Marek Gierlinski1, Andrzej A. Zdziarski2
1Astronomical Observatory, Jagiellonian University,
Cracow, Poland
2Copernicus Astronomical Center, Bartycka 18, 00-716
Warsaw, Poland
We present the results of 4 simultaneous observations of
Cygnus X-1 by Ginga and OSSE. The X-ray/gamma-ray
spectra can be described by an intrinsic continuum and a
component due to Compton reflection including an iron K-alpha
line. The intrinsic spectrum at X-ray energies is a power law
with a photon spectral index of Gamma 
1.6. However,
the broad-band intrinsic spectrum cannot be described in terms of
neither an exponentially cut-off power law, nor thermal
Comptonization. Some distribution of plasma temperature and
optical thickness is required. We have found a good approximation
of the intrinsic continuum by a two-temperature model in which
emission comes predominantly from the optically thin tau ~ 0.4
plasma of kTe ~ 150 keV, with an addition
from optically thick plasma of kTe ~
50 keV.