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., Takacs, 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., et al.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 121:17(2018). [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
Pantaleo F. R.Membro del Collaboration Group
;
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.
