Fundamental Data for Massive Stars Compared with Theoretical Models

A new grid of non rotating stellar models for the upper main sequence has been calculated for a variety of initial chemical compositions and assumed modes of evolution. Theoretical isochrones in the H-R diagram have then been constructed (with the help of published models for the post-main-sequence phases). A comparison of the theoretical data with observational data for massive members of eclipsing binary systems, clusters, and subgroups of associations in the (mass, spectral type)- and (mass, luminosity)-planes suggests that (1) currently adopted initial chemical compositions are probably correct (X 0.70, Z 0.03), although larger variations, particularly in Z , possibly occur; (2) chemical evolution, even in fast rotators, proceeds inhomogeneously; (3) the rotation of normal upper-main- sequence stars is approximately uniform; (4) mass exhange in a close binary system may lead to nonuniform rotation in the new primary component; and (5) mass loss seems to be rather small for normal massive stars, including supergiants. Two independent ages for each cluster or association containing supergiants are derived, by using (1) the spectral type of the main-sequence turnup in the H-R diagram and (2) the average luminosity of the evolved supergiants; the two ages generally agree well with each other, although they differ slightly for several stellar groups, probably as a result of a somewhat larger metals abundance than normal or a fast uniform rotation of the upper-main-sequence stars. The few available kinematic ages are usually much shorter than the nuclear ages.