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-circle dot and 0.30 +/- 0.01 M-circle dot, respectively, and a projected separation of 0 ''.55. 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.