2000A&A...364L...6D

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 [Fe/H]=-2.85 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 λ 4215Å line in the spectrum of HE 1303-2708 ([Sr/Fe]=-0.08), we can only give an upper limit for HE 1353-2735 ([Sr/Fe]←1.2), 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.