Toward an Empirical Theory of Pulsar Emission. IX. On the Peculiar Properties and Geometric Regularity of Lyne & Manchester's "Partial Cone" Pulsars

TL;DR

This study reexamines 'partial cone' pulsars with new polarimetric data, revealing that most exhibit core/cone structures similar to normal pulsars, despite their asymmetric profiles, supporting the geometric regularity of pulsar emission models.

Contribution

The paper provides new observational evidence that 'partial cone' pulsars generally conform to the core/cone emission geometry, challenging previous notions of irregularity.

Findings

Most 'partial cone' pulsars exhibit core/cone structures.

Emission asymmetries are confined to specific polar cap regions.

Geometric scaling of conal dimensions aligns with polar cap size.

Abstract

Lyne & Manchester (1988) identified a group of some 50 pulsars they called "partial cones" which they found difficult to classify and interpret. They were notable for their asymmetric average profiles and asymmetric polarization position-angle (PPA) traverses, wherein the steepest gradient (SG) point fell toward one edge of the total intensity profile. Over the last two decades, this population of pulsars has raised cautions regarding the core/cone model of the radio pulsar-emission beam which implies a high degree of order, symmetry and geometric regularity. In this paper we reinvestigate this population "partial cone" pulsars on the basis of new single pulse polarimetric observations of 39 of them, observed with the Giant Meterwave Radio Telescope in India and the Arecibo Observatory in Puerto Rico. These highly sensitive observations help us to establish that most of these "partial cones" exhibit a core/cone structure just as did the "normal" pulsars studied in the earlier papers of this series. In short, we find that many of these "partial cones" are partial in the sense that the emission above different areas of their polar caps can be (highly) asymmetric. However, when studied closely we find that their emission geometries are overall identical to core/double cone structure encountered earlier-that is, with specific conal dimensions scaling as the polar cap size.