Do Short GRBs Exhibit an Anticorrelation between Their Intrinsic Duration and Redshift?

TL;DR

This study investigates whether an anticorrelation between intrinsic duration and redshift exists in short and long gamma-ray bursts, confirming it for long GRBs but not for short GRBs, with implications for progenitor models.

Contribution

It provides a comprehensive analysis of the intrinsic duration-redshift relationship for both short and long GRBs using expanded datasets, clarifying their differing behaviors.

Findings

Long GRBs show an anticorrelation between intrinsic duration and redshift.

Short GRBs do not exhibit an anticorrelation.

Results suggest different progenitor evolution for short and long GRBs.

Abstract

Gamma-ray bursts (GRBs) are violent stellar explosions that are traditionally divided into two groups: short bursts (SGRBs) with an observed duration T90 < 2 s, and long bursts (LGRBs) with an observed duration T90 > 2 s, where T90 refers to the time needed for 90% of the fluence to be detected. Studies of progenitor models suggest that LGRBs emanate from the core collapse of massive stars, while SGRBs result from the merging of two compact objects, like two neutron stars or a neutron star and a black hole. Recent studies have found evidence that there is an anticorrelation between the intrinsic duration and the redshift of long GRBs. In this study, we first check whether LGRBs exhibit an anticorrelation between their intrinsic duration and redshift using an expanded dataset of long bursts that we have compiled. Next, we investigate whether this anticorrelation applies to SGRBs as well using a sample of short GRBs that we have compiled. Our analysis confirms the results obtained by previous studies regarding the anticorrelation for LGRBs. On the other hand, our results indicate that short GRBs do not exhibit such an anticorrelation. We discuss the implications of our results in the context of how metallicity evolves with redshift and the role that it might play in the aforementioned anticorrelation.