LHS 6343 C: A Transiting Field Brown Dwarf Discovered by the Kepler Mission

We report the discovery of a brown dwarf that transits one member of the M+M binary system LHS 6343 AB every 12.71 days. The transits were discovered using photometric data from the Kepler public data release. The LHS 6343 stellar system was previously identified as a single high proper motion M dwarf. We use adaptive optics imaging to resolve the system into two low-mass stars with masses 0.370 ± 0.009 M _sun and 0.30 ± 0.01 M _sun, respectively, and a projected separation of 0farcs55. High-resolution spectroscopy shows that the more massive component undergoes Doppler variations consistent with Keplerian motion, with a period equal to the transit period and an amplitude consistent with a companion mass of M_C = 62.7 ± 2.4 M _Jup. Based on our analysis of the transit light curve, we estimate the radius of the companion to be R_C = 0.833 ± 0.021 R _Jup, which is consistent with theoretical predictions of the radius of a >1 Gyr brown dwarf.

Based on observations obtained at the W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology. Keck time has been granted by Caltech, the University of California, and NASA.