The CNO cycle powers core H burning, in stars with 𝑀>1.2𝑀⊙, and shell H burning, during the advanced evolutionary phases. Therefore, the uncertainties affecting the reaction rates of proton captures on C, N, and O isotopes limit our understanding of stellar evolution and nucleosynthesis. We aim to develop a general and self-consistent tool for the calculation of nuclear reaction rates and their uncertainties, starting from available experimental data. As a longer term plan, we intend to use this tool to revise the proton-capture reactions of the CNO cycle for which new experimental data are or will be available in the next future. The general procedure consists of 𝑅-matrix cross section calculations based on available measurements of the relevant nuclear parameters (energies, widths, strengths of known resonances, interference patterns, etc.), coupled to a Monte Carlo procedure to evaluate the global reaction rate error. A first application of this method to 17 O (𝑝,𝛾) 18 F and 17 O (𝑝,𝛼) 14 N , the reactions that determine the 17 O destruction in stellar interiors where the CNO cycle is active, is presented. These two reactions also allow us to test the multichannel and multilevel capabilities of the 𝑅-matrix method. In the temperature range of hydrostatic H burning (𝑇<100 MK), we confirm that the median rates are up to a factor of 2 higher than those suggested in reaction rate libraries commonly used in stellar model calculations. In this temperature range, the 17 O destruction mainly proceeds through the 17 O (𝑝,𝛼) 14 N channel, whose rate is known within ±20% (95% C.L.). Based on current stellar models of red giant stars, we show that this uncertainty produces a 10% variation on the predicted 16O / 17 O abundance ratio. Other uncertainties, such as those affecting the 17 O production rate, i.e., the 16O (𝑝,𝛾) 17 F reaction, have a stronger impact on this theoretical prediction, a fact that motivates further experimental investigations of the 17 O production channel.
Revision of the CNO cycle: Rate of 17O destruction in stars / Rapagnani, D.; Straniero, O.; Imbriani, G.; Aliotta, M.; Ananna, C.; Barile, F.; Barbieri, L.; Bemmerer, D.; Best, A.; Boeltzig, A.; Broggini, C.; Bruno, C. G.; Caciolli, A.; Campostrini, M.; Casaburo, F.; Cavanna, F.; Ciani, G. F.; Colombetti, P.; Compagnucci, A.; Corvisiero, P.; Csedreki, L.; Davinson, T.; Depalo, R.; Di Leva, A.; Elekes, Z.; Ferraro, F.; Formicola, A.; Fülöp, Zs.; Gervino, G.; Gesuè, R. M.; Gyürky, Gy.; Guglielmetti, A.; Gustavino, C.; Junker, M.; Lugaro, M.; Marigo, P.; Marsh, J.; Masha, E.; Menegazzo, R.; Mercogliano, D.; Paticchio, V.; Piatti, D.; Prati, P.; Rigato, V.; Robb, D.; Sidhu, R. S.; Skowronski, J.; Szücs, T.; Zavatarelli, S.; Null, Null. - In: PHYSICAL REVIEW C. - ISSN 2469-9985. - 111:2(2025). [10.1103/physrevc.111.025805]
Revision of the CNO cycle: Rate of 17O destruction in stars
Casaburo, F.;
2025
Abstract
The CNO cycle powers core H burning, in stars with 𝑀>1.2𝑀⊙, and shell H burning, during the advanced evolutionary phases. Therefore, the uncertainties affecting the reaction rates of proton captures on C, N, and O isotopes limit our understanding of stellar evolution and nucleosynthesis. We aim to develop a general and self-consistent tool for the calculation of nuclear reaction rates and their uncertainties, starting from available experimental data. As a longer term plan, we intend to use this tool to revise the proton-capture reactions of the CNO cycle for which new experimental data are or will be available in the next future. The general procedure consists of 𝑅-matrix cross section calculations based on available measurements of the relevant nuclear parameters (energies, widths, strengths of known resonances, interference patterns, etc.), coupled to a Monte Carlo procedure to evaluate the global reaction rate error. A first application of this method to 17 O (𝑝,𝛾) 18 F and 17 O (𝑝,𝛼) 14 N , the reactions that determine the 17 O destruction in stellar interiors where the CNO cycle is active, is presented. These two reactions also allow us to test the multichannel and multilevel capabilities of the 𝑅-matrix method. In the temperature range of hydrostatic H burning (𝑇<100 MK), we confirm that the median rates are up to a factor of 2 higher than those suggested in reaction rate libraries commonly used in stellar model calculations. In this temperature range, the 17 O destruction mainly proceeds through the 17 O (𝑝,𝛼) 14 N channel, whose rate is known within ±20% (95% C.L.). Based on current stellar models of red giant stars, we show that this uncertainty produces a 10% variation on the predicted 16O / 17 O abundance ratio. Other uncertainties, such as those affecting the 17 O production rate, i.e., the 16O (𝑝,𝛾) 17 F reaction, have a stronger impact on this theoretical prediction, a fact that motivates further experimental investigations of the 17 O production channel.| File | Dimensione | Formato | |
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