ИСТИНА

W75N is located in the vast Cygnus-X molecular complex with active star-forming process. Toward W75N three radio continuum sources (VLA1, VLA2, and VLA3) have been detected. The first one is a radio jet, and the second has not been spatially resolved and is identified with a protoplanetary disc. Toward both sources methanol, hydroxyl, and water vapour masers are observed. We report the results of our long-term monitoring of the H2O maser in W75N. The observations were carried out on the 22-metre radio telescope of the Pushchino Radio Astronomy Observatory, Russia. There were two cycles of maser activity, in 2006-2012 and 2012-2015. During each of them we observed strong flares of single features as well as of several features with very close radial velocities. Flux densities reached 8000 Jy. The emission radial velocity was 9-12 km/s. Using the data of the VLBA (NRAO) observations for the epochs 2005.89 (Surcis et al. 2011, A&A 527, A48), VLBI (VERA) for 2007 (Kim et al. 2013, ApJ 767, 86), and for 2012.54 (Surcis et al. 2014, A&A 565, L8), we have identified the flares with the sources VLA1 and VLA2. The main flares (there were nine) were associated with the VLA1 radio jet. The analysis of evolution of the flares has shown that the masering medium is turbulent with the probable turbulence scale of the order of the maser spot size and the maser spots themselves can be grouped in tight clusters. Examining the shapes and linewidths of isolated features at flare maxima enables us to admit also the existence of microturbulent motions within the maser spots resulting in line broadening. In all cases the blue wing is steeper than the red one, and it is well approximated with a Gaussian. We discuss mechanisms producing asymmetry of H2O line profiles. Asymmetry may be due to the motion of a maser condensation in the molecular cloud.