First results from the Calan-Hertfordshire Extrasolar Planet Search: Exoplanets and the discovery of an eccentric brown dwarf in the desert

Abstract

We report the discovery of a brown dwarf on an eccentric orbit and with a semimajor axis that places it in the brown dwarf desert region around the star HD 191760. The star has a spectral type of G3IV/V and a metallicity ([Fe/H]) of 0.29 dex. HD 191760 adds to the small number of metal-rich stars with brown dwarf companions. The brown dwarf (HD 191760b) is found to have an orbital period of 505.57 ± 0.40 d and semimajor axis of 1.35 ± 0.01 au, placing it firmly in the brown dwarf desert. The eccentricity of HD 191760b is found to be 0.63 ± 0.01, meaning it reaches as close as 0.5 au from the host star. Dynamical simulations indicate that no inner planets could reside at separations beyond ∼0.17 au due to the disastrous gravity imposed by HD 191760b. In addition to these first results, we also refine the orbits found for the exoplanets around the stars HD 48265, HD 143361 and HD 154672. All one-planet solutions are in agreement with those previously published by the Magellan Planet Search. © 2009 RAS.