Astronomy and Astrophysics – Astrophysics
Scientific paper
Aug 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000a%26a...360.1077s&link_type=abstract
Astronomy and Astrophysics, Vol. 360, p.1077-1085
Astronomy and Astrophysics
Astrophysics
10
Stars: Abundances, Stars: Binaries: Spectroscopic, Stars: Population Ii, Stars: Individual: Bps Cs 22873-139, Nuclear Reactions, Nucleosynthesis, Abundances
Scientific paper
High-resolution spectra of the extremely metal-poor double-lined spectroscopic binary star BPS CS 22873-139 have been analyzed to determine the metallicity and abundance ratios for a number of elements. From the analysis of the collected radial velocities, new orbital elements are derived as well as an improved mass ratio. In spite of its extreme metal deficiency, [Fe/H]= -3.4, the abundance ratios of CS 22873-139 are not similar to those of a typical Population II star. In particular, the α-elements are not enhanced relative to iron, and the strontium abundance is very low. The abundance pattern of CS 22873-139 is compared to the patterns exhibited by other metal-poor stars which exhibit also very low strontium abundances. There is a large spread of elemental abundance ratios among these stars, suggesting that low strontium abundance may be associated with a variety of nucleosynthesis histories. The abundance ratios of CS 22873-139 are, surprisingly, very similar to those found in a common proper-motion pair HD 134439, HD 134440, even though the metallicity of this system is almost two dex higher, [Fe/H] = -1.7. The ratios are compared to those of another very metal-poor binary star BPS CS 22876-032. The unusual abundance pattern of CS 22873-139 is discussed (by comparison to the predicted yields of zero-metal SN II and hypernovae). The lithium doublet at 6707 Å is not detected in CS 22873-139, but an abundance of lithium consistent with the Spite plateau cannot be excluded, based on the present data. Based on observations made at the European Southern Observatory, La Silla, Chile
Beers Timothy C.
Cayrel Roger
Depagne E.
Hill Vanessa
Nordstrom Birgita
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