Abundance ratio for 5 local stellar associations

Within the formulation of the s-process, it is difficult to create a higher Ba abundance without a similar increase in the s-process contributions to other heavy elements (La-Sm). Given that Ba is represented by strong lines of Ba II and La-Sm are represented by rather weak ionized lines, the suggestion, as previously made by other studies, is that the Ba abundance may be systematically overestimated by standard methods of abundance analysis perhaps because the upper reaches of the stellar atmospheres are poorly represented by standard model atmospheres.

A novel attempt to analyse the Ba I line at 5535{AA} gives a solar Ba abundance for stars with effective temperatures hotter than about 5800K but increasingly subsolar Ba abundances for cooler stars with apparent Ba deficiencies of 0.5dex at 5100K. This trend with temperature may signal a serious non-local thermodynamical equilibrium effect on the Ba I line.