Search for lensing signatures in the gravitational-wave observations from the first half of LIGO-Virgo's third observing run

TL;DR

This paper searches for gravitational lensing signatures in LIGO-Virgo gravitational-wave data from their third observing run, finding no compelling evidence but exploring implications for high-redshift mergers and lensing phenomena.

Contribution

It provides the first comprehensive search for lensing signatures in LIGO-Virgo O3a data, analyzing multiple lensing scenarios and their impact on gravitational-wave observations.

Findings

No significant lensing evidence found in the data.

Several signal pairs are consistent with lensing but lack sufficient statistical support.

Implications for high-redshift merger rates and lensing effects are discussed.

Abstract

We search for signatures of gravitational lensing in the gravitational-wave signals from compact binary coalescences detected by Advanced 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.