Gamma-ray burst radio afterglows from Population III stars: Simulation methods and detection prospects with SKA precursors

TL;DR

This study models and simulates the detectability of radio afterglows from Population III gamma-ray bursts using SKA precursors, finding ASKAP could detect a significant fraction under optimistic conditions, with implications for high-redshift universe studies.

Contribution

It introduces a comprehensive simulation framework for Pop III GRB radio afterglows and assesses detection prospects with SKA precursors, considering realistic physical parameters and observation strategies.

Findings

ASKAP could detect up to 35% of Pop III GRB afterglows in optimistic scenarios.

Detection rates vary widely, from about 11 to 6000 per image, depending on assumptions.

High-redshift Pop III GRB afterglows are similar to local long GRB afterglows in radio lightcurves.

Abstract

We investigate the prospects of detecting radio afterglows from long Gamma-Ray Bursts (GRBs) from Population III (Pop III) progenitors using the SKA precursor instruments WMA (Murchison Widefield Array) and ASKAP (Australian SKA Pathfinder). We derive a realistic model of GRB afterglows that encompasses the widest range of plausible physical parameters and observation angles. We define the best case scenario of Pop III GRB energy and redshift distributions. Using probability distribution functions fitted to the observed microphysical parameters of long GRBs, we simulate a large number of Pop III GRB afterglows to find the global probability of detection. We find that ASKAP may be able to detect 35% of Pop III GRB afterglows in the optimistic case, and 27% in the pessimistic case. A negligible number will be detectable by MWA in either case. Detections per image for ASKAP, found by incorporating intrinsic rates with detectable timescales, are as high as $\sim$ 6000 and as low as $\sim$ 11, which shows the optimistic case is unrealistic. We track how the afterglow flux density changes over various time intervals and find that, because of their very slow variability, the cadence for blind searches of these afterglows should be as long as possible. We also find Pop III GRBs at high redshift have radio afterglow lightcurves that are indistinguishable from those of regular long GRBs in the more local universe.