Na I D emission lines evolution across time (time increase from top to bottom). Black color indicates the original spectra (UVES or X-shooter), while the light blue is for the UVES spectra degraded to the X-shooter resolution. Comparing epochs 5 and 6 (UVES) with epochs 7 and 8, it is evident that what appears as a “red wing plateau” in the low-resolution spectra could well be a signature of the non-resolved persistent absorption. Velocities are in the heliocentric rest frame. Y-axis units are erg cm⁻² s⁻¹ Å⁻¹.