The mass of the candidate exoplanet companion to hd136118 from hubble space telescope astrometry and high-precision radial velocities

Abstract

We use Hubble Space Telescope fine guidance sensor astrometry and high-cadence radial velocities for HD136118 from the Hobby-Eberly Telescope with archival data from Lick to determine the complete set of orbital parameters for HD136118b. We find an orbital inclination for the candidate exoplanet of i b = 163.°1 ± 3.°0. This establishes the actual mass of the object, Mb = 42+11-18 MJ , in contrast to the minimum mass determined from the radial velocity data only, Mb sin i ∼ 12 MJ . Therefore, the low-mass companion to HD 136118 is now identified as a likely brown dwarf residing in the "brown dwarf desert." © 2010. The American Astronomical Society. All rights reserved.