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Vol 102, No 3 (2025)
Articles
INFRARED AND X-RAY EMISSION OF A SUPERNOVA REMNANT IN A CLUMPY MEDIUM
Abstract
The infrared (IR) to X-ray luminosity ratio (IRX) is an indicator of the role of the dust plays in cooling of hot gas in supernova remnants (SNR). Using the 3D dynamics of gas and interstellar polydisperse dust grains we analyzed the evolution of SNR in the inhomogeneous medium. We obtained spatial distributions of the surface brightness both of the X-ray emission from hot gas inside SNR and the IR emission from the SNR swept-up shell, as well as, the average gas temperature in the SNR, 𝑇X. We found that the IRX changes significantly (∼ 3–30 times) as a function of impact distance within the SNR and its age. In a low inhomogeneous medium the IRX drops rapidly during the SNR evolution. On the other hand, if large inhomogeneities are present in the medium, the IRX is maintained at higher levels during the late SNR evolution at radiative phase due to replenishment of the dust in the hot gas from incompletely destroyed fragments behind the shock front. We showed that the evolution of the {𝑇X −IRX} diagram is determined by the onset of the radiative phase. We illustrated that decreasing gas metallicity or density leads to high values of temperature and IRX ratio. We discuss how our results can be applied to the observational data to analyse the SNR older than 10 kyr (i. e. when the mass of the swept-up dust in the shell is expected to exceed that produced in the SNR) in the Galaxy and Large Magellanic Cloud.
Astronomičeskij žurnal. 2025;102(3):159–169
159–169
ANISOTROPIC SCATTERING OF THE RADIO EMISSION IN THE DIRECTION TO THE PULSAR B1642–03
Abstract
Observations of the pulsar B1642–03 were carried out with the ground-space interferometer Radioastron during the implementation of the key scientific program of the project. The observations were conducted on September 8, 2013 at frequencies 316–332 MHz. The Westerbork Synthesis RT (WSRT) was used as a ground arm of the interferometer. The baseline projections of the interferometer changed during the observations approximately from 10 000 km to 20 000 km, and the positional angle of the baseline changed almost for 50X. This configuration made it possible to estimate the angular diameter of the scattering disk in different positional angles. It was found that shape of the scattering disk can be presented in the form of an ellipse with an axial ratio of 2:1. Comparison of the angular size of the scattering disk and the delay time of scattered rays indicates a possible irregular structure of the scattering disk, which may be due to lensing of radio waves when passing through the Stromgren zone near the star ζ Oph.
Astronomičeskij žurnal. 2025;102(3):170–177
170–177
NUMERICAL STUDY OF 𝑛 = 1 POLYTROPES WITH DIFFERENTIAL ROTATION
Abstract
The solution space of differentially rotating polytropes 𝑛 = 1 is studied numerically. The existence of three different types of configurations is proved: from spheroids to thick tori, hockey puck-like bodies and spheroids surrounded by a torus, separate from or merging with the central body. It is shown that the last two types appear only at moderate degrees of rotation differentiality, σ ≃ 2. Rigid-body or weakly differential rotation, as well as strongly differential, do not lead to any such “exotic” types of configurations. Many calculated configurations have extremely large values of the parameter τ, which raises the question of their stability with respect to fragmentation.
Astronomičeskij žurnal. 2025;102(3):178–191
178–191
ACTIVITY OF TOI-3568 AND MASS LOSS OF THE ATMOSPHERE OF ITS EXOPLANET IN THE SUB-JOVIAN DESERT
Abstract
We considers the properties of the TOI-3568 system, which has a super-Neptune-type planet and which by its properties falls into the region of the sub-Jovian desert. TOI-3568 is a poorly studied dwarf of the spectral class K. On the base of archival measurements of the brightness of TOI-3568 (Kamogata Wide-field Survey) we estimated the possible cyclic long-term variability of the object equal to 1.3, 1.7 and 4.1 years. It is found that TOI-3568 belongs to the number of old stars and can have only moderate or low activity. Calculations of the mass loss from the planet’s atmosphere were carried out using an approximation formula for the atmosphere loss model with an energy limitation. If the star is a low-activity K dwarf then 𝑀loss can be 1.18 × 109 g/s. If the star’s activity approaches the maximum for stars of this spectral class then the value of 𝑀loss will increase in 6.3 times. Our data are in an agreement with the results characterizing the general behavior of the parameter 𝑀loss for other objects, including the hot Jupiter HD 189733 b and the warm Neptune GJ 436 b. TOI-3568 system is of particular interest because it allows us to study rare objects located on the “mass-period” or “radius-period” diagrams of exoplanets in the region that covers the range between super-Earths and hot Jupiters (called sub-Jovian desert) and which exhibits a deficit in the number of planets. The fact that TOI-3568 is an old star provides a unique opportunity to trace the evolution of the properties of a planetary system currently located in the sub-Jovian desert.
Astronomičeskij žurnal. 2025;102(3):192–196
192–196
MODELING OF TRANSIT ABSORPTIONS OF WARM NEPTUNE WASP-69b IN THE METASTABLE HELIUM LINE
Abstract
This work presents the results of complex numerical modeling of the transit absorptions of the hot exoplanet WASP-69b in the metastable helium HeI(23S) line. The modeling was provided using a 3D MHD code, which allows for the simulation of effects that influence the absorption profile in various spectral lines and predicts a realistic distribution of the density of the main components and the structure of the interacting flows of planetary and stellar material. It was shown that the simulated transit absorption profiles closely match the height and width of the measured transit profiles, which allowed for the estimation of the physicochemical parameters in the area of exoplanet WASP-69b.
Astronomičeskij žurnal. 2025;102(3):197–204
197–204
THE POSSIBILITY OF OBSERVING PHOTON RINGS USING HIGH FREQUENCY VERY LONG BASELINE SPACE RADIO INTERFEROMETRY
Abstract
The paper examines the possibility of observing photon rings in the close vicinity of supermassive black holes using very long baseline space radio interferometry at a frequency of 600 GHz. The 600 GHz range is promising for such observations in very long baseline radio interferometry, because high frequency reduces the contribution of radio emission scattering by the interstellar medium, and also makes it possible to increase the angular resolution of the interferometer. High angular resolution and low scattering, in turn, suggest the possible detection of photon rings in the close vicinity of supermassive black holes. To assess such possibilities, modeling of the visibility amplitude distribution from the baseline projection was performed, taking into account various possible sensitivity parameters of the interferometer. Based on the results, the prospects for the 600 GHz range in terms of observing photon rings are shown. In addition, the requirements for the on-board receiving complex of a space interferometer are formulated, at which detection of photon rings is feasible.
Astronomičeskij žurnal. 2025;102(3):205–212
205–212
PROBLEMS AND METHODS OF MODERN SEARCH FOR COSMIC STRINGS
Abstract
In this paper, the theoretical and observational problems of the search for cosmic strings (CS) by methods of modern astrophysics are discussed, and new possibilities for further observational search for CS are proposed and justified. In recent works by the authors, it was shown for the first time that taking into account the geometry of the CS (tilt and bend) cardinally affects one of the main observational methods of searching for CS: searching for chains of images of galaxies that should be formed due to the effect of gravitational lensing of background galaxies on the CS. Further, these theoretical developments were applied to the analysis of observational data of the double galaxy SDSS J110429.61+233150.3, previously found in the field of the assumed CS (CSc-1), identified, in turn, by the analysis of the CMB anisotropy. Based on these long-term studies, this paper for the first time identifies the fundamental problems of approximate theoretical models, within which the evolution of both CS networks and single CS is traditionally considered, and also for the first time justifies the rejection of the traditional search for extended chains of gravitational-lens pairs. In this paper, a new detailed strategy for searching for CS is proposed by identifying and analyzing the characteristic clustering of gravitational-lens pairs. The strategy is proposed using the example of the analysis of gravitational-lens pairs in the CSc-1 region, and the requirements for future observations are indicated. Arguments are also given that allow for a change in the linear density of CS in a wide range, arguments are given that “heavy” CS do not contradict modern observational data, including on the CMB anisotropy and the gravitational-wave background. A strategy for the systematic analysis of binary quasars (having a gravitationally lensed nature and an unidentified lens object) as lensed on CS is discussed.
Astronomičeskij žurnal. 2025;102(3):213–228
213–228
APPLICATION OF A NEW FORMULA FOR ANGULAR VELOCITY OF ROTATION TO THE PLANETOID HAUMEA
Abstract
The aim of the work is to test a new formula for the angular velocity of rotation Ω of inhomogeneous equilibrium figures on the model of a unique rapidly rotating trans-Neptunian dwarf planet Haumea. The three-axis two-component model of Haumea consists of an ellipsoidal rocky core and a thick confocal ice shell. The parameters of this model are determined from a system of eight algebraic equations that take into account the complete kinematic-photometric information about the planetoid. Using the methods of potential theory, the components of the internal and external gravitational energy of the model on which this Ω depends are found. For this purpose, a refined expression for the gravitational energy of a homogeneous confocal shell and a formula for the mutual energy of the core and the shell are used. It was found that in order to be consistent with the observed rotation period of Haumea τrot = 3h.915, this model should be considered as a polytrope with the index 𝑛 ≈ 0.984. This result confirms the relevance of the developed method for studying inhomogeneous equilibrium figures.
Astronomičeskij žurnal. 2025;102(3):229–236
229–236