AB Aur: the continuum-subtracted forsterite emission at 69 μm (histogram) over-plotted with the best-fit model (red line) which is given by Eq. (2). This model is a sum of the following components: 50 K 3% iron (red dotted line), 50 K with 4% iron (yellow dashed line), 100 K 3% iron (green dash-dotted line) and 100 K 4% iron (blue dash-three-dots line) and 200 K 4% (purple dashed line). Each of the components is multiplied by a fitted weighting factor.