High-resolution, high signal-to-noise ratio spectra have been obtained for 32 metal-poor stars. The equivalent widths of Li γ6708 ? were measured and the lithium abundances were derived. The average lithium abundance...High-resolution, high signal-to-noise ratio spectra have been obtained for 32 metal-poor stars. The equivalent widths of Li γ6708 ? were measured and the lithium abundances were derived. The average lithium abundance of 21 stars on the lithium plateau is 2.33±0.02 dex. The Lithium plateau exhibits a marginal trend along metallicity, dA(Li)/d[Fe/H] = 0.12±0.06, and no clear trend with the effective temperature. The trend indicates that the abundance of lithium plateau may not be primordial and that a part of the lithium was produced in Galactic Chemical Evolution (GCE).展开更多
The abundances of the wide binary pair HD 219175 A and B are determined andcompared using a line-by-line differential analysis. No evidence for difference has been found inthe abundances of Fe, O, Na, Mg, Al, Si, K, C...The abundances of the wide binary pair HD 219175 A and B are determined andcompared using a line-by-line differential analysis. No evidence for difference has been found inthe abundances of Fe, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Ni, Cu and Ba. Our resultssupport a physical relation between the two components of HD 219175.展开更多
We performed an extensive non-LTE analysis of the neutral sodium lines of Na I 5683/5688, 5890/5896, 6154/6161, and 8183/8195 in disk/halo stars of types F-K covering a wide metallicity range (-4 (?) [Fe/H] (?) +0.4),...We performed an extensive non-LTE analysis of the neutral sodium lines of Na I 5683/5688, 5890/5896, 6154/6161, and 8183/8195 in disk/halo stars of types F-K covering a wide metallicity range (-4 (?) [Fe/H] (?) +0.4), using our own data as well as data collected from the literature. For comparatively metal-rich disk stars (-1(?) [Fe/H] (?) +0.4) where the weaker 6154/6161 lines are the best abundance indicators, we confirmed [Na/Fe]- 0 with an 'upturn' (i.e., a shallow/broad dip around -0.5 (?) [Fe/H](?) 0) as already reported in previous studies. For the metal-deficient halo stars, where the much stronger 5890/5896 or 8183/8195 lines subject to considerable (negative) non-LTE corrections amounting to 0.5 dex have to be used, our analysis suggests mildly 'subsolar' [Na/Fe] values down to--0.4 (with a somewhat large scatter of-±0.2 dex) on the average at the typical halo metallicity of [Fe/H] --2, followed by a rise again to a near-solar ratio of [Na/Fe] - 0 at the very metal-poor regime [Fe/H]--3 to -4. These results are discussed in comparison with the previous observational studies along with the theoretical predictions from the available chemical evolution models.展开更多
基金Supported by the National Natural Science Foundation of China
文摘High-resolution, high signal-to-noise ratio spectra have been obtained for 32 metal-poor stars. The equivalent widths of Li γ6708 ? were measured and the lithium abundances were derived. The average lithium abundance of 21 stars on the lithium plateau is 2.33±0.02 dex. The Lithium plateau exhibits a marginal trend along metallicity, dA(Li)/d[Fe/H] = 0.12±0.06, and no clear trend with the effective temperature. The trend indicates that the abundance of lithium plateau may not be primordial and that a part of the lithium was produced in Galactic Chemical Evolution (GCE).
基金Supported by the National Natural Science Foundation of China.
文摘The abundances of the wide binary pair HD 219175 A and B are determined andcompared using a line-by-line differential analysis. No evidence for difference has been found inthe abundances of Fe, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Ni, Cu and Ba. Our resultssupport a physical relation between the two components of HD 219175.
文摘We performed an extensive non-LTE analysis of the neutral sodium lines of Na I 5683/5688, 5890/5896, 6154/6161, and 8183/8195 in disk/halo stars of types F-K covering a wide metallicity range (-4 (?) [Fe/H] (?) +0.4), using our own data as well as data collected from the literature. For comparatively metal-rich disk stars (-1(?) [Fe/H] (?) +0.4) where the weaker 6154/6161 lines are the best abundance indicators, we confirmed [Na/Fe]- 0 with an 'upturn' (i.e., a shallow/broad dip around -0.5 (?) [Fe/H](?) 0) as already reported in previous studies. For the metal-deficient halo stars, where the much stronger 5890/5896 or 8183/8195 lines subject to considerable (negative) non-LTE corrections amounting to 0.5 dex have to be used, our analysis suggests mildly 'subsolar' [Na/Fe] values down to--0.4 (with a somewhat large scatter of-±0.2 dex) on the average at the typical halo metallicity of [Fe/H] --2, followed by a rise again to a near-solar ratio of [Na/Fe] - 0 at the very metal-poor regime [Fe/H]--3 to -4. These results are discussed in comparison with the previous observational studies along with the theoretical predictions from the available chemical evolution models.
