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Europium Isotope Ratios in s-Process-Element-Enhanced, Metal-Poor Stars: A New Probe of the 151 Sm Branching 1 (2003)
BibTeX
@MISC{Aoki03europiumisotope,
author = {Wako Aoki and Sean G. Ryan and Nobuyuki Iwamoto and Timothy C. Beers and John E. Norris and Hiroyasu Ando and Toshitaka Kajino and Grant J. Mathews and Masayuki Y. Fujimoto},
title = {Europium Isotope Ratios in s-Process-Element-Enhanced, Metal-Poor Stars: A New Probe of the 151 Sm Branching 1},
year = {2003}
}
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Abstract
We report on the first measurement of the Eu isotope fractions ( 151 Eu and 153 Eu) in s-process-element-enhanced, metal-poor stars. We use these ratios to investigate the 151 Sm branching of s-process nucleosynthesis. The measurement was made by detailed study of Eu II lines that are significantly affected by hyperfine splitting and isotope shifts in spectra of the carbon-rich, very metal-poor stars LP 625–44 and CS 31062–050, observed with the Subaru Telescope High Dispersion Spectrograph. The 151 Eu fractions [fr ( 151 Eu) = 151 Eu/ ( 151 Eu+ 153 Eu)] derived for LP 625–44 and CS 31062–050 are 0.60 and 0.55, respectively, with uncertainties of about ±0.05. These values are higher than found in solar-system material, but agree well with the predictions of recent s-process models. We derive new constraints on the temperature and neutron density during the s-process based on calculations of pulsed s-process models for the 151 Eu fraction.
Keyphrases
metal-poor star sm branching europium isotope ratio new probe eu fraction metal-poor star lp first measurement solar-system material eu isotope fraction detailed study neutron density eu ii line new constraint pulsed s-process model s-process nucleosynthesis isotope shift hyperfine splitting subaru telescope high dispersion spectrograph recent s-process model
