The stellar beta-decay rate of 134Cs and its impact on the Barium nucleosynthesis in the s process

Abstract

We have calculated the stellar $\beta$-decay rate of the important s-process branching point ${}^{134}$Cs based on the state of the art shell model calculations. At typical $s$-process temperatures ($T\sim$ 0.2-0.3 GK), our new rate is one order of magnitude lower than the widely-used rate from Takahashi and Yokoi (hereafter TY87). The impact on the nucleosynthesis in AGB stars is investigated with various masses and metallicities. Our new decay rate leads to an overall decrease in the ${}^{134}$Ba/${}^{136}$Ba ratio, and well explains the measured ratio in meteorities without introducing the $i$ process. We also derive the elapsed time from the last AGB nucleosynthetic event that polluted the early Solar System to be $>$28 Myr based on the ${}^{135}$Cs/${}^{133}$Cs ratio, which is consistent with the elapsed times derived from ${}^{107}$Pd and ${}^{182}$Hf. The $s$-process abundance sum of ${}^{135}$Ba and ${}^{135}$Cs is found to increase, resulting in a smaller $r$-process contribution of ${}^{135}$Ba in the Solar System.

arXiv commentaccepted for publication in Astrophysical Journal Letters, 2021

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• The s Process and Beyond
• Theoretical estimate of the half-life for the radioactive ${}^{134}$Cs and ${}^{135}$Cs in astrophysical scenarios
• High-temperature ${}^{205}$Tl decay clarifies ${}^{205}$Pb dating in early Solar System
• Slow Neutron-Capture Process: Low-mass AGB stars and presolar silicon carbide grains
• Presolar Silicon Carbide Grains of Types Y and Z: Their Strontium and Barium Isotopic Compositions and Stellar Origins
• Presolar grains
• Impact of $\text{T}$- and $\rho$-dependent decay rates and new (n,$\gamma$) cross sections on the $\text{s}$ process in low-mass AGB stars
• Stellar ${\beta }^{-}$-decay rate of ${}^{63}$Ni and its impact on the $s$-process nucleosynthesis in massive stars