Identifying strongly lensed gravitational waves with the third-generation detectors

Abstract

The joint detection of gravitational wave (GW) signals by a network of instruments will increase the detecting ability of faint and far GW signals with higher signal-to-noise ratios (SNRs), which could improve the ability of detecting the lensed GWs as well, especially for the third-generation (3G) detectors, e.g. Einstein Telescope (ET) and Cosmic Explorer (CE). However, identifying strongly lensed gravitational waves (SLGWs) is still challenging. We focus on the identification ability of 3G detectors in this article. We predict and analyse the SNR distribution of SLGW signals and prove only 50.6 per cent of SLGW pairs detected by ET alone can be identified by lens Bayes factor (LBF), which is a popular method at present to identify SLGWs. For SLGW pairs detected by CEET network, owing to the superior spatial resolution, this number rises to 87.3 per cent. Moreover, we get an approximate analytical relation between SNR and LBF. We give clear SNR limits to identify SLGWs and estimate the expected yearly detection rates of galaxy-scale lensed GWs that can get identified with 3G detector network.