NGC 6362: The Least Massive Globular Cluster with Chemically Distinct Multiple Populations

Alessio Mucciarelli, Emanuele Dalessandro, Davide Massari, Michele Bellazzini, Francesco R. Ferraro, Barbara Lanzoni, Carmela Lardo, Maurizio Salaris, Santi Cassisi

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We present the first measure of Fe and Na abundances in NGC 6362, a low-mass globular cluster (GC) where first- and second-generation stars are fully spatially mixed. A total of 160 member stars (along the red giant branch (RGB) and the red horizontal branch (RHB)) were observed with the multi-object spectrograph FLAMES at the Very Large Telescope. We find that the cluster has an iron abundance of [Fe/H] = -1.09 ± 0.01 dex, without evidence of intrinsic dispersion. On the other hand, the [Na/Fe] distribution turns out to be intrinsically broad and bimodal. The Na-poor and Na-rich stars populate, respectively, the bluest and the reddest RGBs detected in the color-magnitude diagrams including the U filter. The RGB is composed of a mixture of first- and second-generation stars in a similar proportion, while almost all the RHB stars belong to the first cluster generation. To date, NGC 6362 is the least massive GC where both the photometric and spectroscopic signatures of multiple populations have been detected. Based on data obtained at the Very Large Telescope under the programs 073.D-0211 and 093.D-0618.
Original languageEnglish
Pages (from-to)73-80
Number of pages8
JournalThe Astrophysical Journal
Issue number2
Publication statusPublished - 2016


  • globular clusters: individual: NGC 6362
  • stars: abundances
  • techniques: spectroscopic

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