A combined model for the X-ray to gamma-ray emission of Cyg X-1

Abstract

We use recent data obtained by three (OSSE, BATSE, and COMPTEL) of four instruments on board the Compton Gamma Ray Observatory, to construct a model of Cyg X-1 which describes its emission in a broad energy range from soft X-rays to MeV gamma-rays self-consistently. The gamma-ray emission is interpreted to be the result of Comptonization, bremsstrahlung, and positron annihilation in a hot optically thin and spatially extended region surrounding the whole accretion disk. For the X-ray emission a standard corona-disk model is applied. We show that the Cyg X-1 spectrum accumulated by the CGRO instruments during a ~4 year time period between 1991 and 1995, as well as the HEAO-3 gamma1 and gamma2 spectra can be well represented by our model. The derived parameters match the observational results obtained from X-ray measurements.