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50-250 MHz Pulsar Census with an SKA-Low prototype station: Spectra and Polarization

Pratik Kumar, Marcin Sokolowski, Randall Wayth

Abstract

Low-frequency pulsar observations are crucial for understanding pulsar emission spectra and population physics, as well as for probing the interstellar medium (ISM) and Earth's ionosphere. We report the largest low-frequency pulsar census conducted in the southern hemisphere, covering 50-250 MHz, using the EDA2, an SKA-Low prototype station. In this survey, we detected 120 pulsars, including 23 first-time detections below 150 MHz and 5 below 100 MHz. For each source, we provide integrated pulse profiles and flux-density measurements across five sub-bands spanning 50-250 MHz. We also obtained improved dispersion measure (DM) values for 110 pulsars, with a median absolute DM correction of about 0.1 pc cm^-3. We measured significant Faraday rotation for 40 pulsars with improved rotation measure (RM) values for 4 pulsars, as well as phase-resolved RM variation in J1453-6413. Full-polarimetric pulse profiles are provided for all these pulsars, with multi-frequency polarimetric data for 20 of them. These results will enhance future SKA-Low science: refining pulsar population models, informing survey strategies, and advancing characterization of both the ISM and the ionosphere through low-frequency pulsar monitoring.

50-250 MHz Pulsar Census with an SKA-Low prototype station: Spectra and Polarization

Abstract

Low-frequency pulsar observations are crucial for understanding pulsar emission spectra and population physics, as well as for probing the interstellar medium (ISM) and Earth's ionosphere. We report the largest low-frequency pulsar census conducted in the southern hemisphere, covering 50-250 MHz, using the EDA2, an SKA-Low prototype station. In this survey, we detected 120 pulsars, including 23 first-time detections below 150 MHz and 5 below 100 MHz. For each source, we provide integrated pulse profiles and flux-density measurements across five sub-bands spanning 50-250 MHz. We also obtained improved dispersion measure (DM) values for 110 pulsars, with a median absolute DM correction of about 0.1 pc cm^-3. We measured significant Faraday rotation for 40 pulsars with improved rotation measure (RM) values for 4 pulsars, as well as phase-resolved RM variation in J1453-6413. Full-polarimetric pulse profiles are provided for all these pulsars, with multi-frequency polarimetric data for 20 of them. These results will enhance future SKA-Low science: refining pulsar population models, informing survey strategies, and advancing characterization of both the ISM and the ionosphere through low-frequency pulsar monitoring.
Paper Structure (30 sections, 13 equations, 64 figures)

This paper contains 30 sections, 13 equations, 64 figures.

Table of Contents

  1. Introduction
  2. Motivations and science goals
  3. Observations
  4. Target selection
  5. Observations and data reduction
  6. Results and Analysis
  7. Average pulse profile
  8. DM correction
  9. Calibration and mean flux density
  10. Pulsar Spectra
  11. RM-synthesis
  12. Ionospheric RM
  13. Pulsar RM and phase resolved RM
  14. Polarimetry
  15. Discussions
  16. ...and 15 more sections

Figures (64)

  • Figure 1: Distribution of census targets in Galactic coordinates. Red and blue indicate the detected targets, with periods below and above 30 ms, respectively, and non-detected targets are shown in yellow. Contours show the line of equal declination, and the shaded region shows the region inaccessible due to low elevation.
  • Figure 2: (Top) RM$_{ISM}$ for pulsar J0630-2834 as a function of source elevation and observing time in UTC on MJD 60640. (Bottom) Variation of fractional linear polarization with elevation.
  • Figure 3: The top panel of the figure shows the difference between RM$_{ISM}$ from EDA2 and MeerKAT telescopes ($\Delta$ RM) against the ionospheric RM (RM$_{ion}$) measured for EDA2 for each of those pulsars. The bottom panel shows the one-to-one RM$_{ISM}$ for pulsars in Table \ref{['tab:rmtable']} for EDA2 and MeerKAT. The central panel shows $\Delta$ RM vs RM$_{ISM}$ for MeerKAT. The dashed line in both the top and central panels indicates the mean value of $\Delta$ RM
  • Figure 4: Phase resolved RM variation for three pulsars. The top panel of each subplot shows the total intensity, fractional linear polarization, and fractional circular polarization in black, red, and cyan, respectively. The bottom panel shows RM values measured across the pulse phase, along with a colorbar which indicates the S/N of the FDF peak.
  • Figure 5: Plot of pulse width versus pulsar period, along with the Lower boundary line in solid lines (Left) using W50 (Right) using W10. The colors represent respective frequencies in the legend.
  • ...and 59 more figures