The MgI line: a new probe of the atmospheres of evaporating exoplanets

TL;DR

This paper introduces a new method using MgI line observations to probe the upper atmospheres of evaporating exoplanets, providing insights into atmospheric escape processes.

Contribution

It develops a 3D atmospheric escape model to predict MgI line signatures, enabling detection of exospheres in a diverse sample of exoplanets.

Findings

MgI line absorption signatures depend on star brightness and magnesium escape rate.

Potentially detectable in a wide range of exoplanets with current UV instruments.

Identifies candidate exoplanets for atmospheric escape studies.

Abstract

Transit observations of HD209458b in the UV revealed signatures of neutral magnesium escaping the planet's upper atmosphere. The absorption detected in the MgI line provides unprecedented information on the physical conditions at the altitude where the atmospheric blow-off takes place. Here we use a 3D model of atmospheric escape to estimate the transit absorption signatures in the MgI line of their host stars. The detectability of these signatures depends on the brightness of the star and the escape rate of neutral magnesium. We identify a sample of potentially evaporating exoplanets that covers a wide range of stellar and planetary properties, and whose extended exospheres might be detected through MgI line observations with current UV facilities, allowing further steps in comparative exoplanetology.