Transiting exoplanets from the CoRoT space mission II. CoRoT-Exo-2b: A transiting planet around an active G star

TL;DR

The paper reports the discovery and characterization of CoRoT-Exo-2b, a transiting exoplanet around an active G star, with detailed analysis of its parameters and implications for planetary evolution models.

Contribution

First detailed characterization of CoRoT-Exo-2b, including its mass, radius, and density, highlighting discrepancies with existing planetary evolution models.

Findings

Planet radius: 1.465 R_Jup

Planet mass: 3.31 M_Jup

Density: 1.31 g/cm^3

Abstract

Context. The CoRoT mission, a pioneer in exoplanet searches from space, has completed its first 150 days of continuous observations of ~12000 stars in the galactic plane. An analysis of the raw data identifies the most promising candidates and triggers the ground-based follow-up. Aims. We report on the discovery of the transiting planet CoRoT-Exo-2b, with a period of 1.743 days, and characterize its main parameters. Methods. We filter the CoRoT raw light curve of cosmic impacts, orbital residuals, and low frequency signals from the star. The folded light curve of 78 transits is fitted to a model to obtain the main parameters. Radial velocity data obtained with the SOPHIE, CORALIE and HARPS spectro-graphs are combined to characterize the system. The 2.5 min binned phase-folded light curve is affected by the effect of sucessive occultations of stellar active regions by the planet, and the dispersion in the out of transit part reaches a level of 1.09x10-4 in flux units. Results. We derive a radius for the planet of 1.465+-0.029 R_Jup and a mass of 3.31+-0.16 M_Jup, corresponding to a density of 1.31+-0.04 g/cm^3. The large radius of CoRoT-Exo-2b cannot be explained by current models of evolution of irradiated planets.