Large-scale structures in the stellar wind of fast-rotating stars spawned by the presence of Earth-like planets

Abstract

Forming planets around young, fast-rotating solar-like stars are exposed to an intense X-ray/extreme ultraviolet radiation field and strongly magnetized stellar winds, as a consequence of the high magnetic activity of these stars. Under these conditions, Earth-like exoplanets may experience a rapid loss of their primordial hydrogen atmospheres, resulting in atmosphereless rocky obstacles for the stellar winds. The interaction of stellar winds with those planets leads to the formation of potentially observable structures due to the formation of large-scale magnetic field and density disturbances in the vicinity of these planets, such as bow shocks, induced magnetospheres, and comet-like tails. In this work, we study the interaction between the stellar winds of active, fast-rotating solar-like stars in the superfast-magnetosonic regime with Earth-like, unmagnetized, tenuous atmosphere, planetary obstacles through numerical three-dimensional simulations using the PLUTO magnetohydrodynamical code. The properties of AB Doradus, a nearby young star with a small rotation period (0.51 d) and a strong flaring activity, have been used to parametrize this early wind state. Bow shock and induced magnetosphere formation are characterized through the Alfvénic Mach number MA of the wind, for different stellar wind configurations. Large bow shocks, up to an extension of ~7.0 planetary radii, are found for low-MA winds. The general increase of density, temperature, and magnetic field in these large-scale structures formed around planets may result in potentially detectable spectral signatures.