SVOM GRB 250314A at z $\simeq$ 7.3: an exploding star in the era of reionization

TL;DR

This paper reports the detection of a high-redshift gamma-ray burst at z ≈ 7.3, providing insights into early universe stellar explosions during reionization, and discusses strategies for optimizing their identification.

Contribution

First detection and spectroscopic measurement of a gamma-ray burst at z ≈ 7.3, highlighting its significance for studying the early universe and reionization epoch.

Findings

GRB 250314A occurred at z ≈ 7.3, when the universe was about 5% of its current age.

The detection demonstrates the capability of SVOM to observe distant, luminous stellar explosions.

Strategies for identifying high-redshift GRBs with ground follow-up are discussed.

Abstract

Most long Gamma-ray bursts originate from a rare type of massive stellar explosion. Their afterglows, while rapidly fading, can be initially extremely luminous at optical/near-infrared wavelengths, making them detectable at large cosmological distances. Here we report the detection and observations of GRB 250314A by the SVOM satellite and the subsequent follow-up campaign with the near-infrared afterglow discovery and the spectroscopic measurements of its redshift z $\simeq$ 7.3 . This burst happened when the Universe was only $\sim$ 5% of its current age. We discuss the signature of these rare events within the context of the SVOM operating model, and the ways to optimize their identification with adapted ground follow-up observation strategies.