On the beam properties of radio pulsars with interpulse emission

TL;DR

This study uses polarization data from the Parkes telescope to analyze the geometry and emission heights of pulsars with interpulse emission, revealing low emission heights, under-filled beams, and a preference for trailing edge emission, with implications for beam structure models.

Contribution

It provides new constraints on pulsar emission geometry, suggesting larger emission heights at beam edges and favoring fan-like beam models over conal structures.

Findings

Emission heights are typically less than 3% of the light cylinder radius.

Pulsar emission beams are under-filled, with widths about 60% of the maximal beam.

Emission heights are larger at the beam edges than at the center.

Abstract

In the canonical picture of pulsars, radio emission arises from a narrow cone centered on the star's magnetic axis but many basic details remain unclear. We use high-quality polarization data taken with the Parkes radio telescope to constrain the geometry and emission heights of pulsars showing interpulse emission, and include the possibility that emission heights in the main and interpulse may be different. We show that emission heights are low in the centre of the beam, typically less than 3\% of the light cylinder radius. The emission beams are under-filled in longitude, with an average profile width only 60% of the maximal beam width and there is a strong preference for the visible emission to be located on the trailing part of the beam. We show substantial evidence that the emission heights are larger at the beam edges than in the beam centre. There is some indication that a fan-like emission beam explains the data better than conal structures. Finally, there is a strong correlation between handedness of circular polarization in the main and interpulse profiles which implies that the hand of circular polarization is determined by the hemisphere of the visible emission.