Observable signature of merging stellar-mass black holes in active galactic nuclei

TL;DR

This paper proposes that black hole mergers in active galactic nuclei produce detectable electromagnetic signals across multiple wavelengths, providing potential observational evidence for their origin and linking gravitational wave events with electromagnetic counterparts.

Contribution

It introduces a model where jets from merging black holes in AGN disks generate observable electromagnetic transients, offering a new way to identify and study these mergers.

Findings

Jets from merging black holes can produce infrared, optical, and X-ray transients.

The model explains observed associations between gravitational waves and electromagnetic signals.

Future observations of electromagnetic counterparts can confirm the AGN origin of black hole mergers.

Abstract

The origin of stellar-mass black hole mergers discovered through gravitational waves is being widely debated. Mergers in the disks of active galactic nuclei (AGN) represent a promising source of origin, with possible observational clues in the gravitational wave data. Beyond gravitational waves, a unique signature of AGN-assisted mergers is electromagnetic emission from the accreting black holes. Here we show that jets launched by accreting black holes merging in an AGN disk can be detected as peculiar transients by infrared, optical, and X-ray observatories We further show that this emission mechanism can explain the possible associations between gravitational wave events and the optical transient ZTF19abanrhr and the proposed gamma-ray counterparts GW150914-GBM and LVT151012-GBM. We demonstrate how these associations, if genuine, can be used to reconstruct the properties of these events' environments. Searching for infrared and X-ray counterparts to similar electromagnetic transients in the future, once host galaxies are localized by optical observations, could provide a smoking gun signature of the mergers' AGN origin.