Chemical compositions of thin-disk, high-metallicity red
  horizontal-branch field stars
  We present a detailed abundance analysis and atmospheric parameters of 76
stars from a survey to identify field Galactic red horizontal-branch (RHB)
stars. High-resolution echelle spectra (R\simeq60,000, S/N>=100) were obtained
with 2.7 m Smith Telescope at McDonald Observatory. The target stars were
selected only by color and parallax information. Overall metallicities and
relative abundances of proton-capture elements (C I, N I, O I, Li I),
alpha-elements (Ca I and Si I), and neutron-capture elements (Eu II and La II)
were determined by either equivalent width or synthetic spectrum analyses. We
used CN features at 7995-8040 {\AA} region in order to determine 12^C/13^C
ratios of our targets. Investigation of the evolutionary stages, using
spectroscopic T_eff and log g values along with derived 12^C/13^C ratios,
revealed the presence of 18 probable RHB stars in our sample. We also derived
kinematics of the stars with available distance information. Taking into
account both the kinematics and probable evolutionary stages, we conclude that
our sample contains five thick disk and 13 thin disk RHB stars. Up until now,
RHB stars have been considered as members of the thick disk, and were expected
to have large space velocities and sub-solar metallicities. However, our sample
is dominated by low velocity solar-metallicity RHB stars; their existence
cannot be easily explained with standard stellar evolution.
