The N2K Consortium. IV. New Temperatures and Metallicities for More than 100,000 FGK Dwarfs

Abstract

We have created specialized target lists for radial velocity surveys that are biased toward stars that (1) possess planets and (2) are easiest to observe with current detection techniques. We use a procedure that uniformly estimates fundamental stellar properties of Tycho 2 stars, with errors, using spline functions of broadband photometry and proper motion found in Hipparcos /Tycho 2 and 2MASS. We provide estimates of T eff and distance for 2.4 × 10 6 Tycho 2 stars that lack trigonometric distances. For stars that appear to be FGK dwarfs, we also derive [Fe/H] and identify unresolved binary systems with mass ratios 1.25 < M 1 / M 2 < 3.0. For FGK dwarfs with photometric error σ V < 0.05, or V < 9, our temperature model gives a 1 σ error of σ T = +58.7/ - 65.9 K and our metallicity model gives a 1 σ error of σ [Fe/H] = +0.13/ - 0.14 dex. The binarity model can be used to remove 70% of doubles with 1.25 < M 1 / M 2 < 3.0 from a magnitude-limited sample of dwarfs at a cost of cutting 20% of the sample. Our estimates of distance and spectral type enable us to isolate 354,822 Tycho 2 dwarfs, 321,996 absent from Hipparcos , with giant contamination of 2.6% and 7.2%, respectively. Roughly 100,000 of these stars, not in Hipparcos , have sufficiently low photometric errors to retain 0.13-0.3 dex [Fe/H] accuracy and 80-100 K temperature accuracy (1 σ). Our metallicity estimates have been used to identify targets for N2K, a large-scale radial velocity search for hot jupiters, which has verified the errors presented here. The catalogs that we publish can be used to further large-scale studies of Galactic structure and chemical evolution and to provide potential reference stars for narrow-angle astrometry programs such as the Space Interferometry Mission and large-aperture optical interferometry.