Fit to the radial intensity profiles observed by PACS at 70 μm. The blue and green solid lines represent the observed brightness distribution averaged over a narrow range of direction (Cox et al. 2012) and over all directions, respectively. The long dashed red line represents the model with Ṁ = 3 × 10^-10M_⊙ year^-1, inner and outer radius of 40 AU and 1800 AU, respectively, and with grains composed of 40% metallic iron and 60% Ca₂Mg_0.5Al₂Si_1.5O₇. The short dashed black line shows the model with Ṁ = 4 × 10^-10M_⊙ year^-1, inner and outer radius of 50 AU and 1800 AU, respectively, and with grains composed of 50% metallic iron and 50% Ca₂Mg_0.5Al₂Si_1.5O₇. The dotted purple line represents the model for the recent mass-loss history obtained in Sect. 3.7, with parameters given in Fig. 12 and with grains composed of 50% metallic iron and 50% Ca₂Mg_0.5Al₂Si_1.5O₇. The radial distance in AU is given along the upper x-axis for an assumed distance of 78 parsecs.