Sulphur abundance in very metal-poor stars

We have obtained high-resolution high signal-to-noise spectra of the SI near-infrared doublet at 8694 A in eight metal-poor stars with metallicities in the range -0.6 <[Fe/H]< -3.0. Elemental sulphur abundances were derived for six targets and upper limits were set for two of the most metal-poor stars in the sample. The sulphur doublet at 8694.62 A has been detected in three stars (HD19445, HD2665 and HD2796) with [Fe/H]< -1.9. Our observations combined with those available in the literature indicate a monotonic increase of the [S/Fe] ratio as [Fe/H] decreases, reaching values [S/Fe]~0.7-0.8 below [Fe/H]=-2. We discuss plausible scenarios for interpretation of these results.