Nearly half of known exoplanets orbit in less than 10 days around their star. These close-in planets range from small rocky objects to gas giants larger than Jupiter, putting in perspective the origins of the Solar system. Addressing the diversity of these planetary systems is tied to the study of the "hot Neptune desert", a lack of Neptune-size planets on very short orbits that challenges our understanding of planetary formation and evolution.
Atmospheric escape is thought to play a major role in sculpting the desert, eroding Neptune-size planets into mini-Neptunes or bare rocky cores. However, it is not clear at what stage of their life evaporation affects the different classes of planets. Most studies accounting for long-term atmospheric escape assume early atmospheric erosion, kindled during formation or after disk-driven migration. Yet, gaseous planets may avoid the strongest irradiation from the young host star if they migrate long after their formation. Late dynamical migration was indeed proposed as one of the processes shaping the desert, but its coupling with atmospheric evolution needs to be explored further.
The study of this coupling is the main objective of the DREAM (Desert-Rim Exoplanets Atmosphere and Migration) program, which is part of the SPICE DUNE (SpectroPhotometric Inquiry of Close-in Exoplanets around the Desert to Understand their Nature and Evolution) project. This poster will present the first DREAM results, highlighting how measurements of orbital architectures and mass loss in a sample of planets around the desert inform us about the processes behind its formation.