Episodic accretion in focus: revealing the environment of FU Orionis-type stars

TL;DR

This study uses millimeter interferometry to investigate FU Orionis-type stars, revealing they may be in a transitional evolutionary phase influenced by episodic accretion events, which impact star formation processes.

Contribution

It provides the first systematic millimeter interferometry analysis of FU Orionis-type stars, suggesting they are in a transitional phase between Class I and II young stellar objects.

Findings

FU Orionis stars resemble both Class I and II systems.

They may represent a transitional evolutionary phase.

Episodic accretion drives their evolution.

Abstract

The earliest phases of star formation are characterised by intense mass accretion from the circumstellar disk to the central star. One group of young stellar objects, the FU Orionis-type stars exhibit accretion rate peaks accompanied by bright eruptions. The occurrence of these outbursts might solve the luminosity problem of protostars, play a key role in accumulating the final star mass, and have a significant effect on the parameters of the envelope and the disk. In the framework of the Structured Accretion Disks ERC project, we are conducting a systematic investigation of these sources with millimeter interferometry to examine whether they represent normal young stars in exceptional times or they are unusual objects. Our results show that FU Orionis-type stars can be similar to both Class I and Class II systems and may be in a special evolutionary phase between the two classes with their infall-driven episodic eruptions being the main driving force of the transition.