Revisiting BV & BW Draconis: Detailed Study of Intriguing Multiple System
The BV & BW Draconis system is a unique coplanar system of two eclipsing contact binaries. The main objective of this study is to develop a model based on new observations. The only model of the system was obtained 40 years ago. New photometric and spectroscopic data have been collected. Brightness measurements were performed using the differential aperture photometry method, while radial velocity measurements were performed using the cross-correlation method. The resulting curves were analyzed using the Wilson-Devinney method. The resulting model is similar to the one obtained previously; however, the masses of the four components are higher, and the differences are outside the margin of error. In the case of BW Dra, the photometric data indicate the presence of a spot on the star's surface. Based on our spectroscopic and photometric data, the latest measurements of eclipse times have been obtained. These results, together with other new measurements, confirm previous findings: both pairs exhibit eclipse time variability. In the case of BV Dra, the parabolic and sinusoidal trends were confirmed and refined. For the second pair, BW Dra, a change in behavior was observed that may be related to a change in period.