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Vincent Bourrier

Exoplanets on the edge: a survey of orbital architectures to trace the dynamical processes behind the Neptunian desert

The population of close-in exoplanets features a desert of hot Neptunes surmised to have migrated via complex dynamical pathways and to have lost their atmosphere under the resulting strong stellar irradiation. Yet the relative roles and interplay between orbital migration and atmospheric escape remain uncertain, and may depend on the class of planets found around the desert. Observations of these planet transits with high-resolution spectrographs give us access to both absorption signatures from their upper atmosphere, tracing atmospheric escape, and to the angle between their orbital normal and the stellar spin, tracing their dynamical history. In this talk I will present the first part of a comprehensive exploration of the Neptunian desert, in the frame of the ERC project SPICE DUNE (a SpectroPhotometric Inquiry of Close-in Exoplanets around the Desert to Understand their Nature and Evolution). We used transit observations with ESPRESSO, HARPS, HARPS-N, and CARMENES to add and refine spin-orbit angles over a broad sample of planets around the edges of the desert, ranging from hot Jupiters, to warm Neptunes, and ultra-hot rocky planets. These measurements bring new insights into the scenarios that led to the distribution of orbital architecture in close-in planets, and provide stringent constraints on simulations coupling their dynamical and atmospheric evolution. Many of these results could be obtained thanks to the new Rossiter-McLaughlin "Revolutions" technique, which gives access to the signals of super-Earth and Earth-sized planets and opens a new window into the processes governing their formation and evolution.