Absolute dimensions of eclipsing binaries. VI. The F-type system DM Virginis.

New, accurate, and complete uvby light curves (Andersen et al., 1983) of the late F-type, double-lined eclipsing binary DM Virginis have been analysed to determine the absolute dimensions, chemical composition, and evolutionary stage of the components. The favourable geometry of the system leads to very well-determined photometric elements, including the limb darkening coefficients. Above the Balmer discontinuity, the latter are 0.10 - 0.15 smaller than the theoretical values. Combination with Popper's (1971) spectroscopic elements yields very precise absolute masses and radii. The standard uvbyβ indices show DM Vir to have Hyades metal abundance. A low helium abundance (Y = 0.18) is then required to fit Hejlesen's (1980) theoretical models, with a resulting age of 4×10⁹yr.