Information on globular clusters ( GC ) formation mechanisms can be gathered by studying the chemical signature of the multiple populations that compose these stellar systems .
In particular , we are investigating the anticorrelations among O , Na , Al , and Mg to explore the influence of cluster mass and environment on GCs in the Milky Way and in extragalactic systems .
We present here the results obtained on NGC 6139 which , on the basis of its horizontal branch morphology , had been proposed to be dominated by first-generation stars .
In our extensive study based on high resolution spectroscopy , the first for this cluster , we found a metallicity of [ Fe/H ] = -1.579 \pm 0.015 \pm 0.058 ( rms=0.040 dex , 45 bona fide member stars ) on the UVES scale defined by our group .
The stars in NGC 6139 show a chemical pattern normal for GCs , with a rather extended Na-O ( and Mg-Al ) anticorrelation .
NGC 6139 behaves like expected from its mass and contains a large fraction ( about two thirds ) of second-generation stars .