A high-frequency gravitational-wave burst search with LIGO's Hanford site

Abstract

The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a network of long-arm interferometers designed to directly measure gravitational-wave strain. Direct observation of gravitational waves would provide a test of general relativity, as well as new insight into high-energy astrophysics. As of yet there have been no confirmed direct observations of gravitational waves, the largest of which are expected to be near the limit of LIGO's sensitivity. Analyses of LIGO data face the challenge of distinguishing small gravitational-wave signals from noise. This thesis presents a blind analysis of data from LIGO's fifth science run (November 2005-October 2007), searching for high-frequency gravitational-wave bursts coincident in data from the two LIGO interferometers located in Hanford, WA. The search for high-frequency gravitational-wave bursts is motivated by potential astrophysical sources such as supernovae and neutron stars, and enabled by the improvement of LIGO's sensitivity and the extension of the LIGO calibration up to 6 kHz. This analysis searches for gravitational-wave candidates with a duration under 1 second and central frequency from 1 to 6 kHz, of unspecified signal shape, during times when LIGO's two Hanford detectors were in science mode but its detector in Livingston, LA was not in science mode. The search is a blind analysis, developed using a set of background data that was previously established not to contain any gravitational-wave candidates.

(cont.) The background data are the data from the two Hanford detectors during times when the Livingston detector was in science mode. These background data are used to set requirements for identifying a gravitational-wave candidate in the foreground data, which are the data from the two Hanford detectors when the Livingston detector was not in science mode. The analysis identifies no gravitational-wave candidates. However, the analysis does set an upper limit on the rate of high-frequency gravitational-wave bursts as a function of signal strength and frequency. The upper limits converge to an upper limit of 0.018 events per day, or 6.5 events per year, at the 90% confidence level, for bursts at or above a characteristic strain amplitude of 10-19 strain/JH. This work does not reflect the scientific opinion of the LIGO Scientific Collaboration and its results have not been reviewed by the collaboration.