Analysis of first LIGO science data for stochastic gravitational waves

Abstract

We present the analysis of between 50 and 100 h of coincident interferometric strain data used to search for and establish an upper limit on a stochastic background of gravitational radiation. These data come from the first LIGO science run, during which all three LIGO interferometers were operated over a 2-week period spanning August and September of 2002. The method of cross correlating the outputs of two interferometers is used for analysis. We describe in detail practical signal processing issues that arise when working with real data, and we establish an observational upper limit on a f Ϫ3 power spectrum of gravitational waves. Our 90% confidence limit is ⍀ 0 h 100 2 р23Ϯ4.6 in the frequency band 40-314 Hz, where h 100 is the Hubble constant in units of 100 km/sec/Mpc and ⍀ 0 is the gravitational wave energy density per logarithmic frequency interval in units of the closure density. This limit is approximately 10 4 times better than the previous, broadband direct limit using interferometric detectors, and nearly 3 times better than the best narrow-band bar detector limit. As LIGO and other worldwide detectors improve in sensitivity and attain their design goals, the analysis procedures described here should lead to stochastic background sensitivity levels of astrophysical interest.

The ACIGA data analysis programme

“…Some strong correlations were seen, such as a 16Hz line and its harmonics, thought to be caused by regular GPS-synchronised electronic events in the data-logging equipment at the LIGO Hanford and Livingston sites [7].…”

The Newtonian and Relativistic Theory of Orbits and the Emission of Gravitational Waves

“…Intuitively, it is clear that measuring these waves must be difficult -the weakness of the gravitational interaction ensures that the response of any detector to gravitational waves is very small. Nonetheless, technology has brought us to the point where detectors are now beginning to set interesting upper limits on GWs from some sources [84][85][86][87]. The first direct detection could be,hopefully, not too far in the future.…”

The Newtonian and Relativistic Theory of Orbits and the Emission of Gravitational Waves

“…Intuitively, it is clear that measuring these waves must be difficult -the weakness of the gravitational interaction ensures that the response of any detector to gravitational waves is very small. Nonetheless, technology has brought us to the point where detectors are now beginning to set interesting upper limits on GWs from some sources [79][80][81][82]. The first direct detection could be,hopefully, not too far in the future.…”