The giants stars HE 0107-5240 and HE 0557-4840 and new searches for metal-poor stars

Abstract

We report on a new determination of the iron abundance of HE 0107-5240, based on the detection of two Fe II lines in an UV spectrum of the star, which yields [Fe/H]=-5.7. Another interesting metal-poor star recently discovered with Hamburg/ESO Survey (HES) is HE 0557-4840. With [Fe/H]=-4.8, it is the first star located in the "gap" in the metallicity distribution function of the galactic halo, in metallicity between the two stars known at [Fe/H]>-4.0. HE 0557-4840 is carbon-enhanced (i.e., [C/Fe]=+1.7). The abundance ratios of the heavier elements are similar to those seen in the majority of the metal-poor stars at [Fe/H]>-4.0. We also describe two upcoming wide-angle surveys which will be used for searches for metal-poor stars: The Southern Sky Survey (SSS), and a stellar survey to be conducted with the Chinese LAMOST telescope. These efforts are expected to increase the number of known extremely metal-poor stars, including stars below [Fe/H]=-5.0, by about two orders of magnitude. Show more