Photometric light curve analysis of three overcontact binary systems: ATO J255.8159+16.8821, CRTS J034336.4+264312, and NSVS 2669503.

Multi-band photometric observations of three contact binaries (ATO J255.8159+16.8821, CRTS J034336.4+264312, and NSVS 2669503) were carried out using the 1.88 m telescope at the Kottamia Astronomical Observatory (KAO) in Egypt. New times of minima for all three systems have been calculated. In particular, for NSVS 2669503, we performed an [Formula: see text] analysis to investigate period variations. The results indicate a decreasing orbital period, with a rate of [Formula: see text] days yr[Formula: see text]. Analysis using the Wilson-Devinney (W-D) program revealed that all three systems are A-subtype contact binaries with mass ratios (q) of 0.47, 0.34, and 0.28, respectively. The results showed that ATO J255.8159+16.8821 exhibits the O'Connell effect, while the other two systems (CRTS J034336.4+264312 and NSVS 2669503) have a symmetric light curve. The fill-out factors of the systems were determined to be 0.204, 0.157, and 0.069, respectively, indicating all three systems are shallow contact systems. To understand their evolutionary status, mass-luminosity and mass-radius diagrams were plotted. These diagrams indicate that the primary components of the three systems are main sequence stars, whereas the less massive stars have evolved beyond the main sequence. The dynamical evolution of the systems is also discussed.