An interference-based method for the detection of strongly lensed gravitational waves

TL;DR

This paper introduces a wave optics-based method to detect strongly lensed gravitational waves by analyzing frequency-dependent waveform fluctuations, improving identification and host galaxy localization.

Contribution

The proposed method uniquely combines waveform reconstruction and sky localization to identify strongly lensed gravitational waves and their host galaxies, leveraging microlensing effects.

Findings

Approximately 10% of SLGWs can be identified with the method.

The approach reduces false alarms in pairing multiple images.

On average, 1 quadruple-image system can be found every 3 years.

Abstract

The strongly lensed gravitational wave (SLGW) is a promising transient phenomenon. However, the long-wave nature of gravitational waves poses a significant challenge in identification of its host galaxy. To tackle this challenge, we propose a method triggered by the wave optics effect of microlensing. The microlensing interference introduce frequency-dependent fluctuations in the waveform. Our method consists of three steps. First, we reconstruct the waveforms by using the template-independent and template-dependent methods. The mismatch of two reconstructions serves as an indicator of SLGWs. This step can identify approximately $10\%$ SLGWs. Second, we pair the SLGWs' multiple-images by employing the sky localization overlapping. Because we have pre-identified at least one image through microlensing, the false alarm probability for pairing SLGWs is significantly reduced. Third, we search the host galaxy by requiring the consistency of time-delays between galaxy-galaxy lensing and SLGW. By combing the stage-IV galaxy survey and the third-generation gravitational wave detectors, we expect to find, on average, 1 quadruple-image system per 3 years. The merit of this method can significantly facilitate the pursuit of time-delay cosmography, discovery of compact objects and multi-messenger astronomy.