Astronomičeskij žurnal

The paper presents the analysis of observational capabilities of the Millimetron observatory’s very-long- baseline radio interferometry mode for active galactic nuclei to obtain two-dimensional images of these objects with high angular resolution. The observatory, with its 10-meter mirror, will conduct observations in the very long baseline radio interferometry mode together with ground telescopes in the frequency range of 43–345 GHz (wavelength range of 7–0.7 mm). Due to the orbit in the vicinity of the L2 Lagrange point of the Sun-Earth system, the maximum angular resolution will be up to 0.8 (43 GHz), 0.4 (100 GHz), 0.14 (230 GHz) and 0.1 (345 GHz) microarcseconds. Obtaining images with high angular resolution not only allows one to study the vicinity of nearby supermassive black holes, but also opens up new possibilities in studying the structure and dynamics of relativistic jets of active galactic nuclei and investigating the core shift effect. Based on the previously calculated nominal orbit for the Millimetron observatory, an analysis of the observational capabilities of 379 sources previously observed within the Radioastron mission scientific program was performed. The fundamental capabilities of obtaining radio images of 13 sources with a specific possible time and duration of such observations were demonstrated. The obtained results have broad practical significance in terms of further planning and development of the scientific program for the space-ground interferometer mode of the Millimetron observatory.

At the early stage of the protostar existence, gas is mostly in molecular form, and the process of protostars development causes a variety of surrounding matter emission in molecular lines at many frequencies in any diapason. The goal of this work is to measure molecular radio lines parameters in the vicinity of some young protostar objects to improve the understanding of their evolutionary trends. Observations were carried out with the RT-22 radio telescope of the Pushchino Radio Astronomical Observatory of the Lebedev Physical Institute from July 2022 until May 2023. Two standard transistor receivers were used, which operated at frequencies of 20–24 GHz (range 13.5 mm) and 36.2–37.7 GHz (range 8 mm). We studied emission in the lines of four molecules, each one being a “tracer” of the environmental physical state: water (H2O), methanol (CH3OH), ammonia (NH3) and cyanoacetylene (HC3N). Observational results were obtained for three IRDC objects, for two CORE-type objects and for the star forming region Onsala-1. Radio emission in the water vapor line was detected in all studied objects, except for IRDC G027.94–00.47. For three objects: IRDC G028.37+0.07b, IRDC G024.33+0011 and Onsala-1, the rotational and kinetic temperatures in the radiation region were determined from the emission spectra of the ammonia molecule, and estimates of the concentration of ammonia and the density of molecular hydrogen were obtained. Emission in lines of cyanoacetylene was detected in the direction of to sources IRDC G028.37+0.07b and Onsala-1, and the column density of this molecule was determined.

The physical parameters and evolutionary status of the spectroscopic binary Cepheid AU Peg, usually classified as a BL Her variable, are revised. Taking into account previously unpublished radial velocity measurements made with the correlation spectrometer, the parameters of the relative orbit of the system are refined. Based on 74 new radial velocity measurements made in the period 𝐽𝐷 2453930 − 2459490 almost simultaneously with the photometric observations of Gaia DR3 (44 brightness measurements in the period 𝐽𝐷 2456962 − 2457877), the parameters of to orbit and the radius of AU Peg is determined by the pulsating photosphere method to be ((16.0 ± 0.6) 𝑅⊙, with the amplitude of radius variations is about 0.7 𝑅⊙. For the first time, brightness variations at the level of 2% in the 𝐺 band with a half orbital period were found for spectroscopic binary Cepheids, the phases of which are clearly synchronized with the phases of the orbital motion (conjunctions and quadratures) and can be interpreted as a manifestation of the effect of the ellipsoidality of the primary component, filling the Roche sphere by 60–70%. The orbit of the binary system, calculated on the basis of astrometric data from Gaia DR3 and radial velocities, is bounded by a torus with a thickness of S𝑧S ⩽ 300 pc and inner and outer radii equal to 7.2 and 8.8 kpc, respectively, while the vertical velocity lies within S𝑉𝑧S ⩽ 18 km/s. Based on its kinematics and abundance of heavy elements, AU Peg can certainly be classified as a representative of the typical population of a disk of moderate (∼ 1–3 billion years) age, which completely excludes its classification as a BL Her variable. The Cepheid, whose current mass, as follows from the magnitude of the ellipsoidality effect, does not exceed ∼ (0.85 ± 0.05) 𝑀⊙, is at the stage after the mass exchange in the subgiant phase with a companion — a main sequence star, which is currently significantly more massive than the Cepheid.

Convection, differential rotation, and meridional circulation of solar plasma are studied based on helioseismic data covering the period from May 2010 to August 2024, significantly prolonged compared to that previously considered. Depth variation in the spatial spectrum of convective motions indicates a superposition of differently scaled flows. The giant-cell-scale component of the velocity field demonstrates a tendency to form meridionally elongated (possibly banana-shaped) structures. The integrated spectral power of the flows is anticorrelated with the solar-activity level in the near-surface layers and positively correlates with it in deeper layers. An extended 22-year cycle of zonal flows (“torsional oscillations” of the Sun) and variations of the meridional flows are traced. A secondary meridional flow observed at the epoch of the maximum of Solar Cycle 24 to be directed equatorward in the subsurface layers is clearly manifest in Cycle 25.