First detection of CS masers around a high-mass young stellar object,
  W51 e2e
  We report the discovery of maser emission in the two lowest rotational
transitions of CS toward the high-mass protostar W51 e2e with ALMA and the
JVLA. The masers from CS J=1-0 and J=2-1 are neither spatially nor spectrally
coincident (they are separated by ~150 AU and ~30 km/s), but both appear to
come from the base of the blueshifted outflow from this source. These CS masers
join a growing list of rarely-detected maser transitions that may trace a
unique phase in the formation of high-mass protostars.
