New insight into the origin of the GeV flare in the binary system PSR B1259-63 from the 2017 periastron passage

TL;DR

This paper investigates the 2017 GeV flare in PSR B1259-63, proposing a new model that explains the flare as a beamed emission resulting from pulsar wind interactions, supported by optical, X-ray, and gamma-ray data analysis.

Contribution

The paper introduces a novel model combining bremsstrahlung and inverse Compton processes to explain the GeV flare in PSR B1259-63, supported by multi-wavelength observations.

Findings

The GeV flare is explained as a beamed emission from pulsar wind interactions.

Optical observations from 2017 support the new model.

Reanalysis of X-ray and GeV data confirms the proposed emission mechanisms.

Abstract

PSR B1259-63 is a gamma-ray binary system hosting a radio pulsar orbiting around a O9.5Ve star, LS 2883, with a period of ~3.4 years. The interaction of the pulsar wind with the LS 2883 outflow leads to unpulsed broad band emission in the radio, X-rays, GeV and TeV domains. While the radio, X-ray and TeV light curves show rather similar behaviour, the GeV light curve appears very different with a huge outburst about a month after a periastron. The energy release during this outburst seems to significantly exceed the spin down luminosity of the pulsar and the GeV light curve and energy release varies from one orbit to the next. In this paper we present for the first time the results of optical observations of the system in 2017, and also reanalyze the available X-ray and GeV data. We present a new model in which the GeV data are explained as a combination of the bremsstrahlung and inverse Compton emission from the unshocked and weakly shocked electrons of the pulsar wind. The X-ray and TeV emission is produced by synchrotron and inverse Compton emission of energetic electrons accelerated on a strong shock arising due to stellar/pulsar winds collision. The brightness of the GeV flare is explained in our model as a beaming effect of the energy released in a cone oriented, during the time of flare, in the direction of the observer.