We report on the 0.5–200 keV spectral properties of Cyg X-1 observed at different epochs with the Narrow Field Instruments of the BeppoSAX satellite .
The source was in its soft state during the first observation of 1996 June .
In the second observation of 1996 September , the source had parameters characteristic to its hard state .
A soft X-ray excess , a broad Fe K \alpha line and Compton reflection are clearly detected in both states .
The soft-state broad-band continuum is well modeled by a disk blackbody ( accounting for the soft excess ) and Compton upscattering of the disk photons by a hybrid , thermal/non-thermal , plasma , probably forming a corona above the disk ( also giving rise to the Compton-reflection component ) .
In the hard state , the primary hard X-ray spectrum can be well modeled by Compton upscattering of a weak blackbody emission by a thermal plasma at a temperature of \sim 60 keV .
The soft excess is then explained by thermal Comptonization of the same blackbody emission by another hot plasma cloud characterized by a low value of its Compton parameter .
Finally , we find the characteristic ratio of the bolometric flux in the soft state to that in the hard state to be about 3 .
This value is much more compatible with theories of state transitions than the previously reported ( and likely underestimated ) value of 1.5 .