Classical-NOVA CONTRIBUTION to the Milky Way's Al abundance: exit channel of the key Al(p,) Si resonance.
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abstract
Classical novae are expected to contribute to the 1809-keV Galactic -ray emission by producing its precursor 26Al, but the yield depends on the thermonuclear rate of the unmeasured 25Al(p,)26Si reaction. Using the decay of 26P to populate the key J()=3(+) resonance in this reaction, we report the first evidence for the observation of its exit channel via a 1741.60.6(stat)0.3(syst)keV primary ray, where the uncertainties are statistical and systematic, respectively. By combining the measured -ray energy and intensity with other experimental data on 26Si, we find the center-of-mass energy and strength of the resonance to be E(r)=414.90.6(stat)0.3(syst)0.6(lit.)keV and =236(stat)(-10)(+11)(lit.)meV, respectively, where the last uncertainties are from adopted literature data. We use hydrodynamic nova simulations to model 26Al production showing that these measurements effectively eliminate the dominant experimental nuclear-physics uncertainty and we estimate that novae may contribute up to 30% of the Galactic 26Al.