Evolution of the H2O and OH Maser Emission in W75 N

Abstract

The results of a study of H₂O and OH maser emission in the complex region of active star formation W75 N are presented. Observations were obtained using the 22-m radio telescope of the Pushchino Radio Astronomy Observatory (Russia) and the Nan3ay radio telescope (France). Flaring H₂O maser features may be identified with maser spots associated with the sources VLA 1 and VLA 2. Themain H₂O flares occurred in VLA 1. The flare emission was associated with either maser clusters having closely spaced radial velocities and sizes up to ~2 AU or individual features. The maser emission is generated in a medium where turbulence on various scales is present. Analysis of the line shapes during flare maxima does not indicate the presence of the simplest structures—homogeneous maser condensations. Strong variability of the OH maser emission was observed. Zeeman splitting of the 1665-MHz line was detected for several features of the same cluster at a radial velocity of +5.5 km/s. The mean line-of-sight magnetic field in this cluster is ~0.5 mG, directed away from the observer. Flares of the OH masers may be due to gas compression at a shock or MHD wave front.