• DOI:10.3847/1538-4357/aabd3b
• Corpus ID: 89615050

The NANOGrav 11-year Data Set: Pulsar-timing Constraints On The Stochastic Gravitational-wave Background

@article{Arzoumanian2018TheN1,
  title={The NANOGrav 11-year Data Set: Pulsar-timing Constraints On The Stochastic Gravitational-wave Background},
  author={Zaven Arzoumanian and Paul T. Baker and Adam Brazier and Sarah Burke-Spolaor and Sydney JoAnne Chamberlin and Sourav Chatterjee and Brian John Christy and James M. Cordes and Neil J. Cornish and Fronefield Crawford and H. Thankful Cromartie and Kathryn Crowter and Megan E. DeCesar and Paul B. Demorest and Timothy Dolch and J. A. Ellis and Robert D. Ferdman and Elizabeth C. Ferrara and William M. Folkner and Emmanuel Fonseca and Nathan Garver-Daniels and Peter A. Gentile and Roland Haas and Jeffrey S. Hazboun and Eliu A. Huerta and K. Islo and G. Jones and M. L. Jones and David L. Kaplan and Victoria M. Kaspi and Michael T. Lam and T. Joseph W. Lazio and Lina Levin and A. N. Lommen and Duncan R. Lorimer and J. Luo and Ryan S. Lynch and Dustin R. Madison and Maura Mclaughlin and S. T. McWilliams and Chiara M. F. Mingarelli and Cherry Ng and David J. Nice and Ryan S. Park and Timothy T. Pennucci and Nihan S. Pol and Scott M. Ransom and Paul S. Ray and Alexander Rasskazov and Xavier Siemens and Joseph Simon and Ren{\'e}e Spiewak and Ingrid H. Stairs and Daniel R. Stinebring and Kevin Stovall and Joseph K. Swiggum and S. R. Taylor and Michele Vallisneri and Sarah J. Vigeland and W. W. Zhu},
  journal={The Astrophysical Journal},
  year={2018},
  volume={859},
  pages={47}
}

• Z. Arzoumanian, P. Baker, +57 authors W. Zhu
• Published 8 January 2018
• Physics
• The Astrophysical Journal

We search for an isotropic stochastic gravitational-wave background (GWB) in the newly released 11 year data set from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). While we find no evidence for a GWB, we place constraints on a population of inspiraling supermassive black hole (SMBH) binaries, a network of decaying cosmic strings, and a primordial GWB. For the first time, we find that the GWB constraints are sensitive to the solar system ephemeris (SSE) model used and that SSE errors can mimic a GWB signal. We developed an approach that bridges systematic SSE differences, producing the first pulsar-timing array (PTA) constraints that are robust against SSE errors. We thus place a 95% upper limit on the GW-strain amplitude of A_(GWB) < 1.45 × 10^(−15) at a frequency of f = 1 yr^(−1) for a fiducial f^(−2/3) power-law spectrum and with interpulsar correlations modeled. This is a factor of ~2 improvement over the NANOGrav nine-year limit calculated using the same procedure. Previous PTA upper limits on the GWB (as well as their astrophysical and cosmological interpretations) will need revision in light of SSE systematic errors. We use our constraints to characterize the combined influence on the GWB of the stellar mass density in galactic cores, the eccentricity of SMBH binaries, and SMBH–galactic-bulge scaling relationships. We constrain the cosmic-string tension using recent simulations, yielding an SSE-marginalized 95% upper limit of Gμ < 5.3 × 10^(−11)—a factor of ~2 better than the published NANOGrav nine-year constraints. Our SSE-marginalized 95% upper limit on the energy density of a primordial GWB (for a radiation-dominated post-inflation universe) is Ω_(GWB)(f) h^2 < 3.4 × 10^(−10).