CHARACTERIZING THE COOL KEPLER OBJECTS OF INTERESTS. NEW EFFECTIVE TEMPERATURES, METALLICITIES, MASSES, AND RADII OF LOW-MASS KEPLER PLANET-CANDIDATE HOST STARS

Abstract

We report stellar parameters for late-K and M-type planet-candidate host\nstars announced by the Kepler Mission. We obtained medium-resolution, K-band\nspectra of 84 cool (Teff < 4400 K) Kepler Objects of Interest (KOIs) from\nBorucki et al. We identified one object as a giant (KOI 977); for the remaining\ndwarfs, we measured effective temperatures (Teff) and metallicities ([M/H])\nusing the K-band spectral indices of Rojas-Ayala et al. We determine the masses\nand radii of the cool KOIs by interpolation onto the Dartmouth evolutionary\nisochrones. The resultant stellar radii are significantly less than the values\nreported in the Kepler Input Catalogue and, by construction, correlate better\nwith Teff. Applying the published KOI transit parameters to our stellar radius\nmeasurements, we report new physical radii for the planet candidates.\nRecalculating the equilibrium temperatures of the planet-candidates assuming\nEarth's albedo and re-radiation fraction, we find that 3 of the\nplanet-candidates are terrestrial-sized with orbital semi-major axes that lie\nwithin the habitable zones of their host stars (KOI 463.01, KOI 812.03 and KOI\n854.01). The stellar parameters presented in this letter serve as a resource\nfor prioritization of future follow-up efforts to validate and characterize the\ncool KOI planet candidates.\n