The NANOGrav 15 yr Data Set: Running of the Spectral Index
| Title: | The NANOGrav 15 yr Data Set: Running of the Spectral Index |
|---|---|
| Authors: | Agazie G; Anumarlapudi A; Archibald AM; Arzoumanian Z; Baier JG; Baker PT; Becsy B; Blecha L; Brazier A; Brook PR; Burke-Spolaor S; 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; Esmyol D; 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 JTW; Lewandowska N; Lino dos Santos RR; 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; Ng C; Nice DJ; Ocker SK; Olum KD; Pennucci TT; Perera BBP; Pol NS; Radovan HA; Ransom SM; Ray PS; Romano JD; Runnoe JC; Saffer A; Sardesai SC; Schmiedekamp A; Schmiedekamp C; Schmitz K; Schroder T; Shapiro-Albert BJ; Siemens X; Simon J; Siwek MS; Sosa Fiscella SV; Stairs IH; Stinebring DR; Stovall K; Susobhanan A; Swiggum JK; Taylor SR; Turner JE; Unal C; Vallisneri M; van Haasteren R; Vigeland SJ; von Eckardstein R; Wahl HM; Witt CA; Wright D; Young O |
| Source: | Astrophysical Journal Letters, 10 January 2025 |
| Publisher Information: | American Astronomical Society |
| Publication Year: | 2025 |
| Collection: | Newcastle University Library ePrints Service |
| Description: | © 2025. The Author(s)The NANOGrav 15 yr data provide compelling evidence for a stochastic gravitational-wave (GW) background at nanohertz frequencies. The simplest model-independent approach to characterizing the frequency spectrum of this signal consists of a simple power-law fit involving two parameters: an amplitude A and a spectral index γ. In this Letter, we consider the next logical step beyond this minimal spectral model, allowing for a running (i.e., logarithmic frequency dependence) of the spectral index, grun (f ) = g + b ln (f /fref ). We fit this running-power-law (RPL) model to the NANOGrav 15 yr data and perform a Bayesian model comparison with the minimal constant-power-law (CPL) model, which results in a 95% credible interval for the parameter β consistent with no running, b Î [-0.80, 2.96], and an inconclusive Bayes factor, B(RPL versus CPL) = 0.69 ± 0.01. We thus conclude that, at present, the minimal CPL model still suffices to adequately describe the NANOGrav signal; however, future data sets may well lead to a measurement of nonzero β. Finally, we interpret the RPL model as a description of primordial GWs generated during cosmic inflation, which allows us to combine our results with upper limits from Big Bang nucleosynthesis, the cosmic microwave background, and LIGO–Virgo–KAGRA. |
| Document Type: | article in journal/newspaper |
| File Description: | application/pdf |
| Language: | unknown |
| Relation: | https://eprints.ncl.ac.uk/303663; https://eprints.ncl.ac.uk/fulltext.aspx?url=303663/93FCA531-DFFB-486D-A9DD-3B73E1A55AFC.pdf&pub_id=303663 |
| Availability: | https://eprints.ncl.ac.uk/303663 |
| Rights: | https://creativecommons.org/licenses/by/4.0/ |
| Accession Number: | edsbas.4B4D18A0 |
| Database: | BASE |