Apsidal motion and physical parameters of the eclipsing binary system AR Cas

Using the four-channel automatic photoelectric photometer of the Sternberg Astronomical Institute’s Tien Shan Mountain Observatory, we have acquired accurate (σobs≈0.004m) W BV R brightness measurements for the eclipsing binary AR Cas during selected phases before eclipse ingress and after egress, as well as at the center of minima. A joint analysis of these measurements with other published data has enabled us to derive for the first time a self-consistent set of physical and geometrical parameters for the star and the evolutionary age of its components, t=(60±3)×106 years. We have found the period of the apsidal motion (Uobs=1100±160 years, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$\dot \omega _{obs} = 0^\circ .327 \pm 0^\circ .049$$ \end{document} years−1) and the apsidal parameter of the primary, logk2,1obs=−2.41±0.08, with the apsidal parameter being in good agreement with current models of stellar evolution. There is an ultraviolet excess in the primary’s radiation, Δ(U−B)=−0.12m and Δ(B−V)=−0.06m, possibly due to a metal deficiency in the star’s atmosphere.