NGC 6139: a normal massive globular cluster or a first-generation
  dominated cluster? Clues from the light elements
  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 +/- 0.015 +/- 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.
