WASP-38b: a transiting exoplanet in an eccentric, 6.87d period orbit^⋆

¹ Astrophysics Research Centre, School of Mathematics & Physics, Queen’s University Belfast, University Road, Belfast BT7 1NN UK
e-mail: s.barros@qub.ac.uk
² SUPA, School of Physics & Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
³ Las Cumbres Observatory, 6740 Cortona Drive Suite 102, Goleta, CA 93117, USA
⁴ Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
⁵ Observatoire de Geneve, Université de Geneve, 51 Ch. des Maillettes, 1290 Sauverny, Switzerland
⁶ Institut d’Astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, 75014 Paris, France
⁷ Observatoire de Haute-Provence, CNRS/OAMP, 04870 Saint-Michel l’Observatoire, France
⁸ Laboratoire d’Astrophysique de Marseille, Université d’Aix-Marseille & CNRS, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France
⁹ Department of Physics, University of Warwick, Coventry CV4 7AL, UK
¹⁰ Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK
¹¹ Department of Physics and Astronomy, The Open University, Milton Keynes MK7 6AA, UK
¹² Isaac Newton Group of Telescopes, Apartado de Correos 321, 38700 Santa Cruz de la Palma, Tenerife, Spain

Received: 21 September 2010
Accepted: 21 October 2010

Abstract

Aims. We report the discovery of WASP-38b, a long period transiting planet in an eccentric 6.871815 day orbit. The transit epoch is 2   455   335.92050  ±  0.00074 (HJD) and the transit duration is 4.663 h.

Methods. WASP-38b’s discovery was enabled due to an upgrade to the SuperWASP-North cameras. We performed a spectral analysis of the host star HD 146389/BD+10 2980 that yielded T_eff = 6150  ±  80 K, log g  =  4.3  ±  0.1, vsini = 8.6  ±  0.4 km s^-1, M_∗ = 1.16  ±  0.04 M_⊙ and R_∗ = 1.33  ±  0.03 R_⊙, consistent with a dwarf of spectral type F8. Assuming a main-sequence mass-radius relation for the star, we fitted simultaneously the radial velocity variations and the transit light curves to estimate the orbital and planetary parameters.

Results. The planet has a mass of 2.69  ±  0.06 M_Jup and a radius of 1.09  ±  0.03 R_Jup giving a density, ρ_p = 2.1  ±  0.1   ρ_J. The high precision of the eccentricity e = 0.0314  ±  0.0044 is due to the relative transit timing from the light curves and the RV shape. The planet equilibrium temperature is estimated at 1292  ±  33 K. WASP-38b is the longest period planet found by SuperWASP-North and with a bright host star (V = 9.4 mag), is a good candidate for followup atmospheric studies.