THE K2 ECLIPTIC PLANE INPUT CATALOG (EPIC) AND STELLAR CLASSIFICATIONS OF 138,600 TARGETS IN CAMPAIGNS 1-8

The K2 Mission uses the Kepler spacecraft to obtain high-precision photometry over approximate to 80 day campaigns in the ecliptic plane. The Ecliptic Plane Input Catalog (EPIC) provides coordinates, photometry, and kinematics based on a federation of all-sky catalogs to support target selection and target management for the K2 mission. We describe the construction of the EPIC, as well as modifications and shortcomings of the catalog. Kepler magnitudes (Kp) are shown to be accurate to approximate to 0.1 mag for the Kepler field, and the EPIC is typically complete to Kp approximate to 17 (Kp approximate to 19 for campaigns covered by Sloan Digital Sky Survey). We furthermore classify 138,600 targets in Campaigns 1-8 (approximate to 88% of the full target sample) using colors, proper motions, spectroscopy, parallaxes, and galactic population synthesis models, with typical uncertainties for G-type stars of approximate to 3% in T-eff, approximate to 0.3 dex in log g, approximate to 40% in radius, approximate to 10% in mass, and approximate to 40% in distance. Our results show that stars targeted by K2 are dominated by K M dwarfs (approximate to 41% of all selected targets), F-G dwarfs (approximate to 36%), and K giants (approximate to 21%), consistent with key K2 science programs to search for transiting exoplanets and galactic archeology studies using oscillating red giants. However, we find significant variation of the fraction of cool dwarfs with galactic latitude, indicating a target selection bias due to interstellar reddening and increased contamination by giant stars near the galactic plane. We discuss possible systematic errors in the derived stellar properties, and differences with published classifications for K2 exoplanet host stars. The EPIC is hosted at the Mikulski Archive for Space Telescopes (MAST): http://archive.stsci.edu/k2/epic/rsearch.php.