Gamma-ray bursts from massive Population III stars: clues from the radio band

TL;DR

This study explores how late-time radio observations of gamma-ray burst afterglows can identify those originating from massive Population III stars, using simulations and a pilot observational study with the Australia Telescope.

Contribution

It demonstrates through simulations that radio afterglows can distinguish Population III star bursts, and presents initial observational constraints from a pilot study.

Findings

No detections in the pilot study, with upper limits of 20-40 μJy.

Radio observations can potentially identify Population III gamma-ray bursts.

Simulations support the feasibility of using radio afterglows for this purpose.

Abstract

Current models suggest gamma-ray bursts could be used as a way of probing Population III stars - the first stars in the early Universe. In this paper we use numerical simulations to demonstrate that late time radio observations of gamma-ray burst afterglows could provide a means of identifying bursts that originate from Population III stars, if these were highly massive, independently from their redshift. We then present the results from a pilot study using the Australia Telescope Compact Array at 17 GHz, designed to test the hypothesis that there may be Population III gamma-ray bursts amongst the current sample of known events. We observed three candidates plus a control gamma-ray burst, and make no detections with upper limits of 20-40 uJy at 500-1300 days post explosion.