Kepler-91b: a planet at the end of its life: Planet and giant host star properties via light-curve variations

The evolution of planetary systems is intimately linked to the evolution of their host stars. Although several theories have been proposed, the question of how planets die remains open owing to the small number statistics, making it clear that the sample of planets around post-main sequence stars needs to be enlarged. In this work we study the giant star Kepler-91 (KOI-2133) in order to determine the nature of a transiting companion. However, its planetary confirmation is needed due to the large pixel size of the Kepler camera, which can hide other stellar configurations able to mimic planet-like transit events. Kepler-91b could be the previous stage of the planet engulfment, which has recently been detected for BD+48 740. Our estimations show that Kepler-91b will be swallowed by its host star in less than 55 Myr. At pericentre, the star subtends an angle of 48[degrees], covering around 10% of the sky as seen from the planet. The planetary atmosphere seems to be inflated probably due to the high stellar irradiation.