INFRARED ARRAY PHOTOMETRY OF BULGE GLOBULAR-CLUSTERS - I - COMBINED GROUND-BASED JK AND HST-VI PHOTOMETRY OF NGC-6553

JK infrared photometry for the bulge globular cluster NGC 6553, combin ed with high resolution visual VI observations are presented and discu ssed in connection with the bulge metal rich population. The infrared data were taken with IRAC2 at ESO 2.2m telescope while the optical cou nterparts are from Hubble Space Telescope (HST). We find a mean magnit ude for the horizontal branch of V-HB = 16.92, and K-HB = 12.42 +/- 0. 01. Assuming a reddening of E(B - V) = 0.7, the mean distance modulus is (m - M)(0) = 13.6 giving an heliocentric distance of 5.2 Kpc. This distance is slightly higher than that previously published by Ortolani et al. (1990, hereafter OBB90). The brightest giants have been detect ed at K similar to 6.5 and (V - K) = 13.10 transforming to M-K = -7.34 and (V - K)(0) = 11.20. which are exceptionally high values for a glo bular cluster. The metallicity has been found to be consistent with pr evious values and an average of [Fe/H] = -0.22 +/- 0.05 has been adopt ed. The helium abundance estimated via the R' method yields Y-p simila r to 0.28 +/- 0.03.