Discovery of two new methanol masers in NGC 7538
  Context: NGC7538 is known to host a 6.7 and 12.2GHz methanol maser cospatial with a Ultra Compact (UC) HII region, IRS1.   Aims: We report on the serendipitous discovery of two additional 6.7GHz methanol masers in the same region, not associated with IRS1.   Methods: Interferometry maser positions are compared with recent single-dish and interferometry continuum observations.   Results: The positions of the masers agree to high accuracy with the 1.2mm continuum peak emission in NGC7538 IRS9 and NGC7538 S. This clear association is also confirmed by the positional agreement of the masers with existing high resolution continuum observations at cm and/or mm wavelengths.   Conclusions: Making use of the established strong relation between methanol masers and high-mass star formation, we claim that we have accurately positioned the high-mass protostars within the regions where they are detected. The variety of objects hosting a 6.7GHz methanol maser in NGC7538 shows that this emission probably traces different evolutionary stages within the protostellar phase. 
M. Pestalozzi, V. Minier, F. Motte, J. Conway