The NANOGrav 15 yr Dataset: Customized Chromatic Noise Models
Abstract
Pulsar timing arrays (PTAs) conduct low-frequency gravitational-wave (GW) searches, which require comprehensive accounting of various noise sources to achieve robust results. Interstellar propagation effects (e.g., dispersion and scattering) are especially complex noise sources, introducing chromatic delays that can reduce sensitivity to GWs and bias their inference if left unmodeled. These delays also strongly depend on the line-of-sight properties to each individual pulsar. To address this, we present customized chromatic noise models for 67 pulsars in the NANOGrav 15 yr dataset. These models are selected from an expanded suite of Gaussian processes to simultaneously characterize multiple types of chromatic delays and are tailored to each pulsar’s dataset. Alongside probing the interstellar medium, we use these models to infer the solar wind electron density over the course of ∼1.5 solar cycles. We also find evidence for nondispersive chromatic delays in 21 out of 67 NANOGrav pulsars. After applying our chromatic models, we observe significant impacts on the inference of achromatic noise in 19 out of 67 pulsars, finding in several cases that a previously significant achromatic noise process can be partially or entirely described as chromatic. These results demonstrate that refined noise modeling is essential to enhance the sensitivity and accuracy of low-frequency GW searches with PTAs.
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BibTeX
@article{larsen2026nanograv,
title = {{The NANOGrav 15 yr Dataset: Customized Chromatic Noise Models}},
author = {Bjorn Larsen and Jeremy Baier and Daniel Oliver and Kalista Wayt and Yu-Ting Chang and Jeffrey Hazboun and Chiara Mingarelli and Joseph Simon and Matthew Miles and Gabriella Agazie and Akash Anumarlapudi and Anne Archibald and Zaven Arzoumanian and Paul Baker and Paul Brook and H. Thankful Cromartie and Kathryn Crowter and Megan Decesar and Paul Demorest and Timothy Dolch and Elizabeth Ferrara and William Fiore and Emmanuel Fonseca and Gabriel Freedman and Nate Garver-Daniels and Peter Gentile and Joseph Glaser and Deborah Good and Ross Jennings and Megan Jones and David Kaplan and Matthew Kerr and Michael Lam and Duncan Lorimer and Jing Luo and Ryan Lynch and Alexander Mcewen and Maura Mclaughlin and Natasha Mcmann and Bradley Meyers and Cherry Ng and David Nice and Timothy Pennucci and Benetge Perera and Nihan Pol and Henri Radovan and Scott Ransom and Paul Ray and Ann Schmiedekamp and Carl Schmiedekamp and Brent Shapiro-Albert and Ingrid Stairs and Kevin Stovall and Abhimanyu Susobhanan and Joseph Swiggum and Haley Wahl},
journal = {The Astrophysical Journal},
year = {2026},
month = jun,
doi = {10.3847/1538-4357/ae677c},
eprint = {2606.28571},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05842597v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - The NANOGrav 15 yr Dataset: Customized Chromatic Noise Models
AU - Bjorn Larsen
AU - Jeremy Baier
AU - Daniel Oliver
AU - Kalista Wayt
AU - Yu-Ting Chang
AU - Jeffrey Hazboun
AU - Chiara Mingarelli
AU - Joseph Simon
AU - Matthew Miles
AU - Gabriella Agazie
AU - Akash Anumarlapudi
AU - Anne Archibald
AU - Zaven Arzoumanian
AU - Paul Baker
AU - Paul Brook
AU - H. Thankful Cromartie
AU - Kathryn Crowter
AU - Megan Decesar
AU - Paul Demorest
AU - Timothy Dolch
AU - Elizabeth Ferrara
AU - William Fiore
AU - Emmanuel Fonseca
AU - Gabriel Freedman
AU - Nate Garver-Daniels
AU - Peter Gentile
AU - Joseph Glaser
AU - Deborah Good
AU - Ross Jennings
AU - Megan Jones
AU - David Kaplan
AU - Matthew Kerr
AU - Michael Lam
AU - Duncan Lorimer
AU - Jing Luo
AU - Ryan Lynch
AU - Alexander Mcewen
AU - Maura Mclaughlin
AU - Natasha Mcmann
AU - Bradley Meyers
AU - Cherry Ng
AU - David Nice
AU - Timothy Pennucci
AU - Benetge Perera
AU - Nihan Pol
AU - Henri Radovan
AU - Scott Ransom
AU - Paul Ray
AU - Ann Schmiedekamp
AU - Carl Schmiedekamp
AU - Brent Shapiro-Albert
AU - Ingrid Stairs
AU - Kevin Stovall
AU - Abhimanyu Susobhanan
AU - Joseph Swiggum
AU - Haley Wahl
PY - 2026
DA - 2026/06/22
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/ae677c
UR - https://hal.science/hal-05842597v1
AB - Pulsar timing arrays (PTAs) conduct low-frequency gravitational-wave (GW) searches, which require comprehensive accounting of various noise sources to achieve robust results. Interstellar propagation effects (e.g., dispersion and scattering) are especially complex noise sources, introducing chromatic delays that can reduce sensitivity to GWs and bias their inference if left unmodeled. These delays also strongly depend on the line-of-sight properties to each individual pulsar. To address this, we present customized chromatic noise models for 67 pulsars in the NANOGrav 15 yr dataset. These models are selected from an expanded suite of Gaussian processes to simultaneously characterize multiple types of chromatic delays and are tailored to each pulsar’s dataset. Alongside probing the interstellar medium, we use these models to infer the solar wind electron density over the course of ∼1.5 solar cycles. We also find evidence for nondispersive chromatic delays in 21 out of 67 NANOGrav pulsars. After applying our chromatic models, we observe significant impacts on the inference of achromatic noise in 19 out of 67 pulsars, finding in several cases that a previously significant achromatic noise process can be partially or entirely described as chromatic. These results demonstrate that refined noise modeling is essential to enhance the sensitivity and accuracy of low-frequency GW searches with PTAs.
SN - 0004-637X
SN - 1538-4357
ER -