First detection of a THz water maser in NGC 7538-IRS1 with SOFIA and new 22 GHz e-MERLIN maps F. Herpin, A. Baudry, A. M. S. Richards, M. D. Gray, N. Schneider, K. M. Menten, F. Wyrowski, S. Bontemps, R. Simon and H. Wiesemeyer A&A, 606 (2017) A52 Published online: 09 October 2017 DOI: 10.1051/0004-6361/201731056