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تسجيل مستخدم جديدBehavior of Sulfur Abundances in Metal-Poor Giants and Dwarfs
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LTE and NLTE abundances of sulfur in 6 metal-poor giants and 61 dwarfs (62 dwarfs, including the Sun) were explored in the range of -3 lsim [Fe/H] lsim $+0.5$ using high-resolution, high signal-to-noise ratio spectra of the SI 8693.9 AA and 8694.6 AA lines observed by us and measured by Francois (1987, 1988) and Clegg et al. (1981). NLTE effects in S abundances are found to be small and practically negligible. The behavior of [S/Fe] vs. [Fe/H] exhibits a linear increasing trend without plateau with decreasing [Fe/H]. Combining our results with those available in the literature, we find that the slope of the increasing trend is -0.25 in the NLTE behavior of [S/Fe], which is comparable to that observed in [O/Fe]. The observed behavior of S may require chemical evolution models of the Galaxy, in which scenarios of hypernovae nucleosynthesis and/or time-delayed deposition into interstellar medium are incorporated.
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Sulfur is important: the site of its formation is uncertain, and at very low metallicity the trend of [S/Fe] against [Fe/H] is controversial. Below [Fe/H]=-2.0, [S/Fe] remains constant or it decreases with [Fe/H], depending on the author and the mult
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