In this paper, for each visual component of 65 visual binary and multiple stars of the Pulkovo research program, the parallaxes and radial velocities from the Gaia DR3 catalogs (if available) are presented. Uncertainties of these parameters, as well as the RUWE parameter, are analyzed. It has been shown that, if the data for visual components with internal subsystems are excluded from the data under consideration, the typical uncertainties of the Gaia DR3 parallaxes and radial velocities are 0.020 mas (85 components) and 0.14 km/s (60 components), respectively. The other possible causes of large errors of the analyzed data are discussed. We compare the radial velocities from the Gaia DR3, NSS, and ground-based observational data for five systems of stars. The mass estimates for 34 components of 22 systems under consideration are also compared. We found a possible systematic difference between the Gaia DR3 and MSC masses data. This difference amount to –0.06 solar masses for 31 of the 34 components. The paper is partly based on the talk presented at the Modern Stellar Astronomy 2025 conference.
The results of the study of the star-forming region W75 N in the H2O 1.35 cm and OH 18 cm lines during 2021–2025 are presented. Observations in H2O were carried out with the RT-22 telescope in Pushchino, and in the OH lines with the Large Radio Telescope in Nançay (France). Strong, closely timed flares of maser emission were detected in spectral features of H2O in the 22 GHz line and OH in the 1665 and 1720 MHz lines at radial velocities of 10.3, 3.5, and 8.5 km/s, respectively. Fainter and shorter-lasting flares were observed in the OH 1667 MHz line. Flare activity for the principal features in all lines began in 2021. Strong flares in the 22 GHz, 1665 MHz, and 1720 MHz lines are associated with maser spots located in the VLA 1 radio jet. Their occurrence may be related to the passage of MHD waves that excite maser emission in the corresponding layer of the envelope fragment. Flares in the OH 1667 MHz line at radial velocities of 0.22, 0.40, and 4.4 km/s, whose maxima were observed in 2021 and 2024, are associated with the Keplerian disk of VLA 2.
Recent observations at the ALMA ground-based observatory and the James Webb Space Telescope suggest that galaxies are formed at redshifts of z 20. This paper notices that the observed profiles of the velocity dispersion of dark matter (DM) halos in low-mass galaxies of the Local Group are well described by a profile appearing in numerical models of DM halos, and the estimate of entropy of these galaxies is consistent with the theoretical estimates of background entropy of baryons at z 20. It has been shown that the structure of the first dwarf galaxies may be close to the Lane–Emden model, and their minimum mass, Mmin 107 M_⊙ , is determined by the background entropy of baryons formed after recombination due to Compton scattering of the cosmic microwave background radiation on electrons of weakly ionized plasma.
We present the results of monitoring the magnetar RX J2143.0+0654, which is a member of the Magnificent Seven, in a period of 2012 to 2024. The monitoring was carried out on the Big Scanning Array (BSA) radio telescope of the Lebedev Physical Institute of the Russian Academy of Sciences at a frequency of 111 MHz in a receiving band of 2.5 MHz. The radio emission from the magnetar was detected, and the dispersion measure DM = 11 ± 1 pc/cm3 was measured. According to the model of the electron density distribution in the Galaxy, this value corresponds to a distance of 800 pc.
The paper discusses the fraction of extragalactic cosmic iron nuclei with energies of 1019 eV that reached Earth from distant sources without fragmentation in intergalactic space. It is shown that the fraction of particles with energies E = 1019 eV is significant (about 10
