Tidal Capture by a Black Hole and Flares in Galactic Centres

TL;DR

This paper models the tidal capture and disruption of objects by supermassive black holes in galactic centers, highlighting relativistic effects that produce observable flares, and compares simulations with observed flares.

Contribution

It introduces detailed simulations of tidal disruption events incorporating general relativity and relates them to observed galactic center flares, including a simple model for infra-red flares.

Findings

Relativistic effects significantly influence flare brightness and timing.

Simulations match observed flare light curves from galactic centers.

A simple model can explain infra-red flares as disrupted comet-like objects.

Abstract

We present the telltale signature of the tidal capture and disruption of an object by a massive black hole in a galactic centre. As a result of the interaction with the black hole's strong gravitational field, the object's light curve can flare-up with characteristic time of the order of 100 sec \times (M_{bh} / 10^6 M_{Solar}). Our simulations show that general relativity plays a crucial role in the late stages of the encounter in two ways: (i) due to the precession of perihelion, tidal disruption is more severe, and (ii) light bending and aberration of light produce and enhance flares seen by a distant observer. We present our results for the case of a tidally disrupted Solar-type star. We also discuss the two strongest flares that have been observed at the Galactic centre. Although the first was observed in X-rays and the second in infra-red, they have almost identical light curves and we find it interesting that it is possible to fit the infra-red flare with a rather simple model of the tidally disrupted comet-like or planetary object. We discuss the model and possible scenarios how such an event can occur.