DEEP CCD PHOTOMETRY AND THE INITIAL MASS FUNCTION OF THE CORE OF THE OB CLUSTER BERKELEY-86

Based on photometry of deep CCD frames of the central region of the OB cluster Berkeley 86, we derive the cluster mass function. The absence of current star formation, and the cluster's young age of about 6 Myr s, leads to the conclusion that the initial mass function (IMF) and th e current mass function are identical for stars with m <10 m.. In the range of 1.2 - 20 m., an IMF with a slope of Gamma = -1.3 +/- 0.3 is f ound. This value agrees well with other recent determinations of young clusters IMFs which are close to the classical Salpeter IMF with Gamm a = -1.35. Sections of the IMF of Berkeley 86 that are significantly s teeper, or flatter, are most likely the result of a dip in the star's mass distribution in the range of 3.5-10 m.. Similar dips may have led to steep IMFs over narrow mass ranges, as reported in the literature for some other clusters. No sign for a low mass turn-over in the IMF o f Berkeley 86 is found for masses extending down to 0.85 m..