A rotating hollow cone anisotropy of TeV emission from binary systems

We show that TeV gamma-ray emission produced via interactions of high-energy particles with the 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 a period equal to the orbital period of the system. We note that the two-maxima pattern of the TeV energy band light curve 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.