J. Aasi, California Institute of Technology
B. P. Abbott, California Institute of Technology
R. Abbott, California Institute of Technology
T. Abbott, Louisiana State University
M. R. Abernathy, California Institute of Technology
F. Acernese, Università degli Studi di Salerno
K. Ackley, University of Florida
C. Adams, LIGO Livingston
T. Adams, Cardiff University
P. Addesso, Università degli Studi del Sannio
R. X. Adhikari, California Institute of Technology
V. Adya, Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
C. Affeldt, Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
M. Agathos, FOM-Institute of Subatomic Physics - NIKHEF
K. Agatsuma, FOM-Institute of Subatomic Physics - NIKHEF
N. Aggarwal, LIGO, Massachusetts Institute of Technology
O. D. Aguiar, Instituto Nacional de Pesquisas Espaciais
A. Ain, Inter-University Centre for Astronomy and Astrophysics India
P. Ajith, Tata Institute of Fundamental Research, Mumbai
A. Alemic, Syracuse University
B. Allen, Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
A. Allocca, Università degli Studi di Siena
D. Amariutei, University of Florida
S. B. Anderson, California Institute of Technology
W. G. Anderson, University of Wisconsin-Milwaukee
K. Arai, California Institute of Technology
M. C. Araya, California Institute of Technology
C. Arceneaux, University of Mississippi
J. S. Areeda, California State University, Fullerton
N. Arnaud, Laboratoire de l'Accélérateur Linéaire
G. Ashton, University of Southampton
S. Ast, Gottfried Wilhelm Leibniz Universität Hannover
S. M. Aston, LIGO Livingston

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We present results of a search for continuously emitted gravitational radiation, directed at the brightest low-mass x-ray binary, Scorpius X-1. Our semicoherent analysis covers 10 days of LIGO S5 data ranging from 50-550 Hz, and performs an incoherent sum of coherent F-statistic power distributed amongst frequency-modulated orbital sidebands. All candidates not removed at the veto stage were found to be consistent with noise at a 1% false alarm rate. We present Bayesian 95% confidence upper limits on gravitational-wave strain amplitude using two different prior distributions: a standard one, with no a priori assumptions about the orientation of Scorpius X-1; and an angle-restricted one, using a prior derived from electromagnetic observations. Median strain upper limits of 1.3×10-24 and 8×10-25 are reported at 150 Hz for the standard and angle-restricted searches respectively. This proof-of-principle analysis was limited to a short observation time by unknown effects of accretion on the intrinsic spin frequency of the neutron star, but improves upon previous upper limits by factors of ∼1.4 for the standard, and 2.3 for the angle-restricted search at the sensitive region of the detector.

Publication Source (Journal or Book title)

Physical Review D - Particles, Fields, Gravitation and Cosmology