2000A&A...362..223J

As a case study of the solar-stellar connection, we have analysed a prolonged time series of BV photometry of the chromospherically active binary V815 Her . The surface differential rotation in the rapidly rotating G5v primary caused changes of 4.6% in the seasonal photometric rotation periods. This would imply a differential rotation coefficient of k=0.184, if the rotation of the starspots follows the solar law of differential rotation and the activity is confined within the same latitudinal range as in the Sun, having k=0.189 and the spectral-type of G2v. Our analysis of the primary and secondary minima of the seasonal light curves indicated that the regions of stronger activity have concentrated on one active longitude, which has maintained a constant rotation period of 1.79244d for about 14 years. No regular activity cycle was detected in the mean brightness changes of V815 Her.