Milliarcsecond structure of water maser emission in two young high-mass
  stellar objects associated with methanol masers
  The 22.2 GHz water masers are often associated with the 6.7 GHz methanol
masers but owing to the different excitation conditions they likely probe
independent spatial and kinematic regions around the powering young massive
star. We compared the emission of these two maser species on milliarcsecond
scales to determine in which structures the masers arise and to test a
disc-outflow scenario where the methanol emission arises in a circumstellar
disc while the water emission comes from an outflow. We obtained high-angular
and spectral resolution 22.2 GHz water maser observations of the two sources
G31.581+00.077 and G33.641-00.228 using the EVN. In both objects the water
maser spots form complex and filamentary structures of sizes 18-160 AU. The
emission towards the source G31.581+00.077 comes from two distinct regions of
which one is related to the methanol maser source of ring-like shape. In both
targets the main axis of methanol distribution is orthogonal to the water maser
distribution. Most of water masers appear to trace shocks on a working surface
between an outflow/jet and a dense envelope. Some spots are possibly related to
the disc-wind interface which is as close as 100-150 AU to the regions of
methanol emission.
