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

TL;DR

WASP-6b is an inflated sub-Jupiter mass exoplanet orbiting a solar-type star, with detailed measurements of its physical properties and orbital characteristics, suggesting a migration influenced by tidal interactions.

Contribution

This study provides the first detailed characterization of WASP-6b, including its mass, radius, density, and orbital eccentricity, and offers insights into its migration mechanism.

Findings

WASP-6b has a mass of approximately 0.503 M_jup and a radius of 1.224 R_jup.

The planet exhibits a non-zero orbital eccentricity of about 0.054.

The measured sky-projected angle indicates a migration influenced by tidal interactions.

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 M_p = 0.503 +0.019-0.038 M_jup and radius R_p = 1.224 +0.051-0.052 R_jup, resulting in a density rho_p = 0.27 +-0.05 rho_jup. The mass and radius for the host star are M_s = 0.88 +0.05-0.08 M_sun and R_s = 0.870 +0.025-0.036 R_sun. 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 Beta = 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.