BibTex format
@article{Agazie:2025:2041-8213/ad99d3,
author = {Agazie, G and Anumarlapudi, A and Archibald, AM and Arzoumanian, Z and Baier, JG and Baker, PT and Bécsy, B and Blecha, L and Brazier, A and Brook, PR and Burke-Spolaor, S and Casey-Clyde, JA and Charisi, M and Chatterjee, S and Cohen, T and Cordes, JM and Cornish, NJ and Crawford, F and Cromartie, HT and Crowter, K and DeCesar, ME and Demorest, PB and Deng, H and Dey, L and Dolch, T and Esmyol, D and Ferrara, EC and Fiore, W and Fonseca, E and Freedman, GE and Gardiner, EC and Garver-Daniels, N and Gentile, PA and Gersbach, KA and Glaser, J and Good, DC and Gültekin, K and Hazboun, JS and Jennings, RJ and Johnson, AD and Jones, ML and Kaplan, DL and Kelley, LZ and Kerr, M and Key, JS and Laal, N and Lam, MT and Lamb, WG and Larsen, B and Lazio, JTW and Lewandowska, N and Lino, dos Santos RR and Liu, T and Lorimer, DR and Luo, J and Lynch, RS and Ma, CP and Madison, DR and McEwen, A and McKee, JW and McLaughlin, MA and McMann, N and Meyers, BW and Meyers, PM and Mingarelli, CMF and Mit},
doi = {2041-8213/ad99d3},
journal = {Astrophysical Journal Letters},
title = {The NANOGrav 15 yr Data Set: Running of the Spectral Index},
url = {http://dx.doi.org/10.3847/2041-8213/ad99d3},
volume = {978},
year = {2025}
}
RIS format (EndNote, RefMan)
TY - JOUR
AB - 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, g<inf>run</inf> (f ) = g + b ln (f /f<inf>ref</inf> ). 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.
AU - Agazie,G
AU - Anumarlapudi,A
AU - Archibald,AM
AU - Arzoumanian,Z
AU - Baier,JG
AU - Baker,PT
AU - Bécsy,B
AU - Blecha,L
AU - Brazier,A
AU - Brook,PR
AU - Burke-Spolaor,S
AU - Casey-Clyde,JA
AU - Charisi,M
AU - Chatterjee,S
AU - Cohen,T
AU - Cordes,JM
AU - Cornish,NJ
AU - Crawford,F
AU - Cromartie,HT
AU - Crowter,K
AU - DeCesar,ME
AU - Demorest,PB
AU - Deng,H
AU - Dey,L
AU - Dolch,T
AU - Esmyol,D
AU - Ferrara,EC
AU - Fiore,W
AU - Fonseca,E
AU - Freedman,GE
AU - Gardiner,EC
AU - Garver-Daniels,N
AU - Gentile,PA
AU - Gersbach,KA
AU - Glaser,J
AU - Good,DC
AU - Gültekin,K
AU - Hazboun,JS
AU - Jennings,RJ
AU - Johnson,AD
AU - Jones,ML
AU - Kaplan,DL
AU - Kelley,LZ
AU - Kerr,M
AU - Key,JS
AU - Laal,N
AU - Lam,MT
AU - Lamb,WG
AU - Larsen,B
AU - Lazio,JTW
AU - Lewandowska,N
AU - Lino,dos Santos RR
AU - Liu,T
AU - Lorimer,DR
AU - Luo,J
AU - Lynch,RS
AU - Ma,CP
AU - Madison,DR
AU - McEwen,A
AU - McKee,JW
AU - McLaughlin,MA
AU - McMann,N
AU - Meyers,BW
AU - Meyers,PM
AU - Mingarelli,CMF
AU - Mitridate,A
AU - Ng,C
AU - Nice,DJ
AU - Ocker,SK
AU - Olum,KD
AU - Pennucci,TT
AU - Perera,BBP
AU - Pol,NS
AU - Radovan,HA
AU - Ransom,SM
AU - Ray,PS
AU - Romano,JD
AU - Runnoe,JC
AU - Saffer,A
AU - Sardesai,SC
AU - Schmiedekamp,A
AU - Schmiedekamp,C
AU - Schmitz,K
AU - Schröder,T
AU - Shapiro-Albert,BJ
AU - Siemens,X
AU - Simon,J
AU - Siwek,MS
AU - Sosa,Fiscella SV
AU - Stairs,IH
AU - Stinebring,DR
AU - Stovall,K
AU - Susobhanan,A
AU - Swiggum,JK
AU - Taylor,SR
AU - Turner,JE
AU - Unal,C
AU - Vallisneri,M
AU - van,Haasteren R
AU - Vigeland,SJ
DO - 2041-8213/ad99d3
PY - 2025///
SN - 2041-8205
TI - The NANOGrav 15 yr Data Set: Running of the Spectral Index
T2 - Astrophysical Journal Letters
UR - http://dx.doi.org/10.3847/2041-8213/ad99d3
VL - 978
ER -