Hot Jupiters accreting onto their parent stars: Effects on the stellar activity

Abstract

Hot Jupiters (HJs) are massive gaseous planets orbiting close to their host stars.Due to their physical characteristics and proximity to the central star, HJs are the natural laboratories to study the process of stellar-planet interaction (SPI). Phenomena related to SPI may include the inflation and evaporation of planetary atmospheres, the formation of cometary tails and bow shocks and magnetospheric interaction between the magnetic field of the planet and that of the star. Several works suggest that some systems show enhanced stellar activity in phase with the planetary rotation period. In this work, we use a 3D magneto-hydrodynamic model that describes a system composed by a star and a HJ and that includes the corresponding planetary and stellar winds. The aim is to investigate whether the material evaporating from the planet interacts with the stellar extended corona, and generates observable features. Our simulation shows that, in some conditions, the planetary wind expands and propagates mainly along the planetary orbit. Moreover, part of the planetary wind collides with the stellar wind and a fraction of the planet's outflow is funneled by the stellar magnetic field and hits the stellar surface. In both events, the material is heated up to temperatures of a few MK by a shock. These phenomena could manifest in the form of enhanced stellar activity at some orbital phases of the planet.

Impact of stellar flares on the chemical composition and transmission spectra of gaseous exoplanets orbiting M dwarfs

“…However, M-type stars are prone to high levels of stellar activity (Walkowicz et al 2011;Loyd et al 2016Loyd et al , 2018b) that can impact the radial velocity and/or transit signal of such systems through phenomena such as flaring (Tofflemire et al 2012), star spots, plages and faculae (Boisse et al 2011;Llama & Shkolnik 2015;Cauley et al 2018;Roettenbacher et al 2022;Bruno et al 2022), and other activity-induced variability (Dumusque 2018;Rackham et al 2019;Bellotti et al 2022;Collier Cameron et al 2021). Aside from the observational implications, the planet's physical and chemical state can be altered by stellar activity as well due to, for example, coronal mass ejections (CMEs) and stellar particle events (SPEs) (Yamashiki et al 2019;Atri 2017Atri , 2020Segura et al 2010), winds (Vidotto et al 2015;Vidotto & Cleary 2020;Chebly et al 2022;Colombo et al 2022), and stellar flares (Segura et al 2010;Venot et al 2016;Chadney et al 2017;Tilley et al 2019;Chen et al 2021;Louca et al 2022), the latter being sudden releases of radiative energy triggered by magnetic reconnection (Benz & Güdel 2010). Stellar flares result in a temporary increase in incident flux on the planet's atmosphere, which in turn increases the photochemical reaction rates that can change the chemical composition.…”