VERY LOW MASS STELLAR AND SUBSTELLAR COMPANIONS TO SOLAR-LIKE STARS FROM MARVELS. IV. A CANDIDATE BROWN DWARF OR LOW-MASS STELLAR COMPANION TO HIP 67526

Abstract

We report the discovery of a candidate brown dwarf or a very low mass stellar\ncompanion (MARVELS-5b) to the star HIP 67526 from the Multi-object APO Radial\nVelocity Exoplanet Large-area Survey (MARVELS). The radial velocity curve for\nthis object contains 31 epochs spread over 2.5 years. Our Keplerian fit using a\nMarkov Chain Monte Carlo approach, reveals that the companion has an orbital\nperiod of $90.2695^{+0.0188}_{-0.0187}$ days, an eccentricity of $0.4375 \\pm\n0.0040$ and a semi-amplitude of $2948.14^{+16.65}_{-16.55}$ m s$^{-1}$. Using\nadditional high-resolution spectroscopy, we find the host star has an effective\ntemperature $T_{\\rm{eff}}=6004 \\pm 34$ K, a surface gravity $\\log g$ [cgs]\n$=4.55 \\pm 0.17$ and a metallicity [Fe/H] $=+0.04 \\pm 0.06$. The stellar mass\nand radius determined through the empirical relationship of Torres et al.\n(2010), yields 1.10$\\pm$0.09 $M_{\\sun}$ and 0.92$\\pm$0.19 $R_{\\sun}$. The\nminimum mass of MARVELS-5b is $65.0 \\pm 2.9 M_{Jup}$, indicating that it is\nlikely to be either a brown dwarf or a very low mass star, thus occupying a\nrelatively sparsely-populated region of the mass function of companions to\nsolar-type stars. The distance to this system is 101$\\pm$10 pc from the\nastrometric measurements of Hipparcos. No stellar tertiary is detected in the\nhigh-contrast images taken by either FastCam lucky imaging or Keck adaptive\noptics imaging, ruling out any star with mass greater than 0.2$M_{\\sun}$ at a\nseparation larger than 40 AU.\n