Unusual flare activity in the extreme-velocity −81 km s−1 water-maser feature in W49N

We report the detection of significant flaring events of the water masers associated with W49N using the radio telescopes RT-22 (Simeiz) and RT-32 (Torun). Two flares were detected between 2017 September to 2018 November. The −81 km s−1 water-maser feature reached a maximum of ∼50 kJy during these flares. The correlation of the observed exponential growth in flux density with a decreasing line width is consistent with the expected behaviour of an unsaturated maser. Possible mechanisms producing energy releases sufficient to power the water-maser flares in W49N are discussed.