Improved parameters for the transiting hot Jupiters WASP-4b and WASP-5bM. Gillon1, B. Smalley2, L. Hebb3, D. R. Anderson2, A. H. M. J. Triaud1, C. Hellier2, P. F. L. Maxted2, D. Queloz1, and D. M. Wilson2
1 Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290 Sauverny, Switzerland
2 Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
3 School of Physics and Astronomy, University of St. Andrews, North Haugh, Fife, KY16 9SS, UK
Received 7 September 2008 / Accepted 9 December 2008
The gaseous giant planets WASP-4b and WASP-5b are transiting 12-magnitude solar-type stars in the Southern hemisphere. The aim of the present work is to refine the parameters of these systems using high cadence VLT/FORS2 z-band transit photometry and high-resolution VLT/UVES spectroscopy. For WASP-4, the new estimates for the planet radius and mass from a combined analysis of our VLT data with previously published transit photometry and radial velocities are RJ and MJ, resulting in a density . The radius and mass for the host star are and . Our ground-based photometry reaches 550 ppm at time sampling of ~50 s. Nevertheless, we also report the presence of an instrumental effect on the VLT that degraded our photometry for the WASP-5 observations. This effect could be a major problem for similar programs. Our new estimates for the parameters of the WASP-5 system are 0.07 RJ, MJ, , , and . The measured size of WASP-5b agrees well with the basic models of irradiated planets, while WASP-4b is clearly an “anomalously” large planet.
Key words: binaries: eclipsing -- planetary systems -- stars: individual: WASP-4 -- stars: individual: WASP-5 -- techniques: photometric -- techniques: spectroscopic
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