On the flux density spectral property of high linearly polarized signal from Pulsar J0332+5434

TL;DR

This study investigates the spectral properties of highly linearly polarized signals from pulsar J0332+5434 across 300-750 MHz, revealing broadband, narrow, and sometimes inverted spectral features that support incoherent CCR emission mechanisms.

Contribution

It provides the first detailed analysis of the frequency evolution of high linear polarization signals in pulsar emission, linking spectral shapes to CCR models and orthogonal polarization modes.

Findings

High linear polarization signals are broadband and often show narrow, spiky features.

Spectral shapes sometimes resemble inverted parabolas, associated with X-mode emission.

Features are consistent with incoherent addition of CCR from charged solitons.

Abstract

The polarization position angles (PPA) of time samples with high linear polarization often show two parallel tracks across the pulsar profile that follow the rotating vector model (RVM). This feature support coherent curvature radiation (CCR) as the underlying mechanism of radio emission from pulsars, where the parallel tracks of the PPA represent the orthogonal extraordinary X and ordinary O eigen modes of strongly magnetized pair plasma. However, the frequency evolution of these high linearly polarized signals remains unexplored. In this work we explore the flux density spectral nature of high linearly polarized signals by studying the emission from PSR J0332+5434 over a frequency range between 300 MHz and 750 MHz, using the Giant Metrewave Radio Telescope. The pulsar average profile comprises of a central core and a pair of conal components. We find the high linearly polarized time samples to be broadband in nature and in many cases they resemble a narrow spiky feature in the conal regions. These spiky features are localised within a narrow pulse longitude, over the entire frequency range, and their spectral shapes sometimes resemble an inverted parabolic shape. In all such cases the PPA are exclusively along one of the orthogonal RVM tracks, likely corresponding to the X-mode. The inverted spectral shape can in principle be explained if the high linearly polarized emission in these time samples are formed due to incoherent addition of CCR from a large number of charged solitons (charge bunches) exciting the X-mode.