STROMGREN AND H-BETA PHOTOMETRY OF OB ASSOCIATIONS AND OPEN CLUSTERS .1. ARA OB1

Stromgren and Hbeta photometry of 38 stars in the field of Ara OB1 is presented. The excesses, the absolute magnitudes and the temperatures of the stars have been obtained. The masses and the ages are also estimated, based on the models of Maeder & Meynet. Two different groups have been distinguished by their space locations at V0 - M(V) = 10.23 and 12.01 mag (assuming a normal extinction law). The more distant group is younger and more massive. The magnitude and the excess of the WR star MR62 point to its probable membership of this group. There are good reasons to suspect a value of the total-to-selective absorption ratio that is greater than the normal 3.2, which leads to a significant reduction of the true distance moduli.