Abstract EANA2026-5

Some giant exoplanets orbit extremely close to hot stars, where intense stellar radiation can heat and expand their atmospheres to extreme conditions. Like marshmallows placed too close to a campfire, these planets may begin to lose atmospheric material into space. In some systems, the escaping gas can form extended comet-like tails that may alter observed transit signatures, particularly in grazing transit configurations.

This presentation focuses on the atmospheric evolution of close-in gas giant exoplanets orbiting hot host stars in preparation for future observations by Ariel. A central topic is atmospheric escape and the role of the β-ratio, which describes the balance between radiation pressure and gravity and influences the dynamics of evaporating planetary tails. Understanding these processes is important for interpreting unusual transit behaviour and for identifying the most promising targets for future atmospheric characterisation.

To support comparative studies with Ariel, a homogeneous catalogue of planetary and stellar parameters for giant exoplanets around A–F stars is being developed. In parallel, synthetic gas giant planets generated using SPONCHpop are used to investigate how formation and migration histories may influence atmospheric composition. Particular attention is given to sulphur-bearing species as possible tracers of planet formation environments and evolutionary pathways.