VERY LOW MASS STELLAR AND SUBSTELLAR COMPANIONS TO SOLAR-LIKE STARS FROM MARVELS. V. A LOW ECCENTRICITY BROWN DWARF FROM THE DRIEST PART OF THE DESERT, MARVELS-6b

We describe the discovery of a likely brown dwarf (BD) companion with a minimum mass of 31.7 + or - 2.0 M sub(Jup) to GSC 03546-01452 from the MARVELS radial velocity survey, which we designate as MARVELS-6b. For reasonable priors, our analysis gives a probability of 72% that MARVELS-6b has a mass below the hydrogen-burning limit of 0.072 M sub([odot]), and thus it is a high-confidence BD companion. It has a moderately long orbital period of 47.8929 super(+0.0063) sub(-0.0062) days with a low eccentricity of 0.1442 super(+0.0078) sub(-0.0073) and a semi-amplitude of 1644 super(+12) sub(-13) m s super(-1). Moderate resolution spectroscopy of the host star has determined the following parameters: T sub(eff) = 5598 + or - 63, log g = 4.44 + or - 0.17, and [Fe/H] = +0.40 + or - 0.09. Based upon these measurements, GSC 03546-01452 has a probable mass and radius of M sub(*) = 1.11 + or - 0.11 M sub([odot]) and R sub(*) = 1.06 + or - 0.23 R[odot] with an age consistent with less than ~6 Gyr at a distance of 219 + or - 21 pc from the Sun. Although MARVELS-6b is not observed to transit, we cannot definitively rule out a transiting configuration based on our observations. There is a visual companion detected with Lucky Imaging at 7".7 from the host star, but our analysis shows that it is not bound to this system. The minimum mass of MARVELS-6b exists at the minimum of the mass functions for both stars and planets, making this a rare object even compared to other BDs. It also exists in an underdense region in both period/eccentricity and metallicity/eccentricity space.