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Published February 20, 2020 | Version Published
Journal Article Open

NANOGrav 11 yr Data Set: Evolution of Gravitational-wave Background Statistics

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Abstract

An ensemble of inspiraling supermassive black hole binaries should produce a stochastic background of very low frequency gravitational waves. This stochastic background is predicted to be a power law, with a gravitational-wave strain spectral index of −2/3, and it should be detectable by a network of precisely timed millisecond pulsars, widely distributed on the sky. This paper reports a new "time slicing" analysis of the 11 yr data release from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) using 34 millisecond pulsars. Methods to flag potential "false-positive" signatures are developed, including techniques to identify responsible pulsars. Mitigation strategies are then presented. We demonstrate how an incorrect noise model can lead to spurious signals, and we show how independently modeling noise across 30 Fourier components, spanning NANOGrav's frequency range, effectively diagnoses and absorbs the excess power in gravitational-wave searches. This results in a nominal, and expected, progression of our gravitational-wave statistics. Additionally, we show that the first interstellar medium event in PSR J1713+0747 pollutes the common red-noise process with low spectral index noise, and we use a tailored noise model to remove these effects.

Additional Information

© 2020 The American Astronomical Society. Received 2019 September 18; revised 2019 December 24; accepted 2020 January 6; published 2020 February 18. Author contributions. This paper is the result of the work of dozens of people over the course of more than 13 years. We list specific contributions below. J.S.H. ran the sliced analyses and led the paper writing. J.S., S.R.T., M.T.L., S.J.V, K.I., and J.S.K. contributed substantially to paper writing, discussion, and interpretation of results. M.T.L. helped with analyses. J.S.H. and S.R.T. developed the formalism in Section 4. Z.A., K.C., P.B.D., M.E.D., T.D., J.A.E., E.C.F., R.D.F., E.F., P.A.G., G.J., M.L.J., M.T.L., L.L., D.R.L., R.S.L., M.A.M., C.N., D.J.N., T.T.P., S.M.R., P.S.R., R.S., I.H.S., K.S., J.K.S., and W.Z. ran observations and developed the 11 yr data set. The NANOGrav project receives support from National Science Foundation (NSF) PIRE program award No. 0968296 and NSF Physics Frontier Center award No. 1430284. NANOGrav research at UBC is supported by an NSERC Discovery Grant and Discovery Accelerator Supplement and by the Canadian Institute for Advanced Research. J.S.H. would like to thank Joseph Romano for a number of in-depth discussions concerning the results of the numerous analyses done for this project. M.V. and J.S. acknowledge support from the JPL RTD program. Portions of this research were carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. S.R.T. was partially supported by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory, administered by Oak Ridge Associated Universities through a contract with NASA. S.R.T. thanks ERS for fruitful discussions. J.A.E. was partially supported by NASA through Einstein Fellowship grants PF4-150120. S.B.S. was supported by NSF award No. 1458952. P.T.B. acknowledges support from the West Virginia University Center for Gravitational Waves and Cosmology. This work was supported in part by National Science Foundation grant No. PHYS-1066293 and by the hospitality of the Aspen Center for Physics. Portions of this work performed at NRL are supported by the Chief of Naval Research. This research was performed in part using the Zwicky computer cluster at Caltech supported by NSF under MRI-R2 award No. PHY-0960291 and by the Sherman Fairchild Foundation. A majority of the computational work was performed on the Nemo cluster at UWM supported by NSF grant No. 0923409. Parts of the analysis in this work were carried out on the Nimrod cluster made available by S.M.R. Data for this project were collected using the facilities of the National Radio Astronomy Observatory and the Arecibo Observatory. The National Radio Astronomy Observatory and Green Bank Observatory are facilities of the NSF operated under cooperative agreement by Associated Universities, Inc. The Arecibo Observatory is operated by the University of Central Florida, Ana G. Méndez-Universidad Metropolitana, and Yang Enterprises under a cooperative agreement with the NSF (AST-1744119). This research is part of the Blue Waters sustained-petascale computing project, which is supported by the National Science Foundation (awards OCI-0725070 and ACI-1238993) and the state of Illinois. Blue Waters is a joint effort of the University of Illinois at Urbana-Champaign and its National Center for Supercomputing Applications. Some of the algorithms used in this article were optimized using the Blue Waters allocation "Accelerating the detection of gravitational waves with GPUs." The Flatiron Institute is supported by the Simons Foundation. Software: enterprise (Ellis et al. 2017), PTMCMCSampler (Ellis & van Haasteren 2017), enterprise_extensions (Taylor et al. 2018), TEMPO2 (Hobbs et al. 2006), libstempo (Vallisneri 2015), Scipy (Jones) and Numpy (Oliphant).

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Additional details

Identifiers

Eprint ID
101499
Resolver ID
CaltechAUTHORS:20200224-125802735

Funding

NSF
OISE-0968296
NSF
PHY-1430284
Natural Sciences and Engineering Research Council of Canada (NSERC)
Canadian Institute for Advanced Research (CIFAR)
JPL Research and Technology Development Fund
NASA/JPL/Caltech
NASA Postdoctoral Program
NASA Einstein Fellowship
PF4-150120
NSF
OIA-1458952
West Virginia University
NSF
PHYS-1066293
Chief of Naval Research
NSF
PHY-0960291
Sherman Fairchild Foundation
NSF
PHY-0923409
NSF
AST-1744119
NSF
OCI-0725070
NSF
ACI-1238993
State of Illinois
Simons Foundation

Dates

Created
2020-02-24
Created from EPrint's datestamp field
Updated
2021-11-16
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