Towards model-independent identification of lensed gravitational waves using Kramers-Kronig relation

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Main Authors: Tanaka, So, Prabhu, Gopalkrishna, Kapadia, Shasvath J., Suyama, Teruaki
Format: Preprint
Published: 2025
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author Tanaka, So
Prabhu, Gopalkrishna
Kapadia, Shasvath J.
Suyama, Teruaki
author_facet Tanaka, So
Prabhu, Gopalkrishna
Kapadia, Shasvath J.
Suyama, Teruaki
contents Observations of microlensed gravitational waves (GWs) emanated by compact binary coalescences (CBCs) are essential for studying the mass density distribution in the universe, including black holes and dark matter halos. However, no confident detection of microlensed GWs have been reported to date. There are two important challenges in the identification of microlensed GWs. The first is that the source waveform and lens structure models are not known a-priori. The second is that certain classes of unlensed GWs could mimic microlensed GWs, resulting in undesirable false alarms. In this work, we propose to use the Kramers-Kronig relation for gravitational lensing systems. We argue that such systems are essentially linear response systems obeying causality, where KK relation must hold. The power of this method lies in the fact that microlensed GWs, regardless of the lens structure, must obey KK relation, while unlensed GW events are not in general expected to obey it. This, in principle, allows us to identify microlensed GWs while dismissing microlensing mimickers. We provide the first important steps towards a methodology that exploits KK relation, and test its usefulness under idealized conditions.
format Preprint
id arxiv_https___arxiv_org_abs_2504_21320
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Towards model-independent identification of lensed gravitational waves using Kramers-Kronig relation
Tanaka, So
Prabhu, Gopalkrishna
Kapadia, Shasvath J.
Suyama, Teruaki
General Relativity and Quantum Cosmology
Cosmology and Nongalactic Astrophysics
Observations of microlensed gravitational waves (GWs) emanated by compact binary coalescences (CBCs) are essential for studying the mass density distribution in the universe, including black holes and dark matter halos. However, no confident detection of microlensed GWs have been reported to date. There are two important challenges in the identification of microlensed GWs. The first is that the source waveform and lens structure models are not known a-priori. The second is that certain classes of unlensed GWs could mimic microlensed GWs, resulting in undesirable false alarms. In this work, we propose to use the Kramers-Kronig relation for gravitational lensing systems. We argue that such systems are essentially linear response systems obeying causality, where KK relation must hold. The power of this method lies in the fact that microlensed GWs, regardless of the lens structure, must obey KK relation, while unlensed GW events are not in general expected to obey it. This, in principle, allows us to identify microlensed GWs while dismissing microlensing mimickers. We provide the first important steps towards a methodology that exploits KK relation, and test its usefulness under idealized conditions.
title Towards model-independent identification of lensed gravitational waves using Kramers-Kronig relation
topic General Relativity and Quantum Cosmology
Cosmology and Nongalactic Astrophysics
url https://arxiv.org/abs/2504.21320