Left: Schematic representation of a massive star moving on an elliptic orbit around the SMBH. The phase of the star is labelled Φ_⋆ and its distance from the SMBH is labelled D. The observer (obs) is located at the angle α_obs with respect to the plane of the orbit and its phase is Φ_obs. β is the angle between the direction defined by the SMBH and the star and the direction defined by the SMBH and the observer. Right: The geometry of the interaction between the γ-ray photon (γ) and the soft photon (ε) from the star. L is the propagation distance of the γ ray and α is the incident angle of the colliding photons.