Time series analysis of V815 Herculis photometry between 1984 and 1998

As a case study of the solar-stellar connection, we have analysed a prolong ed 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 rotati on of the starspots follows the solar law of differential rotation and the activity is confined within the same latitudinal range as in the Sun, havin g k = 0.189 and the spectral-type of G2v. Our analysis of the primary and s econdary minima of the seasonal light curves indicated that the regions of stronger activity have concentrated on one active longitude, which has main tained a constant rotation period of 1.(d)79244 for about 14 years. No regu lar activity cycle was detected in the mean brightness changes of V815 Her.