Stellar Properties for 138,600 Targets Observed by the K2 Mission
Daniel Huber (University of Sydney), Stephen T. Bryson (NASA Ames), Michael R. Haas (NASA Ames), Tom Barclay (NASA Ames), Geert Barentsen (NASA Ames), et al.

Unlike the Kepler Input Catalog (KIC) for the Kepler Mission, the Ecliptic Plane Input Catalog (EPIC) for the K2 Mission does not include estimates of stellar properties for each cataloged source. Here we present a full set of stellar properties for 138,600 K2 targets in Campaigns 1-8 (~88% of the full target sample) derived from colors, proper motions, spectroscopy, parallaxes, and galactic population synthesis models, with typical uncertainties for G-type stars of ~3% in Teff , ~0.3 dex in log(g), ~40% in radius, ~10% in mass, and ~40% in distance. We show that stars targeted by K2 are dominated by K-M dwarfs (~41% of all selected targets), F-G dwarfs (~36%) and K giants (~21%), consistent with key K2 science programs to search for transiting exoplanets and galactic archeology studies using oscillating red giants. However, we find a significant variation of the fraction of cool dwarfs with galactic latitude, indicating a target selection bias due to interstellar reddening and the increased contamination by giant stars near the galactic plane. We discuss possible systematic errors in the derived stellar properties, and differences to published classifications for K2 exoplanet host stars. The EPIC stellar properties are available through the Mikulski Archive for Space Telescopes (MAST, http://archive.stsci.edu/k2/epic/search.php) and the NASA Exoplanet Archive (NExScI, http://exoplanetarchive.ipac.caltech.edu/).