Black hole central engine for ultra-long gamma-ray burst 111209A and its associated supernova 2011kl

TL;DR

This paper analyzes the ultra-long gamma-ray burst 111209A and its associated supernova 2011kl, proposing a black hole central engine powered by a collapsar with fall-back accretion, and identifying the progenitor as a Wolf-Rayet star.

Contribution

It introduces a collapsar model with fall-back accretion to explain the ultra-long GRB 111209A and identifies the progenitor as a Wolf-Rayet star, providing new insights into such phenomena.

Findings

The X-ray lightcurve shows a fall-back bump indicating a black hole engine.

The progenitor is likely a Wolf-Rayet star, not a blue supergiant.

The black hole central engine explains the ultra-long duration of the GRB.

Abstract

Recently, the first association between an ultra-long gamma-ray burst (GRB) and a supernova is reported, i.e., GRB 111209A/SN 2011kl, which enables us to investigate the physics of central engines or even progenitors for ultra-long GRBs. In this paper, we inspect the broad-band data of GRB 111209A/SN 2011kl. The late-time X-ray lightcurve exhibits a GRB 121027A-like fall-back bump, suggesting a black hole central engine. We thus propose a collapsar model with fall-back accretion for GRB 111209A/SN 2011kl. The required model parameters, such as the total mass and radius of the progenitor star, suggest that the progenitor of GRB 111209A is more likely a Wolf-Rayet star instead of blue supergiant, and the central engine of this ultra-long burst is a black hole. The implications of our results is discussed.