BVR photometry and H alpha spectroscopy of RS CVn type binary MM Herculis

The RS CVn type eclipsing binary MM Herculis was observed photo-electricall y using B, V and R filters in 1998 and 1999 and the light and colour curves were obtained. Spectroscopic observations were carried out in 1999. The ne w light and colour curves are anti-correlated with the observations of 1997 , i.e. the system is bluer when it is faintest. The variations of the brigh tnesses at each special phase (0.0, 0.25, 0.5, and 0.75) show an almost cyc lic change with a period of about 6 years. This value is in good agreement with the migration periods of the spots suggested by us previously. The out side-of-eclipse wave in the light curve shows a minimum at phase approximat e to0.50, and the mean colour of the system is the bluest at the same phase . When the spots located on the cooler component are seen around phase 0.50 , the amplitude of the light variation outside eclipse is larger than the o thers. Such variation may be caused by the effect of the hotter component. Spectroscopic observations of the system were carried out in the spectral r ange 5860-6700 Angstrom. The subtraction of a "synthetic" spectrum, built u p with spectra of inactive standard stars, allows us to detect an H alpha e mission excess only from the cool component. New radial velocity measuremen ts of the system were obtained and analyzed for the orbital parameters.