Orbital eccentricity of WASP-12 and WASP-14 from new radial-velocity monitoring with SOPHIE

TL;DR

This study uses new radial velocity data to reassess the orbital eccentricities of WASP-12 and WASP-14, confirming a near-circular orbit for WASP-12 and a confirmed eccentric orbit for WASP-14, refining their orbital parameters.

Contribution

The paper provides updated eccentricity measurements for WASP-12 and WASP-14 using advanced analysis, clarifying previous uncertainties and confirming the eccentricity of WASP-14.

Findings

WASP-12's orbit is consistent with being circular.

WASP-14 has a confirmed eccentric orbit with refined parameters.

Radial velocity data can be affected by systematic noise, influencing eccentricity estimates.

Abstract

As part of the long-term radial velocity monitoring of known transiting planets -- designed to measure orbital eccentricities, spin-orbit alignments and further planetary companions -- we have acquired radial velocity data for the two transiting systems WASP-12 and WASP-14, each harbouring gas giants on close orbits (orbital period of 1.09 and 2.24 days respectively). In both cases, the initial orbital solution suggested a significant orbital eccentricity, 0.049+-0.015 for WASP-12 and 0.091+-0.003 for WASP-14. Since then, measurements of the secondary eclipse of WASP-12 in the infrared have indicated that one projection of the eccentricity (e cos w) was very close to zero, casting doubt on the eccentricity from the initial radial velocity orbit. Our measurements confirm that the initial eccentricity detection could be spurious, and show that the radial velocity data is compatible with a circular orbit. A MCMC analysis taking into account the presence of correlated systematic noise in both the radial velocity and photometric data gives e=0.017 (+0.015-0.011). By contrast, we confirm the orbital eccentricity of WASP-14, and refine its value to e=0.088+-0.003. WASP-14 is thus the closest presently known planet with a confirmed eccentric orbit.