Evaluating Low-Frequency Pulsar Observations to Monitor Dispersion with the Giant Metrewave Radio Telescope

Abstract

The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) project has the primary goal of detecting and characterizing low-frequency gravitational waves through high-precision pulsar timing. The mitigation of interstellar effects is crucial to achieve the necessary precision for gravitational wave detection. Effects like dispersion and scattering are more influential at lower observing frequencies, with the variation of these quantities over week-month timescales requiring high-cadence multi-frequency observations for pulsar timing projects. In this work, we utilize the dual-frequency observing capability of the Giant Metrewave Radio Telescope (GMRT) and evaluate the potential decrease in dispersion measure (DM) uncertainties when combined with existing pulsar timing array data. We present the timing analysis for four millisecond pulsars observed with the GMRT simultaneously at 322 and 607 MHz, and compare the DM measurements with those obtained through NANOGrav observations with the Green Bank Telescope (GBT) and Arecibo Observatory at 1400 to 2300 MHz frequencies. Measured DM values with the GMRT and NANOGrav program show significant offsets for some pulsars, which could be caused by pulse profile evolution in the two frequency bands. In comparison to the predicted DM uncertainties when incorporating these low-frequency data into the NANOGrav dataset, we find that higher-precision GMRT data is necessary to provide improved DM measurements. Through the detection and analysis of pulse profile baseline ripple in data on test pulsar B1929+10, we find that, while not important for this data, it may be relevant for other timing datasets. We discuss the possible advantages and challenges of incorporating GMRT data into NANOGrav and International Pulsar Timing Array datasets.

14 pages, 8 figures. Accepted to The Astrophysical Journal

References in corpus (11)

• The ATNF Pulsar Catalogue
• A New Electron Density Model for Estimation of Pulsar and FRB Distances
• The International Pulsar Timing Array: Second data release
• The MeerKAT Telescope as a Pulsar Facility: System verification and early science results from MeerTime
• From NANOGrav to LIGO with metastable cosmic strings
• The Parkes Pulsar Timing Array Project: Second data release
• Fingerprint of Low-Scale Leptogenesis in the Primordial Gravitational-Wave Spectrum
• The Photospheric Temperatures of Betelgeuse during the Great Dimming of 2019/2020: No New Dust Required
• A LOFAR census of non-recycled pulsars: extending below 80 MHz
• Scattering study of Pulsars below 100 MHz using LWA1
• Probing pulsar scattering between 120 and 280 MHz with the MWA

Cited by in corpus (2)

• The Galactic distribution of pulsar scattering and the $\tau -\mathrm{DM}$ relation
• Wide-band timing of GMRT discovered millisecond pulsars