THE METALLICITY OF STARS WITH CLOSE COMPANIONS

We examine the relationship between the frequency of close companions (stellar and planetary companions with orbital periods <5 yr) and the metallicity of their Sun-like (~FGK) hosts. We confirm and quantify a ~4 ? positive correlation between host metallicity and planetary companions. We find little or no dependence on spectral type or distance in this correlation. In contrast to the metallicity dependence of planetary companions, stellar companions tend to be more abundant around low-metallicity hosts. At the ~2 ? level, we find an anticorrelation between host metallicity and the presence of a stellar companion. After dividing our sample into FG and K subsamples, we find a negligible anticorrelation in the FG subsample and a ~3 ? anticorrelation in the K subsample. A kinematic analysis suggests that this anticorrelation is produced by a combination of low-metallicity, high-binarity thick-disk stars and higher metallicity, lower binarity thin-disk stars.