Upper limit map of a background of gravitational waves

Simon Chelkowski, Yu Chen, Carlo Colacino, Adrian Cruise, Stuart Aston, Andreas Freise, David Hoyland, Alberto Vecchio, John Veitch, Stefan Hild, Keiko Kokeyama

Research output: Contribution to journalArticle

80 Citations (Scopus)


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 x 10(-48) Hz(-1) (100 Hz/f)(3) and 1.2 x 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 x 10(-49) Hz(-1) and 6.1 x 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
JournalPhysical Review D
Issue number8
Publication statusPublished - 1 Jan 2007


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