Measurement of the Europium Isotope Ratio for the Extremely Metal-Poor, r-Process-Enhanced Star CS31082-001

Abstract

We report the first measurement of the isotope fraction of europium (151Eu and 153Eu) for the extremely metal-poor, r-process-enhanced star CS31082-001, based on high-resolution spectra obtained with the Subaru Telescope High Dispersion Spectrograph. We have also obtained new measurements of this ratio for two similar stars with previous europium isotope measurements, CS22892-052 and HD115444. The measurements were made using observations of the Eu lines in these spectra that are most significantly affected by isotope shifts and hyperfine splitting. The fractions of 151Eu derived for CS31082-001, CS22892-052, and HD115444 are 0.44, 0.51, and 0.46, respectively, with uncertainties of about +/-0.1. CS31082-001, the first star with a meaningful measurement of U outside of the solar system, is known to exhibit peculiar abundance ratios between the actinide and rare-earth elements (e.g., Th/Eu), ratios that are significantly different from those for other stars with large excesses of r-process elements, such as our two comparison objects. Nevertheless, our analysis indicates that the Eu isotope ratio of CS31082-001 agrees, within the errors, with those of other r-process-enhanced objects, and with that of solar-system material.

arXiv comment16 pages, 4 figures, Apj, in press

References in corpus (14)

• Neutron capture in low mass Asymptotic Giant Branch stars: cross sections and abundance signatures
• The extreme r-element rich, iron-poor halo giant CS31082-001: Implications for the r-process site(s) and radioactive cosmochronology
• Measurement of stellar age from uranium decay
• Nucleosynthesis in neutrino-driven winds: II. Implications for heavy element synthesis
• The r-Process Enriched Low Metallicity Giant HD 115444
• Evidence of Multiple r-Process Sites in the Early Galaxy: New Observations of CS 22892-052
• General relativistic effects on neutrino-driven wind from young, hot neutron star and the r-process nucleosynthesis
• Tuning the Clock: Uranium and Thorium Chronometers Applied to CS 31082-001
• The r-process in the neutrino winds of core-collapse supernovae and U-Th cosmochronology
• Neutrino-induced neutron spallation and supernova r-process nucleosynthesis
• Prompt Iron Enrichment, Two r-Process Components, and Abundances in Very Metal-Poor Stars
• Europium Isotopic Abundances in Very Metal-poor Stars
• Chemical composition of carbon-rich, very metal-poor subgiant LP625-44 observed with the Subaru/HDS
• Abundances in the Uranium-Rich Star CS 31082-001

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