Gravitational waves from Scorpius X-1: A comparison of search methods and prospects for detection with advanced detectors
The low-mass X-ray binary Scorpius X-1 (Sco X-1) is potentially the most luminous source of continuous gravitational-wave radiation for interferometers such as LIGO and Virgo. For low-mass X-ray binaries this radiation would be sustained by active accretion of matter from its binary companion. With the Advanced Detector Era fast approaching, work is underway to develop an array of robust tools for maximizing the science and detection potential of Sco X-1. We describe the plans and progress of a project designed to compare the numerous independent search algorithms currently available. We employ a mock-data challenge in which the search pipelines are tested for their relative proficiencies in parameter estimation, computational efficiency, robustness, and most importantly, search sensitivity. The mock-data challenge data contains an ensemble of 50 Scorpius X-1 (Sco X-1) type signals, simulated within a frequency band of 50–1500 Hz. Simulated detector noise was generated assuming the expected best strain sensitivity of Advanced LIGO  and Advanced VIRGO  (4×10^(−24) Hz^(−1/2)). A distribution of signal amplitudes was then chosen so as to allow a useful comparison of search methodologies. A factor of 2 in strain separates the quietest detected signal, at 6.8×10^(−26) strain, from the torque-balance limit at a spin frequency of 300 Hz, although this limit could range from 1.2×10^(−25) (25 Hz) to 2.2×10^(−26) (750 Hz) depending on the unknown frequency of Sco X-1. With future improvements to the search algorithms and using advanced detector data, our expectations for probing below the theoretical torque-balance strain limit are optimistic.
© 2015 American Physical Society. (Received 23 April 2015; published 10 July 2015) The authors are grateful to Badri Krishnan, Paola Leaci, and Reinhard Prix for useful discussions and comments. Y. Z. acknowledges the hospitality of the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in Hannover, Germany. S. G. C. was supported by NSF Grant No. PHY-1204944. J. T. W. was supported by NSF Grants No. PHY-0855494 and No. PHY-1207010. Y. Z. was supported by NSF Grant No. PHY-1207010. K. R., E. G., and G. D. M. were supported by NSF Grants No. PHY-0855422 and No. PHY-1205173. E. G. and G. D. M. have also been supported by the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in Hannover, Germany. G. D. M. conducted some analyses on the LIGO Data Grid clusters at the California Institute of Technology and LIGO Hanford Observatory. P. D. L. and A. M. were supported by Australian Research Council (ARC) Discovery Project DP110103347. P. D. L. is also supported by ARC DP140102578. H. J. B. and R. J. are supported by the research programme of the Foundation for Fundamental Research on Matter (FOM), which is part of the Netherlands Organisation for Scientific Research (NWO). C. M. is supported by a Glasgow University Lord Kelvin Adam Smith Fellowship and the Science and Technology Facilities Council (Grant No. ST/L000946/1). The analysis for several of the searches in this project were performed on the Atlas computing cluster at AEI Hannover, which was funded by the Max Planck Society and the State of Niedersachsen, Germany. This paper has been assigned LIGO Document Number LIGO-P1400217-x3.
Submitted - 1504.05889v1.pdf
Published - PhysRevD.92.023006.pdf