Volume 511, February 2010
|Number of page(s)||11|
|Section||Planets and planetary systems|
|Published online||19 February 2010|
The thermal emission of the young and massive planet CoRoT-2b at 4.5 and 8 μm *,**
Institut d'Astrophysique et de Géophysique, Université
de Liège, Allée du 6 Août 17, Bat. B5C, 4000 Liège, Belgium e-mail: firstname.lastname@example.org
2 Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290 Sauverny, Switzerland
3 Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001, USA
4 Department of Astronomy and Astrophysics, University of California, Santa Cruz, USA
5 LAM, UMR 6110 CNRS, 38 rue Frédéric Joliot-Curie, 13388 Marseille, France
6 Observatoire de Haute Provence, USR 2207 CNRS, OAMP, 04870 St-Michel l'Observatoire, France
7 School of Physics and Astronomy, University of St. Andrews, North Haugh, Fife, KY16 9SS, UK
8 Instituto de Astrofísica de Canarias, C. Via Lactea S/N, 38200 La Laguna, Spain
9 Research and Scientific Support Department, European Space Agency, ESTEC, 220 Noordwijk, The Netherlands
10 Planetary Sciences Group, Department of Physics, University of Central Florida, Orlando, FL 32816, USA
11 Institut fuer Planetenforschung, DLR, Rutherford str. 2, 12489 Berlin, Germany
12 Zentrum fuer Astronomie und Astrophysik, Hardenbergstr. 36, 10623 Berlin, Germany
13 LESIA, UMR 8109 CNRS, Observatoire de Paris, UVSQ, Université Paris-Diderot, 5 Place J. Janssen, 92195 Meudon, France
14 LUTH, UMR 8102 CNRS, Observatoire de Paris-Meudon, 5 Place J. Janssen, 92195 Meudon, France
Accepted: 26 November 2009
We report measurements of the thermal emission of the young and massive planet CoRoT-2b at 4.5 and 8 μm with the Spitzer Infrared Array Camera (IRAC). Our measured occultation depths are 0.510±0.042% at 4.5 and 0.41±0.11% at 8 μm. In addition to the CoRoT optical measurements, these planet/star flux ratios indicate a poor heat distribution on the night side of the planet and agree better with an atmosphere free of temperature inversion layer. Still, such an inversion is not definitely ruled out by the observations and a larger wavelength coverage is required to remove the current ambiguity. Our global analysis of CoRoT, Spitzer, and ground-based data confirms the high mass and large size of the planet with slightly revised values (Mp = 3.47±0.22 MJ, Rp = 1.466±0.044 RJ). We find a small but significant offset in the timing of the occultation when compared to a purely circular orbital solution, leading to = -0.00291±0.00063 where e is the orbital eccentricity and ω is the argument of periastron. Constraining the age of the system to at most a few hundred Myr and assuming that the non-zero orbital eccentricity does not come from a third undetected body, we modeled the coupled orbital-tidal evolution of the system with various tidal Q values, core sizes, and initial orbital parameters. For = 105-106, our modeling is able to explain the large radius of CoRoT-2b if ≤ 10 through a transient tidal circularization and corresponding planet tidal heating event. Under this model, the planet will reach its Roche limit within 20 Myr at most.
Key words: binaries: eclipsing / planetary systems / stars: individual: CoRoT-2 / techniques: photometric
Based on data collected with the VLT/FORS2 instrument at ESO Paranal Observatory, Chile (programs 081.C-0413(B)).
The photometric timeseries used in this work are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/511/A3
© ESO, 2010
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