The thermal emission of the young and massive planet CoRoT-2b at 4.5 and 8 mum

Michel Gillon (1) , A. A. Lanotte (1) , Travis S. Barman (2) , N. Miller (3) , Brice-Olivier Demory (4) , Magali Deleuil (5) , Josefina Montalbán (1) , François Bouchy (6) , A. C. Cameron (7) , Hans J. Deeg (8) , Jonathan J. Fortney (3) , Malcolm C. Fridlund (9) , J. Harrington (10) , Pierre Magain (1) , Claire Moutou (5) , Didier Queloz (4) , Heike Rauer (11) , Daniel Rouan (12) , Jean Schneider (13)

1 Institut d'Astrophysique, Géophysique et Océanographie, Université de Liège
2 Lowell Observatory, Flagstaff
3 Department of Astronomy and Astrophysics, University of California
4 Observatoire Astronomique de l'Université de Genève
5 LAM - Laboratoire d'Astrophysique de Marseille
6 OHP - Observatoire de Haute-Provence
7 School of Physics and Astronomy, University of St Andrews
8 IAC - Instituto de Astrofisica de Canarias
9 RSSD - Research and Scientific Support Department, ESA-ESTEC
10 Planetary Sciences Group, Department of Physics, University of Central Florida, Orlando
11 DLR Institut für Planetenforschung
12 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
13 LUTH (UMR_8102) - Laboratoire Univers et Théories

We report measurements of the thermal emission of the young and massive planet CoRoT-2b at 4.5 and 8 mum 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 mum. 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 (M_p = 3.47±0.22 M_J, R_p = 1.466±0.044 R_J). We find a small but significant offset in the timing of the occultation when compared to a purely circular orbital solution, leading to e \cosomega = -0.00291±0.00063 where e is the orbital eccentricity and omega 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 Q_s' = 10⁵-10⁶, our modeling is able to explain the large radius of CoRoT-2b if Q_p'

Domaines: Astrophysique [astro-ph]

Michel Gillon, A. A. Lanotte, Travis S. Barman, N. Miller, Brice-Olivier Demory, et al.. The thermal emission of the young and massive planet CoRoT-2b at 4.5 and 8 mum. Astronomy and Astrophysics - A&A, 2010, 511, pp.3. ⟨10.1051/0004-6361/200913507⟩. ⟨hal-03785194⟩