Stereoscopic gravitational-wave probe: Gravitational lensing of a binary merger in active galactic nuclei
Abstract
Recent work has shown that, if a large fraction of the LIGO-Virgo-KAGRA compact binary coalescences (CBCs) occur in accretion disks around active galactic nuclei (AGNs), many such AGN-CBC systems will likely experience lensing and produce multiple gravitational-wave (GW) "images" of the CBCs that will become detectable with current or future GW detectors. However, the waveforms produced by such lensed "images" will differ from those produced by other lensing systems because the binary source is orbiting the AGN's central supermassive black hole at a close distance. Here, we show that these systems produce 2 snapshots of the same binary source from 2 different viewing angles. These differences in the effective viewing angle between the images are encoded in the GWs they emit, such that GW detectors can effectively analyse the waveforms from 2 viewpoints. Beyond such "multi-view lensing", the GW images may also differ by their Doppler shift due to the expected relativistic orbital motion of the source around the AGN, an effect which is further amplified by the proximity to the lens. If the AGN's own angular momentum can be related to the binary's orbital angular momentum, we can describe the entire AGN-CBC system using only one additional free parameter compared with a typical point-mass lens system, or with 3 additional parameters when we do not make such an assumption. In this work, we establish a framework of transformation rules that describe both the angles in the 2 points of view, and the Doppler effect that comes from the source's motion around the lens. We also provide the framework to produce consistent AGN-lensed waveforms from any currently available GW waveform. These AGN-CBC systems give 2 unique points of view on a binary merger thus opening up a new window into the merger's properties unlike any other lens system.
Related
- Detectability of bulk viscosity effects on post-merger gravitational wave signals from binary neutron star mergers
- Shaping binary black hole merger efficiency with gravitational wave observations
- COBALT-BLUE: a fast and accurate model for gravitational self-lensing binary systems
- Associating binary black holes with galactic centres using lensed gravitational waves
- Empirical determination of the Galactic neutron star--black hole merger rate using StarTrack models
BibTeX
@misc{martens2026stereoscopic,
title = {{Stereoscopic gravitational-wave probe: Gravitational lensing of a binary merger in active galactic nuclei}},
author = {Paul Martens and Samson H. W. Leong and Ryan Zhang and Otto A. Hannuksela},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.22660},
eprint = {2609.22660},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.22660},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Stereoscopic gravitational-wave probe: Gravitational lensing of a binary merger in active galactic nuclei
AU - Paul Martens
AU - Samson H. W. Leong
AU - Ryan Zhang
AU - Otto A. Hannuksela
PY - 2026
DA - 2026/09/19
PB - arXiv
DO - 10.48550/arxiv.2609.22660
UR - https://arxiv.org/abs/2609.22660
AB - Recent work has shown that, if a large fraction of the LIGO-Virgo-KAGRA compact binary coalescences (CBCs) occur in accretion disks around active galactic nuclei (AGNs), many such AGN-CBC systems will likely experience lensing and produce multiple gravitational-wave (GW) "images" of the CBCs that will become detectable with current or future GW detectors. However, the waveforms produced by such lensed "images" will differ from those produced by other lensing systems because the binary source is orbiting the AGN's central supermassive black hole at a close distance. Here, we show that these systems produce 2 snapshots of the same binary source from 2 different viewing angles. These differences in the effective viewing angle between the images are encoded in the GWs they emit, such that GW detectors can effectively analyse the waveforms from 2 viewpoints. Beyond such "multi-view lensing", the GW images may also differ by their Doppler shift due to the expected relativistic orbital motion of the source around the AGN, an effect which is further amplified by the proximity to the lens. If the AGN's own angular momentum can be related to the binary's orbital angular momentum, we can describe the entire AGN-CBC system using only one additional free parameter compared with a typical point-mass lens system, or with 3 additional parameters when we do not make such an assumption. In this work, we establish a framework of transformation rules that describe both the angles in the 2 points of view, and the Doppler effect that comes from the source's motion around the lens. We also provide the framework to produce consistent AGN-lensed waveforms from any currently available GW waveform. These AGN-CBC systems give 2 unique points of view on a binary merger thus opening up a new window into the merger's properties unlike any other lens system.
ER -