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Centro de Astrofísica da Universidade do Porto

Doppler search for exoplanet candidates and binary stars in a CoRoT field using a multi-fiber spectrograph

B. Loeillet, F. Bouchy, M. Deleuil, F. Royer, C. Moutou, P. Barge, P. de Laverny, F. Pont, A. Recio-Blanco, N. C. Santos

Context. The discovery of the short-period giant exoplanet population, the so-called hot Jupiter population, and their link to brown dwarfs and low-mass stars challenges the conventional view of planet formation and evolution.
Aims. We took advantage of the multi-fiber facilities GIRAFFE and UVES/FLAMES (VLT) to perform the first large radial velocity survey using a multi-fiber spectrograph to detect planetary, brown-dwarf candidates and binary stars.
Methods. We observed 816 stars during 5 consecutive half-nights. These stars were selected within one of the exoplanet fields of the space mission CoRoT.
Results. We computed the radial velocities of these stars and showed that a systematic error floor of 30 ms−1 was reached over 5 consecutive nights with the GIRAFFE instrument. Over the whole sample the Doppler measurements allowed us to identify a sample of 50 binaries, 9 active or blended binary stars, 5 unsolved cases, 14 exoplanets and brown-dwarf candidates. Further higher precision Doppler measurements are now necessary to confirm and better characterize these candidates.
Conclusions. This study demonstrates the efficiency of a multi-fiber approach for large radial-velocity surveys in search for exoplanets as well as the follow-up of transiting exoplanet candidates. The spectroscopic characterization of the large stellar population is an interesting by-product of such missions as the CoRoT space mission.

Astronomy and Astrophysics
Volume 479, Page 865
March 2008

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