OH Maser Emission in the W51M Active Star-Forming Region

We present the results of a study of maser emission in the OH 1665 and 1667 MHz lines in the W51M star-forming region. The observations were carried out in 2022 and 2024 at the Large Radio Telescope in Nançay (France). The research results on the evolution of the flux density and the degree of circular polarization of individual spectral features are presented. The spectral features were spatially identified. It has been found that the degree of linear polarization $${{m}_{{\text{L}}}}$$ in five strongest features (55.92, 57.18, 57.72, 58.27, and 59.5 km/s) in the 1665 MHz line does not exceed 5%. For these features, the vector of the transverse magnetic field is oriented within an angular range of 19.6°–39.2°. Thus, it can be supposed that in this region there is a spatially organized magnetic field, which is of large scale for W51M (e1 and e2).