Author(s): , , , , ,
Institution(s): 1. European Southern Observatory, 2. Harvard-Smithsonian Center for Astrophysics, 3. Max Planck Institute for Radio Astronomy, 4. Shanghai Astronomical Observatory
We report a multi-wavelength study of a recent major (~ 80,000 Jy) flare of the 22-GHz water maser in W49A. In February 2014, we started monthly monitoring with the Effelsberg 100-m radio telescope. In May 2014, we carried out the nearly simultaneous observations of the 22-GHz transition with selected submillimeter water transitions using the IRAM 30-m telescope (at 183 GHz) and the APEX 12-m submillimeter telescope (from 321 to 475 GHz). We have also performed interferometric observations using the NRAO Very Long Baseline Array (VLBA) at 22 GHz and the Submillimeter Array (SMA) at 321 and 325 GHz. One remarkable result is the detection of very high velocity emission features in several transitions. Our data also represent its first detection of the 475-GHz water transition in a star-forming region. Studying these multiple masing transitions in conjunction with theoretical modeling of their excitation not only places strong constraints on the physical conditions of the masing gas but also allows us to study their association with the embedded massive stellar cluster in W49A.