Modelling the light curves of PSR B1259-63/LS 2883-II.The effects of anisotropic pulsar wind and Doppler-boosting

TL;DR

This paper models the light curves of PSR B1259-63/LS 2883, explaining the asymmetric peaks and the GeV flare through anisotropic pulsar wind effects and Doppler-boosted emission.

Contribution

It introduces an anisotropic pulsar wind model and Doppler-boosting effects to explain observed asymmetries and flares in the system's light curves.

Findings

Anisotropic pulsar wind significantly influences light curve asymmetry.

Doppler-boosted synchrotron emission explains the GeV flare.

Model reproduces asymmetric two-peak profiles in X-ray and TeV bands.

Abstract

PSR B1259-63/LS 2883 is a binary system in which a 48-ms pulsar orbits around a Be star in a high eccentric orbit with a long orbital period of about 3.4 yr. It is special for having asymmetric two-peak profiles in both the X-ray and the TeV light curves. Recently, an unexpected GeV flare was detected by $Fermi$ gamma-ray observatory several weeks after the last periastron passage. In this paper, we show that this observed GeV flare could be produced by the Doppler-boosted synchrotron emission in the bow shock tail. An anisotropic pulsar wind model, which mainly affects the energy flux injection to the termination shock in different orbital phase, is also used in this paper, and we find that the anisotropy in the pulsar wind can play a significant role in producing the asymmetric two-peak profiles in both X-ray and TeV light curves. The X-ray and TeV photons before periastron are mainly produced by the shocked electrons around the shock apex and the light curves after periastron are contributed by the emission from the shock apex and the shock tail together, which result in the asymmetric two-peak light curves.