Study of the impact of the post-MS evolution of the host star on the orbits of close-in planets. II. A giant planet in a close-in orbit around the RGB star HIP 63242

Abstract

Context. More than 40 planets have been found around giant stars, revealing a lack of systems orbiting interior to ∼0.6 AU. This observational fact contrasts with the planetary population around solar-type stars and has been interpreted as the result of the orbital evolution of planets through the interaction with the host star and/or because of a different formation/migration scenario of planets around more massive stars. Aims. We are conducting a radial velocity study of a sample of 166 giant stars aimed at studying the population of close-in planets orbiting post-main sequence stars. Methods. We computed precision radial velocities from multi-epoch spectroscopic data to search for planets around giant stars. Results. We present the discovery of a massive planet around the intermediate-mass giant star HIP 63242. The best Keplerian fit to the data leads to an orbital distance of 0.57 AU, an eccentricity of 0.23 and a projected mass of 9.2 MJ. HIP 63242 b is the innermost planet detected around any intermediate-mass giant star and also the first planet detected in our survey.