Thermonuclear ¹⁹F(p, α)¹⁶O Reaction Rate Revised and Astrophysical Implications

We have calculated the thermonuclear 19F(p, α γ )16O reaction rate in a wide temperature region of 0.001-10 GK by re-evaluating the available experimental data. Together with recently evaluated 19(p, α 0)16O and 19(p, α π )16O data, we have derived a new total reaction rate of 19F(p, α)16O using a Monte Carlo technique. The present rate is larger than the NACRE recommended one by factors of 36.4, 2.3, and 1.7 at temperatures of 0.01, 0.05, and 0.1 GK, respectively. This is because we have considered the enhanced low-energy astrophysical S factors in the (p, α γ ) channel, owing to the interference effect between an 11 keV resonance and the well-known 323 keV resonance. It shows that the (p, α γ ) channel dominates the total rate over the entire temperature region, except for a narrow region of 0.05-0.12 GK where the (p, α 0) channel dominates, contrary to the previous conclusion. We have investigated the impact of the 19F(p, α)16O reaction rate using a simple parametric model of extra mixing in low-mass AGB stars, which would lower the fluorine abundance produced and observed in these stars. However, models considering different temperature profiles and more sophisticated approaches, such as extra mixing induced by magnetic fields, are needed to verify the results of our preliminary tests. Interestingly, our new rate has a strong impact on destruction of 19F in the CNO cycle at low temperatures of 0.02-0.03 GK, and this general behavior needs to be analyzed further.