Observational Signatures of Highly Magnified Gravitational Waves from Compact Binary Coalescence

TL;DR

This paper investigates the observable effects and signatures of highly magnified gravitational waves caused by lensing, demonstrating their robustness and potential to probe the distant universe with current detectors.

Contribution

It provides a detailed analysis of the observational signatures of highly magnified GWs and highlights their significance for confirming lensing without electromagnetic counterparts.

Findings

Signatures are robust against modeling details.

Diffraction effects limit maximum magnification.

Current detectors can observe these rare events.

Abstract

Gravitational lensing has empowered telescopes to discover astronomical objects that are otherwise out of reach without being highly magnified by foreground structures. While we expect gravitational waves (GWs) from compact binary coalescences to also experience lensing, the phenomenology of highly magnified GWs has not been fully exploited. In this Letter, we fill this gap and explore the observational signatures of these highly magnified GWs. We find that these signatures are robust against modeling details and can be used as smoking-gun evidence to confirm the detection of lensing of GWs without any electromagnetic observation. Additionally, diffraction becomes important in some cases, which limits the maximum possible magnification and gives waveform signatures of lensing that can only be observed by GW detectors. Even with current-generation observatories, we are already sensitive to these rare, highly magnified GWs and could use them to probe the high-redshift Universe beyond the usual horizon.