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We present stellar parameters and abundances of 13 elements for 18 very metal-poor (VMP; [Fe/H] $<$ -2.0) stars, selected as extremely metal-poor (EMP; [Fe/H] $<$ -3.0) candidates from SDSS and LAMOST survey. High-resolution spectroscopic…

Studies of the early chemical evolution of some larger dwarf galaxies ( $>10^7$ solar masses) are limited by the small number of stars known at low metallicities in these systems. Here we present metallicities and carbon abundances for…

Astrophysics of Galaxies · Physics 2020-10-14 Anirudh Chiti , Kylie Y. Hansen , Anna Frebel

We report Zn abundances for 18 very metal-poor stars studied in our previous work, covering the metallicity range -3.2 < [Fe/H] < -2.5. The [Zn/Fe] values of most stars show an increasing trend with decreasing [Fe/H] in this metallicity…

Solar and Stellar Astrophysics · Physics 2015-05-27 Satoshi Honda , Wako Aoki , Timothy C. Beers , Masahide Takada-Hidai

Ultra-faint dwarf galaxies recently discovered around the Milky Way (MW) contain extremely metal-poor stars, and might represent the building blocks of low-metallicity components of the MW. Among them, the Bo\"otes I dwarf spheroidal galaxy…

Astrophysics of Galaxies · Physics 2014-01-09 Miho N. Ishigaki , Wako Aoki , Nobuo Arimoto , Sakurako Okamoto

Extremely metal-poor stars are keys to understand the early evolution of our Galaxy. The ESO large programme TOPoS has been tailored to analyse a new set of metal-poor turn-off stars, whereas most of the previously known extremely…

We observe two metal-poor main sequence stars that are members of the recently-discovered Sylgr stellar stream. We present radial velocities, stellar parameters, and abundances for 13 elements derived from high-resolution optical spectra…

Astrophysics of Galaxies · Physics 2019-10-02 Ian U. Roederer , Oleg Y. Gnedin

We report on early results from a pilot program searching for metal-poor stars with LAMOST and follow-up high-resolution observation acquired with the MIKE spectrograph attached to the Magellan~II telescope. We performed detailed abundance…

Solar and Stellar Astrophysics · Physics 2015-01-14 Hai-Ning Li , Gang Zhao , Norbert Christlieb , Liang Wang , Wei Wang , Yong Zhang , Yonghui Hou , Hailong Yuan

We present basic stellar parameters of 99 late-type G giants based on high resolution spectra obtained by the High Dispersion Spectrograph attached to Subaru Telescope. These stars are targets of a Doppler survey program searching for…

Solar and Stellar Astrophysics · Physics 2015-05-30 Liang Wang , Yujuan Liu , Gang Zhao , Bun'ei Sato

Aims. This study aims to determine the level and constancy of the Spite plateau as definitively as possible from homogeneous high-quality VLT-UVES spectra of 19 of the most metal-poor dwarf stars known. Methods. Our high-resolution (R ~…

A non-LTE analysis of C I lines at 1.068-1.069 micron was carried out for selected 46 halo/disk stars covering a wide metallicity range (-3.7 <[Fe/H]< +0.3), based on the spectral data collected with IRCS+AO188 of the Subaru Telescope, in…

Solar and Stellar Astrophysics · Physics 2015-06-15 Yoichi Takeda , Masahide Takada-Hidai

We have determined Li abundances for eleven metal-poor turn-off stars, among which eight have [Fe/H]<-3, based on LTE analyses of high-resolution spectra obtained with the HDS on the Subaru telescope. The Li abundances for four of these…

We report the first extensive study of stellar Rb abundances. High-resolution spectra have been used to determine, or set upper limits on, the abundances of this heavy element and the associated elements Y, Zr, and Ba in 44 dwarfs and…

Astrophysics · Physics 2009-10-31 Jocelyn Tomkin , David L. Lambert

We report detailed analysis of high-resolution spectra of nine high velocity metal-rich dwarfs in the solar neighborhood. The stars are super metal-rich and 5 of them have [Fe/H]>=+0.4, making them the most metal-rich stars currently known.…

Astrophysics · Physics 2009-10-30 S. Castro , R. M. Rich , M. Grenon , B. Barbuy , J. K. McCarthy

The abundance of beryllium in the oldest, most metal-poor stars acts as a probe of early star formation and Galactic chemical evolution. We have analyzed high-resolution, high signal-to-noise Keck/HIRES spectra of 24 stars with [Fe/H] from…

Astrophysics of Galaxies · Physics 2011-02-11 Jeffrey A. Rich , Ann Merchant Boesgaard

Detailed chemical composition of stars is of prime interest for a range of topics in modern stellar astrophysics, such as the chemical evolution of the Galaxy or the formation, composition, and structure of exoplanets. In this work, we…

Solar and Stellar Astrophysics · Physics 2024-01-18 C. Duque-Arribas , H. M. Tabernero , D. Montes , J. A. Caballero

We present results from the analysis of high-resolution spectra obtained with the Keck HIRES spectrograph for a sample of 17 candidate extremely metal-poor (EMP) stars originally selected from commissioning data obtained with the SkyMapper…

We present our analysis of VLT/UVES and X-shooter observations of six very metal-poor stars, including four stars at [Fe/H]$\approx$$-3$ in the Fornax and Carina dwarf spheroidal (dSph) galaxies. To date, this metallicity range in these two…

Astrophysics of Galaxies · Physics 2024-06-26 R. Lucchesi , P. Jablonka , Á. Skúladóttir , C. Lardo , L. Mashonkina , F. Primas , K. Venn , V. Hill , D. Minniti

Sulfur is important: the site of its formation is uncertain, and at very low metallicity the trend of [S/Fe] against [Fe/H] is controversial. Below [Fe/H]=-2.0, [S/Fe] remains constant or it decreases with [Fe/H], depending on the author…

We present a comprehensive abundance analysis of 20 elements for 16 new low-metallicity stars from the Chemical Abundances of Stars in the Halo (CASH) project. The abundances have been derived from both Hobby-Eberly Telescope High…

We report the discovery of nine metal-poor stars with high levels of r-process enhancement (+0.81<[Eu/Fe]<+1.13), including six subgiants and three stars on the red horizontal branch. We also analyze four previously-known r-process-enhanced…

Solar and Stellar Astrophysics · Physics 2015-06-22 Ian U. Roederer , John J. Cowan , George W. Preston , Stephen A. Shectman , Chris Sneden , Ian B. Thompson