Left panel: comparison between models with log ɛ_Tc = 0.0, 1.2, 2.5 (red, blue, green) for models broadened with a rotational profile (v_rot = 36 km s⁻¹, solid lines with 0.35 offset) and without rotation (dashed). Right panel: comparison betweena rotationally broadened model without Tc (black) and models with log ɛ_Tc = 1.2 with different levels of artificial noise (S/N of the single observation: red, S/N of co-added spectrum: blue, required S/N: green). For comparison, the observation is shown with an offset of 0.35 (single spectrum: gray, co-added spectra: black).