The Ne-22(p,gamma)Na-23 reaction, part of the neon-sodium cycle of hydrogen burning, may explain the observed anticorrelation between sodium and oxygen abundances in globular cluster stars. Its rate is controlled by a number of low-energy resonances and a slowly varying nonresonant component. Three new resonances at E-p = 156.2, 189.5, and 259.7 keV have recently been observed and confirmed. However, significant uncertainty on the reaction rate remains due to the nonresonant process and to two suggested resonances at E-p = 71 and 105 keV. Here, new Ne-22(p,gamma)Na-23 data with high statistics and low background are reported. Stringent upper limits of 6 x 10(-11) and 7 x 10(-11) eV (90% confidence level), respectively, are placed on the two suggested resonances. In addition, the off-resonant S factor has been measured at unprecedented low energy, constraining the contributions from a subthreshold resonance and the direct capture process. As a result, at a temperature of 0.1 GK the error bar of the Ne-22(p,gamma)Na-23 rate is now reduced by 3 orders of magnitude.
Direct Capture Cross Section and the E-p=71 and 105 keV Resonances in the Ne-22(p,gamma)Na-23 Reaction / F. Ferraro, M. . Takács, D. Piatti, F. Cavanna, R. Depalo, M. Aliotta, D. Bemmerer, A. Best, A. Boeltzig, C. Broggini, C. . Bruno, A. Caciolli, T. Chillery, G. . Ciani, P. Corvisiero, T. Davinson, G. D’Erasmo, A. Di Leva, Z. Elekes, E. . Fiore, A. Formicola, Z. Fülöp, G. Gervino, A. Guglielmetti, C. Gustavino, G. Gyürky, G. Imbriani, M. Junker, A. Karakas, I. Kochanek, M. Lugaro, P. Marigo, R. Menegazzo, V. Mossa, F. . Pantaleo, V. Paticchio, R. Perrino, P. Prati, L. Schiavulli, K. Stöckel, O. Straniero, T. Szücs, D. Trezzi, S. Zavatarelli. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 121:17(2018 Oct 23), pp. 172701.172701-1-172701.172701-6.
Direct Capture Cross Section and the E-p=71 and 105 keV Resonances in the Ne-22(p,gamma)Na-23 Reaction
F. Ferraro;R. Depalo;A. Guglielmetti;D. TrezziMembro del Collaboration Group
;
2018
Abstract
The Ne-22(p,gamma)Na-23 reaction, part of the neon-sodium cycle of hydrogen burning, may explain the observed anticorrelation between sodium and oxygen abundances in globular cluster stars. Its rate is controlled by a number of low-energy resonances and a slowly varying nonresonant component. Three new resonances at E-p = 156.2, 189.5, and 259.7 keV have recently been observed and confirmed. However, significant uncertainty on the reaction rate remains due to the nonresonant process and to two suggested resonances at E-p = 71 and 105 keV. Here, new Ne-22(p,gamma)Na-23 data with high statistics and low background are reported. Stringent upper limits of 6 x 10(-11) and 7 x 10(-11) eV (90% confidence level), respectively, are placed on the two suggested resonances. In addition, the off-resonant S factor has been measured at unprecedented low energy, constraining the contributions from a subthreshold resonance and the direct capture process. As a result, at a temperature of 0.1 GK the error bar of the Ne-22(p,gamma)Na-23 rate is now reduced by 3 orders of magnitude.
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