title: Gravitational waves from binary supermassive black holes missing in pulsar observations.
abstract: Gravitational waves are expected to be radiated by supermassive black hole binaries formed during galaxy mergers. A stochastic superposition of gravitational waves from all such binary systems would modulate the arrival times of pulses from radio pulsars. Using observations of millisecond pulsars obtained with the Parkes radio telescope, we constrained the characteristic amplitude of this background, A(c,yr), to be <1.0 × 10(-15) with 95% confidence. This limit excludes predicted ranges for A(c,yr) from current models with 91 to 99.7% probability. We conclude that binary evolution is either stalled or dramatically accelerated by galactic-center environments and that higher-cadence and shorter-wavelength observations would be more sensitive to gravitational waves.
authors.affiliation: Commonwealth Science and Industrial Research Organization (CSIRO) Astronomy and Space Science, Australia Telescope National Facility, Post Office Box 76, Epping, New South Wales 1710, Australia. International Centre for Radio Astronomy Research, Curtin University, Bentley, Western Australia 6102, Australia.
authors.forename: R M
authors.initials: RM
authors.lastname: Shannon
authors.affiliation: Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Post Office Box 218, Hawthorn, Victoria 3122, Australia.
authors.forename: V
authors.initials: V
authors.lastname: Ravi
authors.affiliation: Astrophysics Group, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, UK.
authors.forename: L T
authors.initials: LT
authors.lastname: Lentati
authors.affiliation: Monash Centre for Astrophysics, School of Physics and Astronomy, Monash University, Post Office Box 27, Victoria 3800, Australia.
authors.forename: P D
authors.initials: PD
authors.lastname: Lasky
authors.affiliation: Commonwealth Science and Industrial Research Organization (CSIRO) Astronomy and Space Science, Australia Telescope National Facility, Post Office Box 76, Epping, New South Wales 1710, Australia.
authors.forename: G
authors.initials: G
authors.lastname: Hobbs
authors.affiliation: Commonwealth Science and Industrial Research Organization (CSIRO) Astronomy and Space Science, Australia Telescope National Facility, Post Office Box 76, Epping, New South Wales 1710, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Kerr
authors.affiliation: Commonwealth Science and Industrial Research Organization (CSIRO) Astronomy and Space Science, Australia Telescope National Facility, Post Office Box 76, Epping, New South Wales 1710, Australia.
authors.forename: R N
authors.initials: RN
authors.lastname: Manchester
authors.affiliation: Department of Electrical and Computer Engineering, University of California-San Diego, La Jolla, CA 92093, USA.
authors.forename: W A
authors.initials: WA
authors.lastname: Coles
authors.affiliation: Monash Centre for Astrophysics, School of Physics and Astronomy, Monash University, Post Office Box 27, Victoria 3800, Australia.
authors.forename: Y
authors.initials: Y
authors.lastname: Levin
authors.affiliation: Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Post Office Box 218, Hawthorn, Victoria 3122, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Bailes
authors.affiliation: International Centre for Radio Astronomy Research, Curtin University, Bentley, Western Australia 6102, Australia.
authors.forename: N D R
authors.initials: ND
authors.lastname: Bhat
authors.affiliation: National Radio Astronomical Observatory, Array Operations Center, Post Office Box O, Socorro, NM 87801-0387, USA.
authors.forename: S
authors.initials: S
authors.lastname: Burke-Spolaor
authors.affiliation: Commonwealth Science and Industrial Research Organization (CSIRO) Astronomy and Space Science, Australia Telescope National Facility, Post Office Box 76, Epping, New South Wales 1710, Australia. Department of Astronomy, School of Physics, Peking University, Beijing 100871, China.
authors.forename: S
authors.initials: S
authors.lastname: Dai
authors.affiliation: Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester M13 9PL, UK.
authors.forename: M J
authors.initials: MJ
authors.lastname: Keith
authors.affiliation: Department of Physics, Universitat Bielefeld, Universitatsstrasse 25, D-33615 Bielefeld, Germany. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Osłowski
authors.affiliation: Monash Centre for Astrophysics, School of Physics and Astronomy, Monash University, Post Office Box 27, Victoria 3800, Australia.
authors.forename: D J
authors.initials: DJ
authors.lastname: Reardon
authors.affiliation: Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Post Office Box 218, Hawthorn, Victoria 3122, Australia.
authors.forename: W
authors.initials: W
authors.lastname: van Straten
authors.affiliation: Commonwealth Science and Industrial Research Organization (CSIRO) Astronomy and Space Science, Australia Telescope National Facility, Post Office Box 76, Epping, New South Wales 1710, Australia.
authors.forename: L
authors.initials: L
authors.lastname: Toomey
authors.affiliation: Xinjiang Astronomical Observatory, Chinese Academy of Sciences, 150 Science 1-Street, Urumqi, Xinjiang 830011, China.
authors.forename: J-B
authors.initials: JB
authors.lastname: Wang
authors.affiliation: School of Physics, University of Western Australia, Crawley, Western Australia 6009, Australia.
authors.forename: L
authors.initials: L
authors.lastname: Wen
authors.affiliation: School of Physics, University of Melbourne, Parkville, Victoria 3010, Australia.
authors.forename: J S B
authors.initials: JS
authors.lastname: Wyithe
authors.affiliation: School of Physics, University of Western Australia, Crawley, Western Australia 6009, Australia.
authors.forename: X-J
authors.initials: XJ
authors.lastname: Zhu