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arXiv · 1906.09824

Chemical abundances in the metal-intermediate GC NGC 6723

Juliana Crestani·Alan Alves-Brito·Giuseppe Bono·Arthur A. Puls·Javier Alonso-García
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Abstract

We have performed a detailed spectral analysis of the inner halo Galactic globular cluster (GC) NGC 6723 using high resolution (R$\approx$ 22000-48000) spectra for for eleven red giant branch stars collected with MIKE (Magellan) and FEROS (MPG/ESO). This globular is located at the minimum of the bimodal metallicity distribution of GCs suggesting that it might be an excellent transitional system between metal-intermediate and metal-rich GCs. In spite of its metal-intermediate status, it is characterized by an extended horizontal branch and by a large number of RR Lyrae stars. We investigated abundances of a variety of species including light, $\alpha$-, Fe-peak, and neutron capture elements. We found a mean metallicity $[Fe/H]=-0.93 \pm 0.05$ dex, and a typical $\alpha$ -enrichment ($[\alpha/Fe] \approx 0.39$) that follows the trend of metal-poor and metal-intermediate GCs. The same outcome applies for light metals (Na, Al), Fe-peak (V, Cr, Mn, Fe, Co, Ni, Cu), $s$/$r$-process elements (Ba, Eu) and for the classical anti-correlation: Na-O and Mg-Al. The current findings further support the evidence that the chemical enrichment of NGC 6723 is in more line with metal-intermediate GCs and their lower metallicity counterparts, and it does not bring forward the prodrome of the metal-rich regime.

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Juliana Crestani, Alan Alves-Brito, Giuseppe Bono, Arthur A. Puls, Javier Alonso-García. 2019-06-24. Chemical abundances in the metal-intermediate GC NGC 6723. https://doi.org/10.1093/mnras/stz1674

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