Electromagnetic cascades in early-type binary systems

M. ORELLANA; ROMERO, GUSTAVO E; L. J. PELLIZZA

Congreso; Reunion Anual de la Asociacion Argentina de Astronomia; 2005

Many of the available models for Galactic high-energy gamma-ray sources are related to binary systems. In fact, the new generation of Cherenkov telescopes have recently confirmed that some binaries containing a massive early-type star are the source of TeV gamma-ray photons. In those systems, the radiative stellar field provides a suitable target for the absorption of gamma-ray photons. Energetic electron-positron pairs are then created. These leptons, in turn, boost the stellar photons to high-energies via Inverse Compton scattering. Under favourable conditions, the gamma-ray absorption and production mechanisms can proceed very fast, so an electromagnetic cascade arises. As a result, the energy of the original photons is distributed between a certain number of secondary particles and photons of lower energy. We have developed a computational code to perform Monte Carlo simulations of one-dimensional cascades traversing the anisotropic radiation field of an early-type star. In this work we present results of some simulations, and point out the relevance of the problem for the correct estimation of detectable spectra at energies greater than some GeVs.