Importance of magnetic fields in highly eccentric discs with applications to tidal disruption events

Abstract

ABSTRACT Whether tidal disruption events (TDEs) circularize or accrete directly as a highly eccentric disc is the subject of current research and appears to depend sensitively on the disc thermodynamics. In a previous paper, we applied the theory of eccentric discs to TDE discs using an α-prescription for the disc stress, which leads to solutions that exhibit extreme, potentially unphysical, behaviour. In this paper, we further explore the dynamical vertical structure of highly eccentric discs using alternative stress models that are better motivated by the behaviour of magnetic fields in eccentric discs. We find that the presence of a coherent magnetic field has a stabilizing effect on the dynamics and can significantly alter the behaviour of highly eccentric radiation-dominated discs. We conclude that magnetic fields are important for the evolution of TDE discs.