The sub-Jupiter mass transiting exoplanet WASP-11b^*

¹ Department of Physics & Astronomy, University of Leicester, Leicester, LE1 7RH, UK e-mail: rgw@astro.le.ac.uk
² School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK
³ Astrophysics Research Centre, School of Mathematics & Physics, Queen's University, University Road, Belfast, BT7 1NN, UK
⁴ Isaac Newton Group of Telescopes, Apartado de Correos 321, 38700 Santa Cruz de la Palma, Tenerife, Spain
⁵ Department of Physics, University of Warwick, Coventry CV4 7AL, UK
⁶ Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
⁷ Institut d'Astrophysique de Paris, CNRS (UMR 7095) – Université Pierre & Marie Curie, 98bis Bvd. Arago, 75014 Paris, France
⁸ Observatoire de Haute-Provence, 04870 St Michel l'Observatoire, France
⁹ Department of Physics and Astronomy, The Open University, Milton Keynes, MK7 6AA, UK
¹⁰ Laboratoire d'Astrophysique de Marseille, OAMP, Université Aix-Marseille & CNRS, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France
¹¹ Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Sauverny, Switzerland
¹² Las Cumbres Observatory, 6740 Cortona Dr. Suite 102, Santa Barbara, CA 93117, USA

Received: 17 September 2008
Accepted: 20 May 2009

Abstract

We report the discovery of a sub-Jupiter mass exoplanet transiting a magnitude host star 1SWASP J030928.54+304024.7. A simultaneous fit to the transit photometry and radial-velocity measurements yield a planet mass M_p = 0.53 ± 0.07 , radius and an orbital period of  days. The host star is an early to mid-K dwarf, with a spectral analysis yielding an effective temperature of 4800 ± 100 K and log g = 4.45 ± 0.2. It is amongst the smallest, least massive and lowest luminosity stars known to harbour a transiting exoplanet. WASP-11b is the third least strongly irradiated transiting exoplanet discovered to date, experiencing an incident flux F_p = 1.910⁸ erg s^-1 cm^-2 and having an equilibrium temperature T_eql = 960 ± 70 K.