Open clusters are historically regarded as single-aged stellar populations representative of star formation within the Galactic disc. Recent literature has questioned this view, based on discrepant Na abundances relative to the field, and concerns about the longevity of bound clusters contributing to a selection bias: perhaps long-lived open clusters are chemically different to the star formation events that contributed to the Galactic disc. We explore a large sample of high-resolution Na, O, Ba and Eu abundances from the literature, homogenized as much as reasonable including accounting for non-local thermodynamic equilibrium (NLTE) effects, variations in analysis and choice of spectral lines. Compared to a template globular cluster and representative field stars, we find no significant abundance trends, confirming that the process producing the Na–O anticorrelation in globular clusters is not present in open clusters. Furthermore, previously reported Na enhancement of open clusters is found to be an artefact of NLTE effects, with the open clusters matching a subset of chemically tagged field stars.
- stars: abundances
- Galaxy: abundances
- Galaxy: formation
- open clusters and associations: general