Absolute dimensions of the A-type eclipsing binary V364 Lacertae

We present photoelectric observations in B and V, as well as spectroscopic observations of the 7.3 day period double-lined eclipsing binary V364 Lacer tae. From the analysis of the light curves and the radial velocity curves w e have determined the absolute dimensions of the components with high preci sion (less than or similar to 1%). The masses for the primary and secondary are M-A = 2.333 +/- 0.015 M-. and M-B = 2.296 +/- 0.025 M-., respectively, and the radii are R-A = 3.307 +/- 0.038 R-. and R-B = 2.985 +/- 0.035 R-.. We derive also effective temperatures of T-eff(A) = 8250 +/- 150 K and T-e ff(B) = 8500 +/- 150 K, and projected rotational velocities of v(A) sin i = 45 +/- 1 km s(-1) and v(B) sin i = 15 +/- 1 km s(-1). Evolutionary tracks from current stellar evolution models are in good agreement with the observ ations for a system age of log t = 8.792 (6.2 x 10(8) yr) and for solar met allicity. Hints of a lower metallicity from spectroscopy and photometry app ear to be ruled out by these models, but a definitive comparison must await a more accurate spectroscopic abundance determination. Analysis of all ava ilable eclipse timings along with our radial velocities of this moderately eccentric system (e = 0.2873 +/- 0.0014) has revealed a small but significa nt motion of the line of apsides of (omega) over dot = 0.00258 +/- 0.00033 deg cycle(-1), corresponding to an apsidal period of U = 2810 +/- 360 yr. T he contribution from general relativity effects is significant (similar to 17%). A comparison with predictions from interior structure models shows th e real stars to be less concentrated in mass than expected. Our measurement s of the projected rotational velocities indicate that the primary star is essentially pseudosynchronized (synchronized at periastron), while the seco ndary is spinning 3 times more slowly and is not yet synchronized. Both the rotational status of the stars and the nonzero eccentricity of the orbit a re consistent with the predictions from tidal theory, specifically for the radiative damping mechanism.