Blanketing effects in the very metal-rich bulge globular cluster terzan 1

Abstract

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. lt 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) ≈ 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 V vs. (B – V) diagram, and an excess blanketing of ∆ (V – I) ~ 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.