The NANOGrav 11 Year Data Set: Pulsar-timing constraints on the Stochastic Gravitational-wave Background
Zaven Arzoumanian, P. T. Baker, Adam Brazier, Sarah Burke-Spolaor, S. J. Chamberlin, Shami Chatterjee, B. Christy, J. M. Cordes, Neil J. Cornish, F. Crawford, H. Thankful Cromartie, Kathryn Crowter, Megan E. DeCesar, Paul B. Demorest, Timothy Dolch, Justin A. Ellis, R. D. Ferdman, E. C. Ferrara, W. M. Folkner, Emmanuel Fonseca, N. Garver-Daniels, Peter A. Gentile, Roland Haas, Jeffrey S. Hazboun, E. A. Huerta, Kristina Islo, G. Jones, Megan L. Jones, Dobie, Dougal, V. M. Kaspi, Michael T. Lam, T. Joseph W. Lazio, L. Levin, A. N. Lommen, D. R. Lorimer, Jing Luo, Ryan S. Lynch, Dustin R. Madison, M. A. McLaughlin, Sean T. McWilliams, Chiara M. F. Mingarelli, Cherry Ng, David J. Nice, Ryan S. Park, Timothy T. Pennucci, Nihan S. Pol, S. M. Ransom, Paul S. Ray, Alexander Rasskazov, Xavier Siemens, Joseph Simon, R. Spiewak, I. H. Stairs, Daniel R. Stinebring, Kevin Stovall, Joseph K. Swiggum, Stephen R. Taylor, Michele Vallisneri, Rutger van Haasteren, Sarah J. Vigeland, Weiwei Zhu
Abstract
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