Limits on Anisotropy in the Nanohertz Stochastic Gravitational Wave Background

S R Taylor, C M F Mingarelli, J R Gair, A Sesana, G Theureau, S Babak, C G Bassa, P Brem, M Burgay, R N Caballero, D J Champion, I Cognard, G Desvignes, L Guillemot, J W T Hessels, G H Janssen, R Karuppusamy, M Kramer, A Lassus, P LazarusL Lentati, K Liu, S Osłowski, D Perrodin, A Petiteau, A Possenti, M B Purver, P A Rosado, S A Sanidas, R Smits, B Stappers, C Tiburzi, R van Haasteren, A Vecchio, J P W Verbiest, EPTA Collaboration

    Research output: Contribution to journalArticlepeer-review


    The paucity of observed supermassive black hole binaries (SMBHBs) may imply that the gravitational wave background (GWB) from this population is anisotropic, rendering existing analyses suboptimal. We present the first constraints on the angular distribution of a nanohertz stochastic GWB from circular, inspiral-driven SMBHBs using the 2015 European Pulsar Timing Array data. Our analysis of the GWB in the ˜2 - 90 nHz band shows consistency with isotropy, with the strain amplitude in l >0 spherical harmonic multipoles ≲40 % of the monopole value. We expect that these more general techniques will become standard tools to probe the angular distribution of source populations.
    Original languageEnglish
    JournalPhysical Review Letters
    Publication statusPublished - 2015


    • Gravitational wave detectors and experiments
    • Gravitational waves: theory
    • Pulsars
    • Galaxy mergers collisions and tidal interactions


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