Exploring the Origin of Lithium, Carbon, Strontium and Barium with four new Ultra Metal-Poor Stars

Abstract

We present an elemental abundance analysis for four newly discovered ultra metal-poor stars from the Hamburg/ESO survey, with $[Fe/H]\le -4$. Based on high-resolution, high signal-to-noise spectra, we derive abundances for 17 elements in the range from Li to Ba. Three of the four stars exhibit moderate to large over-abundances of carbon, but have no enhancements in their neutron-capture elements. The most metal-poor star in the sample, HE~0233$-$0343 ($[Fe/H]=-4.68$), is a subgiant with a carbon enhancement of $[C/Fe]=+3.5$, slightly above the carbon-enhancement plateau suggested by Spite et al. No carbon is detected in the spectrum of the fourth star, but the quality of its spectrum only allows for the determination of an upper limit on the carbon abundance ratio of $[C/Fe]<+1.7$. We detect lithium in the spectra of two of the carbon-enhanced stars, including HE~0233$-$0343. Both stars with Li detections are Li-depleted, with respect to the Li plateau for metal-poor dwarfs found by Spite \& Spite. This suggests that whatever site(s) produced C either do not completely destroy lithium, or that Li has been astrated by early-generation stars and mixed with primordial Li in the gas that formed the stars observed at present. The derived abundances for the $\alpha$-elements and iron-peak elements of the four stars are similar to those found in previous large samples of extremely and ultra metal-poor stars. Finally, a large spread is found in the abundances of Sr and Ba for these stars, possibly influenced by enrichment from fast rotating stars in the early universe.

9 pages, 6 figures

References in corpus (19)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• Two Stellar Components in the Halo of the Milky Way
• Nucleosynthetic signatures of the first stars
• Carbon Enhanced Metal-Poor Stars. I. Chemical Compositions of 26 Stars
• An extremely primitive halo star
• Very low metallicity massive star models: Pre-SN evolution and primary nitrogen production
• HE 0557-4840 - Ultra-Metal-Poor and Carbon-Rich
• NLTE abundances of Mn in a sample of metal-poor stars
• Probing the Formation of the First Low-Mass Stars with Stellar Archaeology
• The s process in massive stars at low metallicity. Effect of primary N14 from fast rotating stars
• Binarity in Carbon-Enhanced Metal-Poor stars
• Silver and palladium help unveil the nature of a second r-process
• First stars X. The nature of three unevolved Carbon-Enhanced Metal-Poor stars
• The chemical compositions of the extreme halo stars HE0107-5240 and HE1327-2326 inferred from 3D hydrodynamical model atmospheres
• From First Stars to the Spite Plateau: a Possible Reconciliation of Halo Stars Observations with Predictions from Big Bang Nucleosynthesis
• Broadband UBVRI Photometry of Horizontal-Branch and Metal-Poor Candidates from the HK and Hamburg/ESO Surveys. I
• Lithium abundances in CEMP stars
• Light element abundances in carbon-enhanced metal-poor stars
• Measuring the Balmer Jump and Effective Gravity in FGK Stars

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• Observational Constraints on First-Star Nucleosynthesis. I. Evidence for Multiple Progenitors of CEMP-no Stars
• TOPoS: II. On the bimodality of carbon abundance in CEMP stars. Implications on the early chemical evolution of galaxies
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• Faint Population III supernovae as the origin of the most iron-poor stars
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• High-resolution spectroscopy of extremely metal-poor stars from SDSS/SEGUE. III. Unevolved Stars with $[Fe/H]\lesssim -3.5$
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• J0815+4729: A chemically primitive dwarf star in the Galactic Halo observed with Gran Telescopio Canarias
• Tracing Pop III supernovae with extreme energies through the Sculptor dwarf spheroidal galaxy
• The energy distribution of the first supernovae
• Pre-supernova mixing in CEMP-no source stars
• On the 12C/13C isotopic ratio at the dawn of chemical evolution
• The evolution of Lithium: implications of a universal Spite plateau
• The Pristine survey XIV: chemical analysis of two ultra-metal-poor stars
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• Espresso observations of HE 0107$-$5240 and other CEMP-no stars with $[Fe/H]\le -4.5$
• Chemical analysis of two extremely metal-poor stars HE 2148-2039 and HE 2155-2043
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• High-Resolution Spectroscopy of Extremely Metal-Poor Stars from SDSS/SEGUE: II. Binary Fraction
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• The true nature of HE0057-5959, the most metal-poor Li-rich star
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• Gaia-Sausage-Enceladus: Lithium evolution from early red-giant-branch and main-sequence stars