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Article overview
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The impact of the 18F(a,p)21Ne reaction on asymptotic giant branch nucleosynthesis | Amanda Karakas
; Hye Young Lee
; Maria Lugaro
; Joachim Goerres
; Michael Wiescher
; | Date: |
18 Dec 2007 | Abstract: | We present detailed models of low and intermediate-mass asymptotic giant
branch (AGB) stars with and without the 18F(a,p)21Ne reaction included in the
nuclear network, where the rate for this reaction has been recently
experimentally evaluated for the first time. The lower and recommended measured
rates for this reaction produce negligible changes to the stellar yields,
whereas the upper limit of the rate affects the production of 19F and 21Ne. The
stellar yields increase by ~50% to up to a factor of 4.5 for 19F, and by
factors of ~2 to 9.6 for 21Ne. While the 18}F(a,p)21Ne reaction competes with
18O production, the extra protons released are captured by 18O to facilitate
the 18O(p,a)15N(a,g)19F chain. The higher abundances of 19F obtained using the
upper limit of the rate helps to match the [F/O] ratios observed in AGB stars,
but only for large C/O ratios. Extra-mixing processes are proposed to help to
solve this problem. Some evidence that the 18F(a,p)21Ne rate might be closer to
its upper limit is provided by the fact that the higher calculated 21Ne/22Ne
ratios in the He intershell provide an explanation for the Ne isotopic
composition of silicon-carbide grains from AGB stars. This needs to be
confirmed by future experiments of the 18F(a,p)21Ne reaction rate. The
availability of accurate fluorine yields from AGB stars will be fundamental for
interpreting observations of this element in carbon-enhanced metal-poor stars. | Source: | arXiv, 0712.2883 | Services: | Forum | Review | PDF | Favorites |
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