Transiting exoplanets from the CoRoT space mission. II. CoRoT-Exo-2b: a transiting planet around an active G star
Mazeh, T.; Aigrain, S.; Alonso, R.; Auvergne, M.; Barbieri, M.; Barge, P.; Bordé, P.; Bouchy, F.; de La Reza, R.; Deleuil, M.; Dvorak, R.; Erikson, A.; Fridlund, M.; Gondoin, P.; Jorda, L.; Lammer, H.; Léger, A.; Llebaria, A.; Magain, P.; Moutou, C.; Ollivier, M.; Pätzold, M.; Pont, F.; Queloz, D.; Rauer, H.; Rouan, D.; Schneider, J.; Wuchterl, G.; Stecklum, B.; Baglin, A.; Benz, W.; Deeg, H. J.; Gillon, M.; Udry, S.; Pepe, F.; Hébrard, G.; Mayor, M.; Almenara, J. M.; Guillot, T.; Hatzes, A.; Kabath, P.; Shporer, A.; Loeillet, B.
France, Spain, United Kingdom, Switzerland, Brazil, Austria, Germany, Netherlands, Belgium, Israel
Abstract
Context: The CoRoT mission, a pioneer in exoplanet searches from space, has completed its first 150 days of continuous observations of ~12 000 stars in the galactic plane. An analysis of the raw data identifies the most promising candidates and triggers the ground-based follow-up.
Aims: We report on the discovery of the transiting planet CoRoT-Exo-2b, with a period of 1.743 days, and characterize its main parameters.
Methods: We filter the CoRoT raw light curve of cosmic impacts, orbital residuals, and low frequency signals from the star. The folded light curve of 78 transits is fitted to a model to obtain the main parameters. Radial velocity data obtained with the SOPHIE, CORALIE and HARPS spectrographs are combined to characterize the system. The 2.5 min binned phase-folded light curve is affected by the effect of sucessive occultations of stellar active regions by the planet, and the dispersion in the out of transit part reaches a level of 1.09×10-4 in flux units.
Results: We derive a radius for the planet of 1.465 ± 0.029 R_Jup and a mass of 3.31 ± 0.16 M_Jup, corresponding to a density of 1.31 ± 0.04 g/cm^3. The large radius of CoRoT-Exo-2b cannot be explained by current models of evolution of irradiated planets.