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Search for associations containing young stars (SACY)
II. Chemical abundances of stars in 11 young Associations in the Solar neighborhood

P. Viana Almeida, N. C. Santos, C. Melo, M. Ammler-von Eiff, C. A. O. Torres, G. R. Quast, J. F. Gameiro, M. Sterzik

Abstract
The recently discovered coeval, moving groups of young stellar objects in the solar neighborhood represent invaluable laboratories to study recent star formation and to search for high metallicity stars which can be included in future exo-planet surveys. In this study we derived through an uniform and homogeneous method stellar atmospheric parameters and abundances for iron, silicium and nickel in 63 post-T Tauri Stars from 11 nearby young associations. We further compare the results with two different pre-main sequence (PMS) and main sequence (MS) star populations. The stellar atmospheric parameters and the abundances presented here were derived using the equivalent width of individual lines in the stellar spectra through the excitation/ionization equilibrium of iron. Moreover, we compared the observed Balmer lines with synthetic profiles calculated for model atmospheres with a different line formation code. We found that the synthetic profiles agree reasonably well with the observed profiles, although the Balmer lines of many stars are substantially filled-in, probably by chromospheric emission. Solar metallicity is found to be a common trend on all the nearby young associations studied. The low abundance dispersion within each association strengthens the idea that the origin of these nearby young associations is related to the nearby Star Forming regions (SFR). Abundances of elements other than iron are consistent with previous results on Main Sequence stars in the solar neighborhood. The chemical characterization of the members of the newly found nearby young associations, performed in this study and intended to proceed in subsequent works, is essential for understanding and testing the context of local star formation and the evolutionary history of the galaxy.

Keywords
stars: pre-main sequence – stars: abundances – open clusters and associations: general – stars: fundamental parameters – solar neighborhood

Notes
Based on observations collected with the UVES spectrograph at the VLT/UT2 8.2-m Kueyen Telescope (ESO run ID. 079.C-556(A)) at the Paranal Observatory, Chile

Astronomy and Astrophysics
Volume 501, Number 3, Page 965
2009 July

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Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa Fundação para a Ciência e a Tecnologia
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