The NANOGrav 15 yr Data Set: Chromatic Gaussian Process Noise Models for Six Pulsars

Abstract Pulsar timing arrays (PTAs) are designed to detect low-frequency gravitational waves (GWs). GWs induce achromatic signals in PTA data, meaning that the timing delays do not depend on radio frequency. However, pulse arrival times are also affected by radio-frequency-dependent “chromatic” noise from sources such as dispersion measure (DM) and scattering delay variations. Furthermore, the characterization of GW signals may be influenced by the choice of chromatic noise model for each pulsar. To better understand this effect, we assess if and how different chromatic noise models affect the achromatic noise properties in each pulsar. The models we compare include existing DM models used by the North American Nanohertz Observatory for Gravitational waves (NANOGrav) and noise models used for the European PTA Data Release 2 (EPTA DR2). We perform this comparison using a subsample of six pulsars from the NANOGrav 15 yr data set, selecting the same six pulsars as from the EPTA DR2 six-pulsar data set. We find that the choice of chromatic noise model noticeably affects the achromatic noise properties of several pulsars. This is most dramatic for PSR J1713+0747, where the amplitude of its achromatic red noise lowers from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>log</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>A</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>RN</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>14.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.1</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>14.7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.3</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , and the spectral index broadens from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>RN</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>2.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.5</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>RN</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>3.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.9</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1.2</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> . We also compare each pulsar's noise properties with those inferred from the EPTA DR2, using the same models. From the discrepancies, we identify potential areas where the noise models could be improved. These results highlight the potential for custom chromatic noise models to improve PTA sensitivity to GWs.

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Publication Details

Journal
The Astrophysical Journal
Published
2024-08-23
DOI
https://doi.org/10.3847/1538-4357/ad5291
Citations
13
Primary Topic
Pulsars and Gravitational Waves Research
Type
article
Field-Weighted Citation Impact
4.31

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The NANOGrav 15 yr Data Set: Chromatic Gaussian Process Noise Models for Six Pulsars

Bjorn Larsen, Ismaël Cognard, A. Chalumeau, H. Thankful Cromartie et al.
13 citations
The Astrophysical Journal
Pulsars and Gravitational Waves Research
4.31
article

The NANOGrav 15 yr Data Set: Chromatic Gaussian Process Noise Models for Six Pulsars

Bjorn Larsen, Ismaël Cognard, A. Chalumeau, H. Thankful Cromartie, Natasha McMann, D. J. Champion, Bradley W. Meyers, Alexander McEwen, James W. McKee, M. A. McLaughlin, Carl Schmiedekamp, Andrea Possenti, Nihan S. Pol, Timothy Dolch, E. C. Ferrara, S. M. Ransom, A. Parthasarathy, Akash Anumarlapudi, David J. Nice, David L. Kaplan, Anne M. Archibald, William Fiore, Gabriel E. Freedman, Michael T. Lam, Deborah C. Good, Haley M. Wahl, Abhimanyu Susobhanan, Joseph Glaser, Peter A. Gentile, G. Shaifullah, Ryan S. Lynch, Ingrid H. Stairs, Brent J. Shapiro-Albert, Kathryn Crowter, Timothy T. Pennucci, Duncan R. Lorimer, P. T. Baker, Paul R. Brook, Ross J. Jennings, Chiara M. F. Mingarelli, Ann Schmiedekamp, Paul B. Demorest, Jeffrey S. Hazboun, Kuo Liu, Kevin Stovall, Matthew T. Kerr, Paul S. Ray, Benetge B. P. Perera, M. J. Keith, H. Hu, Megan L. Jones, Joseph Simon, G. Theureau, Zaven Arzoumanian, Jing Luo, D. Perrodin, Cherry Ng, Gabriella Agazie, Megan E. DeCesar, Joseph K. Swiggum, Emmanuel Fonseca, H. A. Radovan, Lucas Guillemot, Nate Garver-Daniels
article en
13 citations

Abstract

Abstract Pulsar timing arrays (PTAs) are designed to detect low-frequency gravitational waves (GWs). GWs induce achromatic signals in PTA data, meaning that the timing delays do not depend on radio frequency. However, pulse arrival times are also affected by radio-frequency-dependent “chromatic” noise from sources such as dispersion measure (DM) and scattering delay variations. Furthermore, the characterization of GW signals may be influenced by the choice of chromatic noise model for each pulsar. To better understand this effect, we assess if and how different chromatic noise models affect the achromatic noise properties in each pulsar. The models we compare include existing DM models used by the North American Nanohertz Observatory for Gravitational waves (NANOGrav) and noise models used for the European PTA Data Release 2 (EPTA DR2). We perform this comparison using a subsample of six pulsars from the NANOGrav 15 yr data set, selecting the same six pulsars as from the EPTA DR2 six-pulsar data set. We find that the choice of chromatic noise model noticeably affects the achromatic noise properties of several pulsars. This is most dramatic for PSR J1713+0747, where the amplitude of its achromatic red noise lowers from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>log</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>A</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>RN</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>14.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.1</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>14.7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.3</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , and the spectral index broadens from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>RN</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>2.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.5</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>RN</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>3.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.9</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1.2</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> . We also compare each pulsar's noise properties with those inferred from the EPTA DR2, using the same models. From the discrepancies, we identify potential areas where the noise models could be improved. These results highlight the potential for custom chromatic noise models to improve PTA sensitivity to GWs.

The Astrophysical JournalVol. 972(1)
Eötvös Loránd University (HU), West Virginia University (US), Université d'Orléans (FR), United States Naval Research Laboratory (US), Centre National de la Recherche Scientifique (FR), Goddard Space Flight Center (US), Pennsylvania State University (US), Oregon State University (US), National Academy of Sciences (US), Widener University (US), University of British Columbia (CA), Rochester Institute of Technology (US), George Mason University (US), Lafayette College (US), University of Toronto (CA), University of Colorado Boulder (US), University of Hull (GB), Vanderbilt University (US), Université Paris Cité (FR), Curtin University (AU), National Radio Astronomy Observatory (US), Université Paris Sciences et Lettres (FR), Shanghai Astronomical Observatory (CN), Abington Memorial Hospital (US), University of Manchester (GB), Yale University (US), Hillsdale College (US), Laboratoire Univers et Théories (FR), Canadian Institute for Theoretical Astrophysics (CA), Istituto Nazionale di Fisica Nucleare, Sezione di Milano Bicocca (IT), Eureka Scientific (US), Osservatorio Astronomico di Cagliari (IT), Max Planck Institute for Radio Astronomy (DE), International Centre for Radio Astronomy Research (AU), University of Wisconsin–Milwaukee (US), Laboratoire de Physique et Chimie de l’Environnement et de l’Espace (FR), University of Puerto Rico-Mayaguez (PR), University of Milano-Bicocca (IT), University of Maryland, College Park (US), University of Montana (US), University of Birmingham (GB), Newcastle University (GB), Search for Extraterrestrial Intelligence (US), University of Amsterdam (NL), University of Puerto Rico at Arecibo (PR), Netherlands Institute for Radio Astronomy (NL)
National Science Foundation, National Aeronautics and Space Administration, Agence Nationale de la Recherche, University of British Columbia Graduate School, Science and Technology Facilities Council, Central Laser Facility, Science and Technology Facilities Council, H2020 European Research Council
Openalex Percentile: Top 6%
Pulsars and Gravitational Waves Research
4.31
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