New Constraints on the {sup 25}Al(p, ) Reaction and its Influence on the Flux of Cosmic rays from Classical Nova Explosions
Authors
Canete, L.; Lotay, G.; Christian, G; Doherty, D. T.; Catford, W.; Hallam, S.; Seweryniak, D.; Albers, H.; Almaraz-Calderon, S.; Bennett, E.; Carpenter, M. P.; Greene, J. P.; Hoffman, C. R.; Lauritsen, T.
Abstract
The astrophysical Al-25(p, gamma) Si-26 reaction represents one of the key remaining uncertainties in accurately modeling the abundance of radiogenic Al-26 ejected from classical novae. Specifically, the strengths of key proton-unbound resonances in Si-26, that govern the rate of the Al-25(p, gamma) reaction under explosive astrophysical conditions, remain unsettled. Here, we present a detailed spectroscopy study of the Si-26 mirror nucleus Mg-26. We have measured the lifetime of the 3(+), 6.125-MeV state in Mg-26 to be 19(3) fs and provide compelling evidence for the existence of a 1(- )state in the T = 1, A = 26 system, indicating a previously unaccounted for l = 1 resonance in the Al-25(p, gamma) reaction. Using the presently measured lifetime, together with the assumption that the likely 1(-) state corresponds to a resonance in the Al-25 + p system at 435.7(53) keV, we find considerable differences in the Al-25(p, gamma) reaction rate compared to previous works. Based on current nova models, we estimate that classical novae may be responsible for up to approximate to 15% of the observed galactic abundance of Al-26.