A stochastic search for intermittent gravitational-wave backgrounds

A likely source of a gravitational-wave background (GWB) in the frequency band of the Advanced LIGO, Virgo, and KAGRA detectors is the superposition of signals from the population of unresolvable stellar-mass binary-black-hole (BBH) mergers throughout the Universe. Since the duration of a BBH merger in band (∼1 s) is much shorter than the expected separation between neighboring mergers (∼103 s), the observed signal will be "popcornlike"or intermittent with duty cycles of order 10-3. However, the standard cross-correlation search for stochastic GWBs currently performed by the LIGO-Virgo-KAGRA Collaboration is based on a continuous-Gaussian signal model, which does not take into account the intermittent nature of the background. The latter is better described by a Gaussian mixture model, which includes a duty cycle parameter that quantifies the degree of intermittence. Building on an earlier paper by Drasco and Flanagan [Detection methods for non-gaussian gravitational wave stochastic backgrounds, Phys. Rev. D 67, 082003 (2003).PRVDAQ0556-282110.1103/PhysRevD.67.082003], we propose a stochastic-signal-based search for intermittent GWBs. For such signals, this search performs better than the standard continuous cross-correlation search. We present results of our stochastic-signal-based approach for intermittent GWBs applied to simulated data for some simple models, and we compare its performance to the other search methods, in terms of both detection and signal characterization. Additional testing on more realistic simulated datasets, e.g., consisting of astrophysically motivated BBH merger signals injected into colored detector noise containing noise transients, will be needed before this method can be applied with confidence on real gravitational-wave data.