Star-planet interaction through spectral lines

TL;DR

This paper uses 3D simulations to model star-planet interactions in HD 209458b, comparing spectral line profiles with observations to infer magnetic field strength and atmospheric properties.

Contribution

It introduces detailed 3D models of exoplanetary atmospheres interacting with stellar winds, matching spectral observations to constrain magnetic fields.

Findings

HD 209458b likely has a magnetic field less than 1 G.

Spectral line profiles can distinguish different star-planet interaction scenarios.

Magnesium line behavior varies with magnetic field presence.

Abstract

The growth of spectroscopic observations of exoplanetary systems allows the possibility of testing theoretical models and studying the interaction that exoplanetary atmospheres have with the wind and the energetic photons from the star. In this work, we present a set of numerical 3D simulations of HD 209458b for which spectral lines observations of their evaporative atmosphere are available. The different simulations aim to reproduce different scenarios for the star-planet interaction. With our models, we reconstruct the Ly$\alpha$ line during transit and compare with observations. The results allow us to analyse the shape of the line profile under these different scenarios and the comparison with the observations suggests that HD209458b may have a magnetic field off less than 1 G. We also explore the behaviour of the magnesium lines for models with and without magnetic fields.