# Chemical Abundances of Two Stars in the Large Magellanic Cloud Globular Cluster NGC~1718

## TL;DR

This study presents detailed chemical abundances of two stars in the LMC globular cluster NGC 1718, confirming its metallicity and lack of multiple populations, and showing its element trends align with LMC field stars.

## Contribution

First detailed chemical abundance analysis of two stars in NGC 1718, clarifying its metallicity and elemental trends, and challenging previous claims of very low Mg/Fe ratios.

## Key findings

- NGC 1718 has [Fe/H] ~ -0.55, indicating it is fairly metal-rich.
- No evidence of multiple populations based on two star analyses.
- Elemental abundances follow LMC field star trends, with specific deficiencies and enhancements.

## Abstract

Detailed chemical abundances of two stars in the intermediate-age Large Magellanic Cloud (LMC) globular cluster NGC~1718 are presented, based on high resolution spectroscopic observations with the MIKE spectrograph. The detailed abundances confirm NGC~1718 to be a fairly metal-rich cluster, with an average [Fe/H] ~ -0.55+/-0.01. The two red giants appear to have primordial O, Na, Mg, and Al abundances, with no convincing signs of a composition difference between the two stars---hence, based on these two stars, NGC~1718 shows no evidence for hosting multiple populations. The Mg abundance is lower than Milky Way field stars, but is similar to LMC field stars at the same metallicity. The previous claims of very low [Mg/Fe] in NGC~1718 are therefore not supported in this study. Other abundances (Si, Ca, Ti, V, Mn, Ni, Cu, Rb, Y, Zr, La, and Eu) all follow the LMC field star trend, demonstrating yet again that (for most elements) globular clusters trace the abundances of their host galaxy's field stars. Similar to the field stars, NGC~1718 is found to be mildly deficient in explosive $\alpha$-elements, but moderately to strongly deficient in O, Na, Mg, Al, and Cu, elements which form during hydrostatic burning in massive stars. NGC~1718 is also enhanced in La, suggesting that it was enriched in ejecta from metal-poor AGB stars.