  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.
