First cross-correlation analysis of interferometric and resonant-bar gravitational-wave data for stochastic backgrounds

Data from the LIGO Livingston interferometer and the ALLEGRO resonant-bar detector, taken during LIGO's fourth science run, were examined for cross correlations indicative of a stochastic gravitational-wave background in the frequency range 850-950 Hz, with most of the sensitivity arising between 905 and 925 Hz. ALLEGRO was operated in three different orientations during the experiment to modulate the relative sign of gravitational-wave and environmental correlations. No statistically significant correlations were seen in any of the orientations, and the results were used to set a Bayesian 90% confidence level upper limit of Ωgw(f)≤1.02, which corresponds to a gravitational-wave strain at 915 Hz of 1.5×10-23Hz-1/2. In the traditional units of h1002Ωgw(f), this is a limit of 0.53, 2 orders of magnitude better than the previous direct limit at these frequencies. The method was also validated with successful extraction of simulated signals injected in hardware and software. © 2007 The American Physical Society

Search for gravitational waves from binary black hole inspiral, merger, and ringdown

We present the first modeled search for gravitational waves using the complete binary black-hole gravitational waveform from inspiral through the merger and ringdown for binaries with negligible component spin. We searched approximately 2 years of LIGO data, taken between November 2005 and September 2007, for systems with component masses of 1-99Mȯ and total masses of 25-100Mȯ. We did not detect any plausible gravitational-wave signals but we do place upper limits on the merger rate of binary black holes as a function of the component masses in this range. We constrain the rate of mergers for 19Mȯ≤m1, m 2≤28Mȯ binary black-hole systems with negligible spin to be no more than 2.0Mpc-3Myr-1 at 90% confidence