On the lithium abundance of the visual binary components ξ Boo A ( G8V ) and ξ Boo B ( K5V )
Abstract
A spectroscopic investigation of the lithium resonance doublet in ξ Boo A and ξ Boo B in terms of both abundance and isotopic ratio is presented. We obtained new R = 130,000 spectra with a signal‑to‑noise ratio (S/N) per pixel of up to 3200 using the 11.8 m LBT and PEPSI. From fits with synthetic line profiles based on 1D‑LTE MARCS model atmospheres and 3D‑NLTE corrections, we determine the abundances of both isotopes. For ξ Boo A, we find A(Li) = 2.40 ± 0.03 dex and 6Li/7Li <1.5 ± 1.0% in 1D‑LTE, which increases to ≈2.45 for the 3D‑NLTE case. For ξ Boo B we obtain A(Li) = 0.37 ± 0.09 dex in 1D‑LTE with an unspecified 6Li/7Li level. Therefore, no 6Li is seen on any of the two stars. We consider a spot model for the Li fit for ξ Boo B and find A(Li) = 0.45 ± 0.09 dex. The 7Li abundance is 23 times higher for ξ Boo A than the Sun's, but three times lower than the Sun's for ξ Boo B while both fit the trend of single stars in the similar‑aged M35 open cluster. Effective temperatures are redetermined from the TiO band head strength. We note that the best‑fit global metallicities are −0.13 ± 0.01 dex for ξ Boo A but +0.13 ± 0.02 dex for ξ Boo B. Lithium abundance for the K5V benchmark star 61 Cyg A was obtained to A(Li) ≈ 0.53 dex when including a spot model but to ≈0.15 dex without a spot model.
- Publication:
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Astronomische Nachrichten
- Pub Date:
- November 2022
- DOI:
- arXiv:
- arXiv:2211.06336
- Bibcode:
- 2022AN....34320036S
- Keywords:
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- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 18 pages, 8 Figures, 7 Tables. Accepted by Astronomische Nachrichten / Astronomical Notes