Contributed Talk - Splinter Exoplanets

Thursday, 24 September 2020, 10:30   (virtual room D)

Can planets be pushed into a disc inner cavity by a resonant chain?

S. Ataiee(1,2), W. Kley(1)
1) Universität Tübingen, Germany, 2)FUM, Iran

The orbital distribution of exoplanets indicates an accumulation of compact Super-Earth sized planetary systems close to their host stars. Assuming an inward disc-driven migration scenario for their formation, these planets could have been stopped and eventually parked at an inner edge of the disc, or be pushed through the inner disc cavity by a resonant chain. This topic has not been properly and extensively studied. Using numerical simulations we investigate how much the inner planets in a resonant chain can be pushed into the disc inner cavity by outer planets. We perform hydrodynamical and N-body simulations of planetary systems embedded in their nascent disc. The inner edge of the disc is represented in two different ways, resembling either a dead zone (DZ) inner edge or a disc inner boundary (IB), where the main difference lies in the steepness of the surface density profile. The innermost planet has always a mass of 10 MEarth , with equal or higher mass additional outer planets. We found that a steeper profile (DZ models) is able to stop a chain of planets more efficiently than a shallower profile (IB). The final configurations in the DZ models are usually tighter than in their IB counterparts, and therefore more prone to instability. For planets in thinner discs, we found, for the first time, clear signs for overstable librations in the hydrodynamical simulations, leading to very compact systems. We also found that the popular N-body simulations may overestimate the number of planets in the disc inner cavity.