# Searching for black hole echoes from the LIGO-Virgo Catalog GWTC-1

## TL;DR

This study searches for gravitational wave echoes in nine binary black hole mergers from LIGO-Virgo data, using a Kerr spacetime-based template with frequency-dependent reflection, but finds no significant signals.

## Contribution

Introduces a new echo template incorporating frequency-dependent reflection and phase shift based on black hole perturbation theory, applied to LIGO-Virgo data.

## Key findings

- No significant echo signals detected in the analyzed events.
- The template accounts for frequency-dependent reflection and phase shifts.
- Provides constraints on the presence of echoes in binary black hole mergers.

## Abstract

We have examined gravitational wave echo signals for nine binary black hole merger events observed by Advanced LIGO and Virgo during the first and second observation runs. To construct an echo template, we consider Kerr spacetime, where the event horizon is replaced by a reflective membrane. We use frequency-dependent reflection rate at the angular potential barrier, which is fitted to the numerical data obtained by solving Teukolsky equations. This reflection rate gives a frequency-dependent transmission rate that is suppressed at lower frequencies in the template. We also take into account the overall phase shift of the waveform as a parameter, which arises when the wave is reflected at the membrane and potential barrier. Using this template based on black hole perturbation, we find no significant echo signals in the binary black hole merger events.