PURE SCATTERED EMISSION AS AN EXPLANATION FOR THE HARD X-RAY-SPECTRA OF ACTIVE GALACTIC NUCLEI

We have developed a Monte Carlo code to compute the soft gamma-ray spectrum escaping from a simple active galactic nucleus's geometry. We assume a central source emitting a primary power law emission surrounded by matter which may be in the form of a torus and/or clouds. We derive a wide variety of spectral shapes resulting from different values of the basic parameters such as the column density, the power-law index, and the viewing angle. Comparisons with observations between 40 keV and 1 MeV show that the recent surprising results reported by the SIGMA and OSSE experiments can be explained by pure scattering of the power-law spectrum on the matter, while the central source is not seen by the observer.