Low-energy ${}^{23}$Al ${\hat{I}}^2$-delayed proton decay and ${}^{22}$Na destruction in novae

Abstract

The radionuclide ${}^{22}$Na is a target of ${\hat{I}}^3$-ray astronomy searches, predicted to be produced during thermonuclear runaways driving classical novae. The ${}^{22}$Na(p,${\hat{I}}^3$)${}^{23}$Mg reaction is the main destruction channel of ${}^{22}$Na during a nova, hence, its rate is needed to accurately predict the ${}^{22}$Na yield. However, experimental determinations of the resonance strengths have led to inconsistent results. In this work, we report a measurement of the branching ratios of the ${}^{23}$Al ${\hat{I}}^2$-delayed protons, as a probe of the key 204--keV (center-of-mass) ${}^{22}$Na(p,${\hat{I}}^3$)${}^{23}$Mg resonance strength. We report a factor of 5 lower branching ratio compared to the most recent literature value. The variation in ${}^{22}$Na 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 $\sim$2 uncertainty in the maximum detectability distance. This is the first reported scientific measurement using the Gaseous Detector with Germanium Tagging (GADGET) system.