1997A&A...320..586C

We present high-precision UBV(RI)_c photometry as well as soft X-ray light curves for the visual triple system HD 9770 and the visual binary HD 195434, obtained at the European Southern Observatory and extracted from the ROSAT all-sky survey, respectively. The optical photometry revealed that in both systems one component is a very short-period eclipsing binary showing also BY Dra-type variability. We have computed accurate orbital periods, deduced approximate physical parameters, spectral classifications, distances and X-ray luminosities and identified which component of each visual system is responsible for the optical variability. Futhermore, we find that both systems are variable in X-rays, but no correlation with the optical variability is seen.