Speaker
Description
The central engine that powers gamma-ray bursts (GRBs) is still not identified. Besides hyper- accreting black holes, rapidly spinning and highly magnetized neutron stars, known as millisec- ond magnetars, have been suggested to power both long and short GRBs. Indirect indications of a magnetar engine in these merger sources have been observed in the form of plateau fea- tures present in the X-ray afterglow light curves of some short GRBs. Nevertheless, smoking gun evidence is still lacking for a magnetar engine in short GRBs. Here we present a com- prehensive analysis of the broad-band prompt emission data of a peculiar, very bright GRB 230307A. Despite its apparently long duration, the prompt emission and host galaxy properties are consistent with a compact star merger origin, as suggested by its association with a kilo- nova. More intriguingly, an extended X-ray emission component shows up as the γ-ray emission dies out, signifying the emergence of a magnetar central engine. The magnetar-powered X-ray emission is regared as one of the promising EM counterparts of gravitational wave events from compact binary mergers, and would be crucial for identifying the merger remnants. Future multi-messenger observations of similar events hold the promise of unveiling the identity of the progenitor of the peculiar systems such as GRB 230307A.
