The Astrophysical Journal Letters (Jan 2023)

The NANOGrav 15 yr Data Set: Bayesian Limits on Gravitational Waves from Individual Supermassive Black Hole Binaries

  • Gabriella Agazie,
  • Akash Anumarlapudi,
  • Anne M. Archibald,
  • Zaven Arzoumanian,
  • Paul T. Baker,
  • Bence Bécsy,
  • Laura Blecha,
  • Adam Brazier,
  • Paul R. Brook,
  • Sarah Burke-Spolaor,
  • Robin Case,
  • J. Andrew Casey-Clyde,
  • Maria Charisi,
  • Shami Chatterjee,
  • Tyler Cohen,
  • James M. Cordes,
  • Neil J. Cornish,
  • Fronefield Crawford,
  • H. Thankful Cromartie,
  • Kathryn Crowter,
  • Megan E. DeCesar,
  • Paul B. Demorest,
  • Matthew C. Digman,
  • Timothy Dolch,
  • Brendan Drachler,
  • Elizabeth C. Ferrara,
  • William Fiore,
  • Emmanuel Fonseca,
  • Gabriel E. Freedman,
  • Nate Garver-Daniels,
  • Peter A. Gentile,
  • Joseph Glaser,
  • Deborah C. Good,
  • Kayhan Gültekin,
  • Jeffrey S. Hazboun,
  • Sophie Hourihane,
  • Ross J. Jennings,
  • Aaron D. Johnson,
  • Megan L. Jones,
  • Andrew R. Kaiser,
  • David L. Kaplan,
  • Luke Zoltan Kelley,
  • Matthew Kerr,
  • Joey S. Key,
  • Nima Laal,
  • Michael T. Lam,
  • William G. Lamb,
  • T. Joseph W. Lazio,
  • Natalia Lewandowska,
  • Tingting Liu,
  • Duncan R. Lorimer,
  • Jing Luo,
  • Ryan S. Lynch,
  • Chung-Pei Ma,
  • Dustin R. Madison,
  • Alexander McEwen,
  • James W. McKee,
  • Maura A. McLaughlin,
  • Natasha McMann,
  • Bradley W. Meyers,
  • Patrick M. Meyers,
  • Chiara M. F. Mingarelli,
  • Andrea Mitridate,
  • Cherry Ng,
  • David J. Nice,
  • Stella Koch Ocker,
  • Ken D. Olum,
  • Timothy T. Pennucci,
  • Benetge B. P. Perera,
  • Polina Petrov,
  • Nihan S. Pol,
  • Henri A. Radovan,
  • Scott M. Ransom,
  • Paul S. Ray,
  • Joseph D. Romano,
  • Shashwat C. Sardesai,
  • Ann Schmiedekamp,
  • Carl Schmiedekamp,
  • Kai Schmitz,
  • Brent J. Shapiro-Albert,
  • Xavier Siemens,
  • Joseph Simon,
  • Magdalena S. Siwek,
  • Ingrid H. Stairs,
  • Daniel R. Stinebring,
  • Kevin Stovall,
  • Abhimanyu Susobhanan,
  • Joseph K. Swiggum,
  • Jacob Taylor,
  • Stephen R. Taylor,
  • Jacob E. Turner,
  • Caner Unal,
  • Michele Vallisneri,
  • Rutger van Haasteren,
  • Sarah J. Vigeland,
  • Haley M. Wahl,
  • Caitlin A. Witt,
  • Olivia Young,
  • The NANOGrav Collaboration

DOI
https://doi.org/10.3847/2041-8213/ace18a
Journal volume & issue
Vol. 951, no. 2
p. L50

Abstract

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Evidence for a low-frequency stochastic gravitational-wave background has recently been reported based on analyses of pulsar timing array data. The most likely source of such a background is a population of supermassive black hole binaries, the loudest of which may be individually detected in these data sets. Here we present the search for individual supermassive black hole binaries in the NANOGrav 15 yr data set. We introduce several new techniques, which enhance the efficiency and modeling accuracy of the analysis. The search uncovered weak evidence for two candidate signals, one with a gravitational-wave frequency of ∼4 nHz, and another at ∼170 nHz. The significance of the low-frequency candidate was greatly diminished when Hellings–Downs correlations were included in the background model. The high-frequency candidate was discounted due to the lack of a plausible host galaxy, the unlikely astrophysical prior odds of finding such a source, and since most of its support comes from a single pulsar with a commensurate binary period. Finding no compelling evidence for signals from individual binary systems, we place upper limits on the strain amplitude of gravitational waves emitted by such systems. At our most sensitive frequency of 6 nHz, we place a sky-averaged 95% upper limit of 8 × 10 ^−15 on the strain amplitude. We also calculate an exclusion volume and a corresponding effective radius, within which we can rule out the presence of black hole binaries emitting at a given frequency.

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