A Simultaneous Dual-Frequency Scintillation Arc Survey of Six Bright Canonical Pulsars Using the Upgraded Giant Metrewave Radio Telescope

TL;DR

This study uses the upgraded GMRT to perform simultaneous dual-frequency observations of six bright pulsars, analyzing scintillation arcs to understand interstellar medium effects with improved accuracy and revealing new insights into arc properties and their temporal evolution.

Contribution

First simultaneous dual-frequency scintillation arc survey of six pulsars with the upgraded GMRT, providing more robust frequency dependence analysis and insights into arc asymmetries and temporal variations.

Findings

Arc curvature and pseudo-curvature agree with theory and previous studies.

Strong correlation between arc asymmetry and curvature, replicated via simulations.

Evidence of week-long timescale dominance of scattering screens in pulsar signals.

Abstract

We use the upgraded Giant Metrewave Radio Telescope to measure scintillation arc properties in six bright canonical pulsars with simultaneous dual frequency coverage. These observations at frequencies from 300 to 750 MHz allowed for detailed analysis of arc evolution across frequency and epoch. We perform more robust determinations of frequency dependence for arc curvature, scintillation bandwidth, and scintillation timescale, and comparison between arc curvature and pseudo-curvature than allowed by single-frequency-band-per-epoch measurements, which we find to agree with theory and previous literature. We find a strong correlation between arc asymmetry and arc curvature, which we have replicated using simulations, and attribute to a bias in the Hough transform approach to scintillation arc analysis. Possible evidence for an approximately week long timescale over which a given scattering screen dominates signal propagation was found by tracking visible scintillation arcs in each epoch in PSR J1136+1551. The inclusion of a 155 minute observation allowed us to resolve the scale of scintillation variations on short timescales, which we find to be directly tied to the amount of ISM sampled over the observation. Some of our pulsars showed either consistent or emerging asymmetries in arc curvature, indicating instances of refraction across their lines of sight. Significant features in various pulsars, such as multiple scintillation arcs in PSR J1136+1551 and flat arclets in PSR J1509+5531, that have been found in previous works, were also detected. The simultaneous multiple band observing capability of the upgraded GMRT shows excellent promise for future pulsar scintillation work.