Julia Venturini
University of Geneva

Abstract
The existence of a radius valley in the size distribution of exoplanets, which separates super-Earths from mini-Neptunes, stands as one of the most important observational constraints to understand the origin and composition of sub-Neptune size exoplanets. The most popular models to explain the radius valley predict that mini-Neptunes are dry, which is at odds with predictions from pure formation models. In this seminar, I will first show results of combined formation and evolution simulations that predict that mini-Neptunes are mostly water-worlds, and I will explain the dependence of the results on stellar mass. Our results show an excellent agreement with the slope of the location of the valley as a function of stellar mass and orbital period inferred from observations. Also in line with observations, we find that due to the effects of orbital migration and water condensation, the radius valley fades towards M-dwarfs. Instead, when analysing the valley in terms of mean density (normalised by Earth's composition), we find a persistent density valley across all stellar types. I will close by discussing how the radius valley location could change for the case of binary stars, describing briefly a new observational programme that we are pursuing with CHEOPS to characterise the radius valley for binary stars.

2024 April 05, 13:30

IA/U.Porto
Centro de Astrofísica da Universidade do Porto (Auditorium)
Rua das Estrelas, 4150-762 Porto