Europium Isotope Ratios in s -Process Element-enhanced Metal-poor Stars: A New Probe of the 151 Sm Branching | Zendy

Wako Aoki | Zendy; Sean G. Ryan | Zendy; Nobuyuki Iwamoto | Zendy; Timothy C. Beers | Zendy; John E. Norris | Zendy; Hiroyasu Ando | Zendy; Toshitaka Kajino | Zendy; Grant J. Mathews | Zendy; Masayuki Y. Fujimoto | Zendy

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Europium Isotope Ratios in s -Process Element-enhanced Metal-poor Stars: A New Probe of the ¹⁵¹ Sm Branching

Author(s) -

Wako Aoki,

Sean G. Ryan,

Nobuyuki Iwamoto,

Timothy C. Beers,

John E. Norris,

Hiroyasu Ando,

Toshitaka Kajino,

Grant J. Mathews,

Masayuki Y. Fujimoto

Publication year - 2003

Publication title -

the astrophysical journal

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 2.376

H-Index - 489

eISSN - 1538-4357

pISSN - 0004-637X

DOI - 10.1086/377681

Subject(s) - nucleosynthesis , r process , hyperfine structure , s process , isotope , stars , physics , europium , metal , monoisotopic mass , astrophysics , asymptotic giant branch , neutron capture , spectrograph , spectral line , analytical chemistry (journal) , neutron , nuclear physics , materials science , atomic physics , chemistry , astronomy , ion , metallurgy , quantum mechanics , chromatography

We report on the first measurement of the Eu isotope fractions (151Eu and153Eu) in s-process-element-enhanced, metal-poor stars. We use these ratios toinvestigate the 151Sm branching of s-process nucleosynthesis. The measurementwas made by detailed study of Eu II lines that are significantly affected byhyperfine splitting and isotope shifts in spectra of the carbon-rich, verymetal-poor stars LP625-44 and CS31062-050, observed with the Subaru TelescopeHigh Dispersion Spectrograph. The 151Eu fractions [fr(151Eu) =151Eu/(151Eu+153Eu)] derived for LP625-44 and CS31062-050 are 0.60 and 0.55,respectively, with uncertainties of about +/- 0.05. These values are higherthan found in solar-system material, but agree well with the predictions ofrecent s-process models. We derive new constraints on the temperature andneutron density during the s-process based on calculations of pulsed s-processmodels for the 151Eu fraction.Comment: 10 pages, 2 figures, ApJL in pres

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