Astronomy Reports最新文献

The results of a study on the existence of a local integral quadratic relative to velocity components for stationary stellar systems in the absence of any symmetry of the gravitational potential are presented. This refers to a separate isolated invariant surface in phase space, allowing the velocity field to be determined immediately for certain specific initial conditions. All two-dimensional potentials that allow such a local integral for rotating systems are listed. In this first publication, we will limit ourselves to cases of constant energy expansion in powers and coinciding characteristics, which lead to both known and non-trivial potentials allowing a quadratic local integral. The work is partially based on a presentation at the Modern Stellar Astronomy 2024 conference.

Using Gaia DR3 data, we studied the Orion Nebula Cluster (ONC) in the region of the sky where free planets and stars with planetary systems were discovered using the James Webb Space Telescope (JWST). We selected ONC candidate stars for which the probabilities of belonging to the cluster were estimated. Using Gaia DR3 star parallaxes, we determined the distance of the ONC from the Sun to be 393 ± 13 pc. The analysis allowed us to estimate the number of single and binary stars, the number of stars with planets, and the number of free planets in the selected region of space in the central part of the ONC. Our estimates indicate the possibility of obtaining new results from numerical modeling.

In this work, the gravitational instability of small-scale perturbations with an azimuthal wave number (m = 2) in disk-like self-gravitating systems is considered. Calculations of horizontal small-scale oscillation modes ((m;N) = (2;10)) and (2; 20) against the background of a nonlinearly non-equilibrium anisotropic model of a self-gravitating disk are performed. Critical diagrams of the relationship between the virial parameter and the degree of rotation for these modes are constructed, and the increments of instability for different values of the rotation parameter are calculated. The results show that the instability for the oscillation mode (2; 10) begins at a virial parameter value of ({{(2T{text{/}}left| U right|{kern 1pt} )}_{0}} approx 0.217) at (Omega = 0) and reaches 0.413 at (Omega = 1). For the oscillation mode (2; 20), the instability starts at a virial parameter value of ({{(2T{text{/}}left| U right|{kern 1pt} )}_{0}} approx 0.128) at (Omega = 0) and reaches 0.146 at (Omega = 1). It is found that with an increase in the rotation parameter, the instability region also increases, while with an increase in the degree of small-scale structure, the instability region significantly decreases. The work is partially based on a talk presented at the Modern Stellar Astronomy 2024 conference.

In this work, we investigate the problem of gravitational instability in a generalized model of a nonlinearly radially pulsating disk with an anisotropic velocity diagram relative to sectoral modes of perturbations. This model is a nonstationary generalization of the equilibrium self-gravitating disk by Bisnovatyi-Kogan and Zel’dovich. Exact expressions are obtained for the main physical characteristics of the generalized model, such as the components of the kinetic energy of the pulsating disk, velocity dispersions in the radial and transverse directions, the global anisotropy parameter, and others. We also found nonstationary analogs of dispersion equations (NADE) against the background of this generalized model for sectoral modes of perturbations. Based on the results of numerical calculations of NADE, graphs comparing the instability increments depending on the initial virial ratio of the system for various values of the parameters (alpha ) and (beta ), characterizing the difference and degree of anisotropy of nonlinearly nonstationary models of the self-gravitating disk, were constructed. In particular, it is shown that the development of bar-like mode instability will be the same for all anisotropic models, as the NADE of this mode does not depend on the parameters (alpha ) and (beta ). It is also established that the anisotropy parameters (alpha ) and (beta ) of the generalized model have opposite effects during the evolution of sectoral modes of perturbations. The work is partially based on a talk presented at the Modern Stellar Astronomy 2024 conference.

In this paper, observational capabilities of the Millimetron space-ground very long baseline interferometer mode for active galactic nuclei have been analyzed to obtain two dimensional images of these object with high angular resolution. The observatory with its 10-m mirror will conduct observations in the very long baseline radio interferometry mode together with ground telescopes in the frequency range of 43–345 GHz (the 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) μas. Obtaining images with high angular resolution both makes it possible to study the vicinity of nearby supermassive black holes and opens up new possibilities in studying the structure and dynamics of relativistic jets of active galactic nuclei and studying the core shift effect. Based on the previously calculated nominal orbit for the Millimetron observatory, the observational capabilities of 379 sources previously observed within the Radioastron mission scientific program have been analyzed. The fundamental capabilities of obtaining radio images of 13 sources with a specific possible time and duration of such observations have been 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 evolution, gas is mostly in the molecular form, while the process of protostars development causes a variety of surrounding matter emission in molecular lines at many frequencies of any ranges. This work is aimed at measuring the parameters of molecular radio lines in the vicinity of some young protostellar objects to expand our understanding of their evolutionary trends. Observations have been carried out with the RT-22 radio telescope at the Pushchino Radio Astronomical Observatory, Lebedev Physical Institute from July 2022 until May 2023. Two standard transistor receivers, which operated at frequencies of 20–24 GHz (13.5-mm range) and 36.2–37.7 GHz (8-mm range), have been used. Emission in the lines of four molecules, each one being a “tracer” of the environmental physical state: water (({{{text{H}}}_{{text{2}}}}{text{O}})), methanol (({text{C}}{{{text{H}}}_{{text{3}}}}{text{OH}})), ammonia (({text{N}}{{{text{H}}}_{{text{3}}}})), and cyanoacetylene (({text{H}}{{{text{C}}}_{{text{3}}}}{text{N}})) has been studied. Observational results for three IRDC objects, for two CORE-type objects, and for the star forming region Onsala-1 have been obtained. Radio emission in the water vapor line has been 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 have been determined from the emission spectra of the ammonia molecule, and the concentration of ammonia and the density of molecular hydrogen have been estimated. Emission in lines of cyanoacetylene in the direction of to sources IRDC G028.37+0.07b, and Onsala-1 has been detected, and the column density of this molecule has been determined.

In this paper, the calculations of dust temperature and thermal desorption rates in cold molecular clouds with taking into account stochastic heating of dust by an ultraviolet (UV) radiation field and cosmic rays (CRs) including secondary electrons, have been presented. The calculations for dust particles with a core radius in the range from 0.005 to 0.25 μm have been carried out. Grains with silicate and graphite cores covered by ice mantle (H₂O) with a thickness corresponding to the volume proportions between the core and mantle Sil/Gra : H₂O = 3 : 1 and 1 : 1 have been considered. For each dust composition, the most appropriate physical properties (heat capacity, absorption cross sections, and stopping power) have been used. Thermal desorption rates vary up to several orders depending on the dust size and up to a factor of two depending on the position in a cloud and dust core material. The obtained thermal desorption rates differ from the estimates available in the literature up to two orders depending on dust size and ambient conditions.

Convection, differential rotation, and meridional circulation of solar plasma are studied based on helioseismic data covering the period from May 2010 to August 2024, which is 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.

The numerical investigation conducted in this paper addresses the problem of CMB radiation imaging as seen through the throat of the Ellis–Bronnikov–Morris–Thorne wormhole. It is assumed that both throats of the wormhole are relatively close to our stellar neighborhood, so close that the view of the ambient background radiation by an observer at the other throat of the wormhole is virtually identical to that seen from the Solar System neighborhood. A map of the temperature distribution of the cosmic microwave background radiation observed through the mouth of the wormhole has been constructed as well as a view of the Milky Way through the mouth of the wormhole. The resultant image contains characteristic details that enable it to be distinguished from an image produced by a black hole.

Our multicolour photometric measurements of V361 Cam ((P{{ = 8.64}^{d}}), (V{{ = 10.79}^{m}}), (e = 0.12), B5 IV + B9 V) over the past 16 years, as well as TESS data, allowed us to determine for the first time the main physical characteristics of the system and measure the apsidal rotation velocity. The following physical parameters of the component stars were obtained: ({{T}_{1}} = 15{kern 1pt} {kern 1pt} 400 pm 300) K, ({{M}_{1}} = 6.0 pm 0.4{kern 1pt} {{M}_{ odot }}), R₁ = 5.03 ± (0.05{kern 1pt} {{R}_{ odot }}), ({{T}_{2}} = 11{kern 1pt} {kern 1pt} 700 pm 250) K, ({{M}_{2}} = 2.8 pm 0.2{kern 1pt} {{M}_{ odot }}), ({{R}_{2}} = 1.94 pm 0.04{kern 1pt} {{R}_{ odot }}). The photometric parallax of 0.00035″ ± (0.000001^{''} ) matches the Gaia measurement of (0.00035^{''} pm 0.00003^{''} ). The apsidal rotation velocity is ({{dot {omega }}_{{{text{obs}}}}} = 0.024 pm 0.007)°/year, which is less than the theoretical value under the synchronism condition ({{dot {omega }}_{{{text{theor}}}}} = 0.056 pm 0.006)°/year. The age of the system, assuming solar chemical composition, is 70 Myr. Both components are pulsating (beta ) Cephei variables.