Modeling Pulsar Gamma-Ray Light Curves Using Realistic Magnetospheric Geometries

TL;DR

This paper presents the first calculations of pulsar gamma-ray light curves using realistic force-free magnetospheric models, improving understanding of emission regions and light curve features in comparison to traditional vacuum dipole models.

Contribution

It introduces the use of force-free magnetic field models for pulsar light curve simulations, highlighting differences from vacuum dipole models and implications for interpreting observations.

Findings

Force-free models better reproduce double-peak profiles.

Emission mainly occurs near the light cylinder.

Outer-gap models typically produce one peak.

Abstract

Gamma-ray emission from pulsars is thought to arise from accelerating regions in pulsar's outer magnetosphere. The shape of the light curves is thus sensitive to the details of the magnetic geometry of the magnetosphere. In this work, we show the first calculations of light curves from the more realistic force-free field under the framework of conventional emission models. We compare the properties of gamma-ray emission between the commonly used vacuum dipole magnetic field and the new force-free field. We discuss the role of the polar cap shape and aberration effect on the appearance of the light curves as well as the formation of caustics on the sky map. With the force-free field, the double-peak pulse profile is best reproduced if the emission zone lies in a thin layer just outside the current sheet, and the peaks are mainly contributed from regions near the light cylinder. The conventional two-pole caustic model can produce up to four peaks in general, while the conventional outer-gap model can normally produce only one peak. These results will be useful for interpreting Fermi telescope observations.