LAM seminar: Toward a unified view of exo-Neptunian evolution (Vincent Bourrier)

Toward a unified view of exo-Neptunian evolution

Vincent Bourrier, assistant professor at Université de Genève,

Abstract: More than half of known exoplanets orbit in less than 30 days around their star. These close-in planets range from small rocky objects to large gas giants, putting in perspective the origins of the Solar system and the role of formation and evolution processes. Close-in exoplanets are shaped by a complex interplay between atmospheric and dynamical processes, to which exo-Neptunes appear to be particularly sensitive. While atmospheric escape is thought to play a major role in sculpting the Neptunian “Desert” (a dearth of hot Neptunes at short orbital periods), it is not clear how far into the “Savanna” (a milder deficit of warm Neptunes at longer periods) escape is efficient and when in these planets’ life it may erode their atmosphere. Determining how many exo-Neptunes are brought close-in by early disk-driven or late high-eccentricity migration, thus experiencing or avoiding erosion from their young energetic stars, is essential to understand how much atmosphere they lost.

I will review the exploration of the exo-Neptunian landscape and the contribution from the SPICE DUNE project (a SpectroPhotometric Inquiry of Close-in Exoplanets around the Desert to Understand their Nature and Evolution), which aims at combining measurements of 3D orbital architectures (a key tracer of migration) and atmospheric mass loss from exo-Neptunes to understand their overall evolution. In particular I will present the first results of the ATREIDES collaboration, which carries out a homogenous Rossiter-McLaughlin census of 60 close-in Neptunes with the VLT/ESPRESSO to derive their orbital architecture distribution and disentangle their dynamical and atmospheric histories.