T_eff – log(τ) relation for the extrapolated model of scl002_06 (blue), compared with grid models for [Fe/H] = −3.0 (black) and −4.0 (red), and log g= 0.5,1.0,1.5, for T_eff = 4300 K. All these models are interpolated in T_eff between 4250 and 4500 K, but those with log g< 1.0 and [Fe/H] = −4.0 are interpolated between eight models (4250,4500;0.5,1.0;−4.0,−3.0), two of which are extrapolated (4250,4500;0.5;−4.0) from the MARCS grid. By chance, the model interpolated for scl002_06 (full blue curve) almost exactly coincides with the (4300;0.5;−4.0) model (full red curve), except in the range −0.5 < log(τ₅₀₀₀< + 0.4.