Speaker
Description
We present new slow neutron-capture (s) process nucleosynthesis predictions calculated with the Monash post-processing code for low-mass asymptotic giant branch (AGB) stars of solar metallicity, half-solar, and double-solar metallicity. We updated many of the nuclear inputs related to decay and neutron-capture rates and will present several significant results related to presolar stardust grain and other meteoritic data. The new models quantitatively reproduce the minor s-process production of the classical p-only $\mathrm{^{94}Mo}$ observed in stardust silicon carbide (SiC) grains and match the $\mathrm{^{64}Ni}/\mathrm{^{58}Ni}$ values from the SiC grain data. Also, the $\mathrm{^{80}Kr}/\mathrm{^{82}Kr}$ and $\mathrm{^{137}Ba}/\mathrm{^{136}Ba}$ ratios are better fitted to SiC grains than using the previous models, while $\mathrm{^{138}Ba}/\mathrm{^{136}Ba}$ still presents some problems. Our new models still do not match the isotopic composition of W in large SiC stardust grains but do match the W composition observed in other types of meteoritic materials, especially when including the contribution of the long-lived $\mathrm{^{182}Hf}$ to $\mathrm{^{182}W}$. Finally, the first experimental measurement of the $\mathrm{^{205}Tl}$ decay rate in stars allowed us for the first time to use the radioactive s-process isotope $\mathrm{^{205}Pb}$ to determine the isolation time of solar material inside its parent molecular cloud. We obtain positive isolation times of around 10 Myr, consistent with those from $\mathrm{^{107}Pd}$ and $\mathrm{^{182}Hf}$, the other s-process short-lived radionuclides found in the early Solar System.
| Category | Theory |
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