Monitoring of the X-ray binary HD 153919 (3U 1700-37).

Summary. Photo-electric reductions of three long series of observations of the X-ray binary RD 153919 (3 U ) in blue light (Walraven system) are presented. These observations cover the rising branch from the deepest minimum to the nearest maximum. They confirm that the star can go through this stage in 0.1 of the period only (van Genderen, 1973). The increase in brightness has no smooth course, but shows irregularities with a time scale of one hour. Key words: X-ray binaries - photometry