Continuum flux ratio and microlensing signal. Top panel: continuum flux ratio. Middle panel: microlensing magnification ratio using the best fit (red circles) and the 1σ band (light grey region) for Galactic extinction. Bottom panel: microlensing magnification ratio using the best fit (red circles) and the 1σ band (light grey region) for quadratic extinction. In the middle and bottom panels, the microlensing signal from the 1σ bands is linearly interpolated in the spectral regions where the C iv, C iii] and Mg ii emission lines appear. We also show the zero-level for microlensing (dashed lines; μ_BA = 1) and fits to a simple microlensing model (solid lines; see main text).