Search for 7Be in the outbursts of four recent novae
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Following the recent detection of Be-7 II in the outburst spectra of classical novae, we report the search for this isotope in the outbursts of four recent bright novae by means of high-resolution Ultraviolet and Visual Echelle Spectrograph (UVES) observations. The Be-7 II lambda lambda 313.0583,313.1228 nm doublet resonance lines are detected in the high-velocity components of Nova Mus 2018 and ASASSN-18fv during outbursts. However, 7Be?II is not detected in ASASSN-17hx and possibly not in Nova Cir 2018, which shows that 7Be is not always ejected in the thermonuclear runaway. Taking into account the Be-7 decay, we find X(Be-7)/X(H) approximate to 1.5 x 10(-5) and 2.2 x 10(-5) in Nova Mus 2018 and ASASSN-18fv, respectively. A value of 7Be/H approximate to 2 x 10(-5) is found in five out of the seven extant measurements, and it can be considered as a typical 7Be yield for novae. However, this value is almost one order of magnitude larger than predicted by current theoretical models. We argue that the variety of high Be-7/H abundances could be the result of a higher than solar content of 3He in the donor star. The cases with Be-7 not detected might be related to the small mass of the white dwarf (WD) or to relatively little mixing with the core material of the WD. The Be-7/H, or Li-7/H, abundance is approximate to 4 dex above meteoritic abundance, thus confirming the novae as the main sources of Li-7 in the Milky Way.
Originalsprog | Engelsk |
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Tidsskrift | Monthly Notices of the Royal Astronomical Society |
Vol/bind | 492 |
Udgave nummer | 4 |
Sider (fra-til) | 4975-4985 |
Antal sider | 11 |
ISSN | 0035-8711 |
DOI | |
Status | Udgivet - mar. 2020 |
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