Testing dissipative magnetosphere model light curves and spectra with FERMI pulsars

TL;DR

This study tests a dissipative pulsar magnetosphere model against Fermi LAT data, showing good agreement with observed gamma-ray emission features and revealing how conductivity varies with pulsar properties.

Contribution

The paper demonstrates that a dissipative magnetosphere model with finite conductivity can accurately reproduce observed gamma-ray pulsar light curves and spectra, advancing understanding of pulsar magnetospheric physics.

Findings

Model aligns well with observed gamma-ray pulsar features.

Conductivity increases with spin-down rate and decreases with age.

Identifies parameter sets fitting phase-resolved spectra of eight bright pulsars.

Abstract

We explore the emission properties of a dissipative pulsar magnetosphere model introduced by Kalapotharakos et al. (2014), comparing its high energy light curves and spectra, due to curvature radiation, with data collected by the Fermi LAT. The magnetosphere structure is assumed to be near the force-free solution. The accelerating electric field, inside the light-cylinder, is assumed to be negligible, while outside the light-cylinder it rescales with a finite conductivity ({\sigma}). In our approach we calculate the corresponding high energy emission by integrating the trajectories of test particles that originate from the stellar surface, taking into account both the accelerating electric field components and the radiation reaction forces. First we explore the parameter space assuming different value sets for the stellar magnetic field, stellar period, and conductivity. We show that the general properties of the model are in a good agreement with observed emission characteristics of young {\gamma}-ray pulsars, including features of the phase resolved spectra. Second we find model parameters that fit each pulsar belonging to a group of eight bright pulsars that have a published phase-resolved spectrum. The {\sigma} values that best describe each of the pulsars in this group show an increase with the spin-down rate $(\dot{E})$ and a decrease with the pulsar age, expected if pair cascades are providing the magnetospheric conductivity. Finally, we explore the limits of our analysis and suggest future directions for improving such models.