2019A&A...628A..89V

Aims. We present our monitoring observations and analysis of water masers associated with W49N taken in 2017 and 2018. A significant flare occurred during these observations.
Methods. We used ground-based radio telescopes in Simeiz (RT-22), Torun (RT-32), Medicina (RT-32), Effelsberg (RT-100) with broadband spectrometers. Observational data were collected and processed automatically. Results. We report a powerful flare of the v=+6km/s water maser feature; it increased in over ten months to S_1.3cm=84kJy in 2017 December, then decayed to the pre-flare quiescent value of S_1.3cm=8.7kJy in 2018 August. We infer that this flaring feature is unsaturated based on the relationship between line width and flux density.