The Mg i line: a new probe of the atmospheres of evaporating exoplanets

V. Bourrier (1) , A. Lecavelier Des Etangs (1) , A. Vidal-Madjar (1)

1 IAP - Institut d'Astrophysique de Paris

Transit observations of HD 209458b in the UV revealed signatures of neutral magnesium escaping the planet's upper atmosphere. The absorption detected in the Mg i 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 Mg i 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 Mg i line observations with current UV facilities, allowing further steps in comparative exoplanetology.

Mots clés: surveys; planets and satellites: atmospheres; methods: numerical; Astrophysics - Earth and Planetary Astrophysics

Domaines: Planète et Univers [physics]; Astrophysique [astro-ph]

V. Bourrier, A. Lecavelier Des Etangs, A. Vidal-Madjar. The Mg i line: a new probe of the atmospheres of evaporating exoplanets. Astronomy and Astrophysics - A&A, 2015, 573, ⟨10.1051/0004-6361/201323266⟩. ⟨insu-03644793⟩