Sulfur abundances in metal-poor stars based on OAO-1.88 m/HIDES spectra

The LTE abundances of sulfur (S) of 21 metal-poor stars and one normal star were explored in the metallicity range of -3 < [Fe/H] <= 0, based on the equivalent widths of the SI (1) 9212, 9237 angstrom and SI (6) 8693, 9894 angstrom lines measured on high-resolution spectra, which were observed by the OAO 1.88-m telescope equipped with HIDES. Our main results are: (1) The abundances derived from the S 1 (6) lines are consistent with those from the S 1 (1) lines among our sample stars in the range of [Fe/H] > -2 with an average difference of +0.03 +/- 0.05 dex, whereas a significant discrepancy is observed in the range of [Fe/H] <= -2. (2) The behavior of [S(6)/Fe] versus [Fe/H] of our halo sample stars exhibits a nearly flat trend with an average of +0.62 +/- 0.09 dex in the range of -3 < [Fe/H] < -1.25, and shows a distribution around +0.29 dex in -1.25 <= [Fe/H] <= -0.7. Our sample stars with -1.25 <= [Fe/H] <= -0.5 follow an increasing trend with decreasing [Fe/H]. The behavior of [S(1)/Fe] of our sample stars also shows essentially the same trend as [S(6)/Fe], though it is quantitatively different. (3) The S behavior in the range of -3 < [Fe/H] <= 0 inferred from the abundances of multiplets 6 and 1 are qualitatively consistent with each other, and may be represented by a combination of a nearly flat trend and a linearly increasing trend with decreasing [Fe/H]. A transition of the trend is likely to occur at [Fe/H] similar to -1.5 dex.