Physical parameters of stars in the Scorpio-Centaurus OB association.

Walraven photometry is presented of established and probable members of the Scorpio-Centaurus OB association. For each star, effective temperature and surface gravity are derived using Kurucz (1979) atmosphere models. From the Straizys and Kuriliene (1981) tables, absolute magnitudes are calculated. Distance moduli and visual extinctions are determined for all stars. From a comparison of the HR-diagrams of the stars in each subgroup with theoretical isochrones, the ages of the three subgroups are derived. The distances to the three subgroups are shown to be different; there is a general trend (also within each subgroup) for the distances to be larger at higher galactic longitudes. The visual extinction in the youngest subgroup Upper-Scorpius, is well correlated with the IRAS 100-micron map. The distance toward the Ophiuchus dark clouds is found to be 125 pc, based on the photometric distances to the stars. Most of the early-type stars in Upper-Scorpius are located at the far side of the dark clouds.