Flows of X-ray gas reveal the disruption of a star by a massive black hole

TL;DR

This paper reports the detection of ionized X-ray gas flows in a tidal disruption event, revealing insights into the gas dynamics near a black hole during star disruption.

Contribution

It provides the first high-resolution X-ray spectral evidence of ionized gas flows close to a black hole in a tidal disruption event, supporting theoretical models.

Findings

Detection of highly ionized X-ray gas flows.

Gas is close to the black hole with low volume filling factor.

Observed outflow speeds are below escape velocity.

Abstract

Tidal forces close to massive black holes can violently disrupt stars that make a close approach. These extreme events are discovered via bright X-ray and optical/UV flares in galactic centers. Prior studies based on modeling decaying flux trends have been able to estimate broad properties, such as the mass accretion rate. Here we report the detection of flows of highly ionized X-ray gas in high-resolution X-ray spectra of a nearby tidal disruption event. Variability within the absorption-dominated spectra indicates that the gas is relatively close to the black hole. Narrow line widths indicate that the gas does not stretch over a large range of radii, giving a low volume filling factor. Modest outflow speeds of a few hundred kilometers per second are observed, significantly below the escape speed from the radius set by variability. The gas flow is consistent with a rotating wind from the inner, super-Eddington region of a nascent accretion disk, or with a filament of disrupted stellar gas near to the apocenter of an elliptical orbit. Flows of this sort are predicted by fundamental analytical theory and more recent numerical simulations.