Modelling pulsed gamma-ray emissions from millisecond pulsars with double peaks

Abstract

ABSTRACT Pulsed γ-ray properties of 22 millisecond pulsars (MSPs) with double peaks are studied in the revised versions of the outer gap (OG) and the stripped wind (SW) models. The major differences between these two models are magnetic field structures, γ-ray production sites, and radiation mechanisms. In the models, γ-ray light curves of these MSPs are calculated through a Markov chain Monte Carlo (MCMC) method to pick best-fitting model parameters. Our results indicate that (1) both models can reproduce observed double-peak structures of the MSPs well, for most MSPs, a relatively large magnetic inclination angle (α ∼ 50°–90°) and small viewing angle (ζ ∼ 30°–90°) are obtained in the OG model, but a relatively small α ∈ (20°, 60°) and large ζ ∈ (70°, 150°) in the SW model; (2) phase-averaged spectra, cut-off energy, and γ-ray luminosity calculated in both models are consistent with observed those by Fermi-Large Area Telescope (LAT). Therefore, it may be concluded that the OG and the SW models for describing high-energy emissions of MSPs cannot be ruled out at present, and further studies are required.