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

TL;DR

This study presents detailed photometric analysis of four overcontact binary star systems, determining their physical parameters, distances, ages, and period variations, highlighting the need for further observations to understand their complex behaviors.

Contribution

It provides new high-quality multicolor light curves and physical parameter estimates for four overcontact binaries, incorporating recent radial velocity data and period analysis.

Findings

All systems are W UMa type binaries with surface activity.

Achieved mass and radius measurement precisions are 10-20% and 5-10%.

V1128 Tau shows complex period variations suggestive of mass transfer or third body presence.

Abstract

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