Spectra for the S-low stars, ET0322 and ET0147, are shown with black crosses. Red solid lines are the best fits of each S line, and blue dashed lines are the measurement errors, δ_noise, as listed in Table A.2. Green solid lines show [S/Fe] = 0.40 in the upper panel, and [S/Fe] = 0.15 in the lower panel, which are the average (LTE) S abundances in the sample, in the range ± 0.25 from the [Fe/H] of each star.