Modelling of the Mg II line profile for the spectra taken by the NOT and TNG telescopes. Top left: NOT spectrum from May 1. Top middle: TNG spectrum from May 28 (first exposure). Top right: TNG spectrum from May 28 (second exposure). Bottom left: NOT spectrum from June 18. Bottom middle: TNG spectrum from July 3 (first exposure). Bottom right: TNG spectrum from July 3 (second exposure). For the spectra fitted with two Gaussian components plus a linear function, we represent the sum of the narrow component and the continuum in blue, the broad component and the continuum in red, and the total fitted model in black. For the spectra fitted with one Gaussian component plus a linear function we represent the total fitted model in black. The bottom panels show the residuals of the fits.