We analyse high-resolution spectra of two classical novae that exploded in the Small Magellanic Cloud (SMC). 7 Be II resonance transitions are detected in both ASASSN-19qv and ASASSN-20ni novae. This is the first detection outside the Galaxy and confirms that thermo-nuclear runaway reactions, leading to the 7 Be formation, are ef fecti ve also in the low-metallicity regime, characteristic of the SMC. Derived yields are of N( 7 Be = 7 Li)/N(H) = (5.3 ±0.2) ×10 −6 which are a factor 4 lower than the typical values of the Galaxy. Inspection of two historical novae in the Large Magellanic Cloud observed with IUE in 1991 and 1992 showed also the possible presence of 7 Be and similar yields. For an ejecta of M H , ej = 10 −5 M ⊙, the amount of 7 Li produced is of M 7 Li = (3 . 7 ±0 . 6) ×10 −10 M ⊙per nova event. Detailed chemical evolutionary model for the SMC shows that no vae could hav e made an amount of lithium in the SMC corresponding to a fractional abundance of A(Li) ≈2.6. Therefore, it is argued that a comparison with the abundance of Li in the SMC, as measured by its interstellar medium, could ef fecti vely constrain the amount of the initial abundance of primordial Li, which is currently contro v ersial.

Detection of 7Be II in the Small Magellanic Cloud

Molaro P.
Membro del Collaboration Group
;
Cescutti G.
Membro del Collaboration Group
;
Guido E.;
2022-01-01

Abstract

We analyse high-resolution spectra of two classical novae that exploded in the Small Magellanic Cloud (SMC). 7 Be II resonance transitions are detected in both ASASSN-19qv and ASASSN-20ni novae. This is the first detection outside the Galaxy and confirms that thermo-nuclear runaway reactions, leading to the 7 Be formation, are ef fecti ve also in the low-metallicity regime, characteristic of the SMC. Derived yields are of N( 7 Be = 7 Li)/N(H) = (5.3 ±0.2) ×10 −6 which are a factor 4 lower than the typical values of the Galaxy. Inspection of two historical novae in the Large Magellanic Cloud observed with IUE in 1991 and 1992 showed also the possible presence of 7 Be and similar yields. For an ejecta of M H , ej = 10 −5 M ⊙, the amount of 7 Li produced is of M 7 Li = (3 . 7 ±0 . 6) ×10 −10 M ⊙per nova event. Detailed chemical evolutionary model for the SMC shows that no vae could hav e made an amount of lithium in the SMC corresponding to a fractional abundance of A(Li) ≈2.6. Therefore, it is argued that a comparison with the abundance of Li in the SMC, as measured by its interstellar medium, could ef fecti vely constrain the amount of the initial abundance of primordial Li, which is currently contro v ersial.
2022
21-gen-2022
Pubblicato
https://academic.oup.com/mnras/article/510/4/5302/6484816
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/3039381
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