Searching for Electromagnetic Counterpart Candidates to GW231123

TL;DR

This paper searches for electromagnetic counterparts to GW231123, a gravitational wave event possibly originating from an active galactic nucleus, by crossmatching GW localization with AGN flare catalogs, identifying six candidate flares.

Contribution

It introduces a novel crossmatching approach to identify potential EM counterparts to GW events within AGN environments, highlighting candidate flares for future validation.

Findings

Six plausible optical flare candidates identified

Candidates show significant deviations from AGN baseline flux

Further observations needed for confirmation

Abstract

The detection of GW231123, a gravitational-wave (GW) event with exceptionally massive and rapidly spinning black holes, suggests the possible formation within an active galactic nucleus (AGN) disk, which provides a favorable environment for potentially generating an observable electromagnetic (EM) counterpart. We conduct a search for such a counterpart by crossmatching the GW localization with a comprehensive catalog of AGN flares from the Zwicky Transient Facility. Our analysis yields six plausible optical flare candidates that are spatially and temporally coincident with GW231123 and exhibit significant deviations from their AGN baseline flux. Although these candidates represent a crucial first step, their true nature remains inconclusive. Confirming any one of these flares via future observations would provide a landmark validation of the AGN formation channel and unlock the multi-messenger potential of this extraordinary merger.