2016ApJ...818..191T

We report spectroscopic observations of the resonance lines of singly ionized ⁷Be in the blueshifted absorption line systems found in the post-outburst spectra of two classical novae–V5668 Sgr (Nova Sagittarii 2015 No. 2) and V2944 Oph (Nova Ophiuchi 2015). The unstable isotope ⁷Be should have been created during the thermonuclear runaway (TNR) of these novae and decayed to form ⁷Li within a short period (a half-life of 53.22 days). These confirmations of ⁷Be are the second and the third ones following the first case found in V339 Del by Tajitsu et al. The blueshifted absorption line systems in both novae are clearly divided into two velocity components, both of which contain ⁷Be. This means that the absorbing gases in both velocity components consist of products of TNR. We estimated the amounts of ⁷Be produced during the outbursts of both novae and concluded that significant ⁷Li should have been created. These findings strongly suggest that the explosive production of ⁷Li via the reaction ³He(α,γ)⁷Be and its subsequent decay to ⁷Li occurs frequently among classical novae and contributes to the process of Galactic Li enrichment.