THE MOST METAL-POOR STARS. II. CHEMICAL ABUNDANCES OF 190 METAL-POOR STARS INCLUDING 10 NEW STARS WITH [Fe/H] ⩽ −3.5,,

By David Yong, J. Norris, M. Bessell, N. Christlieb, Martin Asplund, Timothy C. Beers, Paul Barklem, A. Frebel, S. Ryan. 2012

203 citations recorded by the source corpus.

We present a homogeneous chemical abundance analysis of 16 elements in 190 metal-poor Galactic halo stars (38 program and 152 literature objects). The sample includes 171 stars with [Fe/H] ⩽ −2.5, of which 86 are extremely metal poor, [Fe/H] ⩽ −3.0. Our program stars include 10 new objects with [Fe/H] ⩽ −3.5. We identify a sample of “normal” metal-poor stars and measure the trends between [X/Fe] and [Fe/H], as well as the dispersion about the mean trend for this sample. Using this mean trend, we identify objects that are chemically peculiar relative to “normal” stars at the same metallicity. These chemically unusual stars include CEMP-no objects, one star with high [Si/Fe], another with high [Ba/Sr], and one with unusually low [X/Fe] for all elements heavier than Na. The Sr and Ba abundances indicate that there may be two nucleosynthetic processes at lowest metallicity that are distinct from the main r-process. Finally, for many elements, we find a significant trend between [X/Fe] versus Teff, which likely reflects non-LTE and/or three-dimensional effects. Such trends demonstrate that care must be exercised when using abundance measurements in metal-poor stars to constrain chemical evolution and/or nucleosynthesis predictions.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/7f2ea4290ef7d1f81611509e7ac2816dc224ab0b

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In Astronomy and Astrophysics

1. A. Helmi
2. A. Frebel
3. Timothy C. Beers
4. C. Sneden
5. J. Norris
6. K. Venn
7. V. Hill
8. James S. Bullock

In Instrumentation

1. A. Helmi
2. A. Frebel
3. C. Sneden
4. K. Venn
5. Timothy C. Beers
6. J. Norris
7. V. Hill
8. James S. Bullock

Citations in the corpus

• A SEARCH FOR STARS OF VERY LOW METAL ABUNDANCE. VI. DETAILED ABUNDANCES OF 313 METAL-POOR STARS (2014, methodology): “To keep the comparisons manageable when comparing with other studies, we limit ourselves to two other studies that also examined large numbers of stars in common with the First Stars analysis, those of McWilliam et al. (1995b) and Yong et al. (2013).”
• Binarity in carbon-enhanced metal-poor stars (2014, background): “…in the Galactic halo with abundance determinations has bloomed recently; now over 150 stars with [Fe/H] < −3 have been examined in high-resolution studies (see for some recent overviews and results: Aoki et al. 2013; Yong et al. 2013a; Cohen et al. 2013; Spite et al. 2013; Placco et al. 2014).”
• THE MASS SPECTRUM OF THE FIRST STARS (2014, result): “The theoretical yields are compared with the observations of two metal-poor systems: (1) First is a metal-poor star that formed in the early universe and is traditionally adopted to study the early chemical evolution (e.g., Yong et al. 2013).”
• Near-Field Cosmology with Extremely Metal-Poor Stars (2015, background): “• A star, likely related to the above three (but which has only an upper limit of [C/Fe] < +1.7) is HE 2136−6030: with [Fe/H] = −2.9, it has [Mg/Fe] = 0.08, but [Si/Fe] = +1.20 (Yong et al. 2013a).”
• Chemical evolution with rotating massive star yields - I. The solar neighbourhood and the s-process elements (2018, background): “G A ] 2004; Frebel 2010; Yong et al. 2013; Roederer et al. 2014) confirmed the constantly high [α/Fe] ratio in low metallicities, and revealed a small dispersion for element ratios [X/Fe] up to the Fe-peak and the presence of a large dispersion in that ratio for heavier than Fe elements.”
• CARBON-ENHANCED METAL-POOR STAR FREQUENCIES IN THE GALAXY: CORRECTIONS FOR THE EFFECT OF EVOLUTIONARY STATUS ON CARBON ABUNDANCES (2014, background): “…al. (1995), Meléndez & Barbuy (2002), Placco et al. (2013, 2014b), Preston & Sneden (2001), Preston et al. (2006), Roederer et al. (2008a, 2008b, 2010, 2014), Simmerer et al. (2004), Sivarani et al. (2006), Sneden et al. (2003), Thompson et al. (2008), Yong et al. (2013), and Zhang et al. (2011).”
• The Pristine survey - I. Mining the Galaxy for the most metal-poor stars (2017, background): “Nevertheless, it seems that, at least in the halo, a very large fraction of observed stars (∼32%, Yong et al. 2013) still displays a high carbon abundance (Beers & Christlieb 2005).”