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Published September 10, 2020 | Published
Journal Article Open

Multimessenger Gravitational-wave Searches with Pulsar Timing Arrays: Application to 3C 66B Using the NANOGrav 11-year Data Set


When galaxies merge, the supermassive black holes in their centers may form binaries and emit low-frequency gravitational radiation in the process. In this paper, we consider the galaxy 3C 66B, which was used as the target of the first multimessenger search for gravitational waves. Due to the observed periodicities present in the photometric and astrometric data of the source, it has been theorized to contain a supermassive black hole binary. Its apparent 1.05-year orbital period would place the gravitational-wave emission directly in the pulsar timing band. Since the first pulsar timing array study of 3C 66B, revised models of the source have been published, and timing array sensitivities and techniques have improved dramatically. With these advances, we further constrain the chirp mass of the potential supermassive black hole binary in 3C 66B to less than (1.65 ± 0.02) × 10⁹ M_⊙ using data from the NANOGrav 11-year data set. This upper limit provides a factor of 1.6 improvement over previous limits and a factor of 4.3 over the first search done. Nevertheless, the most recent orbital model for the source is still consistent with our limit from pulsar timing array data. In addition, we are able to quantify the improvement made by the inclusion of source properties gleaned from electromagnetic data over "blind" pulsar timing array searches. With these methods, it is apparent that it is not necessary to obtain exact a priori knowledge of the period of a binary to gain meaningful astrophysical inferences.

Additional Information

© 2020. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2020 May 14; revised 2020 July 22; accepted 2020 July 31; published 2020 September 7. S.B.S. and C.A.W. were supported in this work by NSF award Nos. 1458952 and 1815664. The NANOGrav collaboration is supported by NSF Physics Frontier Center award No. 1430284. C.A.W. acknowledges support from West Virginia University through the Outstanding Merit Fellowship for Continuing Doctoral Students. S.B.S. is a CIFAR Azrieli Global Scholar in the Gravity and the Extreme Universe program. This research made use of the Super Computing System (Spruce Knob) at WVU, which is funded in part by the National Science Foundation EPSCoR Research Infrastructure Improvement Cooperative Agreement No. 1003907, the state of West Virginia (WVEPSCoR via the Higher Education Policy Commission), and WVU. We acknowledge the use of Thorny Flat at WVU, which is funded in part by National Science Foundation Major Research Instrumentation Program (MRI) award No. 1726534 and WVU. NANOGrav research at UBC is supported by an NSERC Discovery Grant and Discovery Accelerator Supplement and the Canadian Institute for Advanced Research. M.V. and J.S. acknowledge support from the JPL RTD program. S.R.T. was partially supported by an appointment to the NASA Postdoctoral Program at JPL, administered by Oak Ridge Associated Universities through a contract with NASA. J.A.E. was partially supported by NASA through Einstein Fellowship grants PF4-150120. Portions of this work performed at NRL are supported by the Chief of Naval Research. The Flatiron Institute is supported by the Simons Foundation. 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. Data for this project were collected using the facilities of the Green Bank Observatory and the Arecibo Observatory. The Green Bank Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The Arecibo Observatory is a facility of the National Science Foundation operated under cooperative agreement by the University of Central Florida in alliance with Yang Enterprises, Inc., and Universidad Metropolitana. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This work made use of the online cosmology calculator tool (Wright 2006). We also acknowledge use of numpy (Oliphant 2006), scipy (Virtanen et al. 2020), matplotlib (Hunter 2007), and astropy (Price-Whelan et al. 2018). This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Author contributions. We list specific contributions to this paper as follows. C.A.W. led the work on this paper, ran the GW searches, and led the development of the manuscript. J.S., S.R.T., S.J.V., and S.B.S. provided guidance throughout the project and key development of the project motivation and scientific interpretation. J.A.E., S.R.T., P.T.B., S.J.V., and C.A.W. designed and implemented the Bayesian search algorithms in enterprise. J.S.H. performed and interpreted the S/N simulations with hasasia. R.D.E. performed initial literature reviews on 3C 66B. N.J.C., J.S.H., D.L.K., M.T.L., T.J.W.L., M.A.M., C.M.F.M., and D.J.N. contributed valuable scientific comments. The NANOGrav data are the result of the work of dozens of people over the course of more than 13 years. 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., M.L.J., M.T.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. developed the 11-year data set. All authors are key contributing members of the NANOGrav collaboration.

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August 22, 2023
August 22, 2023