Model-Independent Search for Gravitational Wave Echoes

This paper presents a novel approach to search for gravitational wave echoes, which could reveal information about the near-horizon structure of black holes. The model-independent nature of the search is crucial because theoretical predictions for these echoes are uncertain. The authors develop a method that leverages a generalized phase-marginalized likelihood and optimized noise suppression techniques. They apply this method to data from the LIGO-Virgo-KAGRA (LVK) collaboration, specifically focusing on events with high signal-to-noise ratios. The lack of detection allows them to set upper limits on the strength of potential echoes, providing valuable constraints on theoretical models.