Volume 551, March 2013
|Number of page(s)||5|
|Published online||22 February 2013|
VIII. KOI-205 b: a brown-dwarf companion to a K-type dwarf
1 Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille), UMR 7326, 13388 Marseille, France
2 Institut d’Astrophysique de Paris, UMR 7095 CNRS, Université Pierre & Marie Curie, 98bis boulevard Arago, 75014 Paris, France
3 Observatoire de Haute-Provence, CNRS/OAMP, 04870 Saint-Michel-l’ Observatoire, France
4 INAF – Osservatorio Astronomico di Torino, via Osservatorio 20, 10025 Pino Torinese, Italy
Received: 17 January 2013
Accepted: 7 February 2013
We report the discovery of a transiting brown dwarf companion to KOI-205, a K0 main-sequence star, in a 11.720125-day period orbit. The transits were detected by the Kepler space telescope, and the reflex motion of the star was measured using radial velocity observations obtained with the SOPHIE spectrograph. The atmospheric parameters of the host stars were determined from the analysis of high-resolution, high signal-to-noise ratio ESPaDOns spectra obtained for this purpose. Together with spectrophotometric measurements recovered from the literature, these spectra indicate that the star is a mildly metallic K0 dwarf with Teff 5237 ± 60 K. The mass of the companion is 39.9 ± 1.0 MJup and its radius is 0.81 ± 0.02 RJup, in agreement with current theoretical predictions. This is the first time a bona fide brown dwarf companion is detected in orbit around a star of this type. The formation and orbital evolution of brown dwarf companions is briefly discussed in the light of this new discovery.
Key words: techniques: radial velocities / techniques: photometric / brown dwarfs / stars: individual: KIC7046804
Based on observations collected with the SOPHIE spectrograph on the 1.93-m telescope at Observatoire de Haute-Provence (CNRS), France, and with the ESPaDOnS spectrograph on the CFH telescope.
Tables 1 and 2 are available in electronic form at http://www.aanda.org
© ESO, 2013
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