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

Abstract

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 gravitationalwave 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 gw f 1:02, which corresponds to a gravitational-wave strain at 915 Hz of 1:5 10 ÿ23 Hz ÿ1=2 . In the traditional units of h 2 100 gw 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.

Prospects for stochastic background searches using Virgo and LSC interferometers

“…The problem of simulation of the signal in a pair of detectors due to an isotropic and Gaussian SGWB has been considered previously in e.g., [6,13,14]. For this work we generalize that to a network of N GW detectors 6 .…”

“…The continuous frequency-domain idealization (14) needs to be applied with care to finite stretches of real detector data. In the time domain, the multiplication (14) amounts to a convolution…”

Measurement and subtraction of Schumann resonances at gravitational-wave interferometers

“…Backgrounds from pulsars, magnetars, core-collapse supernovae, and various physical processes in the early universe are all possible as well [4][5][6], but their expected amplitudes are not as well constrained as the expected background due to compact binary coalescences. The potential for the contamination of searches for a SGWB is strong due to potential correlated environmental noise between detectors [5,[7][8][9][10][11], which would result in a systematic error in the searches. A related concern exists in searches for transient sources of gravitational waves, such as due to correlated magnetic transients from storms [12].…”

Search for a Stochastic Gravitational-wave Background with Torsion-bar Antennas

“…The cryogenic bar detectors, Explorer and Nautilus, had done at 907 Hz [5]. Also, the ALLEGRO resonant-bar detector and LIGO Livingston had set an upper limit at 917 Hz [6]. At much lower frequency band, the Doppler tracking with the Cassini spacecraft at 10 −6 -10 −3 Hz [7], the pulsar timing by PSR B1855+09 at 10 −9 -10 −7 Hz [8], and measurement of cosmic microwave background has established an upper limit at 10 −18 -10 −16 Hz [8] [9].…”