The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave Background
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Abstract
Abstract We report multiple lines of evidence for a stochastic signal that is correlated among 67 pulsars from the 15 yr pulsar timing data set collected by the North American Nanohertz Observatory for Gravitational Waves. The correlations follow the Hellings–Downs pattern expected for a stochastic gravitational-wave background. The presence of such a gravitational-wave background with a power-law spectrum is favored over a model with only independent pulsar noises with a Bayes factor in excess of 10 14 , and this same model is favored over an uncorrelated common power-law spectrum model with Bayes factors of 200–1000, depending on spectral modeling choices. We have built a statistical background distribution for the latter Bayes factors using a method that removes interpulsar correlations from our data set, finding p = 10 −3 (≈3 σ ) for the observed Bayes factors in the null no-correlation scenario. A frequentist test statistic built directly as a weighted sum of interpulsar correlations yields p = 5 × 10 −5 to 1.9 × 10 −4 (≈3.5 σ –4 σ ). Assuming a fiducial f −2/3 characteristic strain spectrum, as appropriate for an ensemble of binary supermassive black hole inspirals, the strain amplitude is <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>2.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.7</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>15</mml:mn> </mml:mrow> </mml:msup> </mml:math> (median + 90% credible interval) at a reference frequency of 1 yr −1 . The inferred gravitational-wave background amplitude and spectrum are consistent with astrophysical expectations for a signal from a population of supermassive black hole binaries, although more exotic cosmological and astrophysical sources cannot be excluded. The observation of Hellings–Downs correlations points to the gravitational-wave origin of this signal.
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The record
- Venue
- The Astrophysical Journal Letters
- Topic
- Pulsars and Gravitational Waves Research
- Field
- Physics and Astronomy
- Canadian institutions
- Canadian Institute for Theoretical AstrophysicsUniversity of TorontoUniversity of British Columbia
- Funders
- Office of Naval ResearchScience and Technology Facilities CouncilNatural Sciences and Engineering Research Council of CanadaJet Propulsion LaboratoryEötvös Loránd TudományegyetemCouncil for Higher EducationCollege of Science, Oregon State UniversityCalifornia Institute of TechnologyIsrael Academy of Sciences and HumanitiesSpace Telescope Science InstituteOregon State UniversityCanadian Institute for Advanced ResearchResearch Corporation for Science AdvancementVanderbilt UniversityUniversity of TorontoGoddard Space Flight CenterUniversity of WashingtonAlfred P. Sloan FoundationBrinson FoundationAssociated UniversitiesTexas Tech UniversityWest Virginia UniversityGordon and Betty Moore FoundationDeutsche ForschungsgemeinschaftUniversity of Central FloridaJohn Templeton FoundationUniversity of MichiganSimons FoundationFlatiron HealthNational Aeronautics and Space AdministrationNational Science Foundation
- Keywords
- PhysicsAlgorithmData setArtificial intelligenceComputer science
- Has abstract in OpenAlex
- yes