Differential photoelectric photometry in V, B, and U has been obtained for the eclipsing binary MM Her, a member of the RS Canum Venaticorum class. The light outside eclipse was Fourier-analyzed to study the wave. The migration and amplitude of the wave and the mean light level of the system now have been monitored from 1976 through 1980. The phase of wave minimum has decreased from 0P.80 to 0P.25, the wave amplitude has varied between 0m.06 and 0m.12, and the mean light level has fluctuated between 0.94 and 0.99. Observations within eclipse revealed that the eclipses are partial, not total as previously thought, and a new time of mid-eclipse was found to be JD (hel.) = 2444 500.6665 ± 0d.0008. The Russell model was used to solve the 1980 light curve. Elements of the rectified light curve were i = 86.35 ± 0.09, rh = 0.070 ± 0.002, rc = 0.125 ± 0.001, Lh(V) = 0.585 ± 0.008 and Lh(B) = 0.683 ± 0.010. The geometric elements were forced on the pre-1980 light curves and found to be compatible. With these elements and previously obtained double-lined radial velocity curves, new absolute dimensions have been calculated: 1.18 Mꙩ and 1.58Rꙩ for the hotter star and 1.27 Mꙩ and 2.83 Rꙩ for the cooler star. By plotting color indices on the color-color curve, spectral types of G2V and K2IV were found, each uncertain by a couple of subclasses.
J.R. Sowell, D.S. Hall, G.W. Henry, E.W. Burke Jr., E.F. Milone "MM Herculis: An Eclipsing Binary of the RS CVn Type" Astrophysics and Space Science 90 (1983)