Revisiting the transits of CoRoT-7b at a lower activity level

¹ Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
e-mail: susana.barros@lam.fr
² Observatoire Astronomique de l’Université de Genève, 51 chemin des Maillettes, 1290 Versoix, Switzerland
³ Institute of Planetary Research, German Aerospace Center, Rutherfordstrasse 2, 12489 Berlin, Germany
⁴ LESIA, UMR 8109 CNRS, Observatoire de Paris, UVSQ, Université Paris-Diderot, 5 place J. Janssen, 92195 Meudon Cedex, France
⁵ SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK
⁶ Thuringer Landessternwarte, 07778 Tautenburg, Germany
⁷ INAF-Osservatorio Astrofisico di Catania, via S. Sofia, 78, 95123 Catania, Italy
⁸ Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
⁹ Institut d’Astrophysique Spatiale, Université Paris-Sud & CNRS, 91405 Orsay, France
¹⁰ Instituto de Astrofísica de Canarias (IAC), 38200, La Laguna, Tenerife, Spain
¹¹ Dept. Astrofísica, Universidad de La Laguna (ULL), 38206, La Laguna, Tenerife, Spain
¹² Rheinisches Institut für Umweltforschung an der Universität zu Köln, Aachener Strasse 209, 50931 Köln, Germany
¹³ Observatoire de la Côte d’Azur, Laboratoire Cassiopée, BP 4229, 06304 Nice Cedex 4, France
¹⁴ CNRS, Canada-France-Hawaii Telescope Corporation, 65-1238 Mamalahoa Hwy., Kamuela, HI 96743, USA
¹⁵ Center for Astronomy and Astrophysics, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
¹⁶ Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
¹⁷ LUTH, Observatoire de Paris, CNRS, Université Paris Diderot ; 5 place Jules Janssen, 92195 Meudon, France

Received: 3 April 2014
Accepted: 30 July 2014

Abstract

The first super-Earth with measured radius discovered was CoRoT-7b and it has opened the new field of rocky exoplanet characterisation. To better understand this interesting system, new observations were taken with the CoRoT satellite. During this run 90 new transits were obtained in the imagette mode. These were analysed together with the previous 151 transits obtained in the discovery run and HARPS radial velocity observations to derive accurate system parameters. A difference is found in the posterior probability distribution of the transit parameters between the previous CoRoT run (LRa01) and the new run (LRa06). We propose that this is due to an extra noise component in the previous CoRoT run suspected of being transit spot occultation events. These lead to the mean transit shape becoming V-shaped. We show that the extra noise component is dominant at low stellar flux levels and reject these transits in the final analysis. We obtained a planetary radius, R_p = 1.585 ± 0.064 R_⊕ , in agreement with previous estimates. Combining the planetary radius with the new mass estimates results in a planetary density of 1.19 ± 0.27 ρ_⊕ which is consistent with a rocky composition. The CoRoT-7 system remains an excellent test bed for the effects of activity in the derivation of planetary parameters in the shallow transit regime.