The Hamburg/ESO R-process Enhanced Star survey (HERES) VI. The Galactic Chemical Evolution of Silicon

Abstract

We determined the silicon abundances of 253 metal-poor stars in the metallicity range $-4<[Fe/H]<-1.5$, based on non-local thermodynamic equilibrium (NLTE) line formation calculations of neutral silicon and high-resolution spectra obtained with VLT-UT2/UVES. The $T_{\mathrm{eff}}$ dependence of [Si/Fe] noticed in previous investigation is diminished in our abundance analysis due to the inclusion of NLTE effects. An increasing slope of [Si/Fe] towards decreasing metallicity is present in our results, in agreement with Galactic chemical evolution models. The small intrinsic scatter of [Si/Fe] in our sample may imply that these stars formed in a region where the yields of type II supernovae were mixed into a large volume, or that the formation of these stars was strongly clustered, even if the ISM was enriched by single SNa II in a small mixing volume. We identified two dwarfs with $[Si/Fe]\sim +1.0$: HE 0131$-$3953, and HE 1430$-$1123. These main-sequence turnoff stars are also carbon-enhanced. They might have been pre-enriched by sub-luminous supernovae.

arXiv comment12 pages, 9 figures, 1 electronical table. Accepted by A & A

References in corpus (40)

• The Nucleosynthetic Signature of Population III
• First stars V - Abundance patterns from C to Zn and supernova yields in the early Galaxy
• Galactic chemical evolution: Carbon through Zinc
• Nucleosynthesis Yields of Core-Collapse Supernovae and Hypernovae, and Galactic Chemical Evolution
• Nucleosynthesis and Evolution of Massive Metal-Free Stars
• Neutron-Capture Elements in the Early Galaxy: Insights from a Large Sample of Metal-Poor Giants
• Nucleosynthesis of Zinc and Iron-Peak Elements in Pop III Type II Supernovae : Comparison with abundances of Very Metal-Poor Halo Stars
• Carbon Enhanced Metal-Poor Stars. I. Chemical Compositions of 26 Stars
• The Hamburg/ESO R-process Enhanced Star survey (HERES) II. Spectroscopic analysis of the survey sample
• A Reappraisal of the Solar Photospheric C/O Ratio
• Explosive yields of massive stars from Z=0 to Z=Zsun
• Spectroscopic Studies of Extremly Metal-Poor Stars with Subaru/HDS:II.The r-process Elements, Including Thorium
• Detailed Abundances for 28 Metal-poor Stars: Stellar Relics in the Milky Way
• First Stars VIII -- Enrichment of the neutron-capture elements in the early Galaxy
• The Supernova Channel of Super-AGB Stars
• Electron-capture supernovae as the origin of elements beyond iron
• Extremely Metal-Poor Stars. VIII. High-Resolution, High-Signal-To-Noise Analysis of Five Stars with [Fe/H] < -3.5
• First stars XII. Abundances in extremely metal-poor turnoff stars,and comparison with the giants
• The Frequency of Carbon-Enhanced Metal-Poor Stars in the Galaxy from the HERES sample
• Spectroscopic Studies of Very Metal-Poor Stars with the Subaru High Dispersion Spectrograph. III. Light Neutron-Capture Elements
• Nucleosynthesis in Electron Capture Supernovae of AGB Stars
• Abundances In Very Metal Poor Dwarf Stars
• The Hamburg/ESO R-process Enhanced Star survey (HERES) III. HE 0338-3945 and the formation of the r+s stars
• The Hamburg/ESO R-process Enhanced Star survey (HERES). I. Project description, and discovery of two stars with strong enhancements of neutron-capture elements
• The first generation of stars: first steps towards chemical evolution of galaxies
• New Extremely Metal-Poor Stars in the Galactic Halo
• The stellar content of the Hamburg/ESO survey. V. The metallicity distribution function of the Galactic halo
• Uncovering the Chemical Signature of the First Stars in the Universe
• Non-LTE abundances of Mg and K in extremely metal-poor stars and the evolution of [O/Mg], [Na/Mg], [Al/Mg] and [K/Mg] in the Milky Way
• Chemical Composition of the Carbon-rich, Extremely Metal-Poor Star CS 29498--043: A New Class of Extremely Metal-Poor Stars with Excesses of Magnesium and Silicon
• Mg abundances in metal-poor halo stars as a tracer of early Galactic mixing
• A New Type of Extremely Metal Poor Star
• Statistical equilibrium of silicon in the solar atmosphere
• Chemical signatures of the first star clusters
• Stochastic chemical enrichment in metal-poor systems II. Abundance ratios and scatter
• Primordial Stellar Feedback and the Origin of Hyper Metal-Poor Stars
• Statistical equilibrium of silicon in the atmospheres of metal-poor stars
• Stochastic chemical enrichment in metal-poor systems I. Theory
• Chemical Compositions of Kinematically Selected Outer Halo Stars
• Relics of subluminous supernovae in metal-poor stars

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• Carbon-Enhanced Metal-Poor Star Frequencies in the Galaxy: Corrections for the Effect of Evolutionary Status on Carbon Abundances
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• Pre-galactic metal enrichment - The chemical signatures of the first stars
• The Chemical Imprint of Silicate Dust on the Most Metal-Poor Stars
• The chemistry of the most metal-rich damped Lyman $\alpha$ systems at z$\sim 2$ II. Context with the Local Group
• G64-12 and G64-37 are Carbon-Enhanced Metal-Poor Stars
• Star Formation Timescales of the Halo Populations from Asteroseismology and Chemical Abundances
• The Hamburg/ESO R-process Enhanced Star survey (HERES)VII. Thorium abundances in metal-poor stars
• Gaia-Sausage-Enceladus star formation history as revealed by detailed elemental abundances
• Inferring the velocity of early massive stars from the abundances of extremely metal-poor stars
• Carbon Abundances of Metal-Poor Star Determined from the C I 1.068-1.069 micron Lines
• The metal-poor end of the Spite plateau. II. Detailed chemical investigation