67 research outputs found
Preliminary Evaluation of the Kepler Input Catalog Extinction Model Using Stellar Temperatures
The Kepler Input Catalog (KIC) provides reddening estimates for its stars,
based on the assumption of a simple exponential dusty screen. This project
focuses on evaluating and improving these reddening estimates for the KIC's
giant stars, for which extinction is a much more significant concern than for
the nearby dwarf stars. We aim to improve the calibration (and thus
consistency) amongst various photometric and spectroscopic temperatures of
stars in the Kepler field by removing systematics due to incorrect extinction
assumptions. The revised extinction estimates may then be used to derive
improved stellar and planetary properties. We plan to eventually use the large
number of KIC stars as probes into the structure and properties of the Galactic
ISM.Comment: Proc. of the workshop "Asteroseismology of stellar populations in the
Milky Way" (Sesto, 22-26 July 2013), Astrophysics and Space Science
Proceedings, (eds. A. Miglio, L. Girardi, P. Eggenberger, J. Montalban
The Galactic Center: Not an Active Galactic Nucleus
We present 10um-35um Spitzer spectra of the interstellar medium in the
Central Molecular Zone (CMZ), the central 210 pc x 60 pc of the Galactic center
(GC). We present maps of the CMZ in ionic and H2 emission, covering a more
extensive area than earlier spectroscopic surveys in this region. The radial
velocities and intensities of ionic lines and H2 suggest that most of the H2
0-0 S(0) emission comes from gas along the line-of-sight, as found by previous
work. We compare diagnostic line ratios measured in the Spitzer Infrared Nearby
Galaxies Survey (SINGS) to our data. Previous work shows that forbidden line
ratios can distinguish star-forming galaxies from LINERs and AGNs. Our GC line
ratios agree with star-forming galaxies and not with LINERs or AGNs.Comment: Accepted for publication in the ApJ Supplement Serie
A Survey for EHB Stars in the Galactic Bulge
We present a progress report on an extensive survey to find and characterize
all types of blue horizontal-branch stars in the nuclear bulge of the Galaxy.
We have obtained wide, shallow imaging in UBV of ~12 square degrees in the
bulge, with follow-up spectroscopy for radial velocities and metal abundance
determinations. We have discovered a number of metal-rich blue HB stars, whose
presence in the bulge is expected by the interpretation of the extragalactic
ultraviolet excess. Very deep images have been obtained in UBV and SDSS u along
the bulge minor axis, which reveal a significant number of EHB candidates
fainter than B = 19, i.e., with the same absolute magnitudes as EHB stars in
several globular clusters.Comment: To appear in "Extreme Horizontal Branch Stars and Related Objects",
Astrophysics and Space Science, Kluwer Academic Publishers, proceedings of
the meeting held in Keele, UK, June 16-20, 200
A Revised Effective Temperature Scale for the Kepler Input Catalog
We present a catalog of revised effective temperatures for stars observed in
long-cadence mode in the Kepler Input Catalog (KIC). We use SDSS griz filters
tied to the fundamental temperature scale. Polynomials for griz
color-temperature relations are presented, along with correction terms for
surface gravity effects, metallicity, and statistical corrections for binary
companions or blending. We compare our temperature scale to the published
infrared flux method (IRFM) scale for VJKs in both open clusters and the Kepler
fields. We find good agreement overall, with some deviations between (J -
Ks)-based temperatures from the IRFM and both SDSS filter and other diagnostic
IRFM color-temperature relationships above 6000 K. For field dwarfs we find a
mean shift towards hotter temperatures relative to the KIC, of order 215 K, in
the regime where the IRFM scale is well-defined (4000 K to 6500 K). This change
is of comparable magnitude in both color systems and in spectroscopy for stars
with Teff below 6000 K. Systematic differences between temperature estimators
appear for hotter stars, and we define corrections to put the SDSS temperatures
on the IRFM scale for them. When the theoretical dependence on gravity is
accounted for we find a similar temperature scale offset between the
fundamental and KIC scales for giants. We demonstrate that statistical
corrections to color-based temperatures from binaries are significant. Typical
errors, mostly from uncertainties in extinction, are of order 100 K.
Implications for other applications of the KIC are discussed.Comment: Corrected for sign flip errors in the gravity corrections. Erratum to
this paper is attached in Appendix. Full version of revised Table 7 can be
found at http://home.ewha.ac.kr/~deokkeun/kic/sdssteff_v2.dat.g
Chemodynamical Analysis of Metal-rich High-eccentricity Stars in the Milky Way's Disk
We present a chemodynamical analysis of 11,562 metal-rich, high-eccentricity
halo-like main-sequence (MS) stars, which has been referred to as the Splash or
Splashed Disk, selected from Sloan Digital Sky Survey (SDSS) and Large Sky Area
Multi-Object Fiber Spectroscopic Telescope (LAMOST). When divided into two
groups, a low-[/Fe] population (LAP) and a high-[/Fe]
population (HAP), based on kinematics and chemistry, we find that they exhibit
very distinct properties, indicative of different origins. From a detailed
analysis of their orbital inclinations, we suggest that the HAP arises from a
large fraction (~ 90%) of heated disk stars and a small fraction (~ 10%) of in
situ stars from a starburst population, likely induced by interaction of the
Milky Way with Gaia Sausage/Enceladus (GSE) or other early merger. The LAP
comprises about half accreted stars from the GSE and half formed by the
GSE-induced starburst. Our findings further imply that the Splash stars in our
sample originated from at least three different mechanisms - accretion, disk
heating, and a merger induced starburst
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