Flaring water masers associated with W49N

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 thev= +6 km s−1water maser feature; it increased in over ten months toS1.3 cm= 84 kJy in 2017 December, then decayed to the pre-flare quiescent value ofS1.3 cm= 8.7 kJy in 2018 August. We infer that this flaring feature is unsaturated based on the relationship between line width and flux density.