Impact of T- and ρ-dependent decay rates and new (n,γ) cross-sections on the s process in low-mass asymptotic giant branch stars

Abstract

Aims. We study the impact of nuclear input related to weak-decay rates and neutron-capture reactions on predictions for the slow neutron-capture process (s process) in asymptotic giant branch (AGB) stars. We provide the first database of surface abundances and stellar yields of the isotopes heavier than iron from the Monash models.Methods. We ran nucleosynthesis calculations with the Monash post-processing code for seven stellar structure evolution models of low-mass AGB stars with three different sets of nuclear inputs. The reference set has constant decay rates and represents the set used in the previous Monash publications. The second set contains the temperature and density dependence of β decays and electron captures based on the default rates of nuclear NETwork GENerator (NETGEN). In the third set, we further update 92 neutron-capture rates based on re-evaluated experimental cross sections from the ASTrophysical Rate and rAw data Library. We compare and discuss the predictions of the sets relative to each other in terms of isotopic surface abundances and total stellar yields. We also compare the results to isotopic ratios measured in presolar stardust silicon carbide (SiC) grains from AGB stars.Results. The new sets of models result in a ∼66% solar s-process contribution to the p-nucleus ^{152Gd, confirming that this isotope is predominantly made by the s process. The nuclear input updates result in predictions for the 80Kr/82Kr ratio in the He intershell and surface 64Ni/58Ni, 94Mo/96Mo, and 137Ba/136Ba ratios that are more consistent with the corresponding ratios measured in stardust; however, the new predicted 138Ba/136Ba ratios are higher than the typical values of the SiC grains. The W isotopic anomalies are in agreement with data from the analyses of other meteoritic inclusions. We confirm that the production of 176Lu and 205Pb is affected by too large uncertainties in their decay rates from NETGEN.}