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Frequency- and phase-resolved polarimetry of millisecond pulsars and its application to timing

Małgorzata Curyło, Andrew Zic, Shuangqiang Wang, Eric Thrane, Paul D. Lasky, Jacob Cardinal Tremblay, Zu-Cheng Chen, Shi Dai, Valentina Di Marco, George Hobbs, Agastya Kapur, Wenhua Ling, Marcus E. Lower, Saurav Mishra, Daniel J. Reardon, Christopher J. Russell, Ryan M. Shannon, Xing-Jiang Zhu

TL;DR

The paper tackles the challenge of achieving higher-precision pulsar timing by addressing frequency-dependent pulse-shape evolution and instrumental polarization. It introduces a wideband polarimetric portrait framework that uses all four Stokes parameters to model phase- and frequency-dependent pulse structure, employing PCA-derived eigenprofiles and spline interpolation to generate noise-free templates. Applied to Parkes PPTA ultra-wideband data, the method yields TOA uncertainties reduction of about 20–30% compared with scalar templates and provides the first phase- and frequency-resolved polarimetric measurements for these pulsars, with data and code openly available. This approach enhances timing accuracy and enables richer magnetospheric and emission-geometry studies, with meaningful implications for gravitational-wave timing arrays and fundamental physics tests.

Abstract

Pulsar timing is used for a variety of applications including tests of fundamental physics, probing the structure of neutron stars, and detecting nanohertz gravitational waves. Development of robust methods and generation of high-quality timing data is therefore of utmost importance. In this paper, we present a new technique for creating high-fidelity templates that can be used to measure the pulse times of arrival with significantly increased precision compared to existing methods. Our framework makes use of all available polarimetric information to generate frequency-dependent models of pulse-shape evolution of all four Stokes parameters. We apply this method to millisecond pulsars observed by the Parkes Pulsar Timing Array and show that it results in timing measurement uncertainties reduced up to $\sim$20-30\%. We also present, for the first time, phase- and frequency-resolved polarimetric measurements of millisecond pulsars observed with the Parkes Murriyang ultra-widebandwith-low receiver. The data, plots and the code underlying this analysis are made publicly available.

Frequency- and phase-resolved polarimetry of millisecond pulsars and its application to timing

TL;DR

The paper tackles the challenge of achieving higher-precision pulsar timing by addressing frequency-dependent pulse-shape evolution and instrumental polarization. It introduces a wideband polarimetric portrait framework that uses all four Stokes parameters to model phase- and frequency-dependent pulse structure, employing PCA-derived eigenprofiles and spline interpolation to generate noise-free templates. Applied to Parkes PPTA ultra-wideband data, the method yields TOA uncertainties reduction of about 20–30% compared with scalar templates and provides the first phase- and frequency-resolved polarimetric measurements for these pulsars, with data and code openly available. This approach enhances timing accuracy and enables richer magnetospheric and emission-geometry studies, with meaningful implications for gravitational-wave timing arrays and fundamental physics tests.

Abstract

Pulsar timing is used for a variety of applications including tests of fundamental physics, probing the structure of neutron stars, and detecting nanohertz gravitational waves. Development of robust methods and generation of high-quality timing data is therefore of utmost importance. In this paper, we present a new technique for creating high-fidelity templates that can be used to measure the pulse times of arrival with significantly increased precision compared to existing methods. Our framework makes use of all available polarimetric information to generate frequency-dependent models of pulse-shape evolution of all four Stokes parameters. We apply this method to millisecond pulsars observed by the Parkes Pulsar Timing Array and show that it results in timing measurement uncertainties reduced up to 20-30\%. We also present, for the first time, phase- and frequency-resolved polarimetric measurements of millisecond pulsars observed with the Parkes Murriyang ultra-widebandwith-low receiver. The data, plots and the code underlying this analysis are made publicly available.

Paper Structure

This paper contains 47 sections, 10 equations, 5 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Method
  3. Useful definitions
  4. Basics of pulse portraiture
  5. Flux and spectral indices
  6. Data
  7. Results and discussion
  8. Polarised portraits and templates
  9. Polarisation profiles, fractions and position angles
  10. Flux and spectral indices
  11. Summary and conclusions
  12. Notes on individual pulsars
  13. PSR J0030+0451
  14. PSR J0125--2327
  15. PSR J0437--4715
  16. ...and 32 more sections

Figures (5)

  • Figure 1: Polarisation profiles of I (black), L (gold) and V (red) in 8 sub-bands. Left is PSR J1939+2134; right is PSR J2051--0827.
  • Figure 2: Fully band-averaged polarisation profiles, PAs and phase-resolved spectral indices for four pulsars (left to right and top to bottom): PSR J0030+0451, PSR J0125--2327, PSR J1022+1001, PSR J1024--0719. The purple shaded line in the bottom plots shows the phase averaged value of the spectral index.
  • Figure 3: Results for PSR J0900--3144. Top: polarisation profiles and PAs in three bands, middle: waterfall plots of phase- and frequency-resolved polarisation fractions (16 frequency channels), bottom: phase-averaged polarisation fractions (16 frequency channels).
  • Figure 4: Linear and absolute circular polarisation fractions as a function of spin-down energy $\dot{E}$ in three bands. The legend shows median values across all pulsars.
  • Figure 5: Flux density spectra for PSR J0900--3144, PSR J1545--4550, PSR J1600--3053, PSR J1713+0747, PSR J1824--5236 and PSR J2241--5236. Colour scale represent the level of flux variations across all observations.