* Astronomy

Title: CoRoT LRa02_E2_0121: Neptune-size planet candidate turns into a hierarchical triple system with a giant primary
Authors: L. Tal-Or, A. Santerne, T. Mazeh, F. Bouchy, C. Moutou, R. Alonso, D. Gandolfi, S. Aigrain, M. Auvergne, P. Barge, A. S. Bonomo, P. Borde, H. Deeg, S. Ferraz-Mello, M. Deleuil, R. Dvorak, A. Erikson, M. Fridlund, M. Gillon, E. W. Guenther, T. Guillot, A. Hatzes, L. Jorda, H. Lammer, A. Leger, A. Llebaria, M. Ollivier, M. Patzold, D. Queloz, H. Rauer, D. Rouan, Y. Tsodikovich, G. Wuchterl

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. Modelling the lightcurve with EBAS we discovered a secondary eclipse with a depth of ~0.07%, indicating a diluted eclipsing binary. Combined MCMC modelling 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.

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