Modelling the light curves of Fermi LAT millisecond pulsars

TL;DR

This study compares different geometric models to fit radio and gamma-ray light curves of millisecond pulsars, revealing diverse best-fit parameters and trends related to pulsar inclination and luminosity.

Contribution

It systematically evaluates multiple geometric models against observational data, highlighting their relative effectiveness and uncovering trends in pulsar geometry.

Findings

Outer gap and two-pole caustic models fit most light curves.

Best-fit inclination angles are broadly distributed with clustering at large angles.

Outer gap models favor larger inclination angles, while two-pole caustic models suggest an inverse relation with luminosity.

Abstract

We modelled the radio and gamma-ray light curves of millisecond pulsars using outer gap, two-pole caustic, low-altitude slot gap, and pair-starved polar cap geometric models, combined with a semi-empirical conal radio model. We find that no model fits all cases, with the outer gap and two-pole caustic models providing best fits for comparable numbers of millisecond pulsar light curves. We find a broad distribution of best-fit inclination angles as well as a clustering at large observer angles. The outer gap model furthermore seems to require relatively larger inclination angles, while the two-pole caustic model hints at an inverse trend between inclination angle and pulsar spin-down luminosity.