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Published October 29, 2007 | Submitted + Published
Journal Article Open

Upper limit map of a background of gravitational waves


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 the50 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.

Additional Information

© 2007 American Physical Society. Received 31 January 2007. Published 29 October 2007. Publisher error corrected 28 February 2008. The work described in this paper was part of the doctoral thesis of S.W. Ballmer at the Massachusetts Institute of Technology [10]. Furthermore the authors gratefully acknowledge the support of the U.S. National Science Foundation for the construction and operation of the LIGO Laboratory and the Particle Physics and Astronomy Research Council of the United Kingdom, the Max-Planck-Society, and the State of Niedersachsen, Germany, for support of the construction and operation of the GEO600 detector. The authors also gratefully acknowledge the support of the research by these agencies and by the Australian Research Council, the Natural Sciences and Engineering Research Council of Canada, the Council of Scientific and Industrial Research of India, the Department of Science and Technology of India, the Spanish Ministerio de Educacion y Ciencia, The National Aeronautics and Space Administration, the John Simon Guggenheim Foundation, the Alexander von Humboldt Foundation, the Leverhulme Trust, the David and Lucile Packard Foundation, the Research Corporation, and the Alfred P. Sloan Foundation. This paper has been assigned the LIGO document number LIGO-P060029-00-Z.

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Published - PhysRevD.76.082003.pdf

Submitted - 0703234v1.pdf


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