Spectral synthesis plot of CH band around 4310 Å. The dotted lines indicate the synthesised spectra and the solid lines indicate the observed spectra. Two alternative synthetic spectra are shown corresponding to Δ[C/Fe] = +0.05 (long-dashed line) and Δ[C/Fe] = −0.05 (short-dashed line) in panel 1 (for HD 145777); Δ[C/Fe] = +0.15 (long-dashed line) and Δ[C/Fe] = −0.15 (short-dashed line) in panel 2 (for HE 2144−1832); Δ[C/Fe] = +0.30 (long-dashed line) and Δ[C/Fe] = −0.30 (short-dashed line) in panel 3 (for HE 0017+0055); and Δ[C/Fe] = +0.10 (long-dashed line) and Δ[C/Fe] = −0.10 (short-dashed line) in panel 4 (for CD−27 14351).