EDP Sciences
Free Access
Volume 496, Number 1, March II 2009
Page(s) 259 - 267
Section Planets and planetary systems
DOI https://doi.org/10.1051/0004-6361:200810929
Published online 14 January 2009
A&A 496, 259-267 (2009)
DOI: 10.1051/0004-6361:200810929

Improved parameters for the transiting hot Jupiters WASP-4b and WASP-5b

M. 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
    e-mail: michael.gillon@obs.unige.ch
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 $R_{\rm p} = 1.30^{+0.05}_{-0.04}$ RJ and $M_{\rm p} = 1.21^{+0.13}_{-0.08}$ MJ, resulting in a density $\rho_{\rm p} = 0.55^{+0.04}_{-0.02}$ $\rho_J$. The radius and mass for the host star are $R_\ast = 0.87^{+0.04}_{-0.03}$ $R_\odot$ and $M_\ast = 0.85^{+0.11}_{-0.07}$ $M_\odot$. 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 $R_{\rm p} = 1.09$ $\pm$ 0.07 RJ, $M_{\rm p} = 1.58^{+0.13}_{-0.10}$ MJ, $\rho_{\rm p} = 1.23 ^{+0.26}_{-0.16}$ $\rho_J$, $R_\ast = 1.03^{+0.06}_{-0.07}$ $R_\odot$, and $M_\ast = 0.96^{+0.13}_{-0.09}$ $M_\odot$. 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

© ESO 2009

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.