The 0.5M_J transiting exoplanet WASP-13b^*

¹ Isaac Newton Group of Telescopes, Apartado de Correos 321, 38700 Santa Cruz de la Palma, Tenerife, Spain e-mail: wji@ing.iac.es
² Astrophysics Research Centre, School of Mathematics & Physics, Queen's University, University Road, Belfast, BT7 1NN, UK
³ School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK
⁴ Institut d'Astrophysique de Paris, CNRS (UMR 7095) – Université Pierre & Marie Curie, 98 bvd. Arago, 75014 Paris, France
⁵ Observatoire de Haute-Provence, 04870 St Michel l'Observatoire, France
⁶ Department of Physics and Astronomy, California State University, 18111 Nordhoff Street, Northridge, CA, USA
⁷ Laboratoire d'Astrophysique de Marseille, BP 8, 13376 Marseille Cedex 12, France
⁸ Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
⁹ Las Cumbres Observatory, 6740 Cortona Dr. Suite 102, Santa Barbara, CA 93117, USA
¹⁰ Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Sauverny, Switzerland
¹¹ Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK
¹² Department of Physics and Astronomy, The Open University, Milton Keynes, MK7 6AA, UK
¹³ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
¹⁴ Department of Physics, University of Warwick, Coventry CV4 7AL, UK
¹⁵ Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury, Kent, CT2 7NH, UK

Received: 9 March 2009
Accepted: 12 May 2009

Abstract

We report the discovery of WASP-13b, a low-mass transiting exoplanet with an orbital period of 4.35298 ± 0.00004 days. The transit has a depth of 9 mmag, and although our follow-up photometry does not allow us to constrain the impact parameter well (0 < b < 0.46), with radius in the range R_p ~ 1.06-1.21 R_J the location of WASP-13b in the mass-radius plane is nevertheless consistent with H/He-dominated, irradiated, low core mass and core-free theoretical models. The G1V host star is similar to the Sun in mass and metallicity ([M/H] = 0.0±0.2), but is possibly older ( Gyr).