Discovery and characterization of WASP-6b, an inflated sub-Jupiter mass planet transiting a solar-type star

Abstract

We report the discovery of WASP-6b, an inflated sub-Jupiter mass planet transiting every 3.3610060+0.0000022-0.0000035 days a mildly metal-poor solar-type star of magnitude V = 11.9. A combined analysis of the WASP photometry, high-precision followup transit photometry and radial velocities yield a planetary mass Mp = 0.503+0.019-0.038 Mj and radius Rp = 1.224 +0.051-0.052 Rj, resulting in a density ρp = 0.27 ± 0.05 ρj. The mass and radius for the host star are M* = 0.88+0.05-0.08 M⊙ and R* = 0.870+0.025-0.036 R⊙. The non-zero orbital eccentricity e = 0.054 +0.018-0.015 that we measure suggests that the planet underwent a massive tidal heating ∼1 Gyr ago that could have contributed to its inflated radius. High-precision radial velocities obtained during a transit allow us to measure a sky-projected angle between the stellar spin and orbital axis β = 11+14-18 deg. In addition to similar published measurements, this result favors a dominant migration mechanism based on tidal interactions with a protoplanetary disk. © 2009 ESO.