The activity pattern on MM Herculis: spots and faculae

The RS CVn type eclipsing binary MM Herculis was observed using B, V, and R filters in 1997 and the light and colour curves were obtained. The long-te rm (1976-1997) variations in the brightness and colour of the system were r evealed by examining 12 light and colour curves Thp reason fnr thp variatio ns in the B-V colour curves may be the photospheric bright facular structur es that surround starspots. The system is bluest when at its faintest. Migr ation periods of 5.8 and 5.9 years have been found fur the two spots or spo t groups, which are located on the cooler component. The spots that are loc ated within the longitude difference of 180 degrees seem to approach each o ther with a period of six years. In this case the amplitudes of the light c urves increase, the system's mean brightness decreases and its mean colour becomes bluer.