Volume 537, January 2012
|Number of page(s)||7|
|Section||Planets and planetary systems|
|Published online||09 January 2012|
Transiting exoplanets from the CoRoT space mission ⋆
XIX. CoRoT-23b: a dense hot Jupiter on an eccentric orbit
LESIA, UMR 8109 CNRS, Observatoire de Paris, UVSQ, Université
5 place J. Janssen,
2 Instituto de Astrofisica de Canarias, 38205, La Laguna, Tenerife, Spain
3 Institute of Planetary Research, German Aerospace Center, Rutherfordstrasse 2, 12489 Berlin, Germany
4 Laboratoire d’Astrophysique de Marseille, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France
5 Research and Scientic Support Department, ESTEC/ESA, PO Box 299, 2200 AG Noordwijk, The Netherlands
6 School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel
7 Observatoire de la Côte d’Azur, Laboratoire Cassiopée, BP 4229, 06304 Nice Cedex 4, France
8 Department of Physics, Denys Wilkinson Building Keble Road, Oxford, OX1 3RH, UK
9 Institut d’Astrophysique Spatiale, Université Paris XI, 91405 Orsay, France
10 Observatoire de Haute Provence, 04670 Saint Michel l’Observatoire, France
11 Institut d’Astrophysique de Paris, 98bis boulevard Arago, 75014 Paris, France
12 University of Vienna, Institute of Astronomy, Türkenschanzstr. 17, 1180 Vienna, Austria
13 IAG, Universidade de Sao Paulo, Brazil
14 Thüringer Landessternwarte, Sternwarte 5, Tautenburg 5, 07778 Tautenburg, Germany
15 Observatoire de l’Université de Genève, 51 chemin des Maillettes, 1290 Sauverny, Switzerland
16 LUTH, Observatoire de Paris, CNRS, Université Paris Diderot, 5 place Jules Janssen, 92195 Meudon, France
17 Rheinisches Institut für Umweltforschung an der Universität zu Köln, Aachener Strasse 209, 50931, Germany
18 University of Liège, Allée du 6 août 17, Sart Tilman, Liège 1, Belgium
19 Space Research Institute, Austrian Academy of Science, Schmiedlstr. 6, 8042 Graz, Austria
20 Universidad de La Laguna, Dept. de Astrofísica, 38200 La Laguna, Tenerife, Spain
Received: 19 August 2011
Accepted: 3 October 2011
We report the detection of CoRoT-23b, a hot Jupiter transiting in front of its host star with a period of 3.6314 ± 0.0001 days. This planet was discovered thanks to photometric data secured with the CoRoT satellite, combined with spectroscopic radial velocity (RV) measurements. A photometric search for possible background eclipsing binaries conducted at CFHT and OGS concluded with a very low risk of false positives. The usual techniques of combining RV and transit data simultaneously were used to derive stellar and planetary parameters. The planet has a mass of Mp = 2.8 ± 0.3 MJup, a radius of Rpl= 1.05 ± 0.13RJup, a density of ≈ 3 g cm-3. RV data also clearly reveal a nonzero eccentricity of e = 0.16 ± 0.02. The planet orbits a mature G0 main sequence star of V = 15.5 mag, with a mass M⋆ = 1.14 ± 0.08 M⊙, a radius R ⋆ = 1. 61 ± 0.18 R⊙ and quasi-solarabundances. The age of the system is evaluated to be 7 Gyr, not far from the transition to subgiant, in agreement with the rather large stellar radius. The two features of a significant eccentricity of the orbit and of a fairly high density are fairly uncommon for a hot Jupiter. The high density is, however, consistent with a model of contraction of a planet at this mass, given the age of the system. On the other hand, at such an age, circularization is expected to be completed. In fact, we show that for this planetary mass and orbital distance, any initial eccentricity should not totally vanish after 7 Gyr, as long as the tidal quality factor Qp is more than a few 105, a value that is the lower bound of the usually expected range. Even if CoRoT-23b features a density and an eccentricity that are atypical of a hot Jupiter, it is thus not an enigmatic object.
Key words: techniques: spectroscopic / techniques: photometric / stars: fundamental parameters / planetary systems / techniques: radial velocities
The CoRoT space mission, launched on 27 December 2006, has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA, Germany, and Spain. First CoRoT data are available to the public from the CoRoT archive: http://idoc-corot.ias.u-psud.fr. The complementary observations were obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by NRC in Canada, INSU-CNRS in France, and the University of Hawaii; ESO Telescopes at the La Silla and Paranal Observatories under program 184.C0639; the OGS telescope operated by the Instituto de Astrofísica de Tenerife at Tenerife.
© ESO, 2012
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