Eddington envelopes: The fate of stars on parabolic orbits tidally disrupted by supermassive black holes

TL;DR

This study presents detailed simulations of stars tidally disrupted by supermassive black holes, revealing the formation of an outflowing Eddington envelope that explains observed optical/UV emissions in tidal disruption events.

Contribution

First self-consistent simulation capturing relativistic stellar disruption and subsequent debris evolution, demonstrating formation of an Eddington envelope consistent with observations.

Findings

Formation of an asymmetric outflowing envelope extending hundreds of AU

Envelope's properties match observed low-temperature, faint optical/UV emission

Line widths of 10,000–20,000 km/s consistent with observations

Abstract

Stars falling too close to massive black holes in the centres of galaxies can be torn apart by the strong tidal forces. Simulating the subsequent feeding of the black hole with disrupted material has proved challenging because of the range of timescales involved. Here we report a set of simulations that capture the relativistic disruption of the star, followed by one year of evolution of the returning debris stream. These reveal the formation of an expanding asymmetric bubble of material extending to hundreds of astronomical units -- an outflowing Eddington envelope with an optically thick inner region. Such envelopes have been hypothesised as the reprocessing layer needed to explain optical/UV emission in tidal disruption events, but never produced self-consistently in a simulation. Our model broadly matches the observed light curves with low temperatures, faint luminosities, and line widths of 10,000--20,000 km/s.