The NANOGrav 12.5 yr Data Set: Search for an Isotropic Stochastic Gravitational-wave Background

Arzoumanian, Zaven and Baker, Paul T. and Blumer, Harsha and Bécsy, Bence and Brazier, Adam and Brook, Paul R. and Burke-Spolaor, Sarah and Chatterjee, Shami and Chen, Siyuan and Cordes, James M. and Cornish, Neil J. and Crawford, Fronefield and Cromartie, H. Thankful and DeCesar, Megan E. and Demorest, Paul B. and Dolch, Timothy and Ellis, Justin A. and Ferrara, Elizabeth C. and Fiore, William and Fonseca, Emmanuel and Garver-Daniels, Nathan and Gentile, Peter A. and Good, Deborah C. and Hazboun, Jeffrey S. and Holgado, A. Miguel and Islo, Kristina and Jennings, Ross J. and Jones, Megan L. and Kaiser, Andrew R. and Kaplan, David L. and Kelley, Luke Zoltan and Key, Joey Shapiro and Laal, Nima and Lam, Michael T. and W. Lazio, T. Joseph and Lorimer, Duncan R. and Luo, Jing and Lynch, Ryan S. and Madison, Dustin R. and McLaughlin, Maura A. and Mingarelli, Chiara M. F. and Ng, Cherry and Nice, David J. and Pennucci, Timothy T. and Pol, Nihan S. and Ransom, Scott M. and Ray, Paul S. and Shapiro-Albert, Brent J. and Siemens, Xavier and Simon, Joseph and Spiewak, Renée and Stairs, Ingrid H. and Stinebring, Daniel R. and Stovall, Kevin and Sun, Jerry P. and Swiggum, Joseph K. and Taylor, Stephen R. and Turner, Jacob E. and Vallisneri, Michele and Vigeland, Sarah J. and Witt, Caitlin A. (2020) The NANOGrav 12.5 yr Data Set: Search for an Isotropic Stochastic Gravitational-wave Background. The Astrophysical Journal Letters, 905 (2). L34. ISSN 2041-8205

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Abstract

We search for an isotropic stochastic gravitational-wave background (GWB) in the 12.5 yr pulsar-timing data set collected by the North American Nanohertz Observatory for Gravitational Waves. Our analysis finds strong evidence of a stochastic process, modeled as a power law, with common amplitude and spectral slope across pulsars. Under our fiducial model, the Bayesian posterior of the amplitude for an f−2/3 power-law spectrum, expressed as the characteristic GW strain, has median 1.92 × 10−15 and 5%–95% quantiles of 1.37–2.67 × 10−15 at a reference frequency of ${f}_{\mathrm{yr}}=1\,{\mathrm{yr}}^{-1};$ the Bayes factor in favor of the common-spectrum process versus independent red-noise processes in each pulsar exceeds 10,000. However, we find no statistically significant evidence that this process has quadrupolar spatial correlations, which we would consider necessary to claim a GWB detection consistent with general relativity. We find that the process has neither monopolar nor dipolar correlations, which may arise from, for example, reference clock or solar system ephemeris systematics, respectively. The amplitude posterior has significant support above previously reported upper limits; we explain this in terms of the Bayesian priors assumed for intrinsic pulsar red noise. We examine potential implications for the supermassive black hole binary population under the hypothesis that the signal is indeed astrophysical in nature.

Item Type: Article
Subjects: STM One > Physics and Astronomy
Depositing User: Unnamed user with email support@stmone.org
Date Deposited: 17 May 2023 05:42
Last Modified: 06 Sep 2024 08:16
URI: http://publications.openuniversitystm.com/id/eprint/1126

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