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Peculiar Metal Poor Stars as Guides to Key Processes in the Early Halo

Published online by Cambridge University Press:  06 January 2014

Johannes Andersen  and
Birgitta Nordström
Johannes Andersen
Affiliation:
Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100, Copenhagen, Denmark email: ja@nbi.ku.dk, birgitta@nbi.ku.dk Nordic Optical Telescope, Apartado 474, Santa Cruz de La Palma, Spain email: ja@not.iac.es
Birgitta Nordström
Affiliation:
Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100, Copenhagen, Denmark email: ja@nbi.ku.dk, birgitta@nbi.ku.dk
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Abstract

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Large photometric or spectroscopic surveys are used to sort stars into populations and define the main trends that characterise them, as diagnostics of their origin. Stars falling off the trends defined by the ‘normal’ stars are called ‘peculiar’ and typically eliminated in discussions of Galactic structure and evolution. In our programme on extremely metal-poor halo giants, we have recently focused on the small subgroup that is strongly enhanced in r-process elements, asking whether the chemical peculiarity is intrinsic to these stars or due to local surface pollution caused by mass transfer from a binary companion. Precise radial-velocity monitoring over several years turns out to disprove the binary hypothesis and has led to new insight in the processes of chemical enrichment in the early Galactic halo. An ongoing analogous programme on carbon-enhanced metal-poor giants is briefly described at the end.

Keywords

Galaxy: formationGalaxy: halostars: abundancesStars: carbonStars: chemically peculiarStars: abundancesBinaries: general
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 9 , Symposium S298: Setting the scene for Gaia and LAMOST , May 2013 , pp. 59 - 64
Copyright
Copyright © International Astronomical Union 2014 

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