Transiting exoplanets from the CoRoT space mission. II. CoRoT-Exo-2b: a transiting planet around an active G star
2 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
3 Pôle Astronomie du LESIA
4 IAS - Institut d'astrophysique spatiale
5 IAC - Instituto de Astrofisica de Canarias
6 University of Exeter
7 Physikalisches Institut, Universität Bern
8 IAP - Institut d'Astrophysique de Paris
9 Observatório Nacional/MCTI
10 IfA - Institut für Astronomie, Universität Wien
11 DLR Institute of Planetary Research
12 RSSD - Research and Scientific Support Department, ESA-ESTEC
13 ObsGE - Observatoire Astronomique de l'Université de Genève
14 Observatoire de la Côte d'Azur
15 TLS - Thüringer Landessternwarte Tautenburg
16 ÖAW - Osterreichische Akademie der Wissenschaften = Académie autrichienne des sciences
17 ULiège - Université de Liège = University of Liège = Universiteit van Luik = Universität Lüttich
18 TAU - Tel Aviv University
19 RIU - Rheinisches Institut für Umweltforschung
20 LUTH (UMR_8102) - Laboratoire Univers et Théories
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Résumé
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.