The odd-isotope fractions of Barium in the strongly r-process enhanced (r-II) stars

TL;DR

This study measures the odd-isotope fractions of Barium in r-II stars, indicating a common main r-process origin for heavy elements and suggesting odd\'s potential as a key indicator in galactic chemical evolution.

Contribution

It provides the first measurements of odd\, demonstrating its constancy and confirming a single main r-process origin for heavy elements in r-II stars.

Findings

odd\\ values are consistent across four r-II stars.

Heavy elements from Ba to Pb share a common r-process origin.

odd\\ can serve as an indicator of r- and s-process contributions.

Abstract

We determined the \fodd\ values, $0.46\pm0.08$, $0.51\pm0.09$, $0.50\pm0.13$, $0.48\pm0.12$, which correspond to the r-contribution 100\% for four r-II stars, \cs, \hen, \hes\, and \het, respectively. Our results suggest that almost all of the heavy elements (in the range from Ba to Pb) in r-II stars have a common origin, that is, from a single r-process (the main r-process). We found that the \fodd\ has a intrinsic nature, and should keep constant value of about 0.46 in the main r-process yields, which is responsible for the heavy element enhancement of r-II stars and of our Galaxy chemical enhancement. In addition, except the abundance ratio [Ba/Eu] the \fodd\ is also an important indicator, which can be used to study the relative contributions of the r- and s-process during the chemical evolution history of the Milky Way and the enhancement mechanism in stars with peculiar abundance of heavy elements.