The NANOGrav 15 yr Data Set: Harmonic Analysis of the Pulsar Angular Correlations
| Title: | The NANOGrav 15 yr Data Set: Harmonic Analysis of the Pulsar Angular Correlations |
|---|---|
| Authors: | Agazie G; Anumarlapudi A; Archibald AM; Arzoumanian Z; Baier JG; Baker PT; Becsy B; Blecha L; Boddy KK; Brazier A; Brook PR; Burke-Spolaor S; Burnette R; Casey-Clyde JA; Charisi M; Chatterjee S; Cohen T; Cordes JM; Cornish NJ; Crawford F; Cromartie HT; Crowter K; DeCesar ME; Demorest PB; Deng H; Dey L; Dolch T; Ferrara EC; Fiore W; Fonseca E; Freedman GE; Gardiner EC; Garver-Daniels N; Gentile PA; Gersbach KA; Glaser J; Good DC; Gultekin K; Hazboun JS; Jennings RJ; Johnson AD; Jones ML; Kaplan DL; Kelley LZ; Kerr M; Key JS; Laal N; Lam MT; Lamb WG; Larsen B; Lazio TJW; Lewandowska N; Liu T; Lorimer DR; Luo J; Lynch RS; Ma C-P; Madison DR; McEwen A; McKee JW; McLaughlin MA; McMann N; Meyers BW; Meyers PM; Mingarelli CMF; Mitridate A; Nay J; Ng C; Nice DJ; Ocker SK; Olum KD; Pennucci TT; Perera BBP; Petrov P; Pol NS; Radovan HA; Ransom SM; Ray PS; Runnoe JC; Saffer A; Sardesai SC; Schmiedekamp A; Schmiedekamp C; Schmitz K; Shapiro-Albert BJ; Siemens X; Simon J; Siwek MS; Smith TL; Fiscella SVS; Stairs IH; Stinebring DR; Stovall K; Susobhanan A; Swiggum JK; Taylor J; Taylor SR; Turner JE; Unal C; Vallisneri M; van Haasteren R; Vigeland SJ; Wahl HM; Witt CA; Wright D; Young O |
| Source: | Astrophysical Journal, 20 May 2025 |
| Publisher Information: | Institute of Physics |
| Publication Year: | 2025 |
| Collection: | Newcastle University Library ePrints Service |
| Description: | © 2025. The Author(s). Published by the American Astronomical Society.Pulsar timing array observations have found evidence for an isotropic gravitational-wave background with the Hellings-Downs angular correlations between pulsar pairs. This interpretation hinges on the measured shape of the angular correlations, which is predominantly quadrupolar under general relativity. Here we explore a more flexible parameterization: we expand the angular correlations into a sum of Legendre polynomials and use a Bayesian analysis to constrain their coefficients with the 15 yr pulsar timing data set collected by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). When including Legendre polynomials with multipoles ℓ ≥ 2, we only find a significant signal in the quadrupole with an amplitude consistent with general relativity and nonzero at the ∼95% confidence level and a Bayes factor of 200. When we include multipoles ℓ ≤ 1, the Bayes factor evidence for quadrupole correlations decreases by more than an order of magnitude due to evidence for a monopolar signal at approximately 4 nHz, which has also been noted in previous analyses of the NANOGrav 15 yr data. Further work needs to be done in order to better characterize the properties of this monopolar signal and its effect on the evidence for quadrupolar angular correlations. |
| Document Type: | article in journal/newspaper |
| File Description: | application/pdf |
| Language: | unknown |
| Relation: | https://eprints.ncl.ac.uk/306276; https://eprints.ncl.ac.uk/fulltext.aspx?url=306276/A189C4D9-377B-4D64-98CA-C5BEE8900E97.pdf&pub_id=306276 |
| Availability: | https://eprints.ncl.ac.uk/306276 |
| Rights: | https://creativecommons.org/licenses/by/4.0/ |
| Accession Number: | edsbas.12EB8580 |
| Database: | BASE |