Modeling of Gamma-ray Millisecond Pulsar Light Curves Revealed by Fermi-LAT

TL;DR

This study models gamma-ray millisecond pulsar light curves using 3D emission simulations, revealing that most are best explained by slot gap and outer gap models with high-altitude emission, and distinguishing two sub-classes based on light curve features.

Contribution

First comprehensive 3D emission modeling of gamma-ray MSPs incorporating relativistic effects, identifying dominant emission geometries and subclass distinctions.

Findings

Most light curves fit by SG and OG models.

High-altitude emission is implied by all fits.

Distinct gamma-ray MSP subclasses are identified based on light curve and lag characteristics.

Abstract

Fermi Large Area Telescope (LAT) has recently detected 8 gamma-ray millisecond pulsars (MSPs), providing an unprecedented opportunity to probe the magnetospheres of these low-spin-down pulsars. We performed 3D emission modeling, including various Special Relativistic effects, in the context of pair-starved polar cap (PSPC), slot gap (SG), and outer gap (OG) pulsar models. Most of the light curves are best fit by SG and OG models, surprisingly indicating the presence of narrow accelerating gaps limited by robust pair production. All model fits imply high-altitude emission, and we observe exclusive differentiation of the current gamma-ray MSP population into two sub-classes: light curve shapes and lags across wavebands impose either PSPC or SG / OG-type geometries.