Article (Scientific journals)
The chemical composition of the extreme halo stars. II - Green spectra of 20 dwarfs
Zhao, G.; Magain, Pierre
1990In Astronomy and Astrophysics, 238, p. 242-248
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Keywords :
DWARF STARS; METALLICITY; STELLAR ATMOSPHERES; STELLAR COMPOSITION; STELLAR SPECTRA; ABUNDANCE; CASSEGRAIN OPTICS; IRON; SCANDIUM; SODIUM; SPECTRAL LINE WIDTH
Abstract :
[en] The abundances of nine elements in the atmospheres of 20 extreme metal-poor stars are derived from green spectra obtained with the ESO Cassegrain Echelle Spectrograph (CASPEC). Sodium is found to be overabundant with respect to aluminum by as much as one dex. There is some scatter in Ca/Fe which cannot be accounted for by random errors in equivalent widths or atmospheric parameters. Scandium is overabundant relative to iron. Some barium lines may be affected by strong departures from local thermodynamic equilibrium. The nitrogen-rich metal-poor star HD 74000, which was found in previous work to be also Al-rich, also presents higher than usual abundances of Na and of s-process elements. It can thus be considered as a mild barium dwarf of Population II.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Zhao, G.;  European Southern Observatory, Garching, Federal Republic of Germany ; Nanjing University, People's Republic of China
Magain, Pierre  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique et traitement de l'image
Language :
English
Title :
The chemical composition of the extreme halo stars. II - Green spectra of 20 dwarfs
Publication date :
01 November 1990
Journal title :
Astronomy and Astrophysics
ISSN :
0004-6361
eISSN :
1432-0746
Publisher :
EDP Sciences, Les Ulis, France
Volume :
238
Pages :
242-248
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 01 February 2010

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