The odd-isotope fractions of Barium in CEMP-r/s star HE 0338-3945 and r-II star CS 31082-001

Abstract

We report the first measurement of the odd-isotope fractions for barium, \fodd\, in two extremely metal-poor stars: a CEMP-r/s star \he\ (\feh\,$=-2.42\pm 0.11$) and an r-II star \cs\ (\feh\,$=-2.90\pm 0.13$). The measured \fodd\ values are $0.23\pm 0.12$ corresponding to $34.3\pm 34.3$\% of the r-process contributions for \he\ and $0.43\pm 0.09$ corresponding to $91.4\pm 25.7$\% of the r-process contribution to Ba production for \cs. The high r-process signature of barium in \cs\ ($91.4\pm 25.7\%$) suggests that the majority of the heavy elements in this star were synthesised via an r-process path, while the lower r-process value ($34.3\pm 34.3\%$) found in \he\ indicates that the heavy elements in this star formed through a mix of s-process and r-process synthesis. These conclusions are consistent with studies based on AGB model calculations to fit their abundance distributions.

arXiv comment8 pages, 5 figures, accepted for publication in A&A

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