A peculiarly short-duration gamma-ray burst from massive star core collapse

Gamma-ray bursts (GRBs) have been phenomenologically classified into long and short populations based on the observed bimodal distribution of duration(1). Multi-wavelength and multi-messenger observations in recent years have revealed that in general long GRBs originate from massive star core collapse events(2), whereas short GRBs originate from binary neutron star mergers(3). It has been known that the duration criterion is sometimes unreliable, and multi-wavelength criteria are needed to identify the physical origin of a particular GRB(4). Some apparently long GRBs have been suggested to have a neutron star merger origin(5), whereas some apparently short GRBs have been attributed to genuinely long GRBs(6) whose short, bright emission is slightly above the detector's sensitivity threshold. Here, we report the comprehensive analysis of the multi-wavelength data of the short, bright GRB 200826A. Characterized by a sharp pulse, this burst shows a duration of 1 second and no evidence of an underlying longer-duration event. Its other observational properties such as its spectral behaviours, total energy and host galaxy offset are, however, inconsistent with those of other short GRBs believed to originate from binary neutron star mergers. Rather, these properties resemble those of long GRBs. This burst confirms the existence of short-duration GRBs with stellar core-collapse origin(4), and presents some challenges to the existing models.

Automated summary

Gamma-ray bursts are classified into long and short populations based on duration, with long GRBs originating from massive star core collapse while short GRBs come from binary neutron star mergers. Duration criterion may be unreliable, requiring multi-wavelength criteria for identification of origin. Some long GRBs may actually originate from neutron star mergers and some short GRBs may be genuinely long GRBs.