New determination of the 13C(a, n)16O reaction rate and its influence on the s-process nucleosynthesis in AGB stars

Abstract

We present a new measurement of the $\alpha$-spectroscopic factor ($S_{\alpha }$) and the asymptotic normalization coefficient (ANC) for the 6.356 MeV 1/2${}^{+}$ subthreshold state of ${}^{17}$O through the ${}^{13}$C(${}^{11}$B, ${}^7$Li)${}^{17}$O transfer reaction and we determine the $\alpha$-width of this state. This is believed to have a strong effect on the rate of the ${}^{13}$C($\alpha$, $n$)${}^{16}$O reaction, the main neutron source for {\it slow} neutron captures (the $s$-process) in asymptotic giant branch (AGB) stars. Based on the new width we derive the astrophysical S-factor and the stellar rate of the ${}^{13}$C($\alpha$, $n$)${}^{16}$O reaction. At a temperature of 100 MK our rate is roughly two times larger than that by \citet{cau88} and two times smaller than that recommended by the NACRE compilation. We use the new rate and different rates available in the literature as input in simulations of AGB stars to study their influence on the abundances of selected $s$-process elements and isotopic ratios. There are no changes in the final results using the different rates for the ${}^{13}$C($\alpha$, $n$)${}^{16}$O reaction when the ${}^{13}$C burns completely in radiative conditions. When the ${}^{13}$C burns in convective conditions, as in stars of initial mass lower than $\sim$2 $M_\sun$ and in post-AGB stars, some changes are to be expected, e.g., of up to 25% for Pb in our models. These variations will have to be carefully analyzed when more accurate stellar mixing models and more precise observational constraints are available.

References in corpus (2)

• Nucleosynthesis Predictions for Intermediate-Mass AGB Stars: Comparison to Observations of Type I Planetary Nebulae
• Trojan Horse as an indirect technique in nuclear astrophysics. Resonance reactions

Cited by in corpus (16)

• Evolution and nucleosynthesis of asymptotic giant branch stellar models of low metallicity
• LUNA: Status and Prospects
• s-Processing in AGB Stars Revisited. I. Does the Main Component Constrain the Neutron Source in the 13C-Pocket?
• Concurrent application of ANC and THM to assess the ${}^{13}\mathrm{C}(\alpha ,n{)}^{16}\mathrm{O}$ absolute cross section at astrophysical energies and possible consequences for neutron production in low-mass AGB stars
• Deep underground laboratory measurement of ${}^{13}$C($\alpha$,$n$)${}^{16}$O in the Gamow windows of the $s$- and $i$-processes
• New $\alpha$ ANC measurement of the 1/2${}^{+}$ state in ${}^{17}$O at 6.356 MeV, that dominates the ${}^{13}$C($\alpha$,n)${}^{16}$O reaction rate at temperatures relevant for the s-process
• s-Processing from MHD-induced mixing and isotopic abundances in presolar SiC grains
• Partial mixing and the formation of 13C pockets in AGB stars: effects on the s-process elements
• Underground Measurements of Nuclear Reaction Cross-Sections Relevant to AGB Stars
• The impact of ${}^{17}$O$+\alpha$ reaction rate uncertainties on the s-process in rotating massive stars
• Proton widths of the low-lying 16F states from the 15N(7Li, 6Li)16N reaction
• Trojan horse method as surrogate indirect approach to study resonant reactions in nuclear astrophysics
• Microscopic study of the ${}^7$Li-nucleus potential
• Progress in Nuclear Astrophysics of East and Southeast Asia
• Experimental study of 13C(α,n)16O reactions in the Majorana Demonstrator calibration data
• Status and future directions for direct cross-section measurements of the 13C(a,n)16O reaction for astrophysics