Targeted subthreshold search for strongly lensed gravitational-wave events

Strong gravitational lensing of waves can produce duplicate signals separated in time with different amplitudes. We consider the case which strong produces superthreshold gravitational-wave events and weaker subthreshold buried noise background. present GstLAL-based TargetEd Subthreshold Lensing seArch search method for using reduced template banks targeting specific confirmed events. perform a simulation campaign to assess performance proposed method. show that it effectively uprank potential lensed counterparts target event. also compare its other alternative solutions posed problem demonstrate our outperforms solutions. The described this paper has already been deployed recent LVK Collaboration-wide signatures first half LIGO/Virgo third observing run O3a [R. Abbott et al. (LIGO Scientific, Virgo Collaborations), Astrophys. J. 923, 14 (2021).].