Sc and Mn abundances in disk and metal-rich halo stars

Abstract

Sc and Mn abundances are determined for 119 F and G main-sequence stars with -1.4 < [Fe/H] < +0.1, representing stars from the thin disk, the thick disk and the halo. The results indicate that Sc behaves like an alpha-element, showing a decreasing [Sc/Fe] with increasing metallicity in disk stars and a dual pattern in the kinematically selected halo stars. In contrast, Mn shows an increase from [Mn/Fe] = -0.5 at [Fe/H] = -1.4 to zero at solar metallicity. There appears to be a discontinuity or sharp increase of [Mn/Fe] at [Fe/H] = -0.7 corresponding to the transition between the thick and the thin disk. It is discussed if supernovae of Type Ia are a major source of Mn in the Galactic disk or if the trend of [Mn/Fe] vs. [Fe/H] can be explained by nucleosynthesis in Type II supernovae with a strong metallicity dependence of the yield.