mardi 7 mai 2024, par Antranik SEFILIAN (Friedrich-Schiller University in Jena, Germany)
Lundi 13 mai 2024 à 16h00 , Lieu : Salle de confĂ©rence du bâtiment 17
Main-sequence stars are commonly surrounded by debris discs analogous to the Solar System’s asteroid and Kuiper belts. High-resolution observations of debris discs frequently reveal a variety of structures such as gaps, spirals, and warps. Most existing models for explaining such structures focus on the role of planets, ignoring the gravitational effects of the disc itself. This assumption, however, may not always be justified, especially since debris discs could contain tens of Earth masses in planetesimals. In this talk, I will present results showing the importance of disc self-gravity in two regimes. First, I will demonstrate that the secular interactions between a single planet and an external debris disc can sculpt a wide gap within the disc. This happens due to secular apsidal resonances, which, somewhat contrary to naive expectations, occurs when the disc is less massive than the planet. I will also show that the same mechanism may lead to the launching of a long-lived spiral arm beyond the gap as well as the circularization of the planetary orbit. Second, I will demonstrate that when the disc is more massive than the planet, the disc gravity can hinder secular stirring by planets, resulting in strong suppression of planetesimal eccentricities and collisional velocities throughout the disc. Finally, observational implications of these effects will be discussed, both for inferring yet-unseen planets and for indirectly measuring the total masses of debris discs.
