Synthetic solar spectrum in the CH band region around ~4300 Å at the X-shooter resolution (R = 10 000) from the two employed reference grids: the grid computed by Knowles et al. (2021, blue), and the updated BOSZ library (orange). The selected CH bands (see Table 1), where the [C/Fe] abundance is measured, are delimited by the dashed vertical black lines. The flux difference at each wavelength between the two synthetic solar spectra is shown in the bottom panel.