2015MNRAS.453.2576L -
Mon. Not. R. Astron. Soc., 453, 2576-2598 (2015/November-1)
European Pulsar Timing Array limits on an isotropic stochastic gravitational-wave background.
LENTATI L., TAYLOR S.R., MINGARELLI C.M.F., SESANA A., SANIDAS S.A., VECCHIO A., CABALLERO R.N., LEE K.J., VAN HAASTEREN R., BABAK S., BASSA C.G., BREM P., BURGAY M., CHAMPION D.J., COGNARD I., DESVIGNES G., GAIR J.R., GUILLEMOT L., HESSELS J.W.T., JANSSEN G.H., KARUPPUSAMY R., KRAMER M., LASSUS A., LAZARUS P., LIU K., OSLOWSKI S., PERRODIN D., PETITEAU A., POSSENTI A., PURVER M.B., ROSADO P.A., SMITS R., STAPPERS B., THEUREAU G., TIBURZI C. and VERBIEST J.P.W.
Abstract (from CDS):
We present new limits on an isotropic stochastic gravitational-wave background (GWB) using a six pulsar data set spanning 18 yr of observations from the 2015 European Pulsar Timing Array data release. Performing a Bayesian analysis, we fit simultaneously for the intrinsic noise parameters for each pulsar, along with common correlated signals including clock, and Solar system ephemeris errors, obtaining a robust 95 percent upper limit on the dimensionless strain amplitude A of the background of A < 3.0x10–15 at a reference frequency of 1/yr and a spectral index of 13/3, corresponding to a background from inspiralling supermassive black hole binaries, constraining the GW energy density to Ωgw(f)h2 < 1.1x10–9 at 2.8 nHz. We also present limits on the correlated power spectrum at a series of discrete frequencies, and show that our sensitivity to a fiducial isotropic GWB is highest at a frequency of ∼ 5x10–9 Hz. Finally, we discuss the implications of our analysis for the astrophysics of supermassive black hole binaries, and present 95 percent upper limits on the string tension, Gµ/c2, characterizing a background produced by a cosmic string network for a set of possible scenarios, and for a stochastic relic GWB. For a Nambu-Goto field theory cosmic string network, we set a limit Gµ/c2 < 1.3x10–7, identical to that set by the Planck Collaboration, when combining Planck and high-ℓ cosmic microwave background data from other experiments. For a stochastic relic background, we set a limit of Ω^relic_gw(f)h^2<1.2 ×10^-9, a factor of 9 improvement over the most stringent limits previously set by a pulsar timing array.
Abstract Copyright:
© 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society (2015)
Journal keyword(s):
gravitational waves - methods: data analysis - pulsars: general
Simbad objects:
9
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