Star-Planet interaction: HotJupiter wind accreting onto the stellar surface

Hot Jupiters (HJs) are massive gaseous planets orbiting close to their host star. Due to their physical characteristics and proximity to the central star, HJs are the natural laboratories to study the processes of stellar planet interaction (SPI). In fact, HJ’s atmospheres are heated up by the radiation arising from the star. The heated planetary gas may escape from the planet's gravitational field (Lammer et al. 2003). Several works suggested that some systems show stellar activity in phase with the planetary rotation period (e.g. Shkolnik et al. 2003, 2005, 2008, Walker et al. 2008, Pillitteri et al. 2010, 2011, 2014,2015). In this work, we use a 3D magnetohydrodynamic model that includes the planet and the star and both planetary and stellar winds to investigate whether the material evaporating from the planet interacts with the stellar extended corona, and generates observable features. Our preliminary results show that the planetary wind expands and propagates along the planetary orbit. During the expansion, the wind strongly perturbs the stellar magnetic field. A region arises where the magnetic field is strongly perturbed by the dense planetary wind and where phenomena of magnetic reconnection may develop. Moreover, part of the planetary wind collides with the stellar wind and a fraction of the planet’s outflow is funnelled by the stellar magnetic field and hits the stellar surface. In both events the material is heated at temperatures of a few MK by a shock, generating X and UV radiation. These phenomena could manifest as stellar activity in phase with the planetary motion.