Dust in the wind of outbursting young stars

¹ Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
² Department of Astrophysics, The University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
³ Research Institute of Physics, Southern Federal University, Rostov-on-Don 344090, Russia

^★ Corresponding author: kundan.kadam@oeaw.ac.at

Received: 4 February 2025
Accepted: 27 March 2025

Abstract

Context. Young stellar objects (YSOs) have been observed to undergo powerful accretion events known as FU Orionis outbursts (FUors). These types of episodic accretion events are now considered to be commonplace during low-mass star formation, wherein accretion onto the protostar occurs through a surrounding centrifugal disk. Increasing evidence suggests that the magnetic disk winds are crucial for driving disk accretion, as they carry both mass and momentum away from the disk.

Aims. We aim to investigate the phenomenon of the ejection of magnetic disk winds during episodic accretion, with a focus on the dust contained within these winds.

Methods. We conducted magnetohydrodynamic (MHD) simulations of the formation and evolution of a protoplanetary disk (PPD) in the thin-disk limit. We included the evolution of dust with two populations and a realistic prescription for viscosity during outbursts, which depends on the local thermal ionization fraction. The disk evolves with the concurrent action of viscosity, self-gravity, and magnetic disk winds.

Results. The simulated disk exhibits outbursting behavior in the early stages, with the duration and frequency of the bursts, their rise times, and brightness amplitudes resembling the properties observed for FUors. We find that during the outbursts, the winds are over an order of magnitude more dusty, as compared to in quiescence. However, despite this increased dust content, the winds are still dust-depleted as the dust-to-gas ratio is about an order of magnitude lower than the canonical interstellar value of 0.01. The results of our numerical experiments are in general agreement with the available observational findings, shedding light on the mechanism behind the production of dusty winds during outbursting events in YSOs.