Black hole hyperaccretion in collapsars. III. GRB timescale

TL;DR

This paper investigates how jet propagation and progenitor properties in collapsars influence the observed durations and energies of GRBs, offering insights into their physical origins beyond simple duration classification.

Contribution

It introduces a detailed analysis of jet dynamics in collapsars, linking progenitor density profiles to GRB durations and energies, and proposes a new origin scenario for certain SGRBs.

Findings

GRB duration and energy constrain collapsar density profiles.

Jet propagation depends on progenitor envelope structure.

A specific SGRB may originate from a stripped-envelope collapsar.

Abstract

Gamma-ray bursts (GRBs) are classified into long and short populations (i.e., LGRBs and SGRBs) based on the observed bimodal distribution of duration $T_{90}$. Multimessenger observations indicated that most SGRBs and LGRBs should be powered by ultrarelativistic jets launched from black hole (BH) hyperaccretion in compact object mergers and massive collapsars, respectively. However, the duration criterion sometimes cannot correctly reflect the physical origin of a particular GRB. In the collapsar scenario, a GRB can be observed when the jet breaks out from the envelope and circumstellar medium successfully. The observed GRB duration reflects only the time that the engine operates after the jet breaks out. This work studies the propagation of jets driven by the neutrino annihilation or Blandford-Znajek mechanism in massive collapsars. The signatures of the progenitors for producing LGRBs, SGRBs, and failed GRBs in the collapsar scenario are exhibited. The competition between the mass supply onto the BH hyperaccretion and jet propagation into the envelope are definitely dependent on the density profiles of the collapsars. We show that duration and isotropic energy $E_{\rm{\gamma,iso}}$ of GRBs can help constrain the density profiles of collapsars. Finally, we propose that a collapsar-origin SGRB, GRB 200826A, might originate from a neutrino-annihilation-dominated jet launched by a $\sim 10~M_\odot$ collapsar whose progenitor's envelope has been stripped.