Detection of 7Be ii in the Classical Nova V5669 Sgr (Nova Sagittarii 2015 No.3)

Abstract

Abstract We report the new detection of 7Be ii in the ultraviolet spectra of V5669 Sgr during its early decline phase (+24 and +28 d). We identified three blueshifted absorption systems in our spectra. The first two, referred to as low- and high-velocity components, were noticeably identified among H i Balmer, Na i D, and Fe ii whose lower energies of transients are low (<4 eV). The third absorption component was identified among N ii, He i, and C ii lines whose lower energy levels are relatively high (9–21 eV). The absorption lines of 7Be ii at 3130.583 Å and 3132.228 Å were identified as the first and second components in our observations. No evidence suggested the existence of Li i at 6708 Å in any velocity components. The estimated number density ratio of lithium relative to hydrogen, which was finally produced by this object using the equivalent widths of 7Be and Ca ii K, N ( 7 Li ) / N H final , is 4.0 ± 0.7 × 10−6. This value is an order of magnitude lower than the average observed values for classical novae wherein 7Be has been detected, and is comparable to the most optimistic value of theoretical predictions.