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.