# A Search For Gravitational Waves from Perturbed Black Hole Ringdowns in LIGO Data

## TL;DR

This paper describes a search for gravitational waves from black hole ringdowns in LIGO data, using matched filtering and Monte Carlo simulations, but finds no candidates and sets an upper limit on event rates.

## Contribution

It introduces a blind analysis method for detecting black hole ringdowns in LIGO data and estimates the search efficiency and background.

## Key findings

- No gravitational wave candidates detected.
- Upper limit set on black hole ringdown event rate.
- Search sensitivity extends to black holes of 10-500 solar masses up to 300 Mpc.

## Abstract

According to General Relativity a perturbed black hole will return to a stable configuration by the emission of gravitational radiation in a superposition of quasi-normal modes. Such a perturbation will occur due to the coalescence of a black hole binary, following their inspiral and subsequent merger. At late times the waveform, which we refer to as a ringdown, is expected to be dominated by a single mode. As the waveform is well-known the method of matched filtering can be implemented to search for this signal using LIGO data. LIGO is sensitive to the dominant mode of perturbed black holes with masses between 10 and 500 M_sun, the regime of intermediate-mass black holes, to a distance of up to 300 Mpc. We present a search for gravitational waves from black hole ringdowns using data from the fourth LIGO science run. We implement a blind analysis of the data. We use Monte Carlo simulations of the expected waveform, and an estimation of the background from timeslides to tune the search. We present an analysis of the waveform parameter estimation and estimate the efficiency of the search. As there were no gravitational wave candidates found, we place an upper limit on the rate of black hole ringdowns in the local universe.