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Published February 15, 2016 | Submitted + Published
Journal Article Open

First low frequency all-sky search for continuous gravitational wave signals


In this paper we present the results of the first low frequency all-sky search of continuous gravitational wave signals conducted on Virgo VSR2 and VSR4 data. The search covered the full sky, a frequency range between 20 Hz and 128 Hz with a range of spin-down between −1.0×10^(−10) Hz/s and +1.5×10^(−11) Hz/s, and was based on a hierarchical approach. The starting point was a set of short Fast Fourier Transforms (FFT), of length 8192 seconds, built from the calibrated strain data. Aggressive data cleaning, both in the time and frequency domains, has been done in order to remove, as much as possible, the effect of disturbances of instrumental origin. On each dataset a number of candidates has been selected, using the FrequencyHough transform in an incoherent step. Only coincident candidates among VSR2 and VSR4 have been examined in order to strongly reduce the false alarm probability, and the most significant candidates have been selected. The criteria we have used for candidate selection and for the coincidence step greatly reduce the harmful effect of large instrumental artifacts. Selected candidates have been subject to a follow-up by constructing a new set of longer FFTs followed by a further incoherent analysis. No evidence for continuous gravitational wave signals was found, therefore we have set a population-based joint VSR2-VSR4 90% confidence level upper limit on the dimensionless gravitational wave strain in the frequency range between 20 Hz and 128 Hz. This is the first all-sky search for continuous gravitational waves conducted at frequencies below 50 Hz. We set upper limits in the range between about 10^(−24) and 2×10^(−23) at most frequencies. Our upper limits on signal strain show an improvement of up to a factor of ∼2 with respect to the results of previous all-sky searches at frequencies below 80 Hz.

Additional Information

© 2016 American Physical Society. Received 22 October 2015; published 25 February 2016. The authors gratefully acknowledge the support of the United States National Science Foundation (NSF) for the construction and operation of the LIGO Laboratory, as well as the Science and Technology Facilities Council (STFC) of the United Kingdom, the Max Planck Society (MPS), and the State of Niedersachsen/Germany for support of the construction and operation of the GEO600 detector. The authors gratefully acknowledge the Italian Istituto Nazionale di Fisica Nucleare (INFN) and the French Centre National de la Recherche Scientifique (CNRS) for the construction and operation of the Virgo detector and the creation and support of the EGO consortium. The authors also gratefully acknowledge research support from these agencies as well as by the Australian Research Council; the International Science Linkages program of the Commonwealth of Australia; the Council of Scientific and Industrial Research of India, Department of Science and Technology, India; Science and Engineering Research Board, India; Ministry of Human Resource Development, India; the Spanish Ministerio de Economía y Competitividad; the Conselleria d'Economia i Competitivitat and Conselleria d'Educació; Cultura i Universitats of the Govern de les Illes Balears; the Foundation for Fundamental Research on Matter supported by the Netherlands Organisation for Scientific Research; the National Science Centre of Poland; the European Union; the Royal Society; the Scottish Funding Council; the Scottish Universities Physics Alliance; the National Aeronautics and Space Administration; the Hungarian Scientific Research Fund; the Lyon Institute of Origins; the National Research Foundation of Korea; Industry Canada and the Province of Ontario through the Ministry of Economic Development and Innovation; the National Science and Engineering Research Council Canada; the Brazilian Ministry of Science, Technology, and Innovation; the Carnegie Trust; the Leverhulme Trust; the David and Lucile Packard Foundation; the Research Corporation; and the Alfred P. Sloan Foundation. The authors gratefully acknowledge the support of the NSF, STFC, MPS, INFN, CNRS, and the State of Niedersachsen/Germany for the provision of computational resources. The authors are also grateful to the anonymous referees for their comments, which helped to improve the clarity of the paper.

Attached Files

Published - PhysRevD.93.042007.pdf

Submitted - 1510.03621v1.pdf


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