THE ADDITIONAL RADIATION OF CYG X-1 AT PRIMARY MINIMUM

New UBV-photoelectric observations of the well-known massive X-ray bin ary system Cyg X-1/V 1357 Cyg are obtained near the primary minimum. T he detailed analysis of these observations confirms the existence of a dditional blue radiation which appears as a narrow peak with an amplit ude of 0.01-0.02 mag near phase 0.00 on the light curve (the superior conjunction of the relativistic component), firstly detected by Lyuty (1985). This emission does not appear at every orbital cycle. The appe arance of this narrow peak of additional blue radiation on the light c urve of Cyg X-1 can be explained as the radiation of relativistic elec trons in the disturbed magnetic field of the optical star in frames of the model proposed by Ikhsanov and Fabrika (1990).