Planet-disc interactions around eccentric binaries and misaligned ring formation

Abstract

We explore the evolution of a giant planet that interacts with a circumbinary disc that orbits a misaligned binary by means of analytic models and hydrodynamical simulations. Planet-disc interactions lead to mutual tilt oscillations between the planet and the disc. Even if circumbinary gas discs form with an isotropic mutual misalignment to the binary, planet-disc interactions can cause giant planets to evolve towards coplanar or polar alignment. For a low-mass disc, the binary dominates the dynamical evolution of the planet leading to a wide range of circumbinary planet inclinations. For a high-mass disc, the disc dominates the dynamical evolution of the planet and planet inclinations move towards coplanar or polar alignment to the binary orbit, depending upon the initial disc inclination and the binary eccentricity. In addition, for a high-mass disc ($\sim 50\, M_{\rm p}$) and a high initial disc inclination, the planet can undergo Kozai-Lidov oscillations that can result in the planet being ejected from the system. For initially highly misaligned systems, the non-coplanarity of the planet and the disc can lead to long-lived inner misaligned disc rings that can become highly eccentric.