A re-visit of the phase-resolved X-ray and \gamma-ray spectra of the Crab pulsar

TL;DR

This study uses a modified outer gap model to explain the multi-frequency phase-resolved spectra of the Crab pulsar, accounting for emissions from both poles and multiple radiation mechanisms, aligning well with observed data.

Contribution

It introduces a refined outer gap model considering incomplete photon conversion and multiple emission regions, providing a comprehensive explanation of Crab pulsar spectra.

Findings

The model explains the phase-averaged spectrum from 100 eV to 10 GeV.

Different poles dominate emissions in various phases.

Multiple emission mechanisms are involved in the complex spectra.

Abstract

We use a modified outer gap model to study the multi-frequency phase-resolved spectra of the Crab pulsar. The emissions from both poles contribute to the light curve and the phase-resolved spectra. Using the synchrotron self-Compton mechanism and by considering the incomplete conversion of curvature photons into secondary pairs, the observed phase-averaged spectrum from 100 eV - 10 GeV can be explained very well. The predicted phase-resolved spectra can match the observed data reasonably well, too. We find that the emission from the north pole mainly contributes to Leading Wing 1. The emissions in the remaining phases are mainly dominated by the south pole. The widening of the azimuthal extension of the outer gap explains Trailing Wing 2. The complicated phase-resolved spectra for the phases between the two peaks, namely Trailing Wing 1, Bridge and Leading Wing 2, strongly suggest that there are at least two well-separated emission regions with multiple emission mechanisms, i.e. synchrotron radiation, inverse Compton scattering and curvature radiation. Our best fit results indicate that there may exist some asymmetry between the south and the north poles. Our model predictions can be examined by GLAST.