A tale of two exoplanets: the inflated atmospheres of the Hot Jupiters HD 189733 b and CoRoT-2 b

Abstract

Planets in close orbits around their host stars are subject to strong irradiation. High-energy irradiation, originating from the stellar corona and chromosphere, is mainly responsible for the evaporation of exoplanetary atmospheres. We have conducted multiple X-ray observations of transiting exoplanets in short orbits to determine the extent and heating of their outer planetary atmospheres. In the case of HD 189733 b, we find a surprisingly deep transit profile in X-rays, indicating an atmosphere extending out to 1.75 optical planetary radii. The X-ray opacity of those high-altitude layers points towards large densities or high metallicity. We preliminarily report on observations of the Hot Jupiter CoRoT-2 b from our Large Program with XMM-Newton, which was conducted recently. In addition, we present results on how exoplanets may alter the evolution of stellar activity through tidal interaction.

To appear in the Proceedings of the 18th Cool Stars Workshop (Flagstaff 2014)