The results of research of a star formation region S255 IR, where a young high-mass star is forming ( 20 1ptM_⊙ ) are presented. Observations in H2O were carried out with RT-22 in Pushchino, and in the OH lines with the Large Radio Telescope in Nance (France). We used observations in the H2O line at 1.35 cm for the time interval from 2017 to 2023. Our observations in H2O showed the presence of strong flares, especially in 2023. A drift of the source emission along the radial velocity was also observed for most spectral features and predominantly with a tendency to decrease the radial velocity. In OH lines at 18 cm in 2008 no emission was detected. We observed OH emission in the main lines at 1665 and 1667 MHz in 2015, 2023, and 2024. Structures of spectra, degrees of circular and linear polarizations varied greatly during these epochs. However, the longitudinal magnetic field vectors had predominantly two directions ∼ 1pt± 1pt (30^∘- 40^∘ ) relative to the vertical, i.e. almost perpendicular to the jet or along it. Zeeman splitting was detected only in the 1667 MHz line for one pair of features: 2.26 and 2.37 km/s. The splitting value of 0.11 km/s corresponds to a longitudinal magnetic field value of 0.31 mGs; the field is directed towards the observer. It is assumed that the appearance of OH maser emission in 2015 associated with an accretion flares. Significant structure changes of OH spectra, their degrees of polarization and very strong flares of H2O maser in 2023 may be associated with a new possible accretion flares in S255 IR.

The results of the study of the star formation region G 109.871+2.114 (Cep A) in OH lines at 18 cm are presented. Polarization observations (monitoring) were performed with a large Nançay radio telescope (France) in 2007–2024. OH maser emission is highly variable. The structure of the spectrum and the flux density of the individual spectral features are changing. However, the radial velocities of most features changed slightly. Short-term emission flares in individual features were observed. Many features have strong circular polarization, reaching 100 χ is calculated for linearly polarized emission of most spectral features in both main lines at 1665 and 1667 MHz. It is shown that the magnetic field in the H II regions is oriented either along the external magnetic field or along the radio jets.

The results of a study of the variability of OH maser emission in the lines at 18 cm in the S128 star formation region from monitoring data in 2007–2022 with the Large Radio Telescope in Nançay (France) are presented. Maser emission was observed in the main line at 1665 MHz during the entire monitoring, and only short-term emission was observed in the satellite lines at 1612 and 1720 MHz. For the four strongest features in the 1665 MHz line, the variability of the positional angle χ of linearly polarized emission was found. The dependence of the angle χ on the radial velocity to some extent resembles a limited sinusoid, which may be due to the existence of an organized spatial structure of OH maser spots and the associated transverse magnetic field. For two Zeeman pairs in the 1612 MHz line having similar radial velocities (–75.344/–75.236 and –74.980/–74.903 km/s), the detected splits have opposite signs and, therefore, opposite directions of the longitudinal magnetic field. The directions of the transverse magnetic field vectors are also determined for these features. Apparently, the magnetic field is swirling and is associated with a swirling molecular outflows of matter.

Radio recombination lines comprise a powerful tool for studying the interstellar medium. One of the important tasks is to measure the primordial abundance of helium formed during the primordial nucleosynthesis of the Universe, which, in turn, allows us to verify the conclusions of the Standard Cosmological Model. The Orion A nebula is an interesting object for studying this problem. Previously, we found that, in this HII region, the region of ionized helium is smaller than the region of ionized hydrogen. Therefore, the actual helium abundance, n (He)/ n (H), is not less than the maximum measured value of y + = n (He + )/ n( H + ). This makes it possible to obtain restrictions on the primordial helium abundance. This article presents new observations of radio recombination lines in Orion A at a wavelength of 13 mm. It was found that the maximum value of y + is in the range 10.03–11.55%. Therefore, it can be expected that the primordial helium abundance ( Y p , He/H mass ratio) can be not less than ≈24.93–29.40%, which allows deviations from the conclusions of the Standard Model; for instance, it allows the presence of unknown light particles during primordial nucleosynthesis. Observations of doubly ionized helium in Orion A and the planetary nebula NGC 7027 were also made. It was found that the contribution of doubly ionized helium, y ++ = n (He ++ )/ n (H + ), is <7 × 10 –4 in Orion A and 2.7(±1.3)% for NGC 7027. Estimates of the electron temperature are also made. In particular, for NGC7027, it was found that Т e ≈ 11 900–12 300 K, which is higher than for the HII regions.

Results of a study of powerful H2O maser flares in the W51 region from observations (monitoring) in 2009–2022 with the 22-m radio telescope in the Pushchino Radio Astronomy Observatory are presented. Three powerful maser flares were detected at radial velocities of 69.7, 61.6, and 59.0 km/s with flux densities at peaks of 23.1, 29.4, and 66.1 kJy, respectively. The first and third of them are identified with the main source (W51 Main). A probable reason for their occurrence may be the superposition of two maser condensations with close radial velocities on the line of sight. A large number of flares with flux densities above 10 kJy were also detected, most of which were identified with W51 North. The mechanism for the appearance of the asymmetry of the line for the most powerful flare at a radial velocity of 59 km/s is discussed.

We present results of polarization observations of the ON 1 source in the 1665, 1667, and 1612 MHz hydroxyl lines at the Large Radio Telescope in Nançay (France). Spatial identification of the spectral features of OH in the 1665 and 1667 MHz lines with maser spots (condensations) on the VLBI map according to the data of Fish et al. (2005) was carried out. Emission from hitherto unknown spectral features in the 1665 MHz main line at radial velocities of –2.98, 9.35, and 11.8 km/s has been detected. Five Zeeman pairs were found: four in the 1665 MHz line and one in the 1667 MHz line. The vectors of the transverse magnetic field H ⊥ are oriented mainly along the arc (in the upper and lower parts of the UC H II region), while the vectors of the longitudinal magnetic field H|| in the northern and central parts of the UC H II region are oriented away from the observer, while in the southern part toward the observer.

We present results of the study of maser emission variability in the 1665 MHz OH line in the G43.8–0.1 star formation region based on observations (monitoring) in 2008–2022 at the Large Radio Telescope in Nancy (France). Variability of all polarization parameters of the majority of spectral features, which has a monotonic regular character, has been found. Spatial identification of the main spectral features of the OH 1665 MHz line with maser spots (condensations) on the VLA map has been carried out. For the Zeeman pair VLSR=44.15 km/s, a monotonic change of the splitting with time during 2008–2022 was found and, consequently, a change of the magnitude of the longitudinal magnetic field. According to our calculations, at the end of 2012, the direction of the magnetic field changed to the opposite. Сorrelated with H∥, there were changes in the angle χ and, as a consequence, changes in the direction of the vector of the transverse magnetic field H⊥0. For the maser feature at 44.5 km/s, a change of H⊥ by 180° was found. In 2016–2022, some reorientation of the global magnetic field (H⊥) in G43.8–0.1 occurred. The field became less chaotic: in the eastern part, the field in maser condensations is perpendicular to the arc, and in the western part, it is parallel to the arc. It is assumed that the global magnetic field in the entire U H II region of the G43.8–0.1 source has the same direction: along the axis (northeast)—(southwest).

The results of a study of the variability of maser emission in OH lines in the 18 cm range in the G10.624–0.385 star formation region from monitoring data performed at the Large Radio Telescope in Nançay (France) in 2008–2023 are presented. It is obtained that for a Zeeman pair in line 1667 MHz splitting (about 1.96 km/s) and, consequently, the magnitude of the longitudinal magnetic field have been stable for more than 25 years. In the satellite lines of 1612 and 1720 MHz, broadband absorption and emission are observed, respectively. The mirrored profiles of the OH 1612 and 1720 MHz satellite lines indicate that the levels of the corresponding transitions are pumped by IR radiation from a source immersed in a magnetized molecular cloud around the OH maser. Spatial identification of features in both main lines is carried out. It is found that the transverse magnetic field is directed mainly along some organized structure in the form of an arc.

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.

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.

The article presents the results of a research of the possibility of using discrete devices based on gallium nitride of the centimeter wavelength range for receivers of space systems and as part of ground-based radio astronomy observation systems using cryogenic cooling units.

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.

The radio recombination lines (RRLs) of hydrogen, helium (H, He) and carbon (C) have been observed at several positions of the HII region Orion A with the RT-22 radio telescope (Pushchino) at 8 and 13 mm. Information about the ionization structure of the HII region has been obtained. The behavior of y+ = n(He+)/n(H+) over the nebula and model calculations suggest that the effective temperature (Teff) of the star θ1 C Ori is in the range 35 000–37 500 K, corresponding to a spectral type ≈O6.5 V, which is important for the calibration of hot O-B stars. The electron temperatures (Te) of this HII region have been measured by taking into account the departures from local thermodynamic equilibrium (LTE); their distribution over the nebula up to distances of 300 arcsec from the center has been derived. The inferred temperatures are in the range 6600–8400 K, strictly decreasing in the eastward directionwith distance from the center, also tend to drop toward the periphery in the southward and westward directions. The turbulent velocities (Vt) of the ionized gas and their distribution over the nebula have been determined. The values of Vt inferred from H RRLs are in the range 9–13 km s−1.

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.