Uncertainties in the 18F(p, α)15O reaction rate in classical novae

Context. Direct observation of gamma-ray emission from the decay of F-18 ejected in classical nova outbursts remains a major focus of the nuclear astrophysics community. However, modeling the abundance of ejected F-18, and thus the predicted detectability distance of a gamma-ray signal near 511 keV emitted from these transient thermonuclear episodes, is hampered by significant uncertainties in our knowledge of the key F-18(p, alpha) reaction rate. Aims. We analyze uncertainties in the most recent nuclear physics experimental results employed to calculate the F-18(p, alpha) reaction rate. Our goal is to determine which uncertainties have the most profound influence on the predicted abundance of F-18 ejected from novae in order to guide future experimental works. Methods. We calculated a wide range of F-18(p, alpha) reaction rates using the R-Matrix formalism, which allowed us to take all interference effects into account. Using a selection of 16 evenly spaced rates over the full range, we performed 16 new hydrodynamic nova simulations. Results. We have performed one of the most thorough theoretical studies of the impact of the F-18(p, alpha) reaction in classical novae to date. The F-18(p, alpha) rate remains highly uncertain at nova temperatures, resulting in a factor of similar to 10 uncertainty in the predicted abundance of F-18 ejected from nova explosions. We also found that the abundance of F-18 may be strongly correlated with that of F-19. Conclusions. Despite numerous nuclear physics uncertainties affecting the determination of the F-18(p, alpha) reaction rate, dominated by unknown interference signs between 1/2(+) and 3/2(+) resonances, future experimental work should focus on firmly and precisely determining the directly measurable quantum properties of the subthreshold states in the compound nucleus Ne-19 near 6.13 and 6.29 MeV.

Automated summary

The study examined uncertainties in the calculation of the F-18(p, alpha) reaction rate, aiming to identify the factors that most affect the predicted abundance of F-18 ejected from novae. The research highlighted the highly uncertain nature of the F-18(p, alpha) rate at nova temperatures, emphasizing the need for future experimental work to focus on determining quantum properties of subthreshold states more precisely.