A First Investigation of Repeated-Signal Localization of Strongly Lensed Gravitational Waves for Multimessenger Astronomy

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Main Authors: Li, Alvin K. Y., Hannuksela, Otto A.
Format: Preprint
Published: 2026
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author Li, Alvin K. Y.
Hannuksela, Otto A.
author_facet Li, Alvin K. Y.
Hannuksela, Otto A.
contents Accurate sky localization is essential for gravitational-wave (GW) astronomy, particularly for multimessenger follow-up and host galaxy identification. For strongly lensed GW events, achieving localization at the level of $\sim 10~\mathrm{deg}^2$ is critical for associating signals with their lensing structures and enabling targeted searches for additional faint images. We investigate how sky localization improves when combining multiple lensed images of the same source. Using simulated lensed compact binary coalescences and \textsc{BAYESTAR} sky localization, we evaluate localization performance as a function of image multiplicity. We find that combining multiple images leads to a systematic improvement in localization, with the largest gain occurring when combining two images, typically reducing the 90\% credible region area by an order of magnitude. Additional images provide further improvements, with four-image systems achieving localization areas of $\sim 10$--$100~\mathrm{deg}^2$. We also show that subthreshold images contribute modest but non-degrading improvements, enabling their safe inclusion in localization analyses. These results demonstrate that strongly lensed GW events provide a natural pathway to improved localization and motivate hierarchical search strategies for detecting faint lensed images.
format Preprint
id arxiv_https___arxiv_org_abs_2604_16561
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle A First Investigation of Repeated-Signal Localization of Strongly Lensed Gravitational Waves for Multimessenger Astronomy
Li, Alvin K. Y.
Hannuksela, Otto A.
Instrumentation and Methods for Astrophysics
General Relativity and Quantum Cosmology
Accurate sky localization is essential for gravitational-wave (GW) astronomy, particularly for multimessenger follow-up and host galaxy identification. For strongly lensed GW events, achieving localization at the level of $\sim 10~\mathrm{deg}^2$ is critical for associating signals with their lensing structures and enabling targeted searches for additional faint images. We investigate how sky localization improves when combining multiple lensed images of the same source. Using simulated lensed compact binary coalescences and \textsc{BAYESTAR} sky localization, we evaluate localization performance as a function of image multiplicity. We find that combining multiple images leads to a systematic improvement in localization, with the largest gain occurring when combining two images, typically reducing the 90\% credible region area by an order of magnitude. Additional images provide further improvements, with four-image systems achieving localization areas of $\sim 10$--$100~\mathrm{deg}^2$. We also show that subthreshold images contribute modest but non-degrading improvements, enabling their safe inclusion in localization analyses. These results demonstrate that strongly lensed GW events provide a natural pathway to improved localization and motivate hierarchical search strategies for detecting faint lensed images.
title A First Investigation of Repeated-Signal Localization of Strongly Lensed Gravitational Waves for Multimessenger Astronomy
topic Instrumentation and Methods for Astrophysics
General Relativity and Quantum Cosmology
url https://arxiv.org/abs/2604.16561