SOPHIE velocimetry of Kepler transit candidates IX. KOI-415 b: a long-period, eccentric transiting brown dwarf to an evolved Sun

We report the discovery of a long-period brown-dwarf transiting companion of the solar-type star KOI-415. The transits were detected by the Kepler space telescope. We conducted Doppler measurements using the SOPHIE spectrograph at the Observatoire de Haute-Provence. The photometric and spectroscopic signals allow us to characterize a 62.14+-2.69 Mjup, brown-dwarf companion of an evolved 0.94+-0.06 Msun star in a highly eccentric orbit of P = 166.78805+-0.00022 days and e = 0.698+-0.002. The radius of KOI-415 b is 0.79 (-0.07,+0.12) Rjup, a value that is compatible with theoretical predictions for a 10 Gyr, low-metallicity and non-irradiated object.