We derive absolute dimensions of the early B-type detached eclipsing binary V453 Cygni ( B0.4 IV + B0.7 IV , P = 3.89 d ) , a member of the open cluster NGC 6871 .
From the analysis of new , high-resolution , spectroscopy and the UBV light curves of Cohen ( 1974 ) we find the masses to be 14.36 \pm 0.20 { M } _ { \odot } and 11.11 \pm 0.13 { M } _ { \odot } , the radii to be 8.55 \pm 0.06 { R } _ { \odot } and 5.49 \pm 0.06 { R } _ { \odot } , and the effective temperatures to be 26 600 \pm 500 K and 25 500 \pm 800 K for the primary and secondary stars , respectively .
The surface gravity values of \log g = 3.731 \pm 0.012 and 4.005 \pm 0.015 indicate that V453 Cyg is reaching the end of its main sequence lifetime .
We have determined the apsidal motion period of the system to be 66.4 \pm 1.8 yr using the technique of Lacy ( 1992 ) extended to include spectroscopic data as well as times of minimum light , giving a density concentration coefficient of \log k _ { 2 } = -2.226 \pm 0.024 .
Contaminating ( third ) light has been detected for the first time in the light curve of V453 Cyg ; previous analyses without this effect systematically underestimate the ratio of the radii of the two stars .
The absolute dimensions of the system have been compared to the stellar evolution models of the Granada , Geneva , Padova and Cambridge groups .
All model sets fit the data on V453 Cyg for solar helium and metal abundances and an age of 10.0 \pm 0.2 Myr .
The Granada models also agree fully with the observed \log k _ { 2 } once general relativistic effects have been accounted for .
The Cambridge models with convective core overshooting fit V453 Cyg better than those without .
Given this success of the theoretical predictions , we briefly discuss which eclipsing binaries should be studied in order to further challenge the models .