What pebbles are made of: Interpretation of the V883 Ori disk

TL;DR

This paper reinterprets ALMA observations of the V883 Ori disk, suggesting water evaporation and silicate re-coagulation, rather than particle pileup, explain the spectral index variation near the snow line, implying low carbon content in pebbles.

Contribution

It introduces a model focusing on water evaporation and silicate re-coagulation to explain observed disk features, challenging the particle pileup hypothesis.

Findings

Water evaporation and re-coagulation can explain the spectral index variation.

The inner disk was likely already optically thick before the outburst.

Pebbles have low carbon content.

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.