Evolution of LISA Observables for Binary Black Holes Lensed by an SMBH

TL;DR

This paper studies how gravitational waves from binary black holes near supermassive black holes are affected by lensing, revealing potential observational signatures for LISA and implications for understanding active galactic nuclei.

Contribution

It introduces a model for the gravitational wave signatures of lensed binary black holes near SMBHs, highlighting their detectability and astrophysical significance.

Findings

Lensed GW signals vary predictably across frequencies.

Such signals can confound LISA's global fit models if unaccounted for.

Detection offers insights into AGN inclination, disk warping, and SMBH spin.

Abstract

Binary black holes (BBH) are expected to form and merge in active galactic nuclei (AGN), deep in the potential well of a supermassive black hole (SMBH), from populations that exist in a nuclear star cluster (NSC). Here we investigate the gravitational wave (GW) signature of a BBH lensed by a nearby SMBH. For a fiducial GW150914-like BBH orbiting close to a $10^{8}M_{\odot}$ SMBH located at $z=0.1$, the lensed GW signal varies in a predictable manner in and out of the LISA detectability band and across frequencies. The occurrence of such signatures has the potential to confound LISA global fit models if they are not modelled. Detection of these sources provide an independent measure of AGN inclination angles, along with detecting warping of the inner disk, and measuring the SMBH spin.