Inner Engine Shutdown from Transitions in the Angular Momentum Distribution in Collapsars

TL;DR

This study uses 3D simulations to explore how transitions in angular momentum distribution within collapsars affect black hole accretion and gamma-ray burst activity, revealing that subcritical material can prolong accretion and cause engine shutdowns.

Contribution

It demonstrates, through 3D simulations, that subcritical angular momentum material can significantly influence accretion dynamics and engine shutdowns, contrasting previous 2D results.

Findings

Subcritical material lingers around the accretion disk, affecting energy loss.

Increasing subcritical angular momentum extends accretion duration.

Engine shutdown occurs when subcritical material is accreted faster than replenished.

Abstract

For the collapsar scenario to be effective in the production of Gamma Ray Bursts, the infalling star's angular momentum $J(r)$ must be larger than the critical angular momentum needed to form an accretion disk around a blackhole (BH), namely $J_{\rm crit} = 2r_{g}c$ for a Schwarzschild BH. By means of 3D SPH simulations, here we study the collapse and accretion onto black holes of spherical rotating envelopes, whose angular momentum distribution has transitions between supercritical ($J>J_{\rm crit}$) and subcritical ($J<J_{\rm crit}$) values. Contrary to results obtained in previous 2D hydrodynamical simulations, we find that a substantial amount of subcritical material fed to the accretion disk, lingers around long enough to contribute significantly to the energy loss rate. Increasing the amount of angular momentum in the subcritical material increases the time spent at the accretion disk, and only when the bulk of this subcritical material is accreted before it is replenished by a massive outermost supercritical shell, the inner engine experiences a shutdown. Once the muffled accretion disk is provided again with enough supercritical material, the shutdown will be over and a quiescent time in the long GRB produced afterwards could be observed.