Astronomy Reports最新文献

For the effective application of the radio astronomical method for measuring the gain of large antennas, the problems of discrepancies in the flux densities of the main calibration radio sources (remnants of supernova Cassiopeia A and Taurus A and the radio galaxy Cygnus A) have been analyzed according to data from different catalogues, as well as with allowance for their angular sizes and structure. The data on the characteristics of these radio sources obtained at the Nizhny Novgorod Research Institute and other radio astronomical observatories over several decades have been compared.

Within the framework of entropic cosmology, several variants of a model describing the evolution of the Universe are considered, based on the Friedmann–Robertson–Walker (FRW) system of equations reconstructed taking into account a new modification of the Kaniadakis entropy at the cosmological horizon. The modification is carried out by replacing the Bekenstein–Hawking entropy in the dual expression of the Kaniadakis entropy (in which all states have the same probability) by the Barrow entropy associated with the transformation of the horizon of the Universe surface due to quantum-gravitational effects. As a result, various cosmological scenarios of the accelerated expansion of the Universe on the basis of the reconstructed FRW equations containing an additional force term depending on two free parameters of the model are obtained: the deformation parameter κ of the Kaniadakis entropy, which is responsible for taking into account the peculiarities of space-time, due to the long-range nature of gravitation, and the deformation parameter κ of the Barrow entropy, which is responsible for the fractal structure of the cosmological horizon surface, associated with the action of gravitational-quantum effects. The presence of two free parameters allows us to obtain new variants of driving forces in the FRW equations, which cause a deviation from the “standard” Bekenstein–Hawking holographic model and thus lead to a more accurate approximation to reality. The proposed approach meets the known requirements for thermodynamic modeling of the dynamical evolution of the Universe without involving the concept of hypothetical dark energy and based on the use of anti-gravity entropic forces. The obtained results show that the proposed entropic formalism can open additional opportunities for deeper insight into the nature of space-time and fractal properties of the Universe horizon.

In this paper, the design and technical features of the Rayleigh laser guide star (LGS) system as a reference source of an adaptive optical system developed for use on the Zeiss-2000 telescope at the Terskol Peak Astronomical Observatory (coordinates 43°16'34'', 42°29'57'') have been described. Experiments have been performed using the Zeiss-2000 telescope to test the developed system. As a result, a signal from the LGS sufficient for the operation of the wavefront sensor has been received. The presented numerical estimates of the effectiveness of adaptive correction from the Rayleigh LGS have shown that in the future, the use of an adaptive optical system on this telescope will significantly improve the quality of the generated image by increasing the Strehl ratio by at least ten times.

The purpose of the study has been to build a self-consistent gas-dynamic model of the accretion disk of a compact astrophysical object with allowance for viscosity. The matter falling on a compact object consists of proton gas, electrons, and radiation arising from the braking of a rotating gas at a speed comparable to light one. Physical proton viscosity is not sufficient in the gas-dynamic accretion model with laminar flow. It is necessary to introduce the so-called turbulent viscosity probably arising from the development of instabilities to explain the loss of the disk angular momentum. With a quantitative mathematical model of gas dynamics with allowance for the generally accepted turbulent viscosity, we want to demonstrate a solution with such instability. In a recently published study on Kepler disk braking, we have been able to obtain only large-scale vortex structures arising from azimuthal perturbations, for example, due to tidal effects and demonstrated an increase in disk braking against a neutron star due to these vortex structures. While the development of small-scale shear instability on the surface of a neutron star for a Kepler disk has not been demonstrated in calculations. In this study, we have examined a non-Keplerian disk with a non-zero negative radial velocity ensuring the flow of matter to the surface of a compact star, as a result of which shear instability and turbulence appear.

For the first time, pulsed radio emission from the RX J1605.3+3249 magnetar, which is part of the Magnificent Seven, has been detected. Data obtained at the BSA LPI radio telescope at a frequency of 111 MHz in the period from 2012 to 2024 were processed. The peak flux density of (S = 50{kern 1pt} - {kern 1pt} 100) mJy and the dispersion measure of (DM = 4.7 pm 0.5) pc/cm³ have been measured.

Determining the mass of a star is an important and complex process, possible only for the components of 2–3 hundred binary systems of certain observational classes. However, for thousands and tens of thousands of binaries of other observational classes, a simple and fast estimation of component masses is possible. In this paper, a method for estimating the mass ratio of the components from the difference in their luminosity and the total mass of the system has been proposed. The approbation of the technique on test sets of binaries with known component masses has showed a good (at the level of 7%) agreement of the results. The technique can be applied to visual binary systems of the main sequence with known parallaxes and orbital elements. The approximating polynomials have been presented in the paper as Fortran 90, C++, Pascal, and Python codes. The work is partially based on a talk presented at the Modern Stellar Astronomy 2024 conference.

In the paper, the main aspects of practical calculations by the formulas of Keplerian motion have been considered. The initial value under consideration is the mean anomaly and five other constant parameters. Much attention has been paid to solving the Kepler equation. An overview of the methods for solving has been given. A method for specifying the accuracy of calculations with allowance for the limited accuracy of representing numbers in a computer system has been considered. Examples of solving the Kepler equation and examples of motion trajectories have been provided. According to the considered concept, an optimal program for calculations has been compiled in the programming languages C/C++, Fortran, Python and offered on the Internet pages. The user has been given the opportunity to select a method for solving the Kepler equation from those considered in the paper.

In this paper, the results of observations of the XINS 1308.6+2127 (RX J1308.6+2127, RBS 1223) magnetar at a frequency of 111 MHz have been presented. To search for pulsed emission, data from the BSA radio telescope at the Lebedev Physical Institute, which were recorded in the mode of 32 frequency channels with a time resolution of 0.0125 s, and in a receiving band of 2.5 MHz, have been used. As a result of data processing in the period of 2012( - )2023, emission at the specified frequency has been detected. The following pulse parameters were measured in the study: peak flux density of 0.28 ± 0.03 Jy, 10%-width of W₁₀ = 0.2 s, fluence of 55 Jy ms, and dispersion measure of 3.7 ± 0.5 pc/cm³.

The braking index of a pulsar is a key parameter for understanding its radiation characteristics and kinetic energy loss mechanisms. The magnetic dipole radiation (MDR) model predicts a constant value for the braking index (n = 3), as described by a power-law form of the stellar spin-down between the spin angular frequency ((Omega )) and its derivative as ( - dot {Omega } propto {{Omega }^{{n = 3}}}). However, the timing observations indicate that the pulsar PSR J1640–4631 has an unusually high braking index of (n = 3.15 pm 0.03), which is unlike the other pulsars with precisely measured index in between 1 and 3. Therefore, the spin-down of this pulsar should not be controlled by the standard MDR model itself, thus we consider the gravitational wave radiation (GWR) induced by the deformed neutron star to have a contribution, however, which predicts the braking index (n = 5). Thus, we applied the combination of MDR and GWR to explain the higher braking index than 3, and then found that the (n) value is not a constant, but evolves from 5 to 3 with time. We also derived the evolution formula of the braking index and spin period ((P = 2pi {text{/}}Omega )), and their evolution simulations are also presented by assuming the initial spin period of this pulsar to be 1, 10 and 20 ms, respectively. Furthermore, the particular properties of the pulsar PSR J1640–4631 are discussed, and as a comparison, the stellar spin evolution with the constant spin-down power-law index (n = 3.15) is also thoroughly investigated.

The aim of this paper is to investigate the most dynamical properties of the motion of a test particle in the circular restricted 3-body problem with various perturbations such as modified potential, quantum correction, interactions and solar sail etc. The formulation of the problem and the equations of motion are illustrated. Then, we numerically find locations of stationary points, Poincaré surfaces of section, trajectory allocations, basins of attraction and stability of the stationary points. This study will be really helpful to those who are working in the space agencies with modern techniques.