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

We report the discovery of WASP-6b, an inflated sub-Jupiter mass planet transiting every 3.3610060(-0.0000035)(+0.0000022) 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 M(p) = 0.503(-0.038)(+0.019) M(J) and radius R(p) = 1.224(-0.052)(+0.051) R(J), resulting in a density rho(p) = 0.27 +/- 0.05 rho(J). The mass and radius for the host star are M(*) = 0.88(-0.08)(+0.05) M(circle dot) and R(*) = 0.870(-0.036)(+0.025) R(circle dot). The non-zero orbital eccentricity e = 0.054(-0.015)(+0.018) that we measure suggests that the planet underwent a massive tidal heating similar to 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 beta = 11(-18)(+14) deg. In addition to similar published measurements, this result favors a dominant migration mechanism based on tidal interactions with a protoplanetary disk.