# Understanding the radio beam of PSR J1136+1551 through its singlepulses

## TL;DR

This study investigates the emission region of pulsar PSR J1136+1551 using single pulse observations, finding that a fan beam model better explains the frequency-dependent profile widening than the traditional conal beam model.

## Contribution

The paper introduces a comparison of conal and fan beam models using single pulse data to elucidate the pulsar's emission geometry, supporting the fan beam model as more accurate.

## Key findings

- Fan beam model better fits the observed data.
- Profile widening diversity explained by polarized mode propagation.
- Single pulse analysis constrains emission region geometry.

## Abstract

The frequency widening of pulsar profiles is commonly attributed to lower frequencies being produced at greater heights above the surface of the pulsar; so-called radius-to-frequency mapping. The observer's view of pulsar emission is a 1D cut through a 3D magnetosphere: we can only see that emission which points along our line of sight. However, by comparing the frequency evolution of many single pulses positioned at different phases, we can build up an understanding of the shape of the active emission region. We use single pulses observed with the Giant Metrewave Radio Telescope to investigate the emission region of PSR J1136+1551 and test radius-to-frequency mapping. Assuming that emission is produced tangential to the magnetic field lines and that each emission frequency corresponds to a single height, we simulate the single pulse profile evolution resulting from the canonical conal beam model and a fan beam model. Comparing the results of these simulations with the observations, we conclude that the emission region of PSR J1136+1551 is better described by the fan beam model. The diversity of profile widening behaviour observed for the single pulses can be explained by orthogonally polarized modes propagating along differing frequency-dependent paths in the magnetosphere.