Transiting exoplanets from the CoRoT space mission *
VIII. CoRoT-7b: the first super-Earth with measured radius
Institut d'Astrophysique Spatiale, UMR 8617 CNRS, Bât. 121, Université Paris-Sud, 91405 Orsay, France e-mail: email@example.com
2 LESIA, UMR 8109 CNRS, Observatoire de Paris, UVSQ, Université Paris-Diderot, 5 place J. Janssen, 92195 Meudon, France e-mail: firstname.lastname@example.org
3 LUTH, UMR 8102 CNRS, Observatoire de Paris-Meudon, 5 place J. Janssen, 92195 Meudon, France
4 Laboratoire d'Astrophysique de Marseille, UMR 6110 CNRS, Technopôle de Marseille- Etoile, 13388 Marseille Cedex 13, France
5 Research and Scientific Support Department, European Space Agency, ESTEC, 2200 Noordwijk, The Netherlands
6 Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
7 Instituto de Astrofísica de Canarias, C. via Lactea , 38200 La Laguna, Spain
8 School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK
9 Observatoire de Haute Provence, USR 2207 CNRS, OAMP, 04870 St. Michel l'Observatoire, France
10 Institute of Planetary Research, DLR, Rutherfordstr. 2, 12489 Berlin, Germany
11 Rheinisches Institut für Umweltforschung, Universität zu Köln, Abt. Planetenforschung, Aachener Str. 209, 50931 Köln, Germany
12 Institute for Astronomy, University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
13 Instituto de Astronomia, Geofisica e Ciências Atmosféricas, USP, Sao Paulo, Brazil
14 Observatoire de la Côte d'Azur, Laboratoire Cassiopée, CNRS UMR 6202, BP 4229, 06304 Nice Cedex 4, France
15 Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Sauverny, Switzerland
16 Laboratoire de Planétologie et Géodynamique, UMR-CNRS 6112, 2 rue de la Houssiniére, 44322 NANTES Cedex 03, France
17 Institut d'Astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, 98bis Bd Arago, 75014 Paris, France
18 Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
19 School of Physics and Astronomy, R. and B. Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
20 Center for Astronomy and Astrophysics, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
21 Laboratoire d'Astronomie de Lille, Université de Lille 1, 1 impasse de l'Observatoire, 59000 Lille, France
22 Centre National d'Etudes Spatiales, 2 place Maurice Quentin 75039 Paris Cedex 01, France
23 Institute of Robotics and Mechatronics, DLR, Rutherfordstr. 2, 12489 Berlin, Germany
24 Centre Spatial de Liège, ULG Science Park, av. du Pré-Aly, 4031, Angleur-Liège, Belgique
25 Ingenieurbüro Ulmer, Im Technologiepark 1, 15236 Frankfurt/Oder, Germany
Accepted: 28 July 2009
Aims. We report the discovery of very shallow (), periodic dips in the light curve of an active G9V star observed by the CoRoT satellite, which we interpret as caused by a transiting companion. We describe the 3-colour CoRoT data and complementary ground-based observations that support the planetary nature of the companion.
Methods. We used CoRoT colours information, good angular resolution ground-based photometric observations in- and out- of transit, adaptive optics imaging, near-infrared spectroscopy, and preliminary results from radial velocity measurements, to test the diluted eclipsing binary scenarios. The parameters of the host star were derived from optical spectra, which were then combined with the CoRoT light curve to derive parameters of the companion.
Results. We examined all conceivable cases of false positives carefully, and all the tests support the planetary hypothesis. Blends with separation >0.40´´or triple systems are almost excluded with a risk left. We conclude that, inasmuch we have been exhaustive, we have discovered a planetary companion, named CoRoT-7b, for which we derive a period of 0.853 day and a radius of REarth. Analysis of preliminary radial velocity data yields an upper limit of 21 MEarth for the companion mass, supporting the finding.
Conclusions. CoRoT-7b is very likely the first Super-Earth with a measured radius. This object illustrates what will probably become a common situation with missions such as Kepler, namely the need to establish the planetary origin of transits in the absence of a firm radial velocity detection and mass measurement. The composition of CoRoT-7b remains loosely constrained without a precise mass. A very high surface temperature on its irradiated face, ≈1800–2600 K at the substellar point, and a very low one, ≈50 K, on its dark face assuming no atmosphere, have been derived.
Key words: techniques: photometric / techniques: spectroscopic / planetary systems / techniques: high angular resolution / 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 programme ID 081.C-0413(C), DDT 282.C-5015; the IAC80 telescope operated by the Instituto de Astrofísica de Tenerife at the Observatorio del Teide; the Isaac Newton Telescope (INT), operated on the island of La Palma by the Isaac Newton group in the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofisica de Canarias; and at the Anglo-Australian Telescope that have been funded by the Optical Infrared Coordination network (OPTICON), a major international collaboration supported by the Research Infrastructures Programme of the European Commissions Sixth Framework Programme; Radial-velocity observations were obtained with the SOPHIE spectrograph at the 1.93m telescope of Observatoire de Haute Provence, France.
© ESO, 2009