Theoretical curves of growth for the two Ba resonance lines. Equivalent widths (EW) were computed in spectra synthesised by MARCS 1D atmosphere models adopting the atmospheric parameters T_eff = 5540 K, log g = 2.45, [Fe/H] = −2.00 dex, and υ_mic = 1.5 km s⁻¹. The barium abundance in the horizontal axis is neglected on purpose, as the scale depends on the abundance itself and the stellar parameters. The location of our stars is indicated by the red circles, where they are designated according to their evolutionary state as follows: turn-off (TO), subgiant (SG), base of the red giant branch (bRGB), over the clump RGB (ocRGB), and upper RGB (uRGB).