High-precision geometry of a double-pole pulsar

TL;DR

This study precisely determines the geometry and beam shape of the pulsar PSR B0906-49, confirming it as an orthogonal rotator and providing insights into its emission structure and alignment, with implications for high-energy emission models.

Contribution

The paper presents highly-constrained geometric solutions for PSR B0906-49 using polarization data, establishing its orthogonal rotation and detailed beam structure for the first time.

Findings

PSR B0906-49 is an orthogonal rotator.

The emission height is approximately 230 km.

The beam structure of main pulse and interpulse are similar.

Abstract

High time resolution observations of PSR B0906-49 (or PSR J0908-4913) over a wide range of frequencies have enabled us to determine the geometry and beam shape of the pulsar. We have used the position angle traverse to determine highly-constrained solutions to the rotating vector model which show conclusively that PSR B0906-49 is an orthogonal rotator. The accuracy obtained in measuring the geometry is unprecedented. This may allow tests of high-energy emission models, should the pulsar be detected with GLAST. Although the impact parameter, beta, appears to be frequency dependent, we have shown that this is due to the effect of interstellar scattering. As a result, this pulsar provides some of the strongest evidence yet that the position angle swing is indeed related to a geometrical origin, at least for non-recycled pulsars. We show that the beam structures of the main pulse and interpulse in PSR B0906-49 are remarkably similar. The emission comes from a height of ~230 km and is consistent with originating in a patchy cone located about half way to the last open field lines. The rotation axis and direction of motion of the pulsar appear to be aligned.