BLANKETING EFFECTS IN THE VERY METAL-RICH BULGE GLOBULAR-CLUSTER TERZAN-1

We present BVRI and Gunn z CCD photometry for the bulge metal-rich globular cluster Terzan 1. The RGB shows an anomalous shape and the HB is extremely red. It is projected on a very metal-rich bulge population. We demonstrate that this cluster is strongly affected by blanketing in the B and V bands. From the I vs. (V - I) photometry, we obtained a reddening E(B - V) almost-equal-to 1.67, in agreement with previous JHK photometry estimate. We conclude that this cluster has a very high metallicity, as revealed by an anomalous RGB morphology, in particular in the Vvs. (B - V)diagram, and an excess blanketing of DELTA(V - I) approximately 0.8-0.9 relative to the Baade window population. These results should be considered in the modelisation of metal-rich atmospheres and analyses of metal-rich composite spectra and photometric indices.