On the Subpulse Modulation, Polarization and Subbeam Carousel Configuration of Pulsar B1857--26

TL;DR

This study uses GMRT observations to analyze pulse modulation, polarization, and carousel configuration in pulsar B1857--26, revealing a 20-beamlet carousel, nulling behavior, and complex polarization characteristics that challenge existing models.

Contribution

It provides the first detailed analysis of pulse-sequence modulation and polarization properties of pulsar B1857--26, including carousel circulation time and polarization mode insights.

Findings

Carousel circulation time of about 147 rotations.

Outer conal components show 7.4-period modulation.

Pulsar nulls occur 20% of the time without periodicity.

Abstract

New GMRT observations of the five-component pulsar B1857--26 provide detailed insight into its pulse-sequence modulation phenomena for the first time. The outer conal components exhibit a 7.4-rotation-period, longitude-stationary modulation. Several lines of evidence indicate a carousel circulation time $\P3hat$ of about 147 stellar rotations, characteristic of a pattern with 20 beamlets. The pulsar nulls some 20% of the time, usually for only a single pulse, and these nulls show no discernible order or periodicity. Finally, the pulsar's polarization-angle traverse raises interesting issues: if most of its emission is comprised of a single polarization mode, the full traverse exceeds 180\degr; or if both polarization modes are present, then the leading and the trailing halves of the profiles exhibit two different modes. In either case the rotating vector model fails to fit the polarization-angle traverse of the core component.