A Simple Model for Pulse Profiles from Precessing Pulsars, with Special Application to Relativistic Binary PSR B1913+16

TL;DR

This paper introduces a simple geometric model for pulse profiles from precessing pulsars, applies it to PSR B1913+16, and finds that minimal deviations from circular symmetry are needed to explain observed data.

Contribution

The paper presents a novel coordinate system and explores simple beam shapes to model pulse profiles, confirming the need for non-circular emission beams in PSR B1913+16.

Findings

Qualitative pulse profile matches are possible with simple models.

Circular symmetry is insufficient for accurate data fitting.

Minimal deviations from circular beams may suffice for explanation.

Abstract

We study the observable pulse profiles that can be generated from precessing pulsars. A novel coordinate system is defined to aid visualization of the observing geometry. Using this system we explore the different families of profiles that can be generated by simple, circularly symmetric beam shapes. An attempt is then made to fit our model to the observations of relativistic binary PSR B1913+16. It is found that while qualitatively similar pulse profiles can be produced, this minimal model is insufficient for an accurate match to the observational data. Consequently, we confirm that the emission beam of PSR B1913+16 must deviate from circular symmetry, as first reported by Weisberg and Taylor. However, the approximate fits obtained suggest that it may be sufficient to consider only minimal deviations from a circular beam in order to explain the data. We also comment on the applicability of our analysis technique to other precessing pulsars, both binary and isolated.