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Transiting Exoplanets from the Corot Space Mission Astronomy & Astrophysics manuscript no. 11933 c ESO 2009 August 5, 2009 Transiting exoplanets from the CoRoT space mission ⋆ VIII. CoRoT-7b: the first Super-Earth with measured radius A. L´eger1, D. Rouan2, J. Schneider3, P. Barge4, M. Fridlund11, B. Samuel1, M. Ollivier1, E. Guenther5, M. Deleuil4, H.J. Deeg6, M. Auvergne2, R. Alonso4, S. Aigrain8, A. Alapini8, J.M. Almenara6, A. Baglin2, M. Barbieri4, H. Bruntt2, P. Bord´e1, F. Bouchy7, J. Cabrera9,3, C. Catala2, L. Carone18, S. Carpano11, Sz. Csizmadia9, R. Dvorak10, A. Erikson9, S. Ferraz-Mello23, B. Foing11, F. Fressin13, D. Gandolfi5, M. Gillon12, Ph. Gondoin11, O. Grasset19, T. Guillot13, A. Hatzes5, G. H´ebrard20, L. Jorda4, H. Lammer14, A. Llebaria4, B. Loeillet1,4, M. Mayor, M.12, T. Mazeh17, C. Moutou4, M. P¨atzold18, F. Pont8, D. Queloz12, H. Rauer9,22, S. Renner9,24, R. Samadi2, A. Shporer17, Ch. Sotin19, B. Tingley6, G. Wuchterl5, Adda M.2, Agogu P.16, Appourchaux T.1, Ballans H.,1, Baron P.2, Beaufort T.11, Bellenger R.2, Berlin R.25, Bernardi P.2, Blouin D.4, Baudin F.1, Bodin P.16, Boisnard L.16, Boit L.4, Bonneau F.16, Borzeix S.2, Briet R.16, Buey J.-T.2, Butler B.11, Cailleau D.2, Cautain R.4, Chabaud P.-Y.4, Chaintreuil S.2, Chiavassa F.16, Costes V.16, Cuna Parrho V.2, De Oliveira Fialho F.2, Decaudin M.1, Defise J.-M.15, Djalal S.16, Epstein G.2, Exil G.-E.2, Faur C.16, Fenouillet T.4, Gaboriaud A.16, Gallic A.2, Gamet P.16, Gavalda P.16, Grolleau E.2, Gruneisen R.2, Gueguen L.2, Guis V.4, Guivarc’h V.2, Guterman P.4, Hallouard D.16, Hasiba J.14, Heuripeau F.2, Huntzinger G.2, Hustaix H.16, Imad C.2, Imbert C.16, Johlander B.11, Jouret M.16, Journoud P.2, Karioty F.2, Kerjean L.16, Lafaille V.16, Lafond L.16, Lam-Trong T.16, Landiech P.16, Lapeyrere V.2, Larqu´eT.2, Larqu T.16, Laudet P.16, Lautier N.2, Lecann H.4, Lefevre L.2, Leruyet B.2, Levacher P.4, Magnan A.4, Mazy E.15, Mertens F.2, Mesnager J-M16, Meunier J.-C.4, Michel J.-P.2, Monjoin W.2, Naudet D.2, Nguyen-Kim K.1, Orcesi J-L.1, Ottacher H.14, Perez R.16, Peter G.25, Plasson P.2, Plesseria J.-Y.15, Pontet B.16, Pradines A.16, Quentin C.4, Reynaud J.-L.4, Rolland G.16, Rollenhagen F.25, Romagnan R.2, Russ N.25, Schmidt R.2, Schwartz N.2, Sebbag I.16, Sedes G.2, Smit H.11, Steller M.B.14, Sunter W.11, Surace C.4, Tello M.16, Tiph`ene D.2, Toulouse P.16, Ulmer B.21, Vandermarcq O.16, Vergnault E.16, Vuillemin A.4, and Zanatta P.2 (Affiliations can be found after the references) Received February 23, 2009; accepted xxxxx ABSTRACT Aims. We report the discovery of very shallow (∆F/F ≈ 3.410−4), periodic dips in the light curve of an active V = 11.7 G9V star observed by the CoRoT satellite, which we interpret as caused by a transiting companion. We describe the 3-colour CoRoT data and complementary ground-based observations that support the planetary nature of the companion. Methods. We used CoRoT colours information, good angular resolution ground-based photometric observations in- and out- of transit, adaptive optics imaging, near-infrared spectroscopy, and preliminary results from radial velocity measurements, to test the diluted eclipsing binary scenarios. The parameters of the host star were derived from optical spectra, which were then combined with the CoRoT light curve to derive parameters of the companion. Results. We examined all conceivable cases of false positives carefully, and all the tests support the planetary hypothesis. Blends with separation arXiv:0908.0241v3 [astro-ph.EP] 5 Aug 2009 > 0.40′′or triple systems are almost excluded with a 8 10−4 risk left. We conclude that, inasmuch we have been exhaustive, we have discovered a −5 planetary companion, named CoRoT-7b , for which we derive a period of 0.853 59 ± 3 10 day and a radius of Rp = 1.68 ± 0.09 REarth. Analysis of preliminary radial velocity data yields an upper limit of 21 MEarth for the companion mass, supporting the finding. Conclusions. CoRoT-7b is very likely the first Super-Earth with a measured radius. This object illustrates what will probably become a common situation with missions such as Kepler, namely the need to establish the planetary origin of transits in the absence of a firm radial velocity detection and mass measurement. The composition of CoRoT-7b remains loosely constrained without a precise mass. A very high surface temperature on its irradiated face, ≈ 1800 – 2600 K at the substellar point, and a very low one, ≈ 50 K, on its dark face assuming no atmosphere, have been derived. Key words. planetary systems – techniques: photometry – techniques: adaptive optics – techniques:spectroscopy – stars: fundamental parameters ⋆ The CoRoT space mission, launched on 27 December 2006, University of Hawaii; ESO Telescopes at the La Silla and Paranal has been developed and is operated by CNES, with the contribu- Observatories under programme ID 081.C-0413(C), DDT 282.C-5015; tion of Austria, Belgium, Brazil, ESA, Germany, and Spain. First the IAC80 telescope operated by the Instituto de Astrof´ısica de Tenerife CoRoT data are available to the public from the CoRoT archive: at the Observatorio del Teide; the Isaac Newton Telescope (INT), op- http://idoc-corot.ias.u-psud.fr. The complementary observations were erated on the island of La Palma by the Isaac Newton group in the obtained with MegaPrime/MegaCam, a joint project of CFHT and Spanish Observatorio del Roque de Los Muchachos of the Instituto CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which de Astrofisica de Canarias; and at the Anglo-Australian Telescope is operated by NRC in Canada, INSU-CNRS in France, and the that have been funded by the Optical Infrared Coordination network 2 A. L´eger et al.: CoRoT-7 b: the first Super-Earth with measured radius 1. Introduction Table 1: CoRoT-7 IDs, coordinates, and magnitudes. The space mission CoRoT is performing wide-field stellar pho- tometry at ultra-high precision (Rouan et al. 1998; Baglin et al. CoRoT ID 102708694, LRa01 E2 0165 2006). During an observing run, up to 12,000 stars can be mon- USNO-A2 0825-03049717 itored simultaneously and continuously over 150 days of obser- 2-MASS 06434947-0103468 vation. CoRoT is thus particularly well-suited to detecting plan- TYCHO 4799-1733-1 ets with orbital periods shorter than 50 days. Because the transit RA (2000) 06:43:49.0 signal is proportional to the planet’s projected surface, the first DEC (2000) −01:03:46.0 published CoRoT results (Barge et al. 2008; Alonso et al. 2008; B-mag (a) 12.524 ± 0.018 (a) Deleuil et al. 2008; Aigrain et al. 2008; Moutouet al. 2008) V-mag 11.668 ± 0.008 r′-mag (a) 11.378 ± 0.008 were focused on the population of rather massive planets, one ′ (a) of which has even been quoted as “the first inhabitant of the i -mag 10.924 ± 0.017 J (c) 10.301 ± 0.021 brown-dwarf desert”, with a well-defined mass (20 ± 1 M ) Jup H (c) 9.880 ± 0.022 and a well-defined radius (1.0 ± 0.1 RJup) (Deleuil et al. 2008). (c) Ks 9.806 ± 0.019 However, CoRoT has the capability of detecting significantly (b) µα 12.9 mas/yr 1.4 smaller planets, and analysis of the noise on the light curves (LC (b) µδ -4.0 mas/yr 1.5 hereafter) indeed shows that in many cases it is not far from the photon noise limit (see Aigrain et al., this volume). In the same (a) Provided by Exo-Dat, based on observations taken at the INT line, blind tests performed by different teams of the CoRoT con- telescope. sortium on actual LCs where transits were added did confirmthat (b) From TYCHO catalogue. (c) From 2-MASS catalogue. the performances of CoRoT are such that ≈ 2 REarth hot Super- Earth planets1 are within reach. Such planets on close-in orbits should be accessible for stars brighter than mV ≈ 13 (Auvergne 2006). LRa01, the letter a indicating that the field is close to the The study of small hot planets is becoming a major question Galactic anti-centre). Its ID is given in Table 1, based on the (Mayor & Udry 2008; Mayor et al. 2009; Bouchy et al. 2009) Exo-Dat database (Deleuil et al. 2009). Because it is one of the that has a direct link with planetary system formation and evolu- brightest stars monitored in this field, it was a member of the tion. In this paper, we reportthe discoveryof the smallest transit- oversampled (32 sec) target list from the beginning of the LRa01 ing object detected so far around a main-sequence star, an object run. After the first 40 days of data acquisition, the Alarm Mode that deserves the name of Super-Earth. pipeline (Quentin et al. 2006; Surace et al. 2008) detected the In transit surveys, ground-based follow-up is mandatory for first series of transits in the star LC. confirming a transiting planet candidate. In the case of CoRoT- As illustrated by the whole CoRoT LC (Fig 1), CoRoT-7 is 7b an intensive follow-up campaign has been set up, including an active star.
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