TESLA-X: An effective method to search for sub-threshold lensed gravitational waves with a targeted population model

TL;DR

TESLA-X is an improved method for detecting subthreshold lensed gravitational waves by using targeted population models, increasing sensitivity by about 10%, and aiding future lensing signature searches.

Contribution

TESLA-X introduces a targeted population model and template bank to enhance detection of subthreshold lensed gravitational waves over previous methods.

Findings

TESLA-X achieves ~10% higher sensitivity than TESLA.

The method effectively recovers lensed injections in simulations.

TESLA-X is ready for application in upcoming gravitational wave data analyses.

Abstract

Strong gravitational lensing can produce copies of gravitational-wave signals from the same source with the same waveform morphologies but different amplitudes and arrival times. Some of these strongly-lensed gravitational-wave signals can be demagnified and become subthreshold. We present TESLA-X, an enhanced approach to the original GstLAL-based TargetEd Subthreshold Lensing seArch (TESLA) method, for improving the detection efficiency of these potential subthreshold lensed signals. TESLA-X utilizes lensed injections to generate a targeted population model and a targeted template bank. We compare the performance of a full template bank search, TESLA, and TESLA-X methods via a simulation campaign, and demonstrate the performance of TESLA-X in recovering lensed injections, particularly targeting a mock event. Our results show that the TESLA-X method achieves a maximum of $\sim 10\%$ higher search sensitivity compared to the TESLA method within the subthreshold regime, presenting a step towards detecting the first lensed gravitational wave. TESLA-X will be employed for the LIGO-Virgo-KAGRA's collaboration-wide analysis to search for lensing signatures in the fourth observing run.