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R. Wilhelm (Texas Tech), T.C. Beers (Michigan State & JINA), C. Allende Prieto (UT), C. Rockosi (UCSC), B. Yanny (FNAL), H.J. Newberg (RPI), T. Sivarani, Y. Lee (Michigan State & JINA)
The warm star sample (7000 < Teff < 10,000 K) in SDSS is comprised of field horizontal branch (FHB) stars and a large number of blue straggler (BS) stars. Because these stars have a higher intrinsic luminosity than their cooler, turnoff and main-sequence counterparts, they are an ideal sample for probing both the global properties of the thick disk and halo of the Galaxy and the properties of distant halo structures such as the Sagittarius and Monoceros streams.
We have determined stellar parameters of Teff, log g and [Fe/H] for a large sample (N = 5060) of SDSS stars using a combination of photometric color indices and spectroscopic line analysis. In addition we have identified 1110 stars that have significant deviations between the color indices and hydrogen line strength, of which a subsample appear to be RR Lyrae variables with photometry and spectroscopy observations taken out of phase. We present the results of our stellar parameter analysis along with a new distance calibration for the FHB and BS samples and report on metallicity trends as a function of distance out to 60 kiloparsecs from the Sun. In addition we compare the kinematic properties of the halo and thick disk populations and present metal abundances for the old population stars in the Sagittarius and Monoceros streams. Finally, we present evidence that a surprisingly large fraction of the BS sample occupy the Hertzsprung Gap, a result that is consistent with recently published findings for BS stars in globular clusters.
T.C.B., S.T., and Y.L. acknowledge partial support from grant AST 04-06784, as well as from grant PHY 02-16783, Physics Frontier Center/Joint Institute for Nuclear Astrophysics (JINA), awarded by the US National Science Foundation. H.J.N acknowledges partial support from NSF grant AST 03-07571.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.