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Astron. Astrophys. 357, 561-571 (2000)


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Influence of new reaction rates on 18F production in novae

A. Coc 1, M. Hernanz 2, J. José 2,3 and J.-P. Thibaud 1

1 Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, IN2P3-CNRS and Université Paris Sud, Bâtiment 104, 91405 Orsay Campus, France
2 Institut d'Estudis Espacials de Catalunya/CSIC, Edifici Nexus-201, C/Gran Capità 2-4, 08034 Barcelona, Spain
3 Departament de Física i Enginyeria Nuclear (UPC), Avinguda Víctor Balaguer, s/n, 08800 Vilanova i la Geltrú (Barcelona), Spain

Received 28 January 2000 / Accepted 7 March 2000

Abstract

Gamma-ray emission from classical novae is dominated, during the first hours, by positron annihilation resulting from the beta decay of radioactive nuclei. The main contribution comes from the decay of 18F and hence is directly related to 18F formation during the outburst. A good knowledge of the nuclear reaction rates of production and destruction of 18F is required to study 18F synthesis in novae and the resulting gamma-ray emission. The rates relevant for the main mode of 18F destruction (i.e, through proton captures) have been the object of many recent experiments. However, subsequent analyses were focused on providing rates for X-ray burst nucleosynthesis not valid at nova temperatures (lower than 3.5[FORMULA] K). Accordingly, it is crucial to propose and discuss new reaction rates, incorporating all new experimental results, down to the domain of nova nucleosynthesis. We show that in this temperature regime, the 18F(p,[FORMULA]Ne and 18F(p,[FORMULA]O reaction rates remain uncertain and deserve further experimental and theoretical efforts. Our hydrodynamic calculations including the new nuclear rates demonstrate that their impact on 18F synthesis in nova explosions is quite large and, consequently, the early gamma-ray emission from classical novae is also affected.

Key words: nuclear reactions, nucleosynthesis, abundances – stars: novae, cataclysmic variables – gamma rays: theory


© European Southern Observatory (ESO) 2000

Online publication: June 5, 2000

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