Modeling the GeV emission of HESS J0632+057

TL;DR

This paper models the GeV emission of HESS J0632+057 assuming its compact companion is a pulsar, explaining observed orbital modulation through inverse Compton scattering of matter captured from the star's circumstellar disc.

Contribution

It introduces a pulsar-based emission model for HESS J0632+057, linking accretion disc formation and inverse Compton scattering to observed gamma-ray features.

Findings

Predicted GeV light curve with two peaks matching observations.

The larger peak occurs around 0.4 after periastron.

The smaller peak occurs between phases 0 and 0.1, with lower flux.

Abstract

The binary system HESS J0632+057 was recently detected by {Fermi} to possess orbital modulated GeV emission. In this paper, we study the possibility that the compact companion of HESS J0632+057 is a pulsar. Under such a presumption, we focus on the high energy emission mechanism of this system, which is as follows. The pulsar companion travels through the circumstellar disc of the main sequence star twice in each orbit, when some of the matter is gravity-captured. The captured matter develops an accretion disc around the pulsar, and the soft photons from which are inverse Compton scattered by the pulsar wind as the GeV emission from the system. With proper choice of parameters, SED and light curve which are in accordance with observations can be produced. We predict that the light curve of GeV emission has two peaks, the larger one is at around 0.4 after the periastron (or 0.1 after the X-ray maximum), while the smaller one is between phases 0 and 0.1, with integrated flux one forth of the larger one.