Electromagnetic Flares Associated with Gravitational Waves from Binary Black Hole Mergers in AGN Accretion Disks

TL;DR

This paper models electromagnetic emissions from black hole merger remnants within AGN disks to explain observed optical flares associated with gravitational wave events, identifying potential sources and their observable signatures.

Contribution

It introduces detailed shock breakout and cooling emission models for multiple components in AGN disks, linking gravitational wave events to electromagnetic counterparts.

Findings

Outflow or disk cocoon can produce observed electromagnetic signals

Disk cocoon requires more extreme parameters than outflow

Predicted emissions peak in UV and optical bands

Abstract

The gravitational wave (GW) event GW190521, likely originating from a binary black hole (BBH) merger within an active galactic nucleus (AGN) disk, is associated with the optical flare ZTF19abanrhr. The remnant BHs from BBH mergers can launch the jet and outflow and then interact with the disk medium, which can be responsible for the associated electromagnetic radiations. In this \textit{letter}, we examine the shock breakout and subsequent cooling emissions from four potential components: the outflow, jet head, jet cocoon, and disk cocoon, all driven by the remnant BH within the AGN disk. Using dynamic models and observational constraints, for GW190521, we identify the parameter space for each component and conclude that either the outflow or the disk cocoon could produce the observed electromagnetic signal, with the disk cocoon requiring more extreme parameters. We present best-fit light curves and spectral energy distributions (SEDs) for both components, showing peak emissions in the UV band for the outflow and spanning optical to UV for the disk cocoon.