CoRoT LRa02_E2_0121: Neptune-size planet candidate turns into a hierarchical triple system with a giant primary^⋆

¹ School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel
e-mail: levtalo@post.tau.ac.il
² Laboratoire d’Astrophysique de Marseille, Université de Provence & CNRS, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France
³ Observatoire de Haute Provence, CNRS/OAMP, 04870 St Michel l’ Observatoire, France
⁴ Observatoire de l’Université de Genève, 51 chemin des Maillettes, 1290 Sauverny, Switzerland
⁵ Research and Scientific Support Department, ESTEC/ESA, Keplerlaan 1, 2200AG, Noordwijk, The Netherlands
⁶ Oxford Astrophyiscs, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
⁷ LESIA, Observatoire de Paris, Place Jules Janssen, 92195 Meudon Cedex, France
⁸ Institut d’Astrophysique Spatiale, Université Paris XI, 91405 Orsay, France
⁹ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
¹⁰ IAG, University of São Paulo, Brasil
¹¹ University of Vienna, Institute of Astronomy, Türkenschanzstr. 17, 1180 Vienna, Austria
¹² Institute of Planetary Research, German Aerospace Center, Rutherfordstrasse 2, 12489 Berlin, Germany
¹³ Thüringer Landessternwarte, Sternwarte 5, Tautenburg, 07778 Tautenburg, Germany
¹⁴ Université de Nice-Sophia Antipolis, CNRS UMR 6202, Observatoire de la Côte d’Azur, BP 4229, 06304 Nice Cedex 4, France
¹⁵ Space Research Institute, Austrian Academy of Science, Schmiedlstr. 6, 8042 Graz, Austria
¹⁶ Rheinisches Institut für Umweltforschung an der Universität zu Köln, Aachener Strasse 209, 50931 Köln, Germany
¹⁷ Institut d’Astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, 98bis Bd Arago, 75014 Paris, France
¹⁸ Universidad de La Laguna, Dept. de Astrofísica, 38200 La Laguna, Tenerife, Spain
¹⁹ University of Liège, Allée du 6 août 17, Sart Tilman, Liège 1, Belgium
²⁰ Center for Astronomy and Astrophysics, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany

Received: 30 May 2011
Accepted: 26 July 2011

Abstract

This paper presents the case of CoRoT LRa02_E2_0121, which was initially classified as a Neptune-size transiting-planet candidate on a relatively wide orbit of 36.3 days. Follow-up observations were performed with UVES, Sandiford, SOPHIE, and HARPS. These observations revealed a faint companion in the spectra. To find the true nature of the system we derived the radial velocities of the faint companion using TODMOR – a two-dimensional correlation technique, applied to the SOPHIE spectra. Modeling the lightcurve with EBAS we discovered a secondary eclipse with a depth of  ~0.07%, indicating a diluted eclipsing binary. Combined MCMC modeling of the lightcurve and the radial velocities suggested that CoRoT LRa02_E2_0121 is a hierarchical triple system with an evolved G-type primary and an A-type:F-type grazing eclipsing binary. Such triple systems are difficult to discover.