Multi-band photometric study of the short period eclipsing binary ATO J007.0177+43.4841: physical properties and evolutionary status

We present a detailed photometric analysis of the newly identified binary system, \(ATO J007.0177+43.4841\), based on observations from the Kottamia Astronomical Observatory and the Zwicky Transient Facility. The system is classified as an A-type W UMa binary with a low mass ratio of \(q = 0.182 \pm 0.001\). A temperature difference of approximately 450 K between the components is observed, along with evidence of magnetic activity (manifested as the O’Connell effect) in the secondary star. This activity is attributed to a cool spot with a radius of 16 degrees and a temperature 30% lower than the surrounding region. The system’s geometry, characterized by an almost zero fill-out ratio, suggests that it is in a transient phase between detached and contact configurations, commonly referred to as shallow contact. This interpretation is further supported by an analysis of the system’s dynamical evolution and its thermal stability parameter, \(\mathcal {S} = -0.02\), indicating marginal stability. Additionally, the evolutionary status of the system is examined in the context of its position along the zero-age main sequence and terminal-age main sequence. The analysis suggests that the system’s evolution is primarily driven by angular momentum loss due to magnetic stellar wind and tidal coupling mechanisms.