Identifying strong gravitational-wave lensing during the second observing run of Advanced LIGO and Advanced Virgo

Xiaoshu Liu, Ignacio Magana Hernandez, Jolien Creighton

Published 2020-09-14Version 1

We perform Bayesian model selection with parameter estimation to identify lensed gravitational-wave images from the second observing run (O2) of Advanced LIGO and Advanced Virgo. Specifically, We compute the evidence of a pair of events being lensed or not lensed (unlensed) directly from parameter estimation with using nested sampling. We also consider the discrete coalescence phase shifts that can be induced if the gravitational-wave signal interacts with the lens caustics in the model selection. We find that the pair of events, GW170104 and GW170814 with a $\pi/2$ coalescence phase shift, has significant Bayes factor. Nevertheless, after taking into account the large time delay $\sim$ 7 months and the prior odds given current sensitivity of Advanced LIGO and Advanced Virgo, as well as the probability of observing two unlensed events with similar masses and sky localizations, we do not have strong evidence to demonstrate there is a lensed pair of events that were observed during O2.