High-energy pulses and phase-resolved spectra by inverse Compton emission in the pulsar striped wind - Application to Geminga

TL;DR

This paper models high-energy pulsed gamma-ray emission from pulsars using inverse Compton scattering in the striped wind, successfully fitting Geminga's observed spectra and light curves above 10 MeV.

Contribution

It introduces a detailed 3D numerical model of inverse Compton emission in the pulsar striped wind, explaining phase-resolved spectra and pulse shapes.

Findings

Model accurately fits Geminga's gamma-ray spectra from 10 MeV to 10 GeV.

Reproduces pulse shape changes across energy bands.

Provides insights into pulsar emission mechanisms beyond traditional models.

Abstract

(abridged) Although discovered 40 years ago, the emission mechanism responsible for the observed pulsar radiation remains unclear. However, the high-energy pulsed emission is usually explained in the framework of either the polar cap or the outer gap model. The purpose of this work is to study the pulsed component, that is the light-curves as well as the spectra of the high-energy emission, above 10 MeV, emanating from the striped wind model. Gamma rays are produced by scattering off the soft cosmic microwave background photons on the ultrarelativistic leptons flowing in the current sheets. We compute the time-dependent inverse Compton emissivity of the wind, in the Thomson regime, by performing three-dimensional numerical integration in space over the whole striped wind. The phase-dependent spectral variability is then calculated as well as the change in pulse shape when going from the lowest to the highest energies. Several light curves and spectra of inverse Compton radiation with phase resolved dependence are presented. We apply our model to the well-known gamma-ray pulsar Geminga. We are able to fit the EGRET spectra between 10 MeV and 10 GeV as well as the light curve above 100 MeV with good accuracy.