The Nature of the Light Variation of the Unique Binary DK CVn

We present BVR observations of DK CVn from 2007 and 2008. We analysed the BVR light curves of the system and obtained the system's parameters. Using the `q-search' method, we measured the mass ratio of the system (q) as 0.55. Taking the temperature of the primary component as 4040K, the temperature of the secondary was found to be 3123K. Several flares were detected, and the distributions of flare equivalent duration versus flare total duration were modelled using the One-Phase Exponential Association Function for these flares. The parameters of the model demonstrated that the flares are the same as those detected from UV Ceti stars. We also demonstrate that the variation at out-of-eclipse must be caused by some cool spot(s) on one of the components. The star is found to show two active longitudes in which the spots are mainly formed. Consequently, this study reveals that DK CVn should be a chromospherically active binary star.