Variable stars of small amplitude IV. The case of HD 13970.

Summary. The visual binary star HD 13970 is found to be optically variable with a peak-to-peak amplitude of 0m.075 in the magnitude m . The method of Fourier analysis by Deeming (1975) is applied to 130 measurements covering a period of about nine years in the Geneva Photometric System. A quasi-sinusoidal light curve with a period P0 = 1.75462 + 0.00009 days is obtained. The most probable explanation for this light variability is that one of the visual components of HD 13970 is a close binary system. If this conjecture is correct, the real physical period, with two minima, would be twice P0, i.e. 3.50924 days. Key words: - close binary - multicolour photometry - Fourier analysis