On the Papaloizou-Pringle instability in tidal disruption events

Abstract: We demonstrate that the compact, thick disc formed in a tidal disruption event may be unstable to non-axisymmetric perturbations in the form of the Papaloizou-Pringle instability. We show this can lead to rapid redistribution of angular momentum that can be parameterised in terms of an effective Shakura-Sunyaev $\alpha$ parameter. For remnants that have initially weak magnetic fields, this may be responsible for driving mass accretion prior to the onset of the magneto-rotational instability. For tidal disruptions around a $10^6$ M$_{\odot}$ black hole, the measured accretion rate is super-Eddington but is not sustainable over many orbits. We thus identify a method by which the torus formed in tidal disruption event may be significantly accreted before the magneto-rotational instability is established.