Transiting exoplanets from the CoRoT space mission^⋆,⋆⋆

XXVI. CoRoT-24: a transiting multiplanet system

¹ Observatoire de l’Université de Genève, 51 chemin des Maillettes, 1290 Sauverny, Switzerland
e-mail: ras@iac.es
² Instituto de Astrofísica de Canarias, 38205, La Laguna, Tenerife, Spain
³ Dpto. de Astrofísica, Universidad de La Laguna, 38206, La Laguna, Tenerife, Spain
⁴ Laboratoire d’Astrophysique de Marseille, CNRS & Aix-Marseille University, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France
⁵ McDonald Observatory, University of Texas at Austin, Austin TX 78712, USA
⁶ Thüringer Landessternwarte, Sternwarte 5, 07778 Tautenburg, Germany
⁷ Oxford Astrophyiscs, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
⁸ LESIA, Observatoire de Paris, place Jules Janssen, 92195 Meudon Cedex, France
⁹ Institut d’Astrophysique Spatiale, Université Paris-Sud & CNRS, 91405 Orsay, France
¹⁰ Observatoire de Haute-Provence, Saint-Michel-l’Observatoire 04670, France
¹¹ Institut d’Astrophysique de Paris, UMR7095 CNRS, Université Pierre et Marie Curie, 98bis boulevard Arago, 75014 Paris, France
¹² Institute of Planetary Research, German Aerospace Center, Rutherfordstrasse 2, 12489 Berlin, Germany
¹³ Research and Scientific Support Department, ESTEC/ESA, PO Box 299, 2200 AG Noordwijk, The Netherlands
¹⁴ University of Vienna, Institute of Astronomy, Türkenschanzstr. 17, 1180 Vienna, Austria
¹⁵ IAG, University of São Paulo, Department of Astronomy, Office F209, rua do Matão, 1226, Cid. Universitária, 05.508-090 São Paulo 2013 SP, Brazil
¹⁶ University of Liège, allée du 6 août 17, Sart Tilman, Liège 1, Belgium
¹⁷ Rheinisches Institut für Umweltforschung, Abteilung Planetenforschung, an der Universität zu Köln, Aachener Strasse 209, 50931 Köln, Germany
¹⁸ Université de Nice-Sophia Antipolis, CNRS UMR 6202, Observatoire de la Côte d’Azur, BP 4229, 06304 Nice Cedex 4, France
¹⁹ Space Research Institute, Austrian Academy of Science, Schmiedlstr. 6, 8042 Graz, Austria
²⁰ School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, 69978 Tel Aviv, Israel
²¹ Institut für Astrophysik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
²² Center for Astronomy and Astrophysics, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
²³ Centro de Astrofísica, Universidade do Porto, rua das Estrelas, 4150-762 Porto, Portugal
²⁴ LUTH, Observatoire de Paris, CNRS, Université Paris Diderot ; 5 place Jules Janssen, 92195 Meudon, France
²⁵ German Space Operations Center, German Aerospace Center, Münchner Strasse 20, 82234 Weßling, Germany
²⁶ Landessternwarte Königstuhl, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
²⁷ Institut for Fysik og Astronomi, Aarhus Universitet, Ny Munkegade 120, 8000 Aarhus C, Denmark

Received: 16 December 2011
Accepted: 4 June 2014

Abstract

We present the discovery of a candidate multiply transiting system, the first one found in the CoRoT mission. Two transit-like features with periods of 5.11 and 11.76 d are detected in the CoRoT light curve around a main sequence K1V star of r = 15.1. If the features are due to transiting planets around the same star, these would correspond to objects of 3.7 ± 0.4 and 5.0 ± 0.5 R_⊕ , respectively. Several radial velocities serve to provide an upper limit of 5.7 M_⊕ for the 5.11 d signal and to tentatively measure a mass of 28⁺¹¹_-11 M_⊕ for the object transiting with a 11.76 d period. These measurements imply low density objects, with a significant gaseous envelope. The detailed analysis of the photometric and spectroscopic data serves to estimate the probability that the observations are caused by transiting Neptune-sized planets as much as over 26 times higher than a blend scenario involving only one transiting planet and as much as over 900 times higher than a scenario involving two blends and no planets. The radial velocities show a long-term modulation that might be attributed to a 1.5 M_Jup planet orbiting at 1.8 AU from the host, but more data are required to determine the precise orbital parameters of this companion.