Upper limit map of a background of gravitational waves

B. Abbott, C.A. Cantley, N.A. Lockerbie, K. V. Tokmakov, LIGO Scientific Collaboration

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We searched for an anisotropic background of gravitational waves using data from the LIGO S4 science run and a method that is optimized for point sources. This is appropriate if, for example, the gravitational wave background is dominated by a small number of distinct astrophysical sources. No signal was seen. Upper limit maps were produced assuming two different power laws for the source strain power spectrum. For an f-3 power law and using the 50 Hz to 1.8 kHz band the upper limits on the source strain power spectrum vary between 1.2×10-48 Hz-1 (100 Hz/f)3 and 1.2×10-47 Hz-1 (100 Hz/f)3, depending on the position in the sky. Similarly, in the case of constant strain power spectrum, the upper limits vary between 8.5×10-49 Hz-1 and 6.1×10-48 Hz-1. As a side product a limit on an isotropic background of gravitational waves was also obtained. All limits are at the 90% confidence level. Finally, as an application, we focused on the direction of Sco-X1, the brightest low-mass x-ray binary. We compare the upper limit on strain amplitude obtained by this method to expectations based on the x-ray flux from Sco-X1.
Original languageEnglish
Number of pages11
JournalPhysical Review D: Particles and Fields
Issue number8
Publication statusPublished - 15 Oct 2007


  • x-ray
  • isotropic background
  • gravitational waves
  • strain amplitude
  • anisotropic background
  • astrophysics


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