Accretion through the inner hole of transitional disks: What happens to the dust?

TL;DR

This study investigates whether radiation pressure can prevent dust from entering the inner holes of transitional disks, concluding it cannot due to dust pile-up, optical effects, and viscous mixing, thus other mechanisms are needed.

Contribution

The paper demonstrates that radiation pressure alone cannot maintain dust-free inner holes in transitional disks, challenging previous hypotheses and suggesting the need for alternative explanations.

Findings

Radiation pressure cannot stop dust inflow into the inner hole.

Dust pile-up and optical depth effects undermine radiation pressure's effectiveness.

Viscous mixing further prevents dust clearance by radiation pressure.

Abstract

We study the effect of radiation pressure on the dust in the inner rim of transitional disks with large inner holes. In particular, we evaluate whether radiation pressure can be responsible for keeping the inner holes dust-free, while allowing gas accretion to proceed. This has been proposed in a paper by Chiang and Murray-Clay (2007, Nature Physics 3, p. 604) who explain the formation of these holes as an inside-out evacuation due to X- ray-triggered accretion of the innermost layer of the disk rim outside of the hole. We show that radiation pressure is clearly incapable of stopping dust from flowing into the hole because of dust pile-up and optical depth effects, and also because of viscous mixing. Other mechanisms need to be found to explain the persistence of the opacity hole in the presence of accretion, and we speculate on possible solutions.