Classical nova explosions: nuclear physics laboratories in the universe

One of the observational evidences in support of the thermonuclear runaway model for the classical nova outburst relies on the accompanying nucleosynthesis. In this paper, we stress the relevant role played by nucleosynthesis in our understanding of the nova phenomenon by constraining models through a comparison with both the atomic abundance determinations from the ejecta and the isotopic ratios measured in presolar grains of a likely nova origin. We discuss first the interplay between nova outbursts and the Galactic chemical abundances: Classical nova outbursts are expected to be the major source of 13 C, 15 N and 17 O in the Galaxy, and to contribute to the abundances of other species with A < 40, such as 7 Li or 26 Al. We describe the main nuclear path during the course of the explosion, with special emphasis on the synthesis of radioactive species, of particular interest for the gamma-ray output predicted from novae (7 Li, 18 F, 22 Na, 26 Al). (Author)