The Ne22(p,γ)Na23 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 Ep=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 Ep=71 and 105 keV. Here, new Ne22(p,γ)Na23 data with high statistics and low background are reported. Stringent upper limits of 6×10-11 and 7×10-11 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 Ne22(p,γ)Na23 rate is now reduced by 3 orders of magnitude.
Direct Capture Cross Section and the Ep=71 and 105 keV Resonances in the Ne 22 (p,γ) Na 23 Reaction / Ferraro, F.; Takács, M. P.; Piatti, D.; Cavanna, F.; Depalo, R.; Aliotta, M.; Bemmerer, D.; Best, A.; Boeltzig, A.; Broggini, C.; Bruno, C. G.; Caciolli, A.; Chillery, T.; Ciani, G. F.; Corvisiero, P.; Davinson, T.; D'Erasmo, G.; Di Leva, A.; Elekes, Z.; Fiore, E. M.; Formicola, A.; Fülöp, Zs.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, Gy.; Imbriani, G.; Junker, M.; Karakas, A.; Kochanek, I.; Lugaro, M.; Marigo, P.; Menegazzo, R.; Mossa, V.; Pantaleo, F. R.; Paticchio, V.; Perrino, R.; Prati, P.; Schiavulli, L.; Stöckel, K.; Straniero, O.; Szücs, T.; Trezzi, D.; Zavatarelli, S.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 121:17(2018), p. 172701. [10.1103/PhysRevLett.121.172701]
Direct Capture Cross Section and the Ep=71 and 105 keV Resonances in the Ne 22 (p,γ) Na 23 Reaction
Best, A.Investigation
;Di Leva, A.Investigation
;Imbriani, G.Investigation
;
2018
Abstract
The Ne22(p,γ)Na23 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 Ep=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 Ep=71 and 105 keV. Here, new Ne22(p,γ)Na23 data with high statistics and low background are reported. Stringent upper limits of 6×10-11 and 7×10-11 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 Ne22(p,γ)Na23 rate is now reduced by 3 orders of magnitude.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
