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.
@article{arxiv.1605.04660,
title = {Black hole central engine for ultra-long gamma-ray burst 111209A and its associated supernova 2011kl},
author = {He Gao and Wei-Hua Lei and Zhi-Qiang You and Wei Xie},
journal= {arXiv preprint arXiv:1605.04660},
year = {2016}
}