Optical Appearance of Eccentric Tidal Disruption Events

Abstract

Stars approaching supermassive black holes can be tidally disrupted. Despite being expected to emit X-rays, TDEs have been largely observed in optical bands, which is poorly understood. In this Letter, we simulate the tidal disruption of a $1M_{\odot }$ main sequence star on an eccentric ($e=0.95$) orbit with a periapsis distance one or five times smaller than the tidal radius (${\hat{I}}^2=1$ or $5$) using general relativistic smoothed particle hydrodynamics. We follow the simulation for up to a year post-disruption. We show that accretion disks in eccentric TDEs are masked by unbound material outflowing at $\sim 10,000$km/s. Assuming electron scattering opacity, this material would be visible as a $\sim 100$au photosphere at $\sim 10^4$K, in line with observations of candidate TDEs.

11 pages, 5 figures, submitted to ApJL