A Rotating Hollow Cone Anisotropy of TeV Emission from Binary Systems

We show that TeV γ-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 γ-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 γ-ray emission region above the orbital plane.