O, Na, Ba and Eu abundance patterns in open clusters
  Open clusters are historically regarded as single-aged stellar populations
representative of star formation within the Galactic disk. 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 disk. We explore a
large sample of high resolution Na, O, Ba & Eu abundances from the literature,
homogenized as much as reasonable including accounting for 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
anti-correlation 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.
