Propagation of gamma-rays in massive binary Cen X-3: Interaction of cascade gamma-rays with the massive star

We consider the propagation of very high energy (VHE) gamma-rays in the radiation field of the massive star of binary system Cen X-3. VHE gamma-rays or electrons, injected by the compact object close to the surface of a massive companion, develop inverse Compton pair (ICS) cascades. Based on the Monte Carlo simulations, we obtain the fraction of secondary cascade photons which collide with the surface of the massive companion in Cen X-3 system. The distribution of photons falling on the surface of the massive star is investigated. These photons interact with the atmosphere of the star and should excite different gamma-ray lines (nuclear, electron-positron annihilation line). We estimate that these gamma-ray lines can be likely detected by the INTEGRAL telescopes.