SOPHIE velocimetry of Kepler transit candidates XI. Kepler-412 system: probing the properties of a new inflated hot Jupiter

摘要

We confirm the planetary nature of Kepler-412b, listed as planet candidateKOI-202 in the Kepler catalog, thanks to our radial velocity follow-up programof Kepler-released planet candidates, which is on going with the SOPHIEspectrograph. We performed a complete analysis of the system by combining theKepler observations from Q1 to Q15, to ground-based spectroscopic observationsthat allowed us to derive radial velocity measurements, together with the hoststar parameters and properties. We also analyzed the light curve to derive thestar's rotation period and the phase function of the planet, including thesecondary eclipse. We found the planet has a mass of 0.939 $\pm$ 0.085M$_{Jup}$ and a radius of 1.325 $\pm$ 0.043 R$_{Jup}$ which makes it a memberof the bloated giant subgroup. It orbits its G3 V host star in 1.72 days. Thesystem has an isochronal age of 5.1 Gyr, consistent with its moderate stellaractivity as observed in the Kepler light curve and the rotation of the star of17.2 $\pm$ 1.6 days. From the detected secondary, we derived the day sidetemperature as a function of the geometric albedo and estimated the geometricalalbedo, Ag, is in the range 0.094 to 0.013. The measured night side fluxcorresponds to a night side brightness temperature of 2154 $\pm$ 83 K, muchgreater than what is expected for a planet with homogeneous heatredistribution. From the comparison to star and planet evolution models, wefound that dissipation should operate in the deep interior of the planet. Thismodeling also shows that despite its inflated radius, the planet presents anoticeable amount of heavy elements, which accounts for a mass fraction of 0.11$\pm$ 0.04.