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arXiv · 0812.1998

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

M. Gillon·B. Smalley·L. Hebb·D. R. Anderson·A. H. M. J. Triaud·C. Hellier·P. F. L. Maxted·D. Queloz·D. M. Wilson
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Abstract

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_p = 1.30 +0.05-0.04 R_jup and M_p = 1.21 +0.13-0.08 M_jup, resulting in a density rho_p = 0.55 +0.04-0.02 rho_jup. The radius and mass for the host star are R_s = 0.87 +0.04-0.03 R_sun and M_s = 0.85 +0.11-0.07 M_sun. Our ground-based photometry reaches 550 ppm at time sampling of ~50 seconds. 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_p = 1.09 +-0.07 R_jup, M_p = 1.58 +0.13-0.10 M_jup, rho_p = 1.23 +0.26-0.16 rho_jup, R_s = 1.03 +0.06-0.07 R_sun, and M_s = 0.96 +0.13-0.09 M_sun. The measured size of WASP-5b agrees well with the basic models of irradiated planets, while WASP-4b is clearly an `anomalously' large planet.

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M. Gillon, B. Smalley, L. Hebb, D. R. Anderson, A. H. M. J. Triaud, C. Hellier, P. F. L. Maxted, D. Queloz, D. M. Wilson. 2009-01-09. Improved parameters for the transiting hot Jupiters WASP-4b and WASP-5b. https://doi.org/10.1051/0004-6361%3A200810929

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