Water maser monitoring observations of the massive region of active star formation W49N Alexandr Volvach (1), Larisa Volvach (1), Michail Larionov (2) (1) Radio Astronomy of Crimean Astrophysical Observatory RAS, Katsively, Crimea (2) Astro Space Center, Lebedev Physical Institute RAS, Moscow A long-term monitoring has been carried out for two years of the massive region of active star formation W49N. As a result of long-term monitoring using the radio telescope RT-22 of a water vapor maser near a high-velocity line during 2017-2020, a series of flare phenomena were detected in the W49N galactic source. For four flare phenomena, a correlation was found between the natural logarithm of the flux and the reciprocal of the squared line width, which is characteristic of an unsaturated maser. Given that more than half of the stars in our Galaxy are binary or multiple stars, it is possible that we have massive binary (multiple) star systems in the regions of active star formation. In the case of W49N, the central massive star can reach a mass of 60 Mо. Ref. [1] MNRAS, 496, 1, L147РL151 (2020); [2] A&A, 628, A89 (2019); [3] MNRAS 487, L77–L80 (2019).