FLAMES observations of NGC6535

In particular, we need to figure out which stars imprinted the peculiar chemical signature of GCs. One of the best way is to study the light-element anti-correlations in a large sample of GCs, analysed homogeneously.

As part of our spectroscopic survey of GCs with FLAMES, we present here the results of our study of about 30 red giant member stars in the low-mass, low-metallicity Milky Way cluster NGC 6535. We measured its metallicity (finding [Fe/H]=-1.95, rms=0.04dex in our homogeneous scale) and other elements, in particular we concentrate here on O and Na abundances. These elements define the normal Na-O anti-correlation of classical GCs, making NGC 6535 perhaps the lowest mass cluster with confirmed presence of multiple populations.