Discovery of widespread non-metastable ammonia masers in the Milky Way Y. T. Yan, C. Henkel, K. M. Menten, T. L. Wilson, A. Wootten, Y. Gong, F. Wyrowski, W. Yang, A. Brunthaler, A. Kraus and B. Winkel A&A, 686 (2024) A205 Published online: 13 June 2024 DOI: 10.1051/0004-6361/202348931