We report updated nHz gravitational wave (GW) significance, characterization, and interpretations using the customized chromatic-noise models (CNMs) developed in Larsen, Baier et al. (2026). for the NANOGrav 15-year data set. We find increased evidence for the Hellings-Downs (HD) correlation signature of the stochastic gravitational wave background (GWB), with a Bayes factor of1571±14for HD-correlations over a common uncorrelated red-noise process using a power-law model with14Fourier modes. We find this∼8×increase in Bayes factor from Agazie et al. (2023a) is a result of improved noise mitigation. Assuming an analytic null distribution for the frequentist interpulsar correlation statistic, this corresponds to a slightly more significant measurement from3.16σto3.32σagainst the no-correlation scenario. Spectral inference with CNMs brings the power-law GWB amplitude down toA_(\rm GWB) = 2.1^(+0.6)_(-0.5)×10⁻¹⁵at fixedγ_(\rm GWB) = 13/3 . In a varied- γanalysis, the spectral index increases toγ_(\rm GWB)=3.5^(+0.7)_(-0.6) . We report updates on an all-sky continuous gravitational wave (CW) search as well as select targeted searches and calculate a3.2×larger detection volume for the NANOGrav detector. With CNMs, we find reduced evidence for a non-Einsteinian, scalar-transverse mode of gravity. Finally, we reinterpret the GWB first with the assumption of an astrophysical background sourced by SMBHBs and then assuming the more exotic origins of cosmic inflation, a first-order cosmological phase transition, and stable cosmic strings. Under both the SMBHB hypothesis and the cosmological hypotheses, we see only marginal shifts in model parameter posteriors which are consistent with the slightly quieter and steeper power-law GWB spectrum.
- The NANOGrav 15 yr Data Set: Impacts of Customized Chromatic Noise Models on Gravitational Wave Analyses
- Nikita AgarwalGabriella AgazieAlessandra AmossoAkash AnumarlapudiAnne M ArchibaldZaven ArzoumanianAnjana AshokJeremy G BaierPaul T BakerBence BecsyLaura BlechaAdam BrazierPaul R BrookSarah Burke-SpolaorRand BurnetteRobin CaseJ. Andrew Casey-ClydeYu-Ting ChangMaria CharisiShami ChatterjeeTyler CohenJames M CordesNeil J CornishFronefield CrawfordH. Thankful CromartieKathryn CrowterMegan E DeCesarPaul B DemorestHeling DengLankeswar DeyTimothy DolchGraham M DoskochElizabeth C FerraraWilliam FioreEmmanuel FonsecaGabriel E FreedmanEmiko C GardinerNate Garver-DanielsPeter A GentileKyle A GersbachJoseph GlaserDeborah C GoodKayhan GultekinAiden GundersenC. J HarrisDoa Hashemi AslJeffrey S HazbounRoss J JenningsAaron D JohnsonMegan L JonesDavid L KaplanAnala K SreekumarLuke Zoltan KelleyMatthew KerrJoey S KeyNima LaalMichael T LamWilliam G LambBjorn LarsenT. Joseph W LazioNatalia LewandowskaTingting LiuDuncan R LorimerJing LuoRyan S LynchChung-Pei MaDustin R MadisonAshley MartsenCayenne MattAlexander McEwenJames W McKeeMaura A McLaughlinNatasha McMannBradley W MeyersPatrick M MeyersMatthew T MilesChiara M. F MingarelliAndrea MitridateCherry NgDavid J NiceShania NicholsStella K OckerDaniel J OliverKen D OlumTimothy T PennucciBenetge B. P PereraPolina PetrovNihan S PolHenri A RadovanScott M RansomPaul S RayJoseph D RomanoJessie C RunnoeAlexander SafferShashwat C SardesaiAnn SchmiedekampCarl SchmiedekampKai SchmitzLevi SchultBrent J Shapiro-AlbertXavier SiemensJoseph SimonSophia V. Sosa FiscellaIngrid H StairsDaniel R StinebringKevin StovallRobin StrahlerAbhimanyu SusobhananJoseph K SwiggumJacob TaylorStephen R TaylorMercedes S ThompsonJacob E TurnerMichele VallisneriRutger van HaasterenJoris P. W VerbiestSarah J VigelandHaley M WahlKalista WaytKevin P WilsonCaitlin A WittDavid WrightOlivia Young
- 991019767807307081
- Physics
- English
- Preprint