Searching for electromagnetic emission in an AGN from the gravitational wave binary black hole merger candidate S230922g

• Main Authors: Cabrera, Tomás, Palmese, Antonella, Hu, Lei, O'Connor, Brendan, Ford, K. E. Saavik, McKernan, Barry, Andreoni, Igor, Ahumada, Tomás, Amsellem, Ariel, Busmann, Malte, Clark, Peter, Coughlin, Michael W, Dadiani, Ekaterine, Diaz, Veronica, Graham, Matthew J, Gruen, Daniel, Kunnumkai, Keerthi, Postiglione, Jake, Sommer, Julian S, Valdes, Francisco
• Format: Journal Article
• Language: English
• Published: 15-07-2024
• Subjects: Physics - Astrophysics of Galaxies; Physics - High Energy Astrophysical Phenomena
• DOI: 10.48550/arxiv.2407.10698

We carried out long-term monitoring of the LIGO/Virgo/KAGRA binary black hole
(BBH) merger candidate S230922g in search of electromagnetic emission from the
interaction of the merger remnant with an embedding active galactic nuclei
(AGN) accretion disk. Using a dataset primarily composed of wide-field imaging
from the Dark Energy Camera (DECam) and supplemented by additional photometric
and spectroscopic resources, we searched ~ 70% of the sky area probability for
transient phenomena, and discovered 6 counterpart candidates. One especially
promising candidate - AT 2023aagj - exhibited temporally varying asymmetric
components in spectral broad line regions, a feature potentially indicative of
an off-center event such as a BBH merger. This represents the first live search
and multiwavelength, photometric, and spectroscopic monitoring of a GW BBH
optical counterpart candidate in the disk of an AGN.