2004A&A...415..559R

Sulfur abundances have been determined for ten stars to resolve a debate in the literature on the Galactic chemical evolution of sulfur in the halo phase of the Milky Way. Our analysis is based on observations of the Si lines at 9212.9, 9228.1, and 9237.5Å for stars for which the S abundance was obtained previously from much weaker Si lines at 8694.0 and 8694.6Å. In contrast to the previous results showing [S/Fe] to rise steadily with decreasing [Fe/H], our results show that [S/Fe] is approximately constant for metal-poor stars ([Fe/H]≲-1) at [S/Fe]≃+0.3. Thus, sulfur behaves in a similar way to the other α elements, with an approximately constant [S/Fe] for metallicities lower than [Fe/H]≃-1. We suggest that the reason for the earlier claims of a rise of [S/Fe] is partly due to the use of the weak Si 8694.0 and 8694.6Å lines and partly uncertainties in the determination of the metallicity when using FeI lines. The Si 9212.9, 9228.1, and 9237.5Å lines are preferred for an abundance analysis of sulfur for metal-poor stars.