X-Ray Spectrum and Iron Line Emission from Cygnus X-1

X-ray spectra from Cygnus X-1 were observed with Tenma in September 1983. An emission line around 6.5 keV with an equivalent width of about 60--80 eV was found during the observations, except for the phase near the superior conjunction of the X-ray star, where a weak (equivalent width less than 38 eV) or broad iron line was suggested. The absorption column density determined from the low-energy cut off shows significant change with a 5.6-day orbital period. This feature is explained by the stellar wind of the primary star.