Dynamic Evolution of the Eclipsing Overcontact Binary Star System BI CVn

We present a comprehensive analysis of BI CVn, an eclipsing overcontact binary system. New BVR photometric observations, combined with available spectroscopic data, were analyzed simultaneously using the Wilson-Devinney method to derive the orbital and physical parameters of the system. The resulting stellar parameters are M-1 = 0.58 +/- 0.01M(circle dot), M-2 = 1.42 +/- 0.02M(circle dot), R-1 = 0.88 +/- 0.01R(circle dot), R-2 = 1.31 +/- 0.01R(circle dot), with an orbital separation of a = 2.80 +/- 0.01R(circle dot). Based on all available CCD times of minimum light, including both ground-based and TESS observations, the (O - C) diagram of BI CVn was analyzed. The orbital period exhibits a long-term decrease at a rate of -2.3239 (+/- 0.0001) x 10(-8) day yr(-1), likely due to mass transfer from the more massive to the less massive component. Superimposed on this trend is a cyclic variation with a period of 56.84 +/- 0.08 yr, indicative of a light-travel time effect caused by a third body, whose estimated mass is 0.63 +/- 0.02M(circle dot). Using these derived parameters, we modeled the binary's evolution through non-conservative processes with the Binary Star Evolution code. The evolutionary tracks of the components were examined in multiple parameter planes, leading to an estimated merger timescale of approximately 2.70 Gyr.