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Progenitor of GRB220831A remains undetermined

Determine whether GRB220831A originated from a collapsar or from a compact binary merger by establishing an unambiguous progenitor classification based on host-galaxy association, redshift measurement, and distinguishing prompt/afterglow signatures.

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Background

GRB220831A exhibits intermediate-duration and soft prompt emission properties that place it between the short-hard and long-soft GRB populations. Despite extensive follow-up across optical, near-infrared, X-ray, and radio bands, no host galaxy was identified to deep limits, and the event’s prompt properties and afterglow behavior do not uniquely identify a progenitor.

The authors assess both a high-redshift collapsar origin and a low-redshift compact object merger scenario. However, without definitive host or redshift information and with overlapping observational characteristics, the progenitor classification remains unresolved.

References

With the available data, we cannot assign a progenitor to GRB220831A. The attempts to identify GRB220831A’s host galaxy and our study of its prompt emission have left the progenitor uncertain, with either a collapsar or a merger scenario open.

— GRB$\,$220831A: a hostless, intermediate Gamma-ray burst with an unusual optical afterglow (2411.14749 - Freeburn et al., 22 Nov 2024) in Section 4.1 (Discussion)