A NEW PHOTOGRAPHIC C-M DIAGRAM FOR NGC-4833

A color-magnitude diagram for the galactic globular cluster NGC 4833, based on the photographic BV photometry of about 868 stars in a 12' x 12' field with an automatic measuring machine, is presented. It reache s the cluster main sequence turn-off point at V approximate to 19(m).2 ; the difference in V magnitudes between the turn-off and the horizont al branch being normal. This diagram, reaching near three magnitudes f ainter is clearly an improvement over the only two previous CMDs avail able in the literature, both published more than two decades ago by Al caino [A&A 13 (1971) 287] and Menzies [MNRAS 156 (1972) 207], from pho tographic photometry reduced with an iris photometer down to V approxi mate to 16.5. Indications have been found of the presence of a red gia nt branch bump, approximately at the same position with respect to the horizontal branch and main sequence turn-off as in NGC 5897. There is also some hint of the deficiency of stellar population of the subgian t branch just above the turn-off point, similar to that observed in so me other metal-poor globular clusters.