The monitoring results of the OH maser source in W75 N in the main line at 1667 MHz and satellite line at 1720 MHz performed in 2007–2020 using Nancay Radio Telescope (France) are presented. Generally, the maser in 2007–2009 is characterized by high activity in all lines, except for 1612 MHz, where the emission is thermal. During the monitoring, strong time variations in the flux density and polarization parameters were found for most spectral features. We found that the degree of circular polarization ( $${{m}_{{\text{C}}}}$$ ), as well as the degree ( $${{m}_{{\text{L}}}}$$ ) and polarization angle ( $$\chi $$ ) of linear polarization, change with time according to certain regularities, or change very little. There is a correlation between the variability of these parameters and the variability of the flux density. In this case, the radial velocities of the features change very little. The identification of spectral features in both lines (1667 and 1720 MHz) with maser spots on VLBA maps obtained in April 2008 has been carried out. We have identified seven spectral features in the 1667 MHz line and eleven in the 1720 MHz line. They are located in different parts of a large arc and well illustrate the fact that the orientation of the magnetic field vector changes more or less monotonically along the arc. The maser spots projected onto the VLA 2 (Keplerian disk) have been identified with seven spectral features in the 1667 MHz line. They form a small arc that is directed away from VLA 2. The magnetic field vectors associated with maser spots are oriented perpendicular to this arc. After flares of emission at 0.38 and 1.2 km/s, the magnetic field vectors of these features became oriented along the arc. For three Zeeman pairs in the 1667 MHz line (VLA 2), the magnitude of the longitudinal magnetic field was determined. In all cases, the field is directed towards the observer. For two features (–4.9 and 1.2 km/s), a monotonic change in the position angle by 140° and 110° was found, while the rate of rotation of the polarization plane is 5°/month and 7°/month, respectively. It was found that during a short-term flare of the 5.3 km/s feature in VLA 1, all polarization parameters changed, and after the flare, all of them were restored.

The monitoring results of the OH maser source in W75 N in the main line at 1665 MHz performed in 2007–2020 using the Nançay Radio Telescope (France) are presented. Generally, the maser in 2007–2009 is characterized by a high activity. During the monitoring, time variations of the Stokes parameters were found for all spectral features in the radial velocity range from –1 to 14 km/s. We found that its positional angle $$\chi $$ and the degree of linear polarization $${{m}_{{\text{L}}}}$$ , as well as the degree of circular polarization $${{m}_{{\text{C}}}}$$ of most features, change with time according to certain regularities, not chaotically. Or they can change very weakly and there is a correlation with the variability of the flux density. In this case, the radial velocities of the features change very little. It is shown that the main feature at 12 km/s during 50 years since the discovery of the OH maser in W75 N had two maxima of activity with an interval of about 30 years between them. The identification of spectral features in the 1665 MHz line with maser spots on VLBA maps has been carried out. We showed that a strong flare of the main features in 2007–2009 occurred in the VLA 2 source. During this flare, small changes in the angle $$\chi $$ and significant changes in the degree of both linear and circular polarization of features at 1.75, 2.1, and 3.05 km/s were observed. For the 0.65 km/s feature, significant changes in all emission parameters were observed. The emission in the 1612 MHz satellite line is broadband. The broadening of the line to 1.9 km/s indicates that, in addition to thermal motion of matter, there is also turbulent motion of matter in the medium.

ABSTRACT The aim of this work was to continue the monitoring of the H2O maser emission in IRAS 16293–2422 to detect superflares. We have been observing H2O maser emission at a wavelength of 1.35 cm towards the source IRAS 16293–2422 since 1999. The observations have been carried out with the 22-m radio telescope of the Pushchino Radio Astronomy Observatory (Russia). In 2007–2018, we also conducted several sessions of observations in OH lines at a wavelength of 18 cm in both circular polarizations with the Nançay Radio Telescope (France). Between 1997 and 2021, we observed three cycles of high activity of the H2O maser with a period of 8 yr. This variability could be related to the changing activity of the protostar in the tight binary system of IRAS 16293–2422 in the process of its formation. This variability could be related to an increase in the activity of the tight binary protostar IRAS 16293–2422 A, first seen in 2002. The H2O maser variation in flux density and radial velocity suggests that disturbances are propagating through organized structures in the form of chains ∼3.5 au long, with monotonic velocity gradients in the direction of propagation. The 18-cm OH emission in the main and satellite lines is thermal.

We present the results of our observations of the star-forming region located in the Perseus arm and associated with the Sharpless nebula S231 in the lines of H2O at a wavelength of 1.35 cm and OH at a wavelength of 18 cm obtained with the Pushchino 22-m radio telescope (Russia) and the Nançay Large Radio Telescope (France), respectively. We provide a catalog of H2O maser spectra in the period from March 2003 to March 2020. The variability of the integrated flux that we have calculated based on the monitoring by Felli et al. (1987–2007) and our monitoring (2003–2020) has a quasi-cyclic pattern with a cycle duration from 4.3 to 7.7 yr. Flares of maser emission of both single and several features occurred in each activity cycle. The mean rise and decay times of the flare emission were $$0.30 \pm 0.02$$ and $$0.35 \pm 0.02$$ yr, respectively. The observed radial velocity drift and jumps of the H2O emission features can be a consequence of the impact of shocks emerging as the protostar activity rises on them. The complex pattern of variability shows that the H2O masing medium is fragmented and small-scale turbulent motions of matter can occur in it. We have observed the OH maser emission in the 1665 and 1667 MHz main lines and the 1720 MHz satellite line. A large number of OH emission features and their variability have been detected. We have found one Zeeman pair at ‒9.2 km/s with a small splitting, with the longitudinal magnetic field in the period 2008–2020 having decreased monotonically from 0.24 to 0.10 mG. For the three most intense features we have calculated the degrees of linear polarization and position angles. A correlation between the H2O and OH maser activities has been found.

We present the observation results of the star forming region NGC 2071 in the 1.35-cm H2O line and 18-cm OH lines obtained with the 22-m radio telescope in Pushchino (Russia) and the large radio telescope in Nançay (France), respectively. The catalog of H2O maser emission spectra from December 2010 to January 2020 is given. The total flux variability for the entire monitoring period (1979–2020) has two activity cycles of close duration (approximately 20 years), which were accompanied by strong flares at intervals of one to four years. It is shown that the medium for the generation of H2O maser emission is greatly fragmented and contains small-scale turbulent motions of matter. The observed drift and radial velocity jumps of the H2O emission features can be a consequence of the complex, inhomogeneous structure of the maser emission regions. OH emission in the 1665 and 1667 MHz main lines and in the 1612 MHz satellite line in the radial velocity range of 7–12 km/s is broadband. The ratio of intensities differs from equilibrium. The substantiation of the observed ratio between the intensities of this emission and absorption in the 1720 MHz line is given. OH maser emission was observed in 2007 in the left circular polarization in the 1667 MHz line at 13.02 and 13.55 km/s with a flux density of ~0.3 Jy and a width of ~0.25 km/s for each of the velocities.

— The structure and evolution of powerful H 2 O maser flares in the source IRAS 18316–0602 are studied using the results of observations on the 22-m radio telescope of the Pushchino Radio Astronomy Observatory. The main origin of the last powerful, short-term flare in 2017 may be the superposition of two maser condensations with very similar radial velocities along the line of sight. All powerful flares occurring in IRAS 18316–0602 since 2002 can be associated with a cluster of maser condensations whose radial velocities are in the interval 41.0–43.5 km/s. It is suggested that this may be related to turbulent, possibly vortical, motions of material in this region.

Results of observations of the star-forming region S252A in the 1.35-cm H 2 O and 18-cm OH lines obtained using the 22-m Pushchino (Russia) and Nancay (France) radio telescopes are presented. A catalog of H 2 O maser spectra for 1995-2019 is presented. The variability of the integrated flux has two components: a cyclic component with a time interval between cycles ~30-35 yrs and a short-period component with a mean period of about 2.6 yrs. This may reflect non-stationary formation of a protostar. It is shown that the medium where the H 2 O maser emission and thermal OH emission are generated is strongly fragmented, and contains small-scale turbulent motions comparable to the thermal motions of the matter. The observed drift and jumps in the radial velocity of the H 2 O emission features could be a consequence of complex, non-uniform structure of the maser condensations.

The results of observations of water maser emission in the star-forming region G43.8-0.1, performed at a wavelength of 1.35 cm with the 22-m radio telescope of the Pushchino Radio Astronomy Observatory are presented. The integrated intensity of the maser emission in G43.8-0.1 varies quasi-periodically on characteristic time scales between 3.9 and 12.1 yr, possibly related to variations of the activity of the central star during its formation. Nine strong flares with maximum fluxes exceeding 3000 Jy were detected, and were identified with maser spots in high-resolution maps. It is argued that a shell model for the H2O maser in G43.8-0.1 is preferred.

The results of observations of OH maser emission in the star-forming region G43.8–0.1 are presented. In spite of strong flux-density variations in the main lines at 1665 and 1667 MHz, the radial velocities of the spectral features varied only slightly. The main spectral features are identified with maser spots in previously published maps for epochs 1993 and 2001. It is suggested that the regions of OH maser emission may be elongated, nonuniform structures with weak radial velocity gradients (larger-scale analogs of water-maser filaments). The line-of-sight magnetic fields are determined for two Zeeman pairs, which remained essentially constant over at least 17 years.

Results of monitoring hydroxyl and water masers in the star-forming region S128 are presented. A large number of emission features in the 1665 MHz OH line have been detected in both circular polarizations. In spite of the strong variability of the flux density in the main 1665 MHz line, the radial velocities of the features remained constant. Zeeman splitting of the 1720MHz line equal to 0.86 km/s was detected, corresponding to a longitudinal magnetic field of 3.6 mG. The variability of the H 2 O emission has a cyclic character with a quasi-period of 4–14 yrs. The evolution of individual features confirms that the H 2 O sources A and B are associated with an ionization front between two colliding CO clouds, and shows that the activity was transferred from maser B to maser A in 1999–2001.

The results of monitoring the H2O maser observed toward the region GH2O 092.67+03.07 (IRAS 21078+5211) located in the Giant Molecular Cloud Cygnus OB7 are presented. The observations were carried out with the 22-m radio telescope of the Pushchino Radio Astronomy Observatory in 2006–2017. Strong flares of the H2O maser emission with flux densities up to 19 800 Jy were detected. The flares exhibited both global (over the source) and local characters. All the flares were accompanied by strong variations in the H2O spectra within the corresponding radial-velocity ranges. Individual H2O components form both compact clusters and chains 1–2-AU long. Analysis of the variations of the fluxes, radial velocities, and line shapes of features during the flares showed that the medium may be strongly fragmented, with small-scale turbulent motions taking place in the H2Omaser region.