European Pulsar Timing Array Limits On An Isotropic Stochastic Gravitational-Wave Background

By L. Lentati, Stephen R. Taylor, C. Mingarelli, A. Sesana, S. Sanidas, A. Vecchio, R. N. Caballero, K. J. Lee, R. V. Haasteren, Stanislav Babak and 26 more. 2015

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We present new limits on an isotropic stochastic gravitational-wave background (GWB) using a six pulsar dataset 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$\%$ upper limit on the dimensionless strain amplitude $A$ of the background of $A<3.0\times 10^{-15}$ at a reference frequency of $1\mathrm{yr^{-1}}$ and a spectral index of $13/3$, corresponding to a background from inspiralling super-massive black hole binaries, constraining the GW energy density to $\Omega_\mathrm{gw}(f)h^2 < 1.1\times10^{-9}$ 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 $\sim 5\times10^{-9}$~Hz. Finally we discuss the implications of our analysis for the astrophysics of supermassive black hole binaries, and present 95$\%$ upper limits on the string tension, $G\mu/c^2$, characterising 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 $G\mu/c^2<1.3\times10^{-7}$, identical to that set by the {\it Planck} Collaboration, when combining {\it Planck} and high-$\ell$ Cosmic Microwave Background data from other experiments. For a stochastic relic background we set a limit of $\Omega^\mathrm{relic}_\mathrm{gw}(f)h^2<1.2 \times10^{-9}$, a factor of 9 improvement over the most stringent limits previously set by a pulsar timing array.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/8d9bcae60cc614823016186eef782c4a1484e0c6

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Citations in the corpus

Dark, cold, and noisy: constraining secluded hidden sectors with gravitational waves (2018, neutral): “These limits are A−2/3 ≤ 1.45 × 10−15 for NANOGrav [60] and h2ΩSMBHB(2.8 nHz) ≤ 1.1× 10−9 for EPTA [71], which leads to ρthr = 1.19 for EPTA with tobs = 18 yrs and ρthr = 0.697 for NANOGrav with tobs = 11 yrs.”
Primordial black holes and gravitational waves from parametric amplification of curvature perturbations (2019, methodology): “We compare them with the constrain or the sensitivity curves of GW detectors including EPTA [100], NANOGrav [101], PPTA [102], SKA [103], LISA [104], Taiji [105], DECIGO [106], BBO [107], KAGRA [108], aLIGO [109], ET [110].”
Beyond the Standard Models with cosmic strings (2019, background): “By using the EPTA sensitivity curve derived in [134], we obtain the upper bound on Gµ, one order of magnitude higher, 2×10−10, instead of 2×10−11, c.f. Fig.”
New limits on cosmic strings from gravitational wave observation (2017, neutral): “NANOGrav results give of Gµ 4.0× 10−11 [26], while EPTA [25] gives Gµ 1.1× 10−10.”
Generating PBHs and small-scale GWs in two-field models of inflation (2020, background): “It is evident that the PTA limits on SBGW [98–100] already exclude some of the lines.”
Gravitational-wave cosmology across 29 decades in frequency (2015, background): “[60] L.”
Solar-mass primordial black holes explain NANOGrav hint of gravitational waves (2020, background): “The shaded regions are the constraints from the previous PTA observations: EPTA [29], NANOGrav 11-yr [25], and PPTA [26].”
Semianalytic calculation of gravitational wave spectrum nonlinearly induced from primordial curvature perturbations (2018, background): “The blue lines denote existing pulsar timing array constraints from EPTA [53], NANOGrav [54], and PPTA [55].”
THE NANOGRAV NINE-YEAR DATA SET: OBSERVATIONS, ARRIVAL TIME MEASUREMENTS, AND ANALYSIS OF 37 MILLISECOND PULSARS (2015, background): “…of the characteristic gravitational-wave strain hc due to a stochastic background in the nanohertz regime (van Haasteren et al. 2011; Demorest et al. 2013; Shannon et al. 2013; Lentati et al. 2015), where = a - ⎛ ⎝⎜ ⎞ ⎠⎟h f A f 1yr 1c gw 1( ) ( ) and f is the observed gravitational wave frequency.”
European Pulsar Timing Array Limits on Continuous Gravitational Waves from Individual Supermassive Black Hole Binaries (2015, methodology): “We refer the reader to van Haasteren et al. (2009) and to our companion paper Lentati et al. (2015) for exact expressions of the noise variance-covariance matrix.”
Gravitational wave constraints on the primordial black hole dominated early universe (2020, methodology): “With newly derived analytical formulas [35–38], the so-called induced GW are also drawing a lot of interest since they could lie within the future observational window of LISA [39], Taiji [40], Tianqin [41], DECIGO [42, 43], AION/MAGIS [44], ET [45] and PTA [46, 47].”
The NANOGrav 11-year Data Set: High-precision Timing of 45 Millisecond Pulsars (2017, background): “…et al. 2014; Zhu et al. 2014; Arzoumanian et al. 2015a), primordial gravitational waves from inflation (Grishchuk 1976, 1977; Starobinsky 1980; Lentati et al. 2015; Lasky et al. 2016), and gravitational waves originating from cosmic strings (e.g., Kibble 1976; Vilenkin 1981; Sanidas et al.…”