Chemical analysis of the bulge globular cluster NGC 6553

Abstract

ABSTRACT Globular clusters are among the oldest objects in the Galaxy, thus their researchers are key to understanding the processes of evolution and formation that the galaxy has experienced in early stages. Spectroscopic studies allow us to carry out detailed analysis on the chemical composition of globular clusters. The aim of our research is to perform a detailed analysis of chemical abundances to a sample of stars of the bulge globular cluster NGC 6553, in order to determine chemical patterns that allow us to appreciate the phenomenon of Multiple Population in one of the most metal-rich Globular Clusters in the Galaxy. This analysis is being carried out with data obtained by FLAMES/GIRAFFE spectrograph, VVV survey and DR2 of Gaia mission. We analysed 20 red horizontal branch stars, being the first extensive spectroscopic abundance analysis for this cluster and measured 8 chemical elements (O, Na, Mg, Si, Ca, Ti, Cr, and Ni), deriving a mean iron content of [Fe/H] = −0.10 ± 0.01 and a mean of [α/Fe] = 0.21 ± 0.02, considering Mg, Si, Ca, and Ti (errors on the mean). We found a significant spread in the content of Na but a small or negligible in O. We did not find an intrinsic variation in the content of α and iron-peak elements, showing a good agreement with the trend of the bulge field stars, suggesting a similar origin and evolution.