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Astron. Astrophys. 364, L6-L12 (2000)

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Letter to the Editor

Abundance analysis of two extremely metal-poor stars from the Hamburg/ESO Survey *

E. Depagne 1, V. Hill 2, N. Christlieb 3 and F. Primas 2

1 Observatoire de Paris-Meudon, 92125 Meudon Cedex, France (Eric.Depagne@obspm.fr)
2 European Southern Observatory, 85748 Garching, Germany ([vhill,fprimas]@eso.org)
3 Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany (nchristlieb@hs.uni-hamburg.de)

Received 10 August 2000 / Accepted 25 August 2000

Abstract

We report on the first high spectral resolution analysis of extremely metal-poor halo stars from the Hamburg/ESO objective-prism survey (HES). The spectra were obtained with UVES at VLT-UT2. The two stars under investigation (HE 1303-2708 and HE 1353-2735) are main-sequence turnoff-stars having metal abundances of [FORMULA] and -3.20, respectively. The stellar parameters derived from the UVES spectra are in very good agreement with those derived from moderate-resolution follow-up spectra. HE 1353-2735 is a double-lined spectroscopic binary.

The two stars nicely reproduce the strong scatter in [Sr/Fe] observed for extremely metal-poor stars. While we see a strong Sr II [FORMULA] Å line in the spectrum of HE 1303-2708 ([FORMULA]), we can only give an upper limit for HE 1353-2735 ([FORMULA]), since the line is not detected. We report abundances of Mg, Ca, Sc, Ti, Cr for both stars, and Co, Y for HE 1303-2708 only. These abundances do not show any abnormalities with respect to known trends for metal-poor stars. Lithium is also detected in these stars, to a level which places them among Lithium-plateau metal-poor dwarfs.

Key words: stars: abundances – stars: binaries: spectroscopic – stars: fundamental parameters – stars: individual: – stars: subdwarfs – surveys

* Based on observations collected at the European Southern Observatory, Paranal, Chile

Send offprint requests to: Eric.Depagne@obspm.fr

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© European Southern Observatory (ESO) 2000

Online publication: December 15, 2000
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