Directed search for gravitational waves from Scorpius X-1 with initial LIGO data

Benjamin Aylott, Christopher Berry, Charlotte Bond, Daniel Brown, Walter Del Pozzo, Will Farr, Andreas Freise, Carl-Johan Haster, Ilya Mandel, Haixing Miao, Hannah Middleton, Trevor Sidery, Simon Stevenson, Alberto Vecchio, John Veitch, Will Vousden, Haoyu Wang, Mengyao Wang, The LIGO Scientific Collaboration, Virgo Collaboration

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40 Citations (Scopus)


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.
Original languageEnglish
Article number062008
Number of pages20
JournalPhysical Review D
Publication statusPublished - 26 Mar 2015


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