Metal-Poor Stars Observed with the Southern African Large Telescope II. An Extended Sample

Abstract

We present results from high-resolution (R ∼ 40, 000) spectroscopic observations of over 200 metalpoor stars, mostly selected from the RAVE survey, using the Southern African Large Telescope. We were able to derive stellar parameters for a total of 108 stars; an additional sample of 50 stars from this same effort was previously reported on by Rasmussen et al.. Among our newly reported observations, we identify 84 very metal-poor (VMP; [Fe/H] < −2.0, 53 newly identified) stars and 3 extremely metalpoor (EMP; [Fe/H] < −3.0, 1 newly identified) stars. The elemental abundances were measured for carbon, as well as several other 𝛼-elements (Mg, Ca, Sc, Ti), iron-peak elements (Mn, Co, Ni, Zn), and neutron-capture elements (Sr, Ba, Eu). Based on these measurements, the stars are classified by their carbon and neutron-capture abundances into carbon-enhanced metal-poor (CEMP; [C/Fe] > +0.70), CEMP sub-classes, and by the level of their 𝑟-process abundances. A total of 17 are classified as CEMP stars. There are 11 CEMP-𝑟 stars (8 newly identified), 1 CEMP-𝑠 star (newly identified), 2 possible CEMP-𝑖 stars (1 newly identified), and 3 CEMP-no stars (all newly identified) in this work. We found 11 stars (8 newly identified) that are strongly enhanced in 𝑟-process elements (𝑟-II; [Eu/Fe] > +0.70), 38 stars (31 newly identified) that are moderately enhanced in 𝑟-process elements (𝑟-I; +0.30 < [Eu/Fe] ≤ +0.70), and 1 newly identified limited-𝑟 star.

Dynamically Tagged Groups of Metal-Poor Stars II. The Radial Velocity Experiment Data Release 6

“…Based on their classification scheme, there are approximately 50 Group I CEMP stars, 55 Group II CEMP stars, and 5 Group III CEMP stars, with a number of stars that have ambiguous classifications. This list provides a useful reference for high-resolution follow-up targets, some of which has already begun (e.g., Rasmussen et al 2020 andZepeda et al 2021).…”