CHARACTERIZING THE COOL KOIs. II. THE M DWARF KOI-254 AND ITS HOT JUPITER

Abstract

We report the confirmation and characterization of a transiting gas giant\nplanet orbiting the M dwarf KOI-254 every 2.455239 days, which was originally\ndiscovered by the Kepler mission. We use radial velocity measurements, adaptive\noptics imaging and near infrared spectroscopy to confirm the planetary nature\nof the transit events. KOI-254b is the first hot Jupiter discovered around an\nM-type dwarf star. We also present a new model-independent method of using\nbroadband photometry to estimate the mass and metallicity of an M dwarf without\nrelying on a direct distance measurement. Included in this methodology is a new\nphotometric metallicity calibration based on J-K colors. We use this technique\nto measure the physical properties of KOI-254 and its planet. We measure a\nplanet mass of Mp = 0.505 Mjup, radius Rp = 0.96 Rjup and semimajor axis a =\n0.03 AU, based on our measured stellar mass Mstar = 0.59 Msun and radius Rstar\n= 0.55 Rsun. We also find that the host star is metal-rich, which is consistent\nwith the sample of M-type stars known to harbor giant planets.\n