The Hamburg/ESO R-process Enhanced Star survey (HERES)VII. Thorium abundances in metal-poor stars

Abstract

We report thorium abundances for 77 metal-poor stars in the metallicity range of -3.5<[Fe/H]}<-1.0, based on "snapshot" spectra obtained with VLT-UT2/UVES during the HERES Survey. We were able to determine the thorium abundances with better than 1-sigma confidence for 17 stars, while for 60 stars we derived upper limits. For five stars common with previous studies, our results were in good agreement with the literature results. The thorium abundances span a wide range of about 4.0 dex, and scatter exists in the distribution of log(Th/Eu) ratios for lower metallicity stars, supporting previous studies suggesting the r-process is not universal. We derived ages from the log(Th/Eu) ratios for 12 stars, resulting in large scattered ages, and two stars with significant enhancement of Th relative to Eu are found, indicating the "actinide boost" does not seem to be a rare phenomenon and thus highlighting the risk in using log(Th/Eu) to derive stellar ages.

12 pages, 8 figures

References in corpus (8)

• Discovery of HE 1523-0901, a Strongly r-Process Enhanced Metal-Poor Star with Detected Uranium
• Near-UV Observations of HD221170: New Insights into the Nature of r-Process-Rich Stars
• The Frequency of Carbon-Enhanced Metal-Poor Stars in the Galaxy from the HERES sample
• New Rare Earth Element Abundance Distributions for the Sun and Five r-Process-Rich Very Metal-Poor Stars
• The Hamburg/ESO R-process Enhanced Star survey (HERES) III. HE 0338-3945 and the formation of the r+s stars
• Neutron-capture elements in the very metal-poor star HD88609: another st ar with excesses of light neutron-capture elements
• Heavy element abundances in giant stars of the globular clusters M4 and M5
• Rubidium and lead abundances in giant stars of the globular clusters M4 and M5

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• The lanthanide fraction distribution in metal-poor stars: a test of neutron star mergers as the dominant r-process site
• Actinide-rich and Actinide-poor $r$-Process Enhanced Metal-Poor Stars do not Require Separate $r$-Process Progenitors
• The R-Process Alliance: Discovery of the first metal-poor star with a combined r- and s-process element signature
• The Influence of Beta Decay Rates on r-Process Observables
• Decoding the compositions of four bright $r$-process-enhanced stars
• Gaia-Sausage-Enceladus star formation history as revealed by detailed elemental abundances
• Th/Eu abundance ratio of red giants in the Kepler Field