The origin of the optical/ultraviolet emission of optical/ultraviolet tidal disruption events

TL;DR

This paper uses hydrodynamic simulations with radiative transfer to demonstrate that optical/UV emission in tidal disruption events originates from reprocessed emission in optically thick outflows surrounding the accretion flow.

Contribution

It provides a detailed model showing how reprocessing in outflows produces optical/UV emission, explaining observed properties of TDEs.

Findings

Optical/UV photons are generated by reprocessing accretion emission in outflows.

The model reproduces observed emission radius, temperature, and luminosity.

It explains the evolution of optical/UV emission over time.

Abstract

One of the most prominent problems of optical/ultraviolet (UV) tidal disruption events (TDEs) is the origin of their optical/UV emission. It has been proposed that the soft X-rays produced by the stellar debris accretion disk can be reprocessed into optical/UV photons by a surrounding optically thick envelope or outflow. However, there is still no detailed models for this mechanism. In this paper, by performing hydrodynamic simulations with radiative transfer, we calculate the optical/UV emission of the circularized stellar debris accretion flow/outflow system. We find that the optical/UV photons can be generated by reprocessing the emission of the accretion flow in the optically thick outflows. The model can well interpret the observed emission properties of optical/UV TDEs, including the emission radius, the radiation temperature and the luminosity, as well as the evolution of these quantities with time, providing a strong theoretical basis for understanding the origin of optical/UV TDEs.