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Abstract We search for signatures of gravitational lensing in the gravitational-wave signals from compact binary coalescences detected by Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) and Advanced Virgo during O3a, the first half of their third observing run. We study: (1) the expected rate of lensing at current detector sensitivity and the implications of a non-observation of strong lensing or a stochastic gravitational-wave background on the merger-rate density at high redshift; (2) how the interpretation of individual high-mass events would change if they were found to be lensed; (3) the possibility of multiple images due to strong lensing by galaxies or galaxy clusters; and (4) possible wave-optics effects due to point-mass microlenses. Several pairs of signals in the multiple-image analysis show similar parameters and, in this sense, are nominally consistent with the strong lensing hypothesis. However, taking into account population priors, selection effects, and the prior odds against lensing, these events do not provide sufficient evidence for lensing. Overall, we find no compelling evidence for lensing in the observed gravitational-wave signals from any of these analyses.
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This content will become publicly available on April 24, 2027
Strong Gravitational-wave Lensing Posterior Odds
Abstract Like light, gravitational waves are gravitationally lensed by intervening massive astrophysical objects—such as galaxies, clusters, black holes, and stars—resulting in a variety of potentially observable gravitational-wave lensing signatures. Searches for gravitational-wave lensing by the LIGO–Virgo–KAGRA collaboration have begun. One common method focuses on strong gravitational-wave lensing, which produces multiple “images”: repeated copies of the same gravitational wave that differ only in amplitude, arrival time, and overall “Morse phase.” The literature identifies two separate approaches to identifying such repeated gravitational-wave events, based on frequentist and Bayesian approaches. Several works have discussed selection effects and identified challenges similar to the well-known “birthday problem”—namely, the rapidly increasing likelihood of false alarms in an ever-growing catalog of event pairs. Here, we discuss these problems, unify the different approaches in Bayesian language, and derive the posterior odds for strong lensing. In particular, the Bayes factor and prior odds are sensitive to the number of gravitational-wave events in the data, but the posterior odds is insensitive to it once strong-lensing time delays are accounted for. We confirm the Lo et al. finding that selection effects enter the Bayes factor as an overall normalization constant. However, this factor cancels out in the posterior odds and does not affect frequentist approaches to strong-lensing detection.
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- Award ID(s):
- 2513124
- PAR ID:
- 10693960
- Publisher / Repository:
- The Astrophysical Journal
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 1002
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 42
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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