Are there radio-loud and radio-quiet Gamma-Ray Bursts?

TL;DR

This paper examines the proposed division of long-duration gamma-ray bursts into radio-loud and radio-quiet classes, analyzing their properties and arguing that observed differences may be due to selection effects rather than intrinsic distinctions.

Contribution

The study demonstrates that differences between radio-loud and radio-quiet LGRBs can be explained by selection effects, challenging the idea of two distinct GRB populations.

Findings

Much of the evidence for two separate classes is attributable to selection effects.

A significant positive correlation between Eiso and T90z exists in both GRB populations.

The previously observed differences in properties may not indicate intrinsic class distinctions.

Abstract

The potential existence of two separate classes of Long-duration Gamma-Ray Bursts (LGRBs) with and without radio afterglow emission, corresponding to radio-bright/loud and radio-dark/quiet populations, has been recently argued and favored in the GRB literature. The radio-quiet LGRBs have been found to have, on average, lower total isotropic gamma-ray emissions (Eiso) and shorter intrinsic prompt gamma-ray duration (e.g., T90z). In addition, a redshift-T90z anti-correlation has been discovered among the radio-loud LGRBs, which is reportedly missing in the radio-quiet class. Here we discuss the significance of the differences between the energetics and temporal properties of the two proposed classes of radio-loud and radio-quiet LGRBs. We show that much of the proposed evidence in support of the two distinct radio populations of LGRBs can be explained away in terms of selection effects and sample incompleteness. Our arguments are based on the recent discovery of the relatively-strong highly-significant positive correlation between the total isotropic emission (Eiso) and the intrinsic prompt duration (T90z) that is present in both populations of short-hard and long-soft GRBs, predicted, quantified, and reported for the first time by Shahmoradi (2013) and Shahmoradi and Nemiroff (2015).