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We analyze new, high quality multicolor light curves of four overcontactbinaries: AK Her, HI Dra, V1128 Tau and V2612 Oph, and determine their orbitaland physical parameters using the modeling program of G. Djurasevic andrecently published results of radial velocity studies. The achieved precisionin absolute masses is between 10 and 20%, and in absolute radii between 5 and10%. All four systems are W UMa type binaries with bright or dark spotsindicative of mass and energy transfer or surface activity. We estimate thedistances and the ages of the systems using the luminosities computed throughour analysis, and perform an O-C study for V1128 Tau, which reveals a complexperiod variation that can be interpreted in terms of mass loss/exchange andeither the presence of the third body, or the magnetic activity on one of thecomponents. We conclude that further observations of these systems are neededto deepen our understanding of their nature and variability.

Photometric analysis of overcontact binaries AK Her, HI Dra, V1128 Tau and V2612 Oph