DEVIATIONS FROM UNIFORM PERIOD SPACINGS OF GRAVITY MODES AS PROBES OF ROTATIONAL
MIXING NEAR STELLAR CORES
Conny Aerts
Leuven University
GO30017 +data
Our goal is to establish the simultaneous detection of uniform period spacings and
rotational frequency splittings of nonradial gravity mode oscillations in a sample of
carefully selected bright (i.e., Vmag below 13) F-type pulsating main-sequence stars,
which are representative of massive host stars of exoplanetary systems, with the Kepler
satellite. This will allow to deduce if rotational mixing near the stellar core is the
cause of deviations from period spacings and/or if other yet unknown mixing processes
occur. Additionally, we will determine the internal angular momentum distribution from
the stellar core to the surface for all stars with rotational splitting. We plan to use
the novel method we recently developed after the first detection such period spacings of
gravity modes of a main-sequence pulsator, based on 150 consecutive days of high-precision
space photometry gathered with the CoRoT satellite (Degroote et al., 2010, Nature, 464, 259).
The small deviation from the spacing uniformity of the star HD50230 allowed to deduce the
occurrence of a chemically inhomogeneous zone adjacent to the stellar core of this star. The
CoRoT data have a too short time base to allow the additional detection of rotational splitting
of the gravity modes. This prevented us to deduce the internal angular momentum distribution
inside the star despite the readiness of the methodology. We shall overcome this limitation
with Kepler data for a sample of 72 F-type gravity mode pulsators discovered in the public
Q1 Kepler data. This will provide a seismically calibrated law for the near-core mixing and
angular momentum distribution in main sequence stars, thanks to their gravity modes which
penetrate all the way from the core to the surface.
PHOTOMETRY OF AN ECLIPSING SYSTEM WITH A WHITE DWARF COMPONENT
Roi Alonso
Laboratoire d'Astrophysique de Marseille
GO30016 +data
We plan to continue our research on one of the very few systems of a white dwarf with a
M star eclipsing component that is accesible to Kepler FOV. Extending the observations
through Cycle3 will allow us to 1) improve the precision on the orbital parameters, 2)
study the anual evolution of the flare activity on the M companion and its dependance
with the orbital phase, 3) study the evolution of magnetic active regions on any of the
components, 4) improve the precision on the expected detection of a secondary eclipse, 5)
gain valuable data on the O-C residuals of the 1040 eclipses/year that Kepler is able to
obtain, that might allow the detection of small stellar companions and probably substellar,
and 6) search for pulsations of the WD component.
STARSPOT EVOLUTION ON ACTIVE LATE-TYPE STARS IN THE KEPLER FIELD - CYCLE 3
Alexander Brown
University Of Colorado
GO30015 +data
Starspots on late-type stars are a direct manifestation of the photospheric emergence of
strong dynamo-generated magnetic fields. We propose to extend our Cycle 1 and 2 projects
of 30 minute cadence Kepler photometry, in which we are investigating 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 hence convection
zone depth). We expect that such investigations will stimulate and enable theoretical studies
of magnetic flux generation and transport processes in the regime of moderate to fast rotation,
which any successful theory must be able to address. Our Kepler Cycle 1 data shows a rich
variety of photometric variability including starspot rotational modulation, pulsations (both
simple and very complex), flaring, and eclipses. Our proposed Cycle 3 sample of 219 active
stars is based on GALEX Cycles 4 and 5 FUV and NUV imaging of the Kepler field. Accurate
measurements of starspot longitudes and spot filling-factor maps can be obtained from the
Kepler photometry using our newly-developed light-curve inversion methods that fully utilize
the powerful diagnostic capabilities of Kepler time series data. We check results from our
new inversion code, which -- given the high quality of the Kepler lightcurves -- can directly
model the differential rotation, with results from our previous inversion codes. A full suite
of supporting high resolution optical echelle spectroscopy is being obtained using the Hobby-
Eberly, MMT, NOT, and Apache Point Observatory telescopes. These observations will provide
accurate determinations of the stellar properties, such as effective temperature, surface
gravity, and projected rotational velocity, and also which stars are spectroscopic binaries
and measure their radial velocity curves. Supporting X-ray imaging will commence in 2011 with
an approved XMM Large Project and ultraviolet spectroscopy of several Kepler targets will be
proposed in the coming months. Our sample includes stars for which Doppler imaging, both
conventional and magnetic, is feasible using current technology.
MEASUREMENT OF THE SPIN-ORBIT ALIGNMENT IN STELLAR BINARIES
Timothy Brown
University Of Colorado
GO30029 +data
We propose to measure the spin-orbit alignment of the primary in low mass-ratio eclipsing
binaries. Although spin-orbit alignment is a subject of intense study for transiting
planetary systems, only a few measurements have been done so far for stellar eclipsing
binaries. The angle between the star's spin axis and orbital angular momentum axis is a
key piece of information in the study of stellar binary formation and evolution. Naively
one would expect the three angular momentum axes, the self rotation of both stars and the
orbital angular momentum, to be well aligned as they all originate from the angular momentum
of the same primordial molecular cloud. However, this simple view could be misleading.
Several processes have been proposed in the literature that result in misalignment. Moreover,
misalignment for both stellar components was already identified for one system, out of only
three for which the spin orbit angles were accurately measured. Our measurement technique was
never applied before and requires the very high precision photometry provided by Kepler. Our
proposal will significantly extend the science done by Kepler.
A SEARCH FOR ASTEROIDS ORBITING WHITE DWARFS
Rosanne Di Stefano
Smithsonian Institution/Smithsonian Astrophysical Observatory
GO30027 +data
Do white dwarfs host asteroid systems? To answer this question we propose that Kepler
continue the first search for asteroids transiting a white dwarf. Kepler's unique
photometric sensitivity will allow it to detect the passage of 100-km class objects
against the small disk of a white dwarf. To achieve this goal, we propose to continue
our AO2 program to conduct observations of 2 white dwarfs in Kepler's 1-minute cadence
mode. Theoretical arguments, recent observations of metal-enriched white dwarf
atmospheres, and detections of debris disks, suggest that white dwarfs may be orbited
by large populations of asteroids. Data collected by Kepler may provide the most direct
evidence that such populations exist. A second year of observations is essential to
increase the chance of detecting transits and to significantly increase the science
return from any AO2 detections. Public interest in this type of project is high, making
it ideal for education and outreach.
QUIESCENT GALAXIES OBSERVED WITH KEPLER
Michael Fanelli
NASA Ames Research Center
GO30011 +data
We propose to monitor a set of the brightest galaxies located within the Kepler field of view,
the Kepler Galaxy Survey. Our primary objective is to explore the photometric stability of
galactic systems with Kepler's unique blend of high precision and continuous monitoring. With
important exceptions, galaxies provide a population of quiescent, non-variable sources, which
can be used to quantify the photometric stability and noise characteristics of the Kepler
photometer. The proposed survey will be sensitive to both continuous variability, especially
low-level variations from embedded active nuclei, and random episodic events, such as supernovae.
Using a J-band flux limit, we propose to monitor 200 bright galaxies encompassing a range of
morphologies located across the field-of-view. Given the Survey's source brightness and spatial
distribution, these data will form the temporal baseline for extragalactic investigations with Kepler.
CATCHING SUPERNOVAE IN THE ACT
Peter Garnavich
University Of Notre Dame
GO30020 +data
The progenitors of type Ia supernovae remain a mystery despite their importance as
fundamental distance indicators for cosmology. We still do not know if thermonuclear
events come from single degenerate binary stars or binaries made from two white dwarfs.
Recent models show that the secondary star in a single degenerate binary will cause bright
shock emission in the first hours to days after the explosion while double degenerate
explosions are expected to brighten monotonically. We propose to monitor about 100 galaxies
at z<0.05 in the Kepler field to obtain very early observations of a couple of supernovae.
No other experiment ---past, present, or presently planned--- can match the time resolution
and continuous monitoring of the Kepler mission. This program is also sensitive to shock
breakouts in core collapse supernovae which constrain the physics of the early explosion.
A LEGACY SURVEY FOR CIRCUMBINARY COMPANIONS OF INTERMEDIATE-MASS ECLIPSING
BINARY STARS
Douglas Gies
Georgia State University
GO30006 +data
Stellar companions are commonplace among more massive stars, and these companions
probably are the repository of the angular momentum of the original natal cloud. In
order for star formation processes to lead to very close binary stars (with orbital
periods of a few days), a distant third star may be required to carry the bulk of the
angular momentum. Our goal here is to search for such companions surrounding eclipsing
pairs of intermediate-mass stars (of spectral types B, A, and F). We will use the
remarkably accurate light curves from the Kepler Observatory of some 41 eclipsing binaries
to measure carefully the times of the eclipses. We will search for companions by investigating
periodic variations in the eclipse timings caused by the light travel time across the orbital
displacement of the close binary. In favorable circumstances, we will detect companions as
small as brown dwarf stars and/or massive planets. We began this program in Cycle 1, and
preliminary results confirm the feasibility of the research plans. This continuing program
will provide an observational legacy of the orbital, pulsational, and magnetic variations
among stars with the best determined physical properties in the Kepler field of view.
PULSATIONS AND OVER-SIZED M DWARFS
John Gizis
University Of Delaware
GO30021 +data
We have computed models which predict that M dwarf radii can be inflated by the effects
of magnetic fields on convection and which also predict pulsations on the main sequence,
particulary during He 3 burning. We request rapid cadence observations of a select sample
of M dwarfs with spots with Kepler to observe these pulsations. The results will provide
new constraints on the fundamental properties of low-mass stars.
DASCH VARIABLES IN THE KEPLER FIELD
Jonathan Grindlay
Smithsonian Institution/Smithsonian Astrophysical Observatory
GO30023 +data
The Digital Access to a Sky Century at Harvard (DASCH) project has begun to digitize
and analyze the scientific data contained in over half a million Harvard plates from
the 1880s to the 1980s. Here we propose to obtain Kepler light curves for three classes
of variable stars we have discovered in our analysis of 2000 digitized DASCH images with
at least partial coverage of the Kepler field. The first class are 5 K giants which showed
~1 mag changes on timescales of 10-50 years. Our initial discovery (Tang et al. 2010) of 3
such variables near M44, all K2III, has now been expanded to 20 which show ~1 mag changes
on timescales from 10 to 100 yrs. Their light curves do not match known types of variable
stars, or any models for red giants, and their nature remains mysterious. Kepler light
curves will allow us to study the short-term variability of the 5 stars included on the
Kepler CCDs and measure their star spot activities and rotations. Using the tools of
asteroseismology, the stellar parameters will also be estimated. The second group of
variables we propose to monitor are 4 other long-term variables. The third group are
3 Chandra X-ray sources with positional matches to KIC stars which showed variability
in their 100y DASCH light curves, 3 CVs and 6 flare variables bluer than K type found
in DASCH.
CHARACTERIZING AMPLITUDE AND FREQUENCY SPECTRUM VARIABILITY IN HYBRID GAMMA DOR/DELTA
SCT STARS
Joyce Guzik
Los Alamos National Laboratory
GO30014 +data
The delta Scuti and gamma Doradus pulsating variables are main-sequence (core hydrogen-burning)
stars with masses somewhat larger than the sun (1.2 to 2.5 solar masses). The lower-mass gamma
Dor stars are pulsating in nonradial gravity modes with periods of near one day, whereas the
delta Sct stars are radial and nonradial p-mode (acoustic mode) pulsators with periods of order
two hours. Because of the near one-day periods of gamma Dor stars, it is very difficult to
discover and monitor these variables from ground-based photometry or spectroscopy due to the 1
cycle/day alias. Hybrid gamma Dor/delta Sct stars are among the most interesting targets for
asteroseismology because the two types of modes (pressure and gravity) probe different regions
of the star and are sensitive to the details of the two different driving mechanisms. Because
these driving mechanisms are somewhat mutually exclusive, hybrid stars exhibiting both types
of pulsations are expected to exist only in a small overlapping region of temperature-luminosity
space in the Hertzsprung-Russell diagram. However, Kepler Asteroseismic Science Consortium (KASC)
Working Groups 4/10 (delta Sct/gamma Dor) have discovered that hybrid stars are surprisingly
ubiquitous. In a study of 750 KASC A-F stars observed for up to four quarters, 47% show hybrid
pulsations. Despite extensive study of this large sample during the past summer by the KASC WGs,
no obvious frequency or amplitude correlations have emerged, and there seems to be no clear
separation of gamma Dor and delta Sct pulsators in the HR diagram. The known driving mechanisms
cannot explain the pulsation behavior. In our Cycle 1 Guest Observer program, targeting only 14
stars, five show clear hybrid behavior, and five more show gamma Dor pulsations. In addition, at
least six stars showed some amplitude variability between Q2 and Q4 in the long-cadence data. We
are awaiting data on an additional 187 targets from the Cycle 2 GO program, searching for more
hybrids. Here we propose to take advantage of the Kepler unprecedented micromagnitude photometric
precision and ideal cadence length for these pulsation periods to supplement the KASC sample for
fainter stars, and perform longer-term monitoring to quantify and characterize amplitude or
frequency spectrum variation. After Kepler, we will likely not have the opportunity in this
generation of researchers to obtain such data (unless a European mission, Plato, competes
successfully). We propose continued monitoring of the gamma Dor/delta Sct candidates discovered
in Cycle 1, as well as continued monitoring of the Cycle 2 stars. In addition, we propose to
observe 517 new targets to fill in the statistics for the magnitude 14-15 stars with Teff and
log g appropriate for gamma Dor or delta Sct stars. Our aim with this set is to determine whether
there is actually a magnitude cutoff for detecting variability as hinted at in the KASC analysis.
Long-term monitoring of a large sample of these stars with the high-precision Kepler photometry
is essential to help resolve the mysteries surrounding the theoretical model predictions and to
realize the potential for asteroseismology of these stars.
GROUND-BASED FOLLOW-UP AND LIGHT CURVE MODELING OF ECLIPSING BINARIES TO DETERMINE LIMB
DARKENING EFFECTS FOR THE KEPLER BANDPASS
Thomas Harrison
New Mexico State University
GO30004 +data
We will use NMSU facilities to obtain UBVRI light curves of a set of eclipsing binaries in
the Kepler field of view to ascertain the limb darkening for the broad Kepler bandpass. As
we show below, limb darkening strongly affects the values of physical parameters extracted
from exoplanet transits. The Kepler bandpass is very broad, and therefore the derived, mean
limb darkening cannot be easily predicted. This is especially true given that limb darkening
for normal stars has been shown to be in error by +/- 10 to 20%. We have independently analyzed
the Kepler public release data set to identify deep eclipsing binaries spanning the spectral
type range A to K. We concentrate on systems with similar temperatures for both components. We
will obtain ground-based, multi-wavelength light curves and simultaneously model them using a
modified version of JKTEBOP to to derive the limb darkening. In this way, we will construct a
data base of observationally determined limb darkening coefficients for the Kepler bandpass.
EXPLORING THE FUNDAMENTAL PARAMETERS OF LOW MASS STARS
Thomas Harrison
New Mexico State University
GO30005 +data
We are requesting continued 30-minute cadence observations of 99 low-mass, main-sequence,
detached, double-lined, eclipsing binaries in the Kepler field. These systems were identified
from both Q0/Q1 Kepler data (Coughlin et al. 2010, AJ, in press), as well as our existing
Kepler GO program. The Kepler observations we request, coupled with our ongoing ground-based
multi-wavelength photometric and spectroscopic follow-up data, will allow us to more accurately
measure the masses and radii of these stars, and test the theory that binary spin-up is the
primary cause of inflated radii in low-mass stars observed to-date. We will detect relativistic
photometric beaming in 15 of the systems, and apsidal motion due to general relativity in 27 of
the systems, allowing us to independently measure the stellar masses via photometry. We will also
be able to probe the internal density distribution of these stars via measurement of classical
apsidal motion in many of the systems. Finally, we will also measure spot, and therefore magnetic,
activity as a function of spectral type and binary rotation period, and track the temporal
evolution thereof. The full year of observations is needed to have a sufficient temporal baseline
for the apsidal motion and spot variability measurements, as well as to build enough signal to
noise for a robust detection of the relativistic beaming effect.
CHARACTERIZING THE COMPLEX MORPHOLOGY OF FLARES ON GKM DWARFS
Suzanne Hawley
University of Washington
GO30002 +data
Active G, K, and M dwarfs exhibit energetic outbursts caused by magnetic reconnection events,
called flares, which occur over a large range of timescales and energies. While analysis of
high cadence observations has shown that canonical (fast rise, exponential decay) flares can
be represented by a T = 8,000 to 10,000 K blackbody component (Hawley & Fisher 1992, Hawley
et al 2003), flares which exhibit highly complex light curves (characterized by > 15 additional
sub-events) have been phenomenologically modeled as T = 16,000 to 20,000 K hotspots near the
photosphere (Kowalski et al 2010b). Such hotspots require about 14x more heating of the
photosphere than predicted by current radiative hydrodynamic (RHD) models, potentially
indicating a new, significant gap in our understanding of flare physics. We propose to
monitor 2 active G, 1 active K, and 3 active M dwarfs at short (1 minute) cadence for 6
months. These data will enable us to (a) determine when and how often light curve substructure
forms during flares, as a function of total flare energy; and (b) ascertain whether the
prevalence of this complex morphological structure changes with spectral type (G to K to M)
and across the convective boundary in M dwarfs. This program will provide the first statistical
assessment of whether flare-induced hotspots are a common byproduct of flares and whether there
is a threshold flare energy required to trigger the phenomenon, hence constraining efforts to
develop self-consistent models that accurately describe the physics of stellar flares.
INVESTIGATING THE ORIGIN OF LSP PULSATION
Kenneth Hinkle
NOAO
GO30008 +data
Long secondary period (LSP) variables are so named because they are late type giants with
both a long period and shorter period pulsation. While approximately 25-30% of all pulsating
AGB stars show LSP behavior there is no known physical cause for the longer period. LSP
variables are the only form of stellar variability that is not understood. However, LSP
variables are known to obey a period-luminosity (P-L) relation. This limits the possible
causes to two causes: binarity and pulsation. Strong arguments can be made against both
binarity and radial pulsation. The remaining possibility is non-radial pulsation. While
the long period mode fits this violates current interior models.cWe obtained Kepler Cycle
2 time to look for higher order non-radial pulsation modes. While we have yet to see any
Cycle 2 data, Cycle 0 and 1 data snippets suggest strongly that non-radial modes are present.
Fourier analysis of the light curve should readily identify these modes. We proposed extending
these observations to study the stability and power in the very low frequency modes. The
techniques of asteroseismology will be applied. In the absence of non-radial pulsations, we
will explore the detailed long term light curve to see if it agrees to high precision with
models of ellipsoidal variations. Either the binary or the pulsation models allow interesting
outcomes. The binary model involves near-planet sized companions with orbits evolved into a
very specific configuration. The pulsation model is forbidden by present stellar interior models
and will drive now understanding of stellar interior structure.
STELLAR EVOLUTION IN NGC 6791
Kenneth Hinkle
NOAO
GO30022 +data
The extraordinary galactic open cluster NGC 6791 falls in the Kepler field. NGC 6791
is ancient with an age of 8 Gyr, metal rich with [Fe/H]= +0.30, and one of the most
massive open clusters known. We propose to obtain Kepler time series photometry for
a sample of stars on the RGB/AGB of this cluster. From the population of the cluster
and the stellar evolutionary time scales we know that a small fraction of the program
objects are AGB stars but the only way to distinguish the RGB/AGB stars with certainty
is to look at the interior structure. We will do this using Kepler data and the tools
of asteroseismology. This will give us a text book perspective of how stellar interior
structure changes up the RGB, to the giant clump, and then up the AGB for a set of stars
of the same initial composition and near solar mass. Classification of the evolutionary
status of the RGB/AGB stars will enable additional studies of stellar composition, mixing,
and mass loss. This will produce a case study into the cycling of matter through cluster
stars stars and back into the ISM. This project is being undertaken in collaboration with
the Kepler Asteroseismic Science Consortium.
ABSOLUTE CALIBRATION OF KEPLER USING WHITE DWARFS
Jay Holberg
University Of Arizona
GO30026 +data
We propose to continue our efforts to determine the absolute photometric calibration of
Kepler using relatively small samples of white dwarfs during Cycle 3. Since Cycle 1 we
have been observing 8 DA white dwarfs to which were added 7 white dwarfs in Cycle 2. Our
Cycle 1 data show, as expected, no short period or long term variations in any of our
stars that are not associated with instrumental or spacecraft effects. We continue to
study the spacecraft related modulations in the data.
CATACLYSMIC VARIABLES IN THE KEPLER FIELD
Steve Howell
NOAO
GO30013 +data
Cataclysmic variables provide the cleanest available natural laboratories to investigate
the physical behaviour of accretion. The timing capabilities and sensitivity of Kepler
are well matched to the timescales and amplitude of accretion variability in these sources.
This combination provides an unprecedented opportunity to test and refine the paradigms of
stellar accretion with high-precision, uniform data containing no diurnal or seasonal gaps.
We propose a multi-faceted observational and modeling program that puts our current
understanding of accretion to the test and has the potential to measure the spatial
structure of model-dependent disk parameters. Kepler observations of cataclysmic variables
will impact profoundly our understanding of accretion dynamics and the nature of
astrophysical viscosity. Our proposed observations will provide an outstanding
astrophysical legacy for the Kepler mission archive.
MEASURING THE BINARY FRACTION OF PLANETARY NEBULA CENTRAL STARS IN THE
KEPLER FIELD
George Jacoby
Carnegie Institution of Washington
GO30018 +data
We will determine the fraction of planetary nebulae (PN) in the Kepler field that have
central stars with close binary companions. Ground-based measurements of the binary rate
of PN central stars is about 20% whereas the observational evidence based on a diverse
set of arguments is that this fraction should be 50-80%. The observations are so challenging
from the ground that we cannot say whether there is a conflict or not. Kepler's unique
ability to measure small photometric variations will allow an accurate estimate of binary
central stars for the PNe in the field of view. The question of binary frequency has
wide-ranging consequences that impact stellar and galactic evolution.
STUDYING ACTIVITY CYCLES WITH KEPLER: THE STORY OF STELLAR DYNAMOS
Styliani Kafka
Carnegie Institution of Washington
GO30001 +data
Magnetic activity cycles comprise a fundamental parameter for testing and understanding
magnetic activity, stellar dynamos and space weather around stars. Especially at a time
where planetary searches reach their zenith, the understanding of long-term variations
in stellar atmospheres weigh heavily in the long-term stability of stellar habitable
zones and the preservation of biosignatures on the atmospheres of extrasolar earths.
Our proposed Kepler observations aim at exploring long-term (multi-annual) variations
in the stellar activity characteristics of K/M dwarfs in the Kepler field. Specifically,
for the stars in our sample we will derive correlations between rotation, active region
growth and decay, flare rate, flip-flop evolution activity cycles and stellar mass, using
long-term Kepler light curves. In turn, this will provide fundamental input parameters for
the study of stellar dynamos and the determination of the magnetic field action in stars
with deep convection zones.
CONTINUED PHOTOMETRY OF A VARIABLE HOT SUBDWARF STAR IN NGC 6791
Steven Kawaler
Iowa State University
GO30019 +data
The subdwarf B (sdB) stars lie at the extreme blue end (Teff~25,000-35,000K) of the
horizontal branch, and are the remnant cores of stars that have experienced the core
helium flash while on the RGB. They have extremely thin (and inert) hydrogen shells
surrounding a core undergoing helium fusion. How these stars form is currently unknown,
though leading scenarios include mass transfer in a binary system. Single-star mechanisms
have also been proposed and remain viable given the limitations of observables in these
stars. We propose to continue Kepler observations of the unique hot blue star B4 in NGC
6791, one of only a handful of (sdB) stars known to exist in an old open cluster, and the
only cluster sdB known to show photometric variability caused by binarity. Our goals are
twofold - to observe short-period nonradial pulsations in this star, and to study longer
period variations caused by its binarity. Asteroseismic probes of this star, coupled with
the additional constraints of cluster membership and the properties of the binary system,
should provide important clues about the formation mechanism of the sdB stars. At least 75%
of sdB stars with Teff and log g similar to B4 show g-mode pulsations. B4 was selected for
short-cadence observation for Cycle 2. If it is a pulsator, a second year of photometry will
enable us to refine the pulsation periods, reach low-amplitude modes at levels (70ppm) seen
in known Kepler sdB pulsators , and perhaps measure changes in the pulsations driven by
evolution of the star. A pulsator in an open cluster of known metallicity and age will
provide new and unique probes of the pulsation mechanism and interior of these stars. Given
its faintness, the multiperiodic variations (45 to 90 minute periods) and the small amplitude
of the pulsations, Kepler is the only instrument able to measure these oscillations to the
degree of precision needed for asteroseismic analysis. Another year of SC data would allow
us to look for smaller amplitude pulsations than one year alone might reveal, perhaps showing
multiplet structure that can provide mode identification. This star is already known to be a
low-amplitude (2%-9%) variable with a period of less than 1 day. Our second goal is to extend
the high signal-to-noise light curve for analysis of the binary system. High-precision Kepler
photometry, coupled with ground-based spectroscopy that we will obtain, can measure the orbital
properties of the binary, the mass and radius of the companion, and the distance. With a second
year of photometry of the binary light curve, we can begin to place interesting limits on a
tertiary components through timing variations. Because this star is faint (Kepler magnitude Kp
= 18.27), ground-based data have been insufficient to establish the nature of the known variability
or determine the properties of the binary system. Ground-based data are insufficient to detect
short-period variability from pulsations. Only an extended, uninterrupted time series can address
these issues, and at present Kepler is the only instrument capable of providing the needed data.
B4 is a uniquely valuable star: a (possibly) nonradially pulsating star, in a close binary system,
within a cluster. The binary nature will allow mass and radius determination,and its presence in
a cluster secures knowledge of its age, metallicity, and distance. With these known, asteroseismology
will be tightly constrained.
THE CURIOUS LONG TERM PHENOMENA OF C-TYPE RR LYRAE STARS
Karen Kinemuchi
NASA Ames Research Center
GO30024 +data
RR Lyrae variable stars are pulsating stars that are useful objects in the study of
Galactic structure and evolution, and stellar astrophysics. They are easily identifiable
in photometric surveys with their distinctive light curve shapes. However, we focus our
study on the Bailey c-type RR Lyrae stars (RRc), which are relatively shorter period and
less numerous than the ab-type stars. The RRc stars are often confused with eclipsing
binary stars via the light curves, and candidate stars are often hard to classify, even
with good time-series sampling. We propose to look at four RRc stars discovered with the
Q0/Q1 Kepler data that exhibit additional periodic and/or long term phenomena, unusual
for this type of star. We will use Fourier decompositions techniques as well as a new
automated stellar classification software to confirm the status of these RRc stars. We
will also study the new long term phenomena with the additional quarters and identify
the source(s). Coupled with the Kepler data, we will obtain ground based photometric and
spectroscopic followup data.
PILOT STUDY FOR NEW VARIABLE STARS IN THE KEPLER FIELD
Karen Kinemuchi
NASA Ames Research Center
GO30034 +data
The Kepler mission provides the deepest, complete, high precision photometry with uniform
cadence of stars down to the confusion limit of Kp=21. Due to the short lifetime of this
mission, it is crucial to use this resource now and take advantage of the unique catalog
the spacecraft can obtain. Kepler does not record the whole field and only uses a finite
number of masks to observe interesting targets. The precision of the relative photometry
is at 4% accuracy at Kp=20. Pre-launch surveys have completeness down to 16-17th magnitude,
but our new variable star catalog goes down to the confusion limit. Thus, our catalog will
provide a large number of potentially interesting targets for Kepler to observe. This variable
star catalog was constructed from the full frame images taken during the commissioning phase
of Kepler, and we estimate over 265,000 faint variable stars in the field. Given Kepler's
unique capabilities, this survey will provide a unique opportunity to find various variable
stars such as eclipsing binaries, pulsators, rotators, and cataclysmic/eruptor stars. We
propose a pilot study of 45 stars, all of which demonstrate the most interesting large
amplitude variations, to begin this survey.
PROBING NEUTRON STAR/BLACK HOLE ACCRETION DISKS WITH KEPLER AND SWIFT/XRT
Jifeng Liu
Smithsonian Institution/Smithsonian Astrophysical Observatory
GO30038 +data
The Kepler mission, while designed for exoplanet search, has proved powerful in understanding
the accretion disks around compact objects for its unique capability of continous monitoring
with unprecedented photometric precision. Previous Kepler observations of symbiotics and
Cataclysmic Variables have successfully probed the structures of the accretion flows around
white dwarfs. Here we seek to probe the accretion flows around more compact neutron stars and
black holes, a regime never been studied before. For this purpose, a sample of low-mass X-ray
binary (LMXB) candidates in the Kepler field have been selected from the ROSAT All Sky Survey,
and subsequent Chandra/ACIS observations have identified seven LMXBs with unique optical
counterparts suitable for Kepler observations. The proposed Kepler continuous monitoring of
these seven LMXBs, combined with daily and weekly Swift/XRT monitoring for two brightest LMXBs
in X-ray, will probe the accretion disk structure, its evolution with accretion rate, and how
the accretion flow proceeds inward.
KEPLER GO CYCLE 3: IMPROVING THE MODELING OF ECLIPSING BINARIES OBSERVED BY KEPLER
Kenneth Mighell
NOAO
GO30007 +data
We propose to monitor the 57 eclipsing binaries in Cycle 3 that we previously observed
during our program Kepler GO Cycle 1 proposal 08-KEPLER08-0014 "A Calibration Study of
Variable Stars in the Kepler Field". Our goal is to improve the modeling of eclipsing
binaries based on long-cadence Kepler observations. At least 10% (6 of 57 systems) of
our sample exhibit strong evidence of starspots and we seek to determine if and how
those starspots have moved between Cycles 1 and 3. We seek to achieve period measurements
with a precision of better than 0.00001 days (< 0.864 sec). This precision should allow
us to determine small but significant period changes in contact binaries in our sample
that would be due to mass flows from the secondary to the primary star. Observations
spread Cycles 1 and 3 should allow us to determine if any subtle timing effects remain
in the Kepler processing pipeling procedures that are due to seasonal effects. The
non-contact systems will be used to calibrate our new period timing procedures.
USING NON-SINUSOIDAL LIGHT CURVES TO MAP THE CONVECTION ZONES OF GAMMA DORADUS
VARIABLES
Mike Montgomery
University of Texas
GO30033 +data
We propose to use the nonlinearities present in the light curves of large-amplitude Gamma
Doradus variables to constrain the depth of their convection zones. The basis of this
technique is the strong temeperature dependence of stellar convection zones: relatively
small variations in the surface temperature due to pulsation can result in large changes
in the size of the convection zone during a pulsation cycle, and this in turn introduces
nonlinearities into the light curves. This technique has been successfully applied to
pulsating white dwarf stars and should be straightforward to apply to the Gamma Doradus
stars. In addition, we seek to monitor changes in the convection zones of these objects
over multiple epochs. We therefore request continuing long-cadence observations for four
such Gamma Doradus stars in the upcoming Kepler observing cycle. At present there are two
competing proposed mechanisms concerning the source of mode driving based on completely
different assumptions regarding the physics of convection in these objects; our analysis
will help resolve this long-standing question. Finally, we note that our approach is one
of only two techniques that can be used to measure the depth of the convection zone of a
pulsating star, and it is the only one available for stars such as the Gamma Doradus
variables which have only a handful of excited modes. As a result, this investigation
will provide important data with which to test the results of hydrodynamical simulations
of convection in this part of the HR diagram.
HIGH-PRECISION KEPLER MONITORING OF ACTIVE GALACTIC NUCLEI - CYCLE 3
Richard Mushotzky
NOAO
GO30028 +data
We propose continued long-cadence monitoring of 11 confirmed and 8 candidate AGN in
the Kepler FOV. Kepler's unparalleled combination of high precision, good cadence,
long duration and nearly uninterrupted coverage will provide AGN light curves that
will be unsurpassed for many years to come. These will allow the first optical power
spectral density functions capable of determining the form of the PSD and the first
optical/x-ray cross-correlation functions to probe time scales below 1 day. Kepler's
only limitation is that only a small number of AGN had been identified in its FOV; to
rectify this we have identified 9 new AGN candidates in addition to our cycle 2 sample
in order to accumulate the richest achievable data set while this unique instrument is
still operating.
MILLIMAGNITUDE VARIABILITY OF GALAXIES IN THE KEPLER FIELD
Robert Olling
University of Maryland
GO30032 +data
We propose to monitor about 400 small galaxies in Kepler's field of view for photometric
variations at the millimagnitude (mmag) level to detect active galactic nuclei (AGN) at
unprecedented low amplitude of variability or brightness. Since ~8% of galaxies are known
AGNs (Sarajedini, 2008), we expect to find of order 32 normal AGN in our sample, but an
unknown number of low amplitude AGN. The excellent photometric accuracy of Kepler makes
it an ideal instrument to investigate the unexplored regime of very-low amplitude variability
in AGN, on timescales from a year down to a week, or less. The technical goal of our proposal
is to improve the long-term absolute photometry by a factor of several (10x is the photon-noise
limit) so that we can push the limiting Eddington ratio even further into the unexplored region
of AGN variability for low luminosity objects. Our current-best photometric stability is already
better than 3 mmag for data extracted within a given quarter in the Kepler full-frame images.
CORE OVERSHOOTING AND ROTATION INSIDE MAIN-SEQUENCE B PULSATORS
Peter Papics
Leuven University
GO30036 +data
For a sample of 9 carefully selected B stars (based on the public Q1 data of non-KASC targets,
see Debosscher et al., submitted to A&A) we will deduce the core overshooting parameter value
from frequency and period spacings (see Degroote et al. 2010, Nature, 464, 259), and check if
we can establish a relation between it and the stellar mass. Via the detection of rotational
splitting (see Aerts et al. 2003, Science, 300, 1926) - which was not achieved yet from CoRoT
data for B stars - we plan to check the internal rotational law of these carefully selected
hot massive stars. To have a sufficient frequency resolution, we need at least one year of
ong cadence data. We have guaranteed access at the 1.2 meter Mercator telescope on La Palma
to take high resolution HERMES spectra for the brighter targets simultaneously with the Kepler
observations during the entire season in 2011 and 2012 when the field is visible, and we plan
to submit proposals for other spectrographs on larger telescopes to extend our coverage. The
first spectroscopic measurements already confirmed that the targets are main-sequence stars
of spectral type B, with various projected surface rotational velocity values.
ECLIPSING BINARIES IN THE OLD OPEN CLUSTER NGC 6791
Ruth Peterson
Lick Observatory
GO30012 +data
We propose 130 photometrically-selected targets with V < 17.3 within 14' of the center
of the old, metal-rich open cluster NGC 6791 for Kepler 30-min long-cadence observations.
Sixty-six of these were granted as targets to this program in Cycle 2. The goal is to
detect eclipsing binaries suitable for determining the masses of the components, through
future ground-based observations of radial velocities. Our targets are giants and subgiants,
not main-sequence stars, in order to reduce confusion in the Kepler field and to provide
feasible targets for spectroscopy. We need a large target sample to isolate favorable
binaries, as some stars will be non-members, only half of the members will be in binaries,
many of these will have merged, and only a few of those remaining are useful. Suitable binary
systems should not be triple, and should include a giant and a main-sequence turnoff star so
that both components can be detected spectroscopically. The components must not have previously
exchanged or lost mass. Binary periods must be one to a few years, the orientation must be nearly
edge-on, and the eccentricity will be finite but should not be large. Kepler is already looking
at many targets near the cluster center, where proper motions provide membership information. We
are including a number of these, many of which were granted as targets to this program in Cycle
2, and most of which are brighter giants for which we have membership information from a decade-long
radial-velocity survey. But we also need to go to the outer regions of the cluster and to fainter
stars, to increase the binary sample, mitigate against possible binary interactions at high cluster
density and large stellar radii, and include a wider range of evolutionary stage. Consequently we
are including many more targets, those relatively uncrowded stars that fall on the cluster color
magnitude diagrams defined by the inner members. From this sample we expect to detect roughly a
half-dozen binaries from which meaningful masses can be obtained. Follow-up ground-based
high-resolution spectra will derive their parameters and confirm cluster membership, as well as
define the primary velocity curve, the secondary velocity offset, and the system period. This
should stringently constrain comparisons of observed color-magnitude diagrams to produce meaningful
cluster parameters. Such constraints would have major significance for the derivation of age and
metallicity from the broadband colors and integrated spectra of old elliptical galaxies, for which
NGC 6791 is a critical resolved template.
KEPLER OBSERVATIONS OF LONG-TERM ACTIVITY IN ALGOL-TYPE INTERACTING BINARY
SYSTEMS
Geraldine Peters
University Of Southern California
GO30035 +data
We propose a combination of high and low cadence Kepler observations of ten Algol-type
binaries in the Kepler fields to study the physics of mass accretion in these interacting
systems. Emphasis will be placed on long-term variability, especially the Double Periodic
Phenomenon identified by Mennickent et al. (2003). Double Periodic Variables (DPVs) display
cyclic photometric variations on the short time scales of their orbital periods and long
cycles of hundreds of days. The cause for the long cycle is unknown, but it might be the
result of the waxing and waning of an obscuring circumstellar (CS) disk about the mass
gainer precipitated by critical rotation of the gainer. Variability in an identified hot
accretion spot at the site of the gas stream impact (photosphere or disk) and its size
and longitude on the time scale of the long period will be investigated. We will look for
changes in possible accretion-induced photospheric pulsations that might help drive mass
loss to a CS disk and study its depth dependence. We will also search for variable
micro-flaring that might result from shocks due to a clumpy gas stream. Since the radiative
energy from hot spots and disk mass loss at L3 can precipitate systemic mass loss, their
existence influences the evolution of close binaries. We expect that a hot spot and
micro-flaring will be visible only on the trailing hemisphere of the system. Pulsations
should be global, but perhaps of an irregular nature on hemisphere experiencing the impact.
Although we have a general understanding of how Algol systems are formed and their evolutionary
state, little is known about the details of the mass accretion. We will investigate both short
and long-term variability over many orbital cycles to identify unique light curve structure
that will provide insight into the physics of mass transfer. The Kepler photometry will be
analyzed with the latest version of the Wilson-Devinney light curve analysis program. The
residual light will be analyzed using standard Fourier techniques. Frequencies found in the
residuals will be interpreted with the aid of current asteroseismology software. The project
addresses NASA¿s Strategic Subgoal 3D, Discover the origin, structure, evolution, and destiny
of the universe, and search for Earth-like planets, as it will advance our understanding of
the evolution of early-type close binary stars
IMPROVED AGES FROM ECLIPSING BINARIES IN OPEN STAR CLUSTERS NGC 6791 AND
NGC 6819
Eric Sandquist
San Diego State University
GO30037 +data
Age is difficult to measure to extreme precision for stars other than the Sun. In the
field being observed by Kepler, the open star clusters NGC 6791 and NGC 6819 offer the
opportunity to test a variety of methods of age determination, including several capable
of high precision. We propose to use Kepler to push the limits of age determination using
weakly-interacting binary stars that contain evolved stars. Because mass and radius can
be measured extremely precisely (to better than 1%) for such binaries and require minimal
theoretical interpretation, we can make use of the rapid changes in size that begin when
a star leaves the main sequence to constrain ages tightly. With a minimal investment of
short-cadence observations, we demonstrate that we can push the age precision in both
clusters to better than 7% via this method. These two open clusters are becoming extremely
strong tests of stellar evolution theory, and will have an important influence well beyond
stellar astrophysics.
KEPLER OBSERVATIONS OF FLARES ON SOLAR-TYPE STARS
David Soderblom
Space Telescope Science Institute
GO30009 +data
We have found solar-type stars (G and K stars on and near the main sequence) in the
Kepler Q1 data release that exhibit dramatic flares, with energies at least ~100 to
1,000 times those seen in the largest solar flares. These flaring stars are worth
examining in much greater detail, both to understand better the physics of flaring,
and to understand why these particular stars exhibit this extraordinary behavior and
what that may mean for the nearby environments of these stars. If they are, in fact,
the youngest stars in the Kepler sample, then these flares are putting energies into
their surrounding environments at a critical phase in planet formation. However, we
believe for several reasons that these stars are not simply the youngest stars in the
Kepler sample and are likely to be older stars. If that is true then we are witnessing
solar-type stars exhibit behavior not ever seen before, and there are important
implications. Our working hypothesis is that these stars show flares episodically.
This proposal has been written to ensure continued observation of the flaring stars,
to ensure access to those data, and to obtain one-minute cadence observations of a
subset of the flaring stars in order to derive precise physical parameters for these
extraordinary objects and to better study the flares themselves. That can then permit
gaining a fuller understanding of the context of the extraordinary flaring behavior.
UNDERSTANDING BLAZAR VARIABILITY THROUGH KEPLER, PART 2
Ann Wehrle
Space Science Institute
GO30010 +data
We propose to double the time baseline of our approved Cycle 2 program to search for
variability in four flat spectrum radio quasars (blazars) and one powerful radio galaxy,
Cygnus A, on timescales comparable to the light crossing time of the accretion disk (AD)
around the central supermassive black hole (SMBH) or the base of the relativistic jet.
When the quasars are quiescent, a quasi-periodic light curve indicates an AD origin, and
provides a way to estimate the mass of the SMBH. When the quasars are active, long-lived
quasi-periodic oscillations (QPOs) are very probably from helical features in the jets;
if several different short-lived QPOs are seen in one quasar, then the emission is probably
coming from turbulence behind a shock. When we instead see aperiodic variations during a
faint state, high and low frequency breaks in the power spectral density (PSD) yield the
inner and outer edges of ADs, hence the BH mass. Breaks in the PSD could yield physical
cales in the relativistic jet. Kepler is ideally suited to the necessary measurements by
delivering highly stable photometry continuously on timescales from minutes to days. By
adding a second year of data, we will: see more of the quasars' faint quiescent states,
thus measuring the duration and occurrence rate of QPO-emitting blobs in the AD; use the
better SNR in the PSD to improve our ability to detect the inner and outer edges of the
AD; and reduce the error on the SMBH mass estimate by 30%. For bright states, we will
observe: long-timescale QPO-producing helical features in the jet; short-timescale
QPO-emitting blobs near shocks; for aperiodic signals, we could detect twice as large
physical scales in the jet, and use the better SNR to reduce error bars on the smallest
strong structures in the jet by 30%.
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