Evidence for lensing of gravitational waves from LIGO-Virgo data

Recently, the LIGO-Virgo Collaboration (LVC) has concluded there is no evidence for lensed gravitational waves (GWs) in the first half of the O3 run [LIGO Scientific Collaboration and Virgo Collaboration, Search for lensing signatures in the gravitational-wave observations from the first half of LIGO-Virgo’s third observing run], claiming “We find the observation of lensed events to be unlikely, with the fractional rate at μ>2 being 3.3×10−4.” While we agree that the chance of an individual GW event being lensed at μ>2 is smaller than <10−3, the number of observed events depends on the product of this small probability times the rate of mergers at high redshift. Observational constraints from the stochastic GW background indicate that the rate of conventional mass binary black hole (BBH) mergers (8<M/M⊙<15) in the redshift range 1<z