The runaway instability in general relativistic accretion disks

TL;DR

This paper demonstrates through advanced 3D relativistic simulations that the runaway instability in accretion disks around black holes can occur under certain conditions, resolving previous uncertainties about its onset.

Contribution

First self-consistent general relativistic simulations show the development of runaway instability in accretion disks, confirming theoretical predictions.

Findings

Runaway instability occurs in specific disk configurations.

Fully relativistic simulations are essential to observe the instability.

The instability leads to rapid mass accretion by the black hole.

Abstract

When an accretion disk falls prey to the runaway instability, a large portion of its mass is devoured by the black hole within a few dynamical times. Despite decades of effort, it is still unclear under what conditions such an instability can occur. The technically most advanced relativistic simulations to date were unable to find a clear sign for the onset of the instability. In this work, we present three-dimensional relativistic hydrodynamics simulations of accretion disks around black holes in dynamical space-time. We focus on the configurations that are expected to be particularly prone to the development of this instability. We demonstrate, for the first time, that the fully self-consistent general relativistic evolution does indeed produce a runaway instability.