  Stellar multiplicity lies at the heart of many problems in modern
astrophysics, including the physics of star formation, the observational
properties of unresolved stellar populations, and the rates of interacting
binaries such as cataclysmic variables, X-ray binaries, and Type Ia supernovae.
However, little is known about the stellar multiplicity of field stars in the
Milky Way, in particular about the differences in the multiplicity
characteristics between metal-rich disk stars and metal-poor halo stars. In
this study we perform a statistical analysis of ~14,000 F-type dwarf stars in
the Milky Way through time-resolved spectroscopy with the sub-exposures
archived in the Sloan Digital Sky Survey. We obtain absolute radial velocity
measurements through template cross-correlation of individual sub-exposures
with temporal baselines varying from minutes to years. These sparsely sampled
radial velocity curves are analyzed using Markov chain Monte Carlo techniques
to constrain the very short-period binary fraction for field F-type stars in
the Milky Way. Metal-rich disk stars were found to be 30% more likely to have
companions with periods shorter than 12 days than metal-poor halo stars.
