Chemical analysis of eight giant stars of the globular cluster NGC 6366

TL;DR

This study provides a detailed chemical analysis of eight giant stars in the globular cluster NGC 6366, revealing its metallicity, lack of multiple populations, and similarities to other inner halo clusters.

Contribution

First detailed chemical analysis of NGC 6366's giant stars, characterizing its metallicity and stellar populations using high-resolution spectra.

Findings

Mean [Fe/H] = -0.60 ± 0.03 for NGC 6366

No significant star-to-star variation in element abundances

Short Na-O anticorrelation observed

Abstract

The metal-rich Galactic globular cluster NGC 6366 is the fifth closest to the Sun. Despite its interest, it has received scarce attention, and little is known about its internal structure. Its kinematics suggests a link to the halo, but its metallicity indicates otherwise. We present a detailed chemical analysis of eight giant stars of NGC 6366, using high resolution and high quality spectra (R > 40000, S/N > 60) obtained at the VLT (8.2 m) and CFHT (3.6 m) telescopes. We attempted to characterize its chemistry and to search for evidence of multiple stellar populations. The atmospheric parameters were derived using the method of excitation and ionization equilibrium of FeI and FeII lines and from those atmospheric parameters we calculated the abundances for other elements and found that none of the elements measured presents star-to-star variation greater than the uncertainties. We compared the derived abundances with those of other globular clusters and field stars available in the literature. We determined a mean [Fe/H] = -0.60 +- 0.03 for NGC 6366 and found some similarity of this object with M 71, another inner halo globular cluster. The Na-O anticorrelation extension is short and no star-to-star variation in Al is found. The presence of second generation stars is not evident in NGC 6366.