High-precision photometry of WASP-12 b transits^⋆,⋆⋆

¹ Astrophysikalisches Institut und Universitäts-Sternwarte, Schillergässchen 2–3, 07745 Jena, Germany
e-mail: gm@astro.uni-jena.de
² Toruń Centre for Astronomy, N. Copernicus University, Gagarina 11, 87100 Toruń, Poland

Received: 6 December 2010
Accepted: 19 January 2011

Abstract

Aims. The transiting extrasolar planet WASP-12 b was found to be one of the most intensely irradiated exoplanets. It is unexpectedly bloated and is losing mass that may accrete into the host star. Our aim was to refine the parameters of this intriguing system and search for signs of transit timing variations.

Methods. We gathered high-precision light curves for two transits of WASP-12 b. Assuming various limb-darkening laws, we generated best-fitting models and redetermined the parameters of the system. Error estimates were derived by the prayer-bead method and Monte Carlo simulations.

Results. System parameters obtained by us are found to agree with previous studies within one sigma. Use of the non-linear limb-darkening laws results in the best-fitting models. With two new mid-transit times, the ephemeris was refined to BJD_TDB  =  (2   454   508.97682 ± 0.00020) + (1.09142245 ± 0.00000033)E. Interestingly, indications of transit timing variation are detected at the level of 3.4 sigma. This signal can be induced by an additional planet in the system. Simplified numerical simulations show that a perturber could be a terrestrial-type planet if both planets are in a low-order orbital resonance. However, we emphasise that further observations are needed to confirm variation and to constrain properties of the perturber.