Searches for gravitational waves from perturbed black holes in data from LIGO detectors

Abstract

Black hole perturbation theory predicts that a perturbed black hole will emit gravitational waves in a superposition of quasi-normal modes. Various astrophysical processes can produce such a black hole including the merger of two compact binary neutron stars or black holes. The final form of the waveform from such a system is known as a ringdown. We discuss the search through data from LIGO's fifth science run for ringdown gravitational waves from intermediate mass black holes using a matched filtering pipeline. We outline the improvements to the pipeline since LIGO's fourth science run including the creation of a fully automated post-processing pipeline for coincident triggers, updated waveform simulation code, a new 3D coincidence test to check simultaneously for coincidence in frequency, quality factor, and time, and the use of a new detection statistic through a multi-variate statistical classifier. Results from four months of S5 data have been obtained so far and no gravitational wave candidates were found. The results of the search are ongoing. We demonstrate the improvement in the upper limit on the rate of black hole ringdowns in the local universe over the upper limit of the fourth science run. We investigate parameter recovery of full inspiral-merger-ringdown waveforms using a ringdown matched filter. Finally, we explore the Reduced Basis approach which provides very compact and high-accuracy representations of multi-mode ringdown gravitational waves.