Star-planet interactions

Abstract

Context. Tidal interactions and planetary evaporation processes impact the evolution of close-in star–planet systems. Aims. We study the impact of stellar rotation on these processes. Methods. We compute the time evolution of star–planet systems consisting of a planet with an initial mass between 0.02 and 2.5 MJup (6 and 800 MEarth) in a quasi-circular orbit with an initial orbital distance between 0.01 and 0.10 au, around a solar-type star evolving from the pre-main-sequence (PMS) phase until the end of the main-sequence phase. We account for the evolution of: the stellar structure, the stellar angular momentum due to tides and magnetic braking, the tidal interactions (equilibrium and dynamical tides in stellar convective zones), the mass evaporation of the planet, and the secular evolution of the planetary orbit. We consider that at the beginning of the evolution, the proto-planetary disk has fully dissipated and planet formation is complete. Results. We find that both a rapid initial stellar rotation and a more efficient angular momentum transport inside the star, in general, contribute to the enlargement of the domain that is devoid of planets after the PMS phase, in the plane of planet mass versus orbital distance. Comparisons with the observed distribution of exoplanets orbiting solar mass stars, in the plane of planet mass versus orbital distance (addressing the “Neptunian desert” feature), show an encouraging agreement with the present simulations, especially since no attempts have been made to fine-tune the initial parameters of the models to fit the observations. We also obtain an upper limit for the orbital period of bare-core planets that agrees with observations of the “radius valley” feature in the plane of planetary radius versus the orbital period. Conclusions. The two effects, namely, tides and planetary evaporation, should be accounted for simultaneously and in a consistent way, with a detailed model for the evolution of the star.