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Lookup NU author(s): Dr Anne ArchibaldORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2026. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the https://creativecommons.org/licenses/by/4.0/. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Evidence for a low-frequency gravitational-wave background using pulsar timing arrays has generated recent interest in its underlying contributing sources. However, multiple investigations have seen that the significance of the evidence does not change with the choice of pulsar modeling techniques, but the resulting parameters from the gravitational wave searches do. PSR J1455−3330 is one of the longest-observed pulsars in the array monitored by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), but showed no evidence for long-timescale red noise, either intrinsic or the common signal found among many pulsars in the array. In this work, we argue that NANOGrav’s piecewise-constant function used to model variations in radio-frequency-dependent dispersive delay should not be used for this pulsar, and a much simpler physical model of a fixed solar wind density plus a linear or quadratic trend in dispersion measure is preferred. When the original model is replaced, (i) the pulsar’s timing parallax signal changes from an upper limit to a significant detection, (ii) red noise becomes significant, and (iii) the red noise is consistent with the common signal found for the other pulsars. Neither of these signals is radio-frequency dependent. While the same physical motivation will not apply to many of the pulsars currently used in pulsar timing arrays, we argue for careful, physically motivated timing and noise modeling of pulsars used in precision timing experiments.
Author(s): Lam MT, Kaplan DL, Agazie G, Anumarlapudi A, Archibald AM, Arzoumanian Z, Baker PT, Brook PR, Combs OA, Cromartie HT, Crowter K, DeCesar ME, Demorest PB, Dolch T, Ferrara EC, Fiore W, Fonseca E, Freedman GE, Garver-Daniels N, Gentile PA, Glaser J, Good DC, Hazboun JS, Jennings RJ, Jones ML, Kerr M, Lorimer DR, Luo J, Lynch RS, McEwen A, McLaughlin MA, McMann N, Meyers BW, Ng C, Nice DJ, Pennucci TT, Perera BBP, Pol NS, Radovan HA, Ransom SM, Ray PS, Schmiedekamp A, Schmiedekamp C, Shapiro-Albert BJ, Simon J, Stairs IH, Stovall K, Susobhanan A, Swiggum JK, Wahl HM
Publication type: Article
Publication status: Published
Journal: Astrophysical Journal
Year: 2026
Volume: 1004
Issue: 1
Print publication date: 10/06/2026
Online publication date: 09/06/2026
Acceptance date: 10/05/2026
Date deposited: 24/06/2026
ISSN (print): 0004-637X
ISSN (electronic): 1538-4357
Publisher: American Astronomical Society
URL: https://doi.org/10.3847/1538-4357/ae6c1c
DOI: 10.3847/1538-4357/ae6c1c
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