A rotating hollow cone anisotropy of TeV emission from binary systems

TL;DR

This paper proposes a model where TeV gamma-ray emission in binary systems exhibits a rotating hollow cone anisotropy pattern, explaining observed lightcurve features and constraining system geometry.

Contribution

It introduces a novel rotating hollow cone anisotropy model for TeV emission in binary systems, linking emission patterns to system geometry and orbital motion.

Findings

The model explains the two maxima in LS 5039's TeV lightcurve.

It constrains the inclination angle of the binary orbit.

It estimates the elevation of the gamma-ray emission region.

Abstract

We show that TeV gamma-ray emission produced via interactions of high-energy particles with anisotropic radiation field of a massive star in binary systems should have a characteristic rotating hollow cone anisotropy pattern. The hollow cone, whose axis is directed away from the massive star, rotates with the period equal to the orbital period of the system. We note that the two maxima pattern of the TeV energy band lightcurve of the gamma-ray loud binary LS 5039 can be interpreted in terms of this rotating hollow cone model. Adopting such an interpretation, we are able to constrain the geometry of the system - either the inclination angle of the binary orbit, or the elevation of the gamma-ray emission region above the orbital plane.