Volume 519, September 2010
|Number of page(s)||6|
|Section||Planets and planetary systems|
|Published online||17 September 2010|
Institut d'Astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie,
98bis Bd Arago, 75014 Paris, France e-mail: firstname.lastname@example.org
2 Observatoire de Haute-Provence, CNRS/OAMP, 04870 St. Michel l'Observatoire, France
3 Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA
4 SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, UK
5 Isaac Newton Group of Telescopes, Apartado de Correos 321, 38700 Santa Cruz de la Palma, Tenerife, Spain
6 Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
7 Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Sauverny, Switzerland
8 Department of Physics and Astronomy, The Open University, Milton Keynes, MK7 6AA, UK
9 Astrophysics Research Centre, School of Mathematics and Physics, Queen's University, University Road, Belfast, BT7 1NN, UK
10 NASA Exoplanet Science Institute, Caltech, MS 100-22, 770 South Wilson Avenue, Pasadena, CA 91125, USA
11 Laboratoire d'Astrophysique de Marseille, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France
12 Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden
13 Las Cumbres Observatory, 6740 Cortona Drive Suite 102, Goleta, CA 93117, USA
14 Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK
15 Department of Physics, University of Warwick, Coventry CV4 7AL, UK
Accepted: 13 May 2010
We report the discovery of WASP-21b, a new transiting exoplanet discovered by the Wide Angle Search for Planets (WASP) Consortium and established and characterized with the FIES, SOPHIE, CORALIE and HARPS fiber-fed echelle spectrographs. A 4.3-d period, 1.1% transit depth and 3.4-h duration are derived for WASP-21b using SuperWASP-North and high precision photometric observations at the Liverpool Telescope. Simultaneous fitting to the photometric and radial velocity data with a Markov Chain Monte Carlo procedure leads to a planet in the mass regime of Saturn. With a radius of 1.07 RJup and mass of 0.30 MJup, WASP-21b has a density close to 0.24 ρJup corresponding to the distribution peak at low density of transiting gaseous giant planets. With a host star metallicity [Fe/H] of –0.46, WASP-21b strengthens the correlation between planetary density and host star metallicity for the five known Saturn-like transiting planets. Furthermore there are clear indications that WASP-21b is the first transiting planet belonging to the thick disc.
Key words: planetary systems / techniques: photometric / techniques: radial velocities
Based on observations made with the SuperWASP-North camera hosted by the Isaac Newton Group on La Palma, the FIES spectrograph on the Nordic Optical Telescope, the CORALIE spectrograph on the 1.2-m Euler Swiss telescope on La Silla Observatory, the SOPHIE spectrograph on the 1.93-m telescope on Haute Provence Observatory and the HARPS spectrograph on the 3.6-m ESO telescope at La Silla Observatory under programs 081.C-0388, 082.C-0040, 084.C-0185.
Tables of photometric data are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (126.96.36.199) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/519/A98
© ESO, 2010
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