Speaker
Description
The new K/Q/W tri-band receivers cover a number of important maser transitions
of methanol, water, SiO and other molecules. Many of these transitions are
excited in the vicinity of massive young stellar objects (MYSOs). Different
molecules and transitions have different excitation mechanisms and may originate
in different parts of the MYSO's environment, such as the circumstellar disk,
the envelope or the outflow. The evolution of such MYSOs is relatively fast and
dynamic. Single-dish (tri-band) monitoring can track the temporal flux density
and spectral variability that may be caused by accretion bursts, shocks,
outflows and maser cloud movements (superposition). However, only high angular
resolution and astrometrically registered tri-band VLBI observations can unravel
the spatial and spectral distribution of the various maser transitions to
interpret the variability origin and the physical conditions in the close
vicinity of the MYSO. In this talk we give an overview of the available
transitions and how a combination of these can be used to obtain new information
about the immediate environment of the forming star and how this advances
studies of star formation.
