Volume 475, Number 3, December I 2007
|Page(s)||1125 - 1129|
|Section||Planets and planetary systems|
|Published online||02 October 2007|
Characterization of the hot Neptune GJ 436 b with Spitzer and ground-based observations*
Observatoire de Genève, Université de Genève, 1290 Sauverny, Switzerland e-mail: firstname.lastname@example.org
2 Observatoire François-Xavier Bagnoud – OFXB, 3961 Saint-Luc, Switzerland
3 Institut d'Astrophysique et de Géophysique, Université de Liège, 4000 Liège, Belgium
4 Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001, USA
5 Observatório Astronómico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal
6 School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel
7 Institut d'Astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, 98bis Bd. Arago, 75014 Paris, France
8 Laboratoire d'Astrophysique de Grenoble, Observatoire de Grenoble, UMR5571 de l'Université J.Fourier et du CNRS, BP 53, 38041 Grenoble, France
Accepted: 11 September 2007
We present Spitzer Space Telescope infrared photometry of a secondary eclipse of the hot Neptune GJ 436 b. The observations were obtained using the 8-μm band of the InfraRed Array Camera (IRAC). The data spanning the predicted time of secondary eclipse show a clear flux decrement with the expected shape and duration. The observed eclipse depth of 0.58 mmag allows us to estimate a blackbody brightness temperature of Tp = 717 ± 35 K at 8 μm. We compare this infrared flux measurement to a model of the planetary thermal emission, and show that this model reproduces properly the observed flux decrement. The timing of the secondary eclipse confirms the non-zero orbital eccentricity of the planet, while also increasing its precision (e = 0.14 ± 0.01). Additional new spectroscopic and photometric observations allow us to estimate the rotational period of the star and to assess the potential presence of another planet.
Key words: techniques: photometric / techniques: spectroscopic / eclipses / stars: individual: GJ 436 / planetary systems / infrared: general
© ESO, 2007
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