Authors: Hawley, S. L.; Panov, K. P.; Pettersen, B. R.; Sundland, S. R.
1989A&A...220..218H Altcode:
Both red dwarf components of the system Gliese 277 AB show the Ca
II HK and H I Balmer lines in emission. Extensive photoelectric
monitoring has revealed flare activity in the bright star but not in
the faint. Estimates of an upper limit for the flare activity level
of the faint star place it among the very inactive dM stars despite
its prominent emission lines. The activity level of the bright star
is typical for its spectral class.
---------------------------------------------------------
Title: A spectroscopic survey of red dwarf flare stars.
Authors: Pettersen, B. R.; Hawley, S. L.
1989A&A...217..187P Altcode:
Low resolution CCD spectra of dKe and dMe stars, many of which are
active flare stars and spotted stars are presented. Most objects are
covered from 3500 A to 7500 A; some have coverage extending to 9000
A. The strength of various chromospheric emission lines and photospheric
molecular features is measured, and the run of these quantities with
stellar intrinsic brightness is investigated.
---------------------------------------------------------
Title: An Observational and Theoretical Investigation of Stellar
Flares.
Authors: Hawley, Suzanne Louise
1989PhDT.........1H Altcode:
Multi-wavelength observations of a giant flare on the star AD Leo were
obtained with the 2.1m and 0.9m telescopes at McDonald Observatory and
the International Ultraviolet Explorer satellite. The quality, spectral
coverage and time resolution of the data represent a major improvement
over any published stellar flare data. A self -consistent theoretical
model was developed to investigate the effects of chromospheric
heating by thermal conduction and soft x-ray irradiation from a flare
heated corona. Assuming a one-dimensional coronal loop geometry,
atmospheres were produced for overlying coronal temperatures of 8,
10, 15, and 20 million degrees Kelvin. The atmospheres satisfy the
equations of hydrostatic equilibrium, steady state energy balance,
and statistical equilibrium and radiative transfer in many optically
thick transitions of hydrogen, ionized calcium and ionized magnesium. A
second theoretical model was then developed to predict the temporal
evolution of the coronal temperature under the influence of a time
varying flare heating rate. Combining the models, the chromospheric
emission model predictions in the hydrogen Balmer lines, Ca II K, Mg
II h + k and the optical continuum were compared to the observations,
with the result that much of the gradual phase flare emission could
be produced by the x-ray and conductive heated atmospheres. However,
some additional heating and a more complex flare geometry, including
several emitting regions, are probably required to reproduce all the
flare emission features in detail. The models also lend insight into
the impulsive phase flare emission, but do not reproduce it. Soft x-ray
and conductive heating of the chromosphere is a natural consequence of
the coronal temperatures that have been observed during the gradual
phase of flares on the sun and on M dwarf stars. The improved flare
observations and quantitative flare models presented here show that
these heating mechanisms can produce atmospheres whose emission
matches many of the observed stellar flare features. Future studies
must incorporate these effects as well as considering other heating
mechanisms and more complex flare geometries.
---------------------------------------------------------
Title: Independence of chromospheric active and soft X-ray flaring
on the flare star EV Lacertae.
Authors: Ambruster, C. W.; Pettersen, B. R.; Hawley, S. L.; Coleman,
L. A.; Sciortino, S.
1989sasf.confP..27A Altcode: 1988sasf.conf...27A; 1989IAUCo.104P..27A
EXOSAT observed the flare star EV Lacertae for 17 hr over 2 days in
October 1985. Two flaring episodes were recorded. During a significant
fraction of these observations, IUE, photometric and spectroscopic
coverage was available. A 2-hour long period of X-ray flaring was
observed during which there was no U-band activity and almost no
chromospheric activity. On the other hand, two ΔU ≡ 1<SUP>m</SUP>5
optical flares produced normal chromospheric enhancements, but only
a weak X-ray response. The authors suggest that these and a few other
observations of stellar flares may imply the occasional existence of
magnetically isolated regions in M-dwarf atmospheres.
---------------------------------------------------------
Title: Stellar flares: observations and theory.
Authors: Hawley, S. L.
1989sasf.confP..49H Altcode: 1988sasf.conf...49H; 1989IAUCo.104P..49H
Photometric and spectroscopic observations of a very large flare on AD
Leo are presented. A self consistent model of a flare corona, transition
region and chromosphere is developed; in particular the chromospheric
temperature distributions resulting from X-ray and EUV irradiation by
coronae of various temperatures are determined. The predicted line
fluxes in Hγ are compared to the observed line fluxes to find the
coronal temperature as a function of time during the flare. This run
of temperature with time is then compared with the predictions of an
independent theoretical flare model based on a dynamic scaling law.
---------------------------------------------------------
Title: A dynamic scaling law for solar and stellar flare loops.
Authors: Fisher, G. H.; Hawley, S. L.
1989sasf.confP.353F Altcode: 1989IAUCo.104P.353F; 1988sasf.conf..353F
The authors discuss an ordinary differential equation which describes
how the pressure in a coronal loop may evolve in time under the
influence of a uniform, but time varying heating rate.
---------------------------------------------------------
Title: Contemporaneous Photometry and Radial Velocities of RR
Lyrae Stars
Authors: Barnes, Thomas G., III; Moffett, Thomas J.; Hawley, Suzanne
L.; Slovak, Mark H.; Frueh, Marian L.
1988ApJS...67..403B Altcode:
Contemporaneous BVRI photometry and radial velocities of seven RR Lyrae
variables covering nearly the full span in Delta S and including the
RRc star T Sex are reported. Over 3000 BVRI measures at 100 s time
resolution and over 400 radial velocity measures are included. The
photometric uncertainties are of order + or - 0.007 mag in V, (B -
V) and (V - R) and + or - 0.014 in (R - I). The radial velocity
uncertainties range from + or - 3.8 to + or - 8.0 km/s, correlated
with the metal deficiency. Light, color, and velocity curves are given.
---------------------------------------------------------
Title: V1589 Cyg=B19: A foreground dMe flare star in the direction
of NGC 7000
Authors: Pettersen, B. R.; Tsvetkov, M. K.; Hawley, S. L.; Coleman,
L. A.; Amirkhanyan, A. S.
1988Ap.....29..445P Altcode: 1989Ap.....29..445P
No abstract at ADS
---------------------------------------------------------
Title: Radiation losses in chromospheric and transition region
emission lines from AD Leo (dM4e)
Authors: Sundland, S. R.; Pettersen, B. R.; Hawley, S. L.;
Kjeldseth-Moe, O.; Andersen, B. N.
1988ASSL..143...61S Altcode: 1988acse.conf...61S
The authors present line surface fluxes from the red dwarf flare star
AD Leo in its quiescent state. IUE and ground-based instruments cover
the UV and optical (1000 - 9000 Å) domains of the spectrum. The
observed radiation losses from chromospheric and transition region
lines amount to 4.0×10<SUP>6</SUP>erg cm<SUP>-2</SUP>s<SUP>-1</SUP> and
2.7×10<SUP>5</SUP>erg cm<SUP>-2</SUP>s<SUP>-1</SUP>, respectively. The
authors estimate the total radiative energy loss in all lines formed
between 25.000K and 250.000K to be of the order of 10<SUP>6</SUP> -
10<SUP>7</SUP>erg cm<SUP>-2</SUP>s<SUP>-1</SUP>.
---------------------------------------------------------
Title: B-19-A flare star in front of the NGC 7000 aggregate
Authors: Tsvetkov, M. K.; Pettersen, B. R.; Hawley, S. L.
1988ASSL..143...77T Altcode: 1988acse.conf...77T
No abstract at ADS
---------------------------------------------------------
Title: V1589 Cyg-B19- a foreground dMe flare star in the direction
of NGC 7000.
Authors: Pettersen, B. R.; Tsvetkov, M. K.; Hawley, S. L.; Coleman,
L. A.; Amirkhanian, A. S.
1988Afz....29...67P Altcode:
Photographic and photoelectric flare observations of V1589 Cyg show
that flare durations from minutes to hours, with amplitudes up to
2 magnitudes in the U-filter, occur. V1589 Cyg is suggested to be a
dM4.5e flare star at a distance of 23 - 32 parsecs.
---------------------------------------------------------
Title: Contemporaneous Photometry and Radial Velocities of RR
Lyrae Stars
Authors: Barnes, T. G., III; Moffett, T. J.; Hawley, S. L.; Slovak,
M. H.; Frueh, M. L.
1987BAAS...19.1052B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Surface Brightness Analysis of RR Lyrae Stars
Authors: Hawley, S. L.; Barnes, T. G., III; Hindsley, R. G.; Moffett,
T. J.
1987BAAS...19Q1053H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Discovery of flare activity on BD +3 4138B.
Authors: Pettersen, B. R.; Hawley, S. L.
1987A&A...181..402P Altcode:
A Cassegrain spectrograph spectrum has been obtained for BD + 3 deg
4138 B. The wavelength-calibrated spectrum subsequently derived shows
a typical M dwarf profile with numerous atomic lines and molecular
features. H-beta, H-gamma, and H-delta appear in emission, and the
spectrum is noted to be a close match for the flare star Gliese 494
in both chromospheric and photospheric features.
---------------------------------------------------------
Title: The Cepheid Surface-Brightness Relation and the Slope of the
P-L Relation
Authors: Barnes, T. G.; Moffett, T. J.; Jefferys, W. H.; Hawley, S. L.
1987BAAS...19..754B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Surface Brightness Analysis of Eight RR Lyrae Stars
Authors: Hawley, Suzanne L.; Barnes, Thomas G.; Moffett, Thomas J.
1987LNP...274..235H Altcode: 1987stpu.conf..235H
We have used a surface brightness, (V-R) relation to analyze new
contemporaneous photometry and radial velocity data for 6 RR-ab type
stars and to re-analyze previously published data for RR Lyrae and X
Arietis. Systematic effects were found in the surface brightness at
phases near minimum radius. Excluding these phases, we determine the
slope of the surface brightness relation and the mean radius for each
star. We also find a zero point which includes both a distance term
and the zero point of the surface brightness relation.
---------------------------------------------------------
Title: An episode of mass expulsion from the M-dwarf flare star EV
Latertae ?
Authors: Ambruster, C. W.; Pettersen, B. R.; Hawley, S.; Coleman,
L. A.; Sandmann, W. H.
1986ESASP.263..137A Altcode: 1986NIA86......137A; 1986niia.conf..137A
In October 1985, observations of the M-dwarf flare star EV Lacertae were
conducted for nine consecutive days with IUE, along with contemporaneous
ground-based photometric and spectrophotometric coverage, and two
extended pointings by EXOSAT to search for atmospheric anomalies which
might help to explain the unusually violent flaring behavior of this
star. On the night of 8 October 1985 all measured UV fluxes dropped
by a factor 2 for 1.5 hr, apparently the result of a major episode of
mass expulsion. The simultaneous Ca K (lambda 3934) and H beta light
curves imply that a significant flare took place shortly before the
start of the IUE observations on this night. No rotational modulation
of the light curve was detected, and the mean Mg II (lamdba 2800) and
C IV (lamdba 1550) fluxes are very similar to the values for YZ CMi,
from which no superflares are reported.
---------------------------------------------------------
Title: Optical and UV observations of a giant stellar flare on AD Leo
Authors: Pettersen, B. R.; Hawley, S. L.; Andersen, B. N.
1986ESASP.263..157P Altcode: 1986NIA86......157P; 1986niia.conf..157P
A giant stellar flare has been observed on the dM4e star AD Leo
simultaneously with IUE and ground-based instrumentation. The
authors present and discuss observations obtained in a 15 minutes
interval around flare maximum. A continuum flux distribution of
flare light is obtained, based on a SWP spectrum and UBVR photometry
corrected for the influence of emission lines. A high temperature
(10<SUP>7</SUP>K) free-free distribution describes the optical data
well, but the observed ultraviolet flux is at least one order of
magnitude smaller. No single radiation process describes the time
averaged flux distribution. Line broadening is evident in hydrogen
Balmer emission lines. The Inglis-Teller formula implies an upper
limit of 6×10<SUP>13</SUP>cm<SUP>-3</SUP> for the electron density.
---------------------------------------------------------
Title: Periodic variability of AD Leo and GL 490A.
Authors: Spiesman, W. J.; Hawley, S. L.
1986AJ.....92..664S Altcode:
BVRI photometric observations of AD Leo and Gl 490A, obtained using
a two-star photometer on the 24-inch telescope at Table Mountain
Observatory during March-April 1981 are reported. V and R light curves
are presented for each star, and the periods and m(v) amplitudes of the
variations are given as 2.7 + or - 0.05 d and 0.024 + or - 0.002 mag
for AD Leo and 3.3 + or - 0.05 d and 0.072 + or - 0.002 mag for Gl 490A.
---------------------------------------------------------
Title: On the Absolute Magnitudes of RR Lyrae Stars
Authors: Barnes, T. G., III; Hawley, S. L.
1986ApJ...307L...9B Altcode:
The photometric data base used by Hawley and colleagues in 1986 to
determine a mean absolute magnitude for RR Lyrae stars has been
examined for systematic errors. Both the magnitudes published by
Fitch et al. in 1966 and Clube and Dawe in 1980 for RR Lyrae stars
are shown to differ systematically from intensity mean magnitudes. On
the basis of new photometry, better relations are determined for
inferring intensity mean magnitudes from partial light curves, using
both the Fitch et al. and Clube and Dawe methods. In addition, it is
shown that the Fitch et al. photometry requires magnitude-dependent
corrections. After correcting the data base for the above effects,
the statistical analysis was repeated to determine the mean absolute
magnitude for 142 RRab stars with the result +0.68 + or - 0.14 mag. This
is 0.08 mag brighter than the previous determination by Hawley et al.
---------------------------------------------------------
Title: Absolute Magnitudes and Kinematic Properties of RR Lyrae Stars
Authors: Hawley, S. L.; Jefferys, W. H.; Barnes, T. G., III; Lai, W.
1986ApJ...302..626H Altcode:
A maximum-likelihood statistical analysis of several subgroups of
the field RR Lyrae stars was performed to determine the relative
solar motion, velocity ellipsoid parameters, and mean absolute visual
magnitude for each group. The full sample of 159 stars was taken from a
recent Chinese proper-motion survey, and new mean radial velocities were
used for 46 of the stars. A geometric minimization technique known as
simplex optimization was used to apply a rigorous maximum-likelihood
model to the data. The best estimate for the mean absolute visual
magnitude is 0.76 + or - 0.14 mag for the entire RR ab-type sample.
---------------------------------------------------------
Title: Radial velocities of RR Lyrae stars.
Authors: Hawley, S. L.; Barnes, T. G., III
1985PASP...97..551H Altcode:
The authors obtained 283 spectra of 57 RR Lyrae stars using the 2.1-m
telescope at McDonald Observatory. Radial velocities were determined
using a software cross-correlation technique. New mean radial velocities
were determined for 46 of the stars.
---------------------------------------------------------
Title: A Maximum Likelihood Investigation of RR Lyrae Kinematics
and Absolute Magnitudes
Authors: Hawley, S. L.; Barnes, T. G., III; Jefferys, W. H.
1984BAAS...16S.966H Altcode:
No abstract at ADS
