Transiting exoplanets from the CoRoT space mission IV: CoRoT-Exo-4b: A transiting planet in a 9.2 day synchronous orbit

S. Aigrain (1) , A. Collier Cameron (2) , M. Ollivier (3) , F. Pont (1) , L. Jorda (4) , J. M. Almenara (5) , R. Alonso (4) , P. Barge (4) , Pascal Bordé (3) , F. Bouchy (6, 7) , H. Deeg (6) , R. de La Reza (5) , M. Deleuil (4) , R. Dvorak (8) , A. Erikson (9) , M. Fridlund (10) , P. Gondoin (11) , M. Gillon (10) , T. Guillot (12) , A. Hatzes (13) , H. Lammer (14) , A. F. Lanza (15, 16) , A. Leger (3) , A. Llebaria (4) , P. Magain (5) , T. Mazeh (17) , C. Moutou (4) , M. Paetzold (18) , C. Pinte (1) , D. Queloz (7) , H. Rauer (9) , D. Rouan (19) , Jodi Schneider (20) , G. Wuchter (13) , S. Zucker (17)

1 School of Physics
2 University of St Andrews [Scotland]
3 IAS - Institut d'astrophysique spatiale
4 LAM - Laboratoire d'Astrophysique de Marseille
5 IAC - Instituto de Astrofisica de Canarias
6 IAP - Institut d'Astrophysique de Paris
7 ObsGE - Observatoire Astronomique de l'Université de Genève
8 ON/MCT, 20921-030, Rio de Janeiro, Brazil) - ON/MCT
9 DLR Institute of Planetary Research
10 RSSD - Research and Scientific Support Department, ESTEC
11 Geneva Observatory
12 CASSIOPEE - Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides
13 TLS - Thüringer Landessternwarte Tautenburg
14 IWF - Space Research Institute of Austrian Academy of Sciences
15 OACT - INAF - Osservatorio Astrofisico di Catania
16 CRPRA - Centre de recherches politiques Raymond Aron
17 TAU - School of Physics and Astronomy [Tel Aviv]
18 RIU - Rheinisches Institut für Umweltforschung
19 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
20 LUTH (UMR_8102) - Laboratoire Univers et Théories

CoRoT, the first space-based transit search, provides ultra-high precision light curves with continuous time-sampling over periods, of up to 5 months. This allows the detection of transiting planets with relatively long periods, and the simultaneous study of the host star's photometric variability. In this letter, we report on the discovery of the transiting giant planet CoRoT-Exo-4b and use the CoRoT light curve to perform a detailed analysis of the transit and to determine the stellar rotation period. The CoRoT light curve was pre-processed to remove outliers and correct for orbital residuals and artefacts due to hot pixels on the detector. After removing stellar variability around each transit, the transit light curve was analysed to determine the transit parameters. A discrete auto-correlation function method was used to derive the rotation period of the star from the out-of-transit light curve. We derive periods for the planet's orbit and star's rotation of 9.20205 +/- 0.00037 and 8.87 +/- 1.12 days respectively, consistent with a synchronised system. We also derive the inclination, i = 90.00 -0.085 +0.000 in degrees, the ratio of the orbital distance to the stellar radius, a/R_s = 17.36 -0.25 +0.05, and the planet to star radius ratio R_p/R_s = 0.1047 -0.0022 +0.0041. We discuss briefly the coincidence between the orbital period of the planet and the stellar rotation period and its possible implications for the system's migration and star-planet interaction history.

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]

S. Aigrain, A. Collier Cameron, M. Ollivier, F. Pont, L. Jorda, et al.. Transiting exoplanets from the CoRoT space mission IV: CoRoT-Exo-4b: A transiting planet in a 9.2 day synchronous orbit. 2008. ⟨hal-00324975⟩