Title: What pebbles are made of: Interpretation of the V883 Ori disk,
Abstract: Recently, an Atacama Large Millimeter/submillimeter Array (ALMA) observation
of the water snow line in the protoplanetary disk around the FU Orionis star
V883 Ori was reported. The radial variation of the spectral index at
mm-wavelengths around the snow line was interpreted as being due to a pileup of
particles interior to the snow line. However, radial transport of solids in the
outer disk operates on timescales much longer than the typical timescale of an
FU Ori outburst ($10^{1}$--$10^{2}$ yr). Consequently, a steady-state pileup is
unlikely. We argue that it is only necessary to consider water evaporation and
re-coagulation of silicates to explain the recent ALMA observation of V883 Ori
because these processes are short enough to have had their impact since the
outburst. Our model requires the inner disk to have already been optically
thick before the outburst, and our results suggest that the carbon content of
pebbles is low.