1996A&AS..120C.159W

The X-ray spectrum of the prominent galactic black hole candidate Cyg X-1 has historically been modeled by thermal Comptonization or Compton reflection models. However, data from instruments covering different energy ranges have produced different model parameters, indicating that broad band spectra should be used to constrain the models. To find a model which can overcome this problem, we have collected broad band data from 1keV to 1MeV. We describe this spectrum by a new self-consistent accretion disk corona model where the corona is situated above a cold disk. The coronal compactness is l_C=0.75 and the optical depth of the corona is τ_e=0.18, resulting in an equilibrium temperature of ≃150keV. We also report the tentative detection of a S Kα- and a Si Kα-fluorescent line, both being much weaker than the lines expected from our models.