Absolute parameters of the eclipsing binary V821 Cas from UBVRI light curves and radial velocities

Abstract

We present UBVRI photometric measurements and spectroscopic observations of the double-lined eclipsing binary V821 Cas. The radial velocities were obtained by means of the cross-correlation technique. Simultaneous analyses of the multi-band light curves and RVs give the absolute parameters for the stars as: M${}_1$=2.05$\pm$0.07 M${}_{\odot }$, M${}_2$=1.63$\pm$0.06 M${}_{\odot }$, R${}_1$=2.31$\pm$0.03 R${}_{\odot }$, R${}_2$=1.39$\pm$0.02 R${}_{\odot }$, T${}_{ef{f}_1}$=9 400$\pm$400 K, and T${}_{ef{f}_2}$=8 600$\pm$400 K. Analysis of the O-C residuals yielded an apsidal motion in the binary at a rate of $\dot{\omega }$=0$^{\degr}$.0149$\pm0^{\degr}$.0023 cycle${}^{-1}$, corresponding to an apsidal period of U=118$\pm$19 yr. Subtracting the relativistic contribution we find that $\log k_{2obs}$=-2.590 which is in agreement with the value predicted by theoretical models. Comparison with current stellar evolution models gives an age of $5.6\times 10^8$ yr for the system.

11 pages, including 6 figures and 6 tables, accepted for publication in MNRAS