Metal-poor Stars Observed with the Southern African Large Telescope
Kaitlin C. Rasmussen, Joseph Zepeda, Timothy C. Beers, Vinicius M. Placco, É. Depagne, Anna Frebel, Sarah Dietz, Tilman Hartwig
Abstract
Abstract We present the first release of a large-scale study of relatively bright ( V < 13.5) metal-poor stars observed with the Southern African Large Telescope (SALT), based on high-resolution spectra of 50 stars with a resolving power of R ∼ 40,000 and S/N ∼ 20 per pixel at 4300 Å. The elemental abundances of C, Sr, Ba, and Eu are reported, as well as several α -elements (Mg, Ca, Sc, Ti, and V) and iron-peak elements (Mn, Co, Ni, and Zn). We find a diverse array of abundance patterns, including several consistent with the signatures of carbon-enhanced metal-poor CEMP- i and CEMP- r stars. We find that 15 of 50 (30%) are carbon enhanced (with [C/Fe] > +0.70), and that a large fraction (26 of 50, 52%) are enhanced in r -process elements. Among the r -process-enhanced stars, five are strongly enhanced r -II ([Eu/Fe] > +1.0) stars (two of which are newly discovered) and 21 are newly discovered moderately enhanced r -I (+0.3 ≤ [Eu/Fe] ≤ +1.0) stars. There are eight stars in our sample that, on the basis of their abundances and kinematics, are possible members of the metal-weak thick-disk population. We also compare our measured abundances to progenitor-enrichment models, and find that the abundance patterns for the majority of our stars can be attributed to a single (rather than multiple) enrichment event.