Influence of new reaction rates on F-18 production in novae

Gamma-ray emission from classical novae is dominated, during the first hour s, by positron annihilation resulting from the beta decay of radioactive nu clei. The main contribution comes from the decay of F-18 and hence is direc tly related to F-18 formation during the outburst. A good knowledge of the nuclear reaction rates of production and destruction of F-18 is required to study F-18 synthesis in novae and the resulting gamma-ray emission. The ra tes relevant for the main mode of 18F destruction (i.e, through proton capt ures) have been the object of many recent experiments. However, subsequent analyses were focused on providing rates for X-ray burst nucleosynthesis no t valid at nova temperatures (lower than 3.5 x10(8) K). Accordingly, it is crucial to propose and discuss new reaction rates, incorporating all new ex perimental results, down to the domain of nova nucleosynthesis. We show tha t in this temperature regime, the F-18(p,gamma)Ne-19 and F-18(p,alpha)O-15 reaction rates remain uncertain and deserve further experimental and theore tical efforts. Our hydrodynamic calculations including the new nuclear rate s demonstrate that their impact on F-18 synthesis in nova explosions is qui te large and, consequently, the early gamma-ray emission from classical nov ae is also affected.