Evidence for alignment of the rotation and velocity vectors in pulsars. II. Further data and emission heights

TL;DR

This study observes 22 pulsars at multiple frequencies to examine the alignment of their rotation and velocity vectors and to estimate emission heights, confirming some alignment and revealing frequency-dependent emission regions.

Contribution

It provides new observational data on pulsar polarization and emission heights, supporting partial alignment of vectors and frequency-dependent emission origins.

Findings

Approximately half of the pulsars show plausible alignment of vectors.

Emission from the profile center originates lower in the magnetosphere.

Emission heights vary with frequency, with lower regions for central emission.

Abstract

We have conducted observations of 22 pulsars at frequencies of 0.7, 1.4 and 3.1 GHz and present their polarization profiles. The observations were carried out for two main purposes. First we compare the orientation of the spin and velocity vectors to verify the proposed alignment of these vectors by Johnston et al. (2005). We find, for the 14 pulsars for which we were able to determine both vectors, that 7 are plausibly aligned, a fraction which is lower than, but consistent with, earlier measurements. Secondly, we use profiles obtained simultaneously at widely spaced frequencies to compute the radio emission heights. We find, similar to other workers in the field, that radiation from the centre of the profile originates from lower in the magnetosphere than the radiation from the outer parts of the profile.