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