Detection of anisotropies in the gravitational-wave stochastic background

Bruce Allen and Adrian C. Ottewill
Phys. Rev. D 56, 545 – Published 15 July 1997
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Abstract

By correlating the signals from a pair of gravitational-wave detectors, one can undertake sensitive searches for a stochastic background of gravitational radiation. If the stochastic background is anisotropic, then this correlated signal varies harmonically with Earth’s rotation. We calculate how the harmonics of this varying signal are related to the multipole moments which characterize the anisotropy, and give a formula for the signal-to-noise ratio of a given harmonic. The specific case of the two LIGO (Laser Interferometric Gravitational Observatory) detectors, which will begin operation around the year 2000, is analyzed in detail. We consider two possible examples of anisotropy. If the gravitational-wave stochastic background contains a dipole intensity anisotropy whose origin (like that of the cosmic background radiation) is the motion of our local system, then that anisotropy will be observable by the advanced LIGO detector (with 90% confidence in one year of observation) if ΩGW>5.3×108h1002. We also study the signal produced by stochastic sources distributed in the same way as the luminous matter in the galactic disk, and in the same way as the galactic halo. The anisotropy due to sources distributed as the galactic disk or as the galactic halo will be observable by the advanced LIGO detector (with 90% confidence in one year of observation) if ΩGW>1.8×1010h1002 or ΩGW>6.7×108h1002, respectively.

  • Received 26 July 1996

DOI:https://doi.org/10.1103/PhysRevD.56.545

©1997 American Physical Society

Authors & Affiliations

Bruce Allen

  • Department of Physics, University of Wisconsin–Milwaukee, P.O. Box 413, Milwaukee, Wisconsin 53211

Adrian C. Ottewill

  • Department of Mathematical Physics, University College Dublin, Belfield, Dublin 4, Ireland

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Vol. 56, Iss. 2 — 15 July 1997

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