Transiting exoplanets from the CoRoT space mission : XXVI. CoRoT-24: A transiting multiplanet system

Alonso, R. and Moutou, C. and Endl, M. and Almenara, J. -M. and Guenther, E. W. and Deleuil, M. and Hatzes, A. and Aigrain, S. and Auvergne, M. and Baglin, A. and Barge, P. and Bonomo, A. S. and Bordé, P. and Bouchy, F. and Cavarroc, C. and Cabrera, J. and Carpano, S. and Csizmadia, Szilárd and Cochran, W. D. and Deeg, H. J. and Díaz, R. F. and Dvorak, R. and Erikson, A. and Ferraz-Mello, S. and Fridlund, M. and Fruth, T. and Gandolfi, D. and Gillon, M. and Grziwa, S. and Guillot, T. (2014) Transiting exoplanets from the CoRoT space mission : XXVI. CoRoT-24: A transiting multiplanet system. ASTRONOMY & ASTROPHYSICS, 567. ISSN 0004-6361

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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 serve to estimate the probability that the observations are caused by transiting Neptune-sized planets as >26× higher than a blend scenario involving only one transiting planet and >900× 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 MJup planet orbiting at 1.8 A.U. from the host, but more data are required to determine the precise orbital parameters of this companion.

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