The NANOGrav 15 yr Dataset: Customized Chromatic Noise Models
Year: 2026
Type: article
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.
Source: The Astrophysical Journal
Authors: Bjorn Larsen, Jeremy G. Baier, Daniel J. Oliver, Kalista Wayt, Yu-Ting Chang, Jeffrey S. Hazboun, Chiara M. F. Mingarelli, Joseph Simon, Matthew T. Miles, Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald, Zaven Arzoumanian, Paul T. Baker, Paul R. Brook, H. Thankful Cromartie, Kathryn Crowter, Megan E. DeCesar, Paul B. Demorest, Timothy Dolch, Elizabeth C. Ferrara, William Fiore, Emmanuel Fonseca, Gabriel E. Freedman, Nate Garver-Daniels, Peter A. Gentile, Joseph Glaser, Deborah C. Good, Ross J. Jennings, Megan L. Jones, David L. Kaplan, Matthew Kerr, Michael T. Lam, Duncan R. Lorimer, Jing Luo, Ryan S. Lynch, Alexander McEwen, Maura A. McLaughlin, Natasha McMann, Bradley W. Meyers, Cherry Ng, David J. Nice, Timothy T. Pennucci, Benetge B. P. Perera, Nihan S. Pol, Henri A. Radovan, Scott M. Ransom, Paul S. Ray, Ann Schmiedekamp, Carl Schmiedekamp, Brent J. Shapiro-Albert, Ingrid H. Stairs, Kevin Stovall, Abhimanyu Susobhanan, Joseph K. Swiggum, Haley M. Wahl
Institutions: Yale University, Oregon State University, Flatiron Institute, Vanderbilt University, University of Wisconsin–Milwaukee, Newcastle University, Widener University, University of Birmingham, National Academy of Sciences, University of British Columbia, George Mason University, National Radio Astronomy Observatory, Hillsdale College, Eureka Scientific, Goddard Space Flight Center, University of Maryland, College Park, West Virginia University, University of Montana, Rochester Institute of Technology, Search for Extraterrestrial Intelligence, University of Toronto, Curtin University, Lafayette College, Eötvös Loránd University, Arecibo Observatory, Texas Tech University, University of Puerto Rico System, Indian Institute of Science Education and Research Thiruvananthapuram
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funders: National Science Foundation, National Aeronautics and Space Administration, Gordon and Betty Moore Foundation, Yale University, Connecticut Space Grant College Consortium, Oregon Space Grant Consortium, Canadian Institute for Advanced Research, University of Central Florida, Flatiron Health, University of Toronto, Eötvös Loránd Tudományegyetem, Natural Sciences and Engineering Research Council of Canada, Science and Technology Facilities Council, Office of Naval Research, U.S. Naval Research Laboratory
Awards: NANOGrav@UPRM: Growing and Characterizing the NANOGrav Gravitational-Wave Detector, The First Multi-Messenger Study of Supermassive Black Hole Growth, G2500807902, G2656910879, CAREER: More Accurate Galaxy Merger Rates to Propel Studies of Gravitational Waves and Star Formation in Galaxy Mergers, WoU-MMA: Pulsar Timing Arrays Around the World CHIME in on Gravitational Waves, G3653412478, G3782671888, Astrophysics at the University of Birmingham - Consolidated grant 2022-2025, G4961910479, Collaborative Research: An Empirical Blueprint for the Gravitational-Wave Background, RII Track-1: Gravitational Wave Astronomy and the Appalachian Freshwater Initiative, Management and Operations of the Arecibo Observatory, G540792204, G5429681523, Collaborative research: Completing the most sensitive low-frequency survey for radio pulsars and transients, G6057698366, The Construction of a Pulsar Interstellar Medium Array Detector, CAREER: Multimessenger Astrophysics with Pulsar Timing Arrays in the Detection Era, The NANOGrav Physics Frontiers Center, G8097610682, Kavli Institute for Theoretical Physics
OpenAlex ID: W7165528263