The Bulge Cluster Origin (BulCO) survey with CRIRES at the ESO-VLT: a chemical screening of the Globular Cluster NGC 6553

TL;DR

This study presents a detailed chemical analysis of stars in the globular cluster NGC 6553, revealing its metallicity, element abundances, multiple populations, and in-situ formation within the Galactic bulge, as part of the BulCO survey.

Contribution

It provides the first comprehensive chemical screening of NGC 6553 using CRIRES, demonstrating its metal-rich nature and in-situ bulge origin with new chemical diagnostics.

Findings

NGC 6553 has a mean [Fe/H] = -0.20 dex, one of the most metal-rich in the Milky Way.

Detected multiple populations with Na, N, C spreads and Na-O anti-correlation.

Confirmed in-situ formation within the Galactic bulge using chemical DNA tests.

Abstract

In this paper we present the chemical screening of the stellar population belonging to the globular cluster NGC 6553 in the Galactic bulge. This study has been conducted in the contest of the Bulge Cluster Origin (BulCO) survey, an ESO-VLT Large Program currently ongoing with CRIRES in the NIR domain. This survey is performing an unprecedented chemical screening of 17 stellar systems orbiting the Milky Way bulge, with the aim of unveiling their origin and true nature. Here we present and discuss the abundances of 18 elements produced via distinct nucleosynthetic channels for 14 red giant branch stars belonging to NGC 6553. We found a mean [Fe/H] = -0.20 $\pm$ 0.01 dex, and about solar-scaled iron-peak elements, confirming that this is one of the most metal-rich globular clusters in the Milky Way. We also found [X/Fe] enhancement of $\alpha$ and several other light elements. Furthermore, we assess the presence of multiple populations typical of genuine globular clusters from the significant spreads in Na, N, and C, and an almost vertical Na-O anti-correlation. Finally, by using classical ([$\alpha$/Fe] vs [Fe/H]) and newly-defined ([V/Fe] and [Zn/Fe] vs [Fe/H]) "chemical DNA tests", we prove its in-situ formation within the Galactic bulge.