Transiting exoplanets from the CoRoT space mission⋆. XXVIII. CoRoT-33b, an object in the brown dwarf desert with 2:3 commensurability with its host star

Abstract

We report the detection of a rare transiting brown dwarf with a mass of 59 M<SUB>Jup</SUB> and radius of 1.1 R<SUB>Jup</SUB> around the metal-rich, [Fe/H] = +0.44, G9V star CoRoT-33. The orbit is eccentric (e = 0.07) with a period of 5.82 d. The companion, CoRoT-33b, is thus a new member in the so-called brown dwarf desert. The orbital period is within 3% to a 3:2 resonance with the rotational period of the star. CoRoT-33b may be an important test case for tidal evolution studies. The true frequency of brown dwarfs close to their host stars (P< 10 d) is estimated to be approximately 0.2% which is about six times smaller than the frequency of hot Jupiters in the same period range. We suspect that the frequency of brown dwarfs declines faster with decreasing period than that of giant planets. <P />The CoRoT space mission, launched on December 27th 2006, has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA (RSSD and Science Programme), Germany and Spain. Based on observations made with HARPS (High Accuracy Radial velocity Planet Searcher) spectrograph on the 3.6-m European Organisation for Astronomical Research in the Southern Hemisphere telescope at La Silla Observatory, Chile (ESO program 188.C-0779).Based on observations obtained with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, in time allocated by the Spanish Time Allocation Committee (CAT).