Constraining Pulsar Magnetosphere Geometry with Gamma-Ray Light Curves

TL;DR

This paper introduces a method to compare gamma-ray pulsar light curves with magnetosphere models, improving constraints on emission zones and magnetic field structures using Fermi LAT data.

Contribution

It presents a quantitative comparison technique for pulsar light curves with magnetosphere models, favoring Outer Gap models and force-free dipole fields.

Findings

OG models and force-free dipole fields are statistically preferred.

The method enhances understanding of pulsar emission zone geometry.

Application to full LAT data will reveal emission zone evolution.

Abstract

We demonstrate a method for quantitatively comparing gamma-ray pulsar light curves with magnetosphere beaming models. With the Fermi LAT providing many pulsar discoveries and high quality pulsar light curves for the brighter objects, such comparison allows greatly improved constraints on the emission zone geometry and the magnetospheric physics. Here we apply the method to Fermi LAT light curves of a set of bright pulsars known since EGRET or before. We test three approximate models for the magnetosphere structure and two popular schemes for the location of the emission zone, the Two Pole Caustic (TPC) model and the Outer Gap (OG) model. We find that OG models and relatively physical B fields approximating force-free dipole magnetospheres are preferred at high statistical significance. An application to the full LAT pulsar sample will allow us to follow the emission zone's evolution with pulsar spindown.