Constraints on viewing geometries from radio observations of $\gamma$-ray-loud pulsars using a novel method

TL;DR

This study uses a novel method to analyze radio observations of gamma-ray-loud pulsars, constraining their viewing geometries and revealing unexpected distributions of magnetic inclination angles.

Contribution

The paper introduces a new approach to constrain pulsar geometries by combining polarization data and beam models, challenging existing gamma-ray emission predictions.

Findings

Magnetic inclination angles peak at low values, contrary to models.

No correlation between radio-inferred and gamma-ray-inferred inclination angles.

Similar inclination distributions for pulsars with single and multiple radio components.

Abstract

We present radio intensity and polarisation profiles of 28 $\gamma$-ray-detected pulsars with the aim of putting constraints on their viewing geometries using data from the Parkes telescope. Constraints are formed both from the goodness-of-fit of the position angles to the Rotating Vector Model and from the beam opening angle considering aberration and retardation effects. Uncertainties on the relevant parameters are systematically taken into account in order to produce a more robust constraint, using a new approach. Surprisingly, we find that the distribution of the magnetic inclination angle ($\alpha$) in this subset of pulsars peaks at low values, contrary to the predictions of $\gamma$-ray models. We find a lack of correlation between these and a set of $\alpha$ values which were derived using $\gamma$-ray light curves, suggesting a problem in the interpretation of the data in one or both of these domains. Finally, we also show that the $\alpha$ distribution of pulsars with multiple radio components is no different to that of single-component pulsars.