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Placing limits on the stochastic gravitational-wave background using European Pulsar Timing Array data

Authors

  • R. van Haasteren,

    Corresponding author
    1. Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands
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  • Y. Levin,

    1. Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands
    2. School of Physics, Monash University, PO Box 27, VIC 3800, Australia
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  • G. H. Janssen,

    1. University of Manchester, Jodrell Bank Centre for Astrophysics, Alan Turing Building, Manchester M13 9PL
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  • K. Lazaridis,

    1. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
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  • M. Kramer,

    1. University of Manchester, Jodrell Bank Centre for Astrophysics, Alan Turing Building, Manchester M13 9PL
    2. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
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  • B. W. Stappers,

    1. University of Manchester, Jodrell Bank Centre for Astrophysics, Alan Turing Building, Manchester M13 9PL
    2. Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo, the Netherlands
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  • G. Desvignes,

    1. LPC2E, Université d’Orléans - CNRS, 3A Av de la Recherche Scientifique, F45071 Orléans Cedex 2, France
    2. Station de Radioastronomie de Nançay, Observatoire de Paris, CNRS/INSU, F18330 Nançay, France
    3. Department of Astronomy and Radio Astronomy Laboratory, University of California, Berkeley, CA 94720, USA
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  • M. B. Purver,

    1. University of Manchester, Jodrell Bank Centre for Astrophysics, Alan Turing Building, Manchester M13 9PL
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  • A. G. Lyne,

    1. University of Manchester, Jodrell Bank Observatory, Macclesfield, Cheshire, SK11 9DL
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  • R. D. Ferdman,

    1. LPC2E, Université d’Orléans - CNRS, 3A Av de la Recherche Scientifique, F45071 Orléans Cedex 2, France
    2. Station de Radioastronomie de Nançay, Observatoire de Paris, CNRS/INSU, F18330 Nançay, France
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  • A. Jessner,

    1. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
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  • I. Cognard,

    1. LPC2E, Université d’Orléans - CNRS, 3A Av de la Recherche Scientifique, F45071 Orléans Cedex 2, France
    2. Station de Radioastronomie de Nançay, Observatoire de Paris, CNRS/INSU, F18330 Nançay, France
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  • G. Theureau,

    1. LPC2E, Université d’Orléans - CNRS, 3A Av de la Recherche Scientifique, F45071 Orléans Cedex 2, France
    2. Station de Radioastronomie de Nançay, Observatoire de Paris, CNRS/INSU, F18330 Nançay, France
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  • N. D’Amico,

    1. Dipartimento di Fisica, Universitá Degli Studi di Cagliari, SP Monserrato-Sestu km 0.7, 90042 Monserrato (CA), Italy
    2. INAF Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, 09012 Capoterra (CA), Italy
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  • A. Possenti,

    1. INAF Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, 09012 Capoterra (CA), Italy
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  • M. Burgay,

    1. INAF Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, 09012 Capoterra (CA), Italy
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  • A. Corongiu,

    1. INAF Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, 09012 Capoterra (CA), Italy
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  • J. W. T. Hessels,

    1. Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo, the Netherlands
    2. Astronomical Institute ‘Anton Pannekoek’, University of Amsterdam, 1098 SJ Amsterdam, the Netherlands
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  • R. Smits,

    1. University of Manchester, Jodrell Bank Centre for Astrophysics, Alan Turing Building, Manchester M13 9PL
    2. Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo, the Netherlands
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  • J. P. W. Verbiest

    1. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
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E-mail: haasteren@strw.leidenuniv.nl

ABSTRACT

Direct detection of low-frequency gravitational waves (GWs, inline image Hz) is the main goal of pulsar timing array (PTA) projects. One of the main targets for the PTAs is to measure the stochastic background of gravitational waves (GWB) whose characteristic strain is expected to approximately follow a power-law of the form inline image, where f is the GW frequency. In this paper we use the current data from the European PTA to determine an upper limit on the GWB amplitude A as a function of the unknown spectral slope α with a Bayesian algorithm, by modelling the GWB as a random Gaussian process. For the case α=−2/3, which is expected if the GWB is produced by supermassive black hole binaries, we obtain a 95 per cent confidence upper limit on A of 6 × 10−15, which is 1.8 times lower than the 95 per cent confidence GWB limit obtained by the Parkes PTA in 2006. Our approach to the data analysis incorporates the multitelescope nature of the European PTA and thus can serve as a useful template for future intercontinental PTA collaborations.

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