Highly enriched 7Be in the ejecta of Nova Sagittarii 2015 No. 2 (V5668 Sgr) and the Galactic 7Li origin

DOI: 
10.1093/mnrasl/slw169
Publication date: 
01/11/2016
Main author: 
Molaro P.
IAA authors: 
Izzo, L.
Authors: 
Molaro P., Izzo L., Mason E., Bonifacio P., Della Valle M.
Journal: 
Monthly Notices of the Royal Astronomical Society: Letters
Refereed: 
Yes
Publication type: 
Article
Volume: 
463
Pages: 
L117-L121
Number: 
Abstract: 
We report on the evidence of highly blueshifted resonance lines of the singly ionized isotope of 7Be II in high resolution UVES spectra of Nova Sagittarii 2015 No. 2 (V5668 Sgr). The resonance doublet lines 7Be II at λλ313.0583, 313.1228 nm are clearly detected in several non-saturated and partially resolved high velocity components during the evolution of the outburst. The total absorption identified with Be II has an equivalent width much larger than all other elements and comparable to hydrogen. We estimate an atomic fraction N(7Be)/N(Ca) ≈ 53-69 from unsaturated and resolved absorption components. The detection of 7Be in several high velocity components shows that 7Be has been freshly created in a thermonuclear runaway via the reaction 3He(α, γ)7Be during the Nova explosion, as postulated by Arnould & Norgaar, however in much larger amounts than predicted by current models. 7Be II decays to 7Li II with a half-life of 53.22 d, comparable to the temporal span covered by the observations. The non-detection of 7Li i requires that 7Li remains ionized throughout our observations. The massive Be ii ejecta result into a 7Li production that is ≈ 4.7-4.9 dex above the meteoritic abundance. If such a high production is common even in a small fraction (≈5 per cent) of Novae, they can make all the stellar 7Li of the Milky Way. © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
Database: 
SCOPUS
ADS
URL: 
https://ui.adsabs.harvard.edu/#abs/2016MNRAS.463L.117M/abstract
ADS Bibcode: 
2016MNRAS.463L.117M
Keywords: 
Galaxy: evolutioncover-date; Novae, cataclysmic variables; Nuclear reactions, nucleosynthesis, abundances; Stars: individual: V5668 Sgr