The fate of EMRI-IMRI pairs in AGN accretion disks: hydrodynamic and three body simulations

Kavli Affiliate: Xian Chen

| First 5 Authors: Peng Peng, Alessia Franchini, Matteo Bonetti, Alberto Sesana, Xian Chen

| Summary:

Extreme-mass-ratio inspirals (EMRIs) and intermediate-mass-ratio inspirals
(IMRIs) are important gravitational wave (GW) sources for the Laser
Interferometer Space Antenna (LISA). It has been recently suggested that EMRIs
and IMRIs can both form in the accretion disk of an active galactic nucleus
(AGN). Considering the likely encounter between a sBH and an IMBH during the
migration in the AGN disk, Paper I showed that a gap-opening IMBH can drive a
surrounding sBH to migrate synchronously. In this work, we extend the study in
Paper I with a more sophisticated model. We first use 3D hydrodynamical
simulations to study the co-evolution of the disk and the migration of a sBH in
the vicinity of an IMBH. We find that the gaseous torque, together with the
tidal torque exerted by the IMBH, can drive synchronized migration until $sim
10$ Schwarzschild radii from the central supermassive black hole (SMBH). We
further use a relativistic three-body code to study the final fate of the sBH
in the GW-dominated regime. We find that the sBH can be either captured or
kicked out by the IMBH, which will result in either two subsequent IMRIs or an
EMRI followed by an IMRI. These events will bring rich information about the
formation and evolution of sBHs and IMBHs in AGNs.

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