Explosive lithium production in the classical nova V339 Del (Nova Delphini 2013)

The origin of lithium (Li) and its production process have long been uncertain. Li could be produced by Big Bang nucleosynthesis, interactions of energetic cosmic rays with interstellar matter, evolved low-mass stars, novae, and supernova explosions. Chemical evolution models and observed stellar Li abundances suggest that at least half the Li may have been produced in red giants, asymptotic giant branch (AGB) stars, and novae(1-3). No direct evidence, however, for the supply of Li from evolved stellar objects to the Galactic medium has hitherto been found. Here we report the detection of highly blue-shifted resonance lines of the singly ionized radioactive isotope of beryllium, Be-7, in the near-ultraviolet spectra of the classical nova V339 Del (Nova Delphini 2013) 38 to 48 days after the explosion. Be-7 decays to form Li-7 within a short time (half-life of 53.22 days(4)). The Be-7 was created during the nova explosion via the alpha-capture reaction He-3(alpha,gamma)Be-7 (ref. 5). This result supports the theoretical prediction that a significant amount of 7Li is produced in classical nova explosions.