Gravitational Instabilities, Chondrule Formation, and the FU Orionis Phenomenon

TL;DR

This paper investigates whether gravitational instabilities in protoplanetary disks can simultaneously explain chondrule formation and FU Orionis outbursts through analytic and numerical methods.

Contribution

It demonstrates that burst-like gravitational instabilities can produce shocks for chondrule formation and cause outbursts, with detailed analysis of different radial locations and disk stability.

Findings

GIs near 4-5 AU can produce chondrule-forming shocks under extreme conditions.

GIs can generate high mass fluxes associated with FU Orionis outbursts.

Disks remain stable against fragmentation despite high resolution and varying opacities.

Abstract

Using analytic arguments and numerical simulations, we examine whether chondrule formation and the FU Orionis phenomenon can be caused by the burst-like onset of gravitational instabilities (GIs) in dead zones. At least two scenarios for bursting dead zones can work, in principle. If the disk is on the verge of fragmention, GI activation near $r\sim4$ to 5 AU can produce chondrule-forming shocks, at least under extreme conditions. Mass fluxes are also high enough during the onset of GIs to suggest that the outburst is related to an FU Orionis phenomenon. This situation is demonstrated by numerical simulations. In contrast, as supported by analytic arguments, if the burst takes place close to $r\sim1$ AU, then even low pitch angle spiral waves can create chondrule-producing shocks and outbursts. We also study the stability of the massive disks in our simulations against fragmentation and find that although disk evolution is sensitive to changes in opacity, the disks we study do not fragment, even at high resolution and even for extreme assumptions.