Optical Appearance of Eccentric Tidal Disruption Events

Abstract

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

Keywords

• Supermassive black holes
• X-ray transient sources
• Ultraviolet transient sources
• Transient sources