Multi-wavelength emission region of gamma-ray pulsars

TL;DR

This paper models the multi-wavelength emission regions of gamma-ray pulsars using the outer gap model, explaining observed pulse behaviors and suggesting that emission altitude depends on inclination angle.

Contribution

It introduces a parametrized outer gap model that accounts for multi-wavelength emission and links emission altitude to inclination angle, refining pulsar emission understanding.

Findings

Outer gap model explains multi-wavelength pulse behavior.

Emission altitude correlates with inclination angle.

Low inclination angles imply emission from inner magnetosphere regions.

Abstract

Recent obserbations by Fermi Gamma-Ray Space Telescope of gamma-ray pulsars have revealed further details of the structure of the emission region. We investigate the emission region for the multi-wavelength light curve using outer gap model. We assume that gamma-ray and non-thermal X-ray photons are emitted from a particle acceleration region in the outer magnetosphere, and UV/optical photons originate above that region. We also assume that gamma-rays are radiated only by outwardly moving particles, whereas the other photons are produced by particles moving inward and outward. We parametrize the altitude of the emission region. We find that the outer gap model can explain the multi-wavelength pulse behavior. From observational fitting, we also find a general tendency for the altitude of the gamma-ray emission region to depend on the inclination angle. In particular, the emission region for low inclination angle is required to be located in very low altitude, which corresponds to the inner region within the last-open field line of rotating dipole in vacuum. This model suggests a modification of statistics about observed gamma-ray pulsars.