The ratio of profile peak separations as a probe of pulsar radio-beam structure

TL;DR

This paper introduces a new ratio-based method to analyze pulsar radio-beam structures, demonstrating that fan-shaped beam models better match observed data than traditional conal models, independent of emission altitude or dipole tilt.

Contribution

The study proposes the R_W ratio as a robust measure of beam shape, providing evidence that fan-shaped beams are more consistent with pulsar profile data than conal models.

Findings

Fan beam models fit the data better than conal models.

Conal models require strong observational biases to match data.

R_W ratio is independent of emission altitude and dipole tilt.

Abstract

The known population of pulsars contains objects with four and five component profiles, for which the peak-to-peak separations between the inner and outer components can be measured. These Q and M type profiles can be interpreted as a result of sightline cut through a nested cone beam, or through a set of azimuthal fan beams. We show that the ratio R_W of the components' separations provides a useful measure of the beam shape, which is mostly independent of parameters that determine the beam scale and complicate interpretation of simpler profiles. In particular, the method does not depend on the emission altitude and the dipole tilt distribution. The different structures of the radio beam imply manifestly different statistical distributions of R_W, with the conal model being several orders of magnitude less consistent with data than the fan beam model. To bring the conal model into consistency with data, strong effects of observational selection need to be called for, with 80% of Q and M profiles assumed to be undetected because of intrinsic blending effects. It is concluded that the statistical properties of Q and M profiles are more consistent with the fan-shaped beams, than with the traditional nested cone geometry.