092256

Over recent years a dearth of planets with radii between 1.5 and 2 times thatof the Earth has been uncovered in the observed population of short periodplanets. Several nearby multi-planet systems have been discovered hostingplanets on both sides of this gap dubbed the radius valley. One of theleading mechanisms for forming the gap is the stripping of small H/He envelopesby X-ray and EUV-driven photoevaporation. Systems boasting planets on eitherside of the valley provide a powerful testing ground for this hypothesis as allplanets in the system have been subject to the same high-energy irradiationhistory. We propose XMM-Newton observations of five such systems spanning arange of system architectures as well as stellar ages and masses with the aim of determining which are compatible [truncated! Please see actual data for full text]