On the difference between gamma-ray-detected and non-gamma-ray-detected pulsars

TL;DR

This study compares radio profiles of young pulsars with and without gamma-ray detection, revealing differences linked to energy loss and viewing geometry, and supporting current emission models.

Contribution

It demonstrates that pulsar gamma-ray detectability depends on energy loss rate and viewing angle, providing insights into pulsar emission geometry and model validation.

Findings

Non-gamma-ray pulsars have wider radio profiles.

Radio profile width correlates with gamma-ray peak separation.

Differences in detectability relate to viewing geometry and energy loss.

Abstract

We compare radio profile widths of young, energetic gamma-ray-detected and non-gamma-ray-detected pulsars. We find that the latter typically have wider radio profiles, with the boundary between the two samples exhibiting a dependence on the rate of rotational energy loss. We also find that within the sample of gamma-ray-detected pulsars, radio profile width is correlated with both the separation of the main gamma-ray peaks and the presence of narrow gamma-ray components. These findings lead us to propose that these pulsars form a single population where the main factors determining gamma ray detectability are the rate of rotational energy loss and the proximity of the line of sight to the rotation axis. The expected magnetic inclination angle distribution will be different for radio pulsars with and without detectable gamma rays, naturally leading to the observed differences. Our results also suggest that the geometry of existing radio and outer-magnetosphere gamma-ray emission models are at least qualitatively realistic, implying that information about the viewing geometry can be extracted from profile properties of pulsars.