Left: optical depth τ and surface density profiles Σ as a function of distance from the star for compact pebbles. Right: spectral index as a function of distance from the star for our benchmark model with compact pebbles of initial size 0.5 cm pre-outburst (dotted dark blue line) and post-outburst (solid dark blue line), and for our post-outburst model with porous pebbles of packing fraction 0.1 and initial size 5.0 cm (light blue line). The gray line with error bars corresponds to the data from Cieza et al. (2016).