Low-energy Al 23 β -delayed proton decay and Na 22 destruction in novae

The radionuclide Na22 is a target of γ-ray astronomy searches, predicted to be produced during thermonuclear runaways driving classical novae. The Na22(p,γ)Mg23 reaction is the main destruction channel of Na22 during a nova, hence, its rate is needed to accurately predict the Na22 yield. However, experimental determinations of the resonance strengths have led to inconsistent results. In this Rapid Communication, we report a measurement of the branching ratios of the Al23β-delayed protons as a probe of the key 204-keV (center-of-mass) Na22(p,γ)Mg23 resonance strength. We report a factor of 5 lower branching ratio compared to the most recent literature value. The variation in Na22 yield due to nuclear data inconsistencies was assessed using a series of hydrodynamic nova outburst simulations and has increased to a factor of 3.8, corresponding to a factor of ≈2 uncertainty in the maximum detectability distance. This is the first reported scientific measurement using the Gaseous Detector with Germanium Tagging system.