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Astron. Astrophys. 353, 722-728 (2000)


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

P.E. Nissen 1, Y.Q. Chen 1,2,3, W.J. Schuster 4 and G. Zhao 3

1 Institute of Physics and Astronomy, University of Aarhus, 8000 Aarhus C, Denmark
2 Department of Astronomy, Beijing Normal University, Beijing 100875, P.R. China
3 Beijing Astronomical Observatory, Chinese Academy of Sciences, Beijing 100012, P.R. China
4 Observatorio Astronomico National, UNAM, Apartado Postal 877, 22800 Ensenada, B.C., México

Received 7 October 1999 / Accepted 8 November 1999

Abstract

Sc and Mn abundances are determined for 119 F and G main-sequence stars with [FORMULA], representing stars from the thin disk, the thick disk and the halo. The results indicate that Sc behaves like an [FORMULA] 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] [FORMULA] at [FORMULA] to zero at solar metallicity. There appears to be a discontinuity or sharp increase of [Mn/Fe] at [FORMULA] 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.

Key words: nuclear reactions, nucleosynthesis, abundances – stars: abundances – stars: late-type – Galaxy: evolution – Galaxy: halo – Galaxy: solar neighbourhood

* Based on observations carried out at the European Southern Observatory, La Silla, Chile, and Beijing Astronomical Observatory, Xinglong, China

Send offprint requests to: P.E. Nissen (pen@obs.aau.dk)

© European Southern Observatory (ESO) 2000

Online publication: December 17, 1999

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