Astronomy Reports最新文献

The article presents the results of determining the parameters of the Earth’s gravitational field by gradiometric measurements in the geocentric terrestrial coordinate system. The calculations were performed using the regularization method, according to which a regularization matrix multiplied by the regularization parameter is added to the matrix of normal equations. As a result of calculations for various regularization parameters, corrections to harmonic coefficients of degree and order were obtained 200 and 201, presented in the article in the form of graphs. Based on the obtained corrections, the power-law dispersions presented in Tables 1 and 2 were calculated.

The work is devoted to the construction of a gas-dynamic model of the accretion disk around a neutron star (NS). The developed multidimensional code is used to study the stability of stationary axially symmetrical models by carry out of evolutionary calculations in 3D taking into account viscosity, as well as taking into account the diffusion of radiation in 2D. It is shown that an arbitrary stationary axially symmetrical disk with a monotonic decrease in density with a cylindrical radius transforms, due to viscosity, braking and spreading of matter along the NS, into a new quasi-stationary toroidal configuration. The stability study of the stationary toroidal configuration confirmed the formation of large-scale vortex structures at the initial periodic disturbance of angular velocity in azimuth, now taking into account the “turbulent” viscosity. It turned out that the presence of large-scale structures leads to an acceleration of braking, i.e., an effective increase in viscosity.

New high-precision photometric measurements of the V957 Cep system ((P{{ = 1.99}^{d}}), (V{{ = 11.17}^{m}}), (e = 0.127), B6 V+B8 V), as well as an integrated approach to determining orbital parameters based both on photometric solutions of the light curves and the study of the course of residual deviations of the minima timings from the linear formula (O - C) made it possible for the first time to accurately measure the apsidal motion rate: ({{dot {omega }}_{{{text{obs}}}}} = 2.91^circ )/year, which coincided with the theoretical value under the condition of the orbital and axial rotation synchronism: ({{dot {omega }}_{{{text{theor}}}}} = 2.92^circ )/year. The physical parameters of the component stars were obtained: ({{T}_{1}} = 14,550 pm 300) K, ({{M}_{1}} = 4.0 pm 0.2{kern 1pt} {{M}_{ odot }}), ({{R}_{1}} = 2.55 pm 0.05{kern 1pt} {{R}_{ odot }}), ({{T}_{2}} = 12,400 pm 250) K, M₂ = 3.0 ± (0.15{kern 1pt} {{M}_{ odot }}), ({{R}_{2}} = 1.88 pm 0.05{kern 1pt} {{R}_{ odot }}). This set of parameters corresponds to stars of zero age, recently descended to ZAMS. The secondary component is a pulsating variable star of the (beta ) Cephei type.

This study is based on observations of the pulsar B1133+16 conducted on the BSA PRAO antenna array at a frequency of 111 MHz with continuous recording of undetected signal (voltage) in the 2.5 MHz band, providing time resolution 0.2 µs. From 30 observation sessions, 570 strong pulses were selected for the subsequent analysis of microstructure parameters. The analysis was performed by computing autocorrelation functions separately for the three components of the mean profile: two extreme main components I and II and for the central weak component (S) in the profile saddle. For the component (S), microstructure analysis was performed for the first time. Distributions have been constructed by the following parameters: time scales ({{tau }_{mu }}), modulation depth ({{m}_{mu }}), and parameter (d), which characterizes the shape of the micropulses. Noticeable differences were found in some parameters for different profile components. The discovered features were interpreted in the model of hollow cone with a central component. It was believed that the radio emission of the extreme components (I and II) is generated by ordinary mode O, and the radio emission of the central component is provided by extraordinary mode X. Under this interpretation the radio emission output heights above the polar cap, were estimated to be 45 and 280 km for the X and O modes, respectively. A noticeable deformation of the X mode emission cone relative to the central component S was mentioned. Considerations are presented that point to the spatial structure of the secondary plasma flow, elongated along the meridians of the magnetic field.

The study of the kinematics and genetics of stellar populations in the Galaxy continued within a sphere with a radius of 300 parsecs based on the Gaia catalog (AG300). The main attention is paid to the chemical composition and genetics of stars in the corona of the core (halo) of the Galaxy with highly elliptical orbits and stars with hyperbolic orbits from the vicinity of the Sun. The possible role of various mechanisms of acceleration of the spatial motion of stars in the formation of the stellar corona (halo) of the Galaxy and stars with high hyperbolic (({v}) > 500 km/s) velocities in the vicinity of the Sun is considered. Supernova explosions in close binaries and the disintegration of unstable close triple stars have been proposed as possible mechanisms for the acceleration of these stars. The abundance of iron in corona stars coincides with the abundance of iron in globular clusters, which is an argument in favor of their relationship. It is shown that about 7% of low metallicity stars ([Fe/H] < 3), judging by the position of their apexes, may belong to the “first” stars of the Galaxy, or they are products of the decay of low-mass satellites of the Galaxy.

The results of research of a star formation region S255 IR, where a young high-mass star is forming ((20{kern 1pt} {{M}_{ odot }})) are presented. Observations in H₂O were carried out with RT-22 in Pushchino, and in the OH lines with the Large Radio Telescope in Nance (France). We used observations in the H₂O line at 1.35 cm for the time interval from 2017 to 2023. Our observations in H₂O showed the presence of strong flares, especially in 2023. A drift of the source emission along the radial velocity was also observed for most spectral features and predominantly with a tendency to decrease the radial velocity. In OH lines at 18 cm in 2008 no emission was detected. We observed OH emission in the main lines at 1665 and 1667 MHz in 2015, 2023, and 2024. Structures of spectra, degrees of circular and linear polarizations varied greatly during these epochs. However, the longitudinal magnetic field vectors had predominantly two directions ( sim {kern 1pt} pm {kern 1pt} (30^circ {-} 40^circ )) relative to the vertical, i.e. almost perpendicular to the jet or along it. Zeeman splitting was detected only in the 1667 MHz line for one pair of features: 2.26 and 2.37 km/s. The splitting value of 0.11 km/s corresponds to a longitudinal magnetic field value of 0.31 mGs; the field is directed towards the observer. It is assumed that the appearance of OH maser emission in 2015 associated with an accretion flares. Significant structure changes of OH spectra, their degrees of polarization and very strong flares of H₂O maser in 2023 may be associated with a new possible accretion flares in S255 IR.

This study presents generalized solutions to the Kepler problem involving the gravitational perturbation of a third body external to a two-body system. The spatial case of the non-coplanar motion of perturbing and perturbed bodies is considered. The expression for the relative position of the perturbing body relative to that of the perturbed body is expanded in Legendre polynomials. This expansion allows us to obtain the equation of motion and the energy of the system in terms of the orbital elements (I, Ω, ω, ν) for both the perturbed body and the perturbing body. By applying the Sundman transformation to regularize the dynamics of the problem, we eliminate a singularity and find two regularized equations of motion. Solutions to these equations are obtained by employing the families of the Battin and Stumpff functions. From these solutions, we derive formulas that are universally applicable and free from indeterminacy. This includes the expression for the radial distance, the generalized Kepler’s equation, the closed-form expressions for the coefficients f and g, along with their derivative forms, and the expressions for the orbital state vectors.

In the framework of entropic cosmology and Prigogine’s gravitational theory about the connection between geometry and matter, providing the production of particles in the cosmological fluid, as well as in the assumption of exchange entropy at the event horizon, a one-liquid model of the evolution of a spatially flat, homogeneous and isotropic Universe is constructed. For its construction the energy conservation equation is derived from the first law of thermodynamics taking into account gravitationally induced creation of matter and exchange energy processes on the visible horizon of the Universe. On the basis of the energy equation and the fundamental Friedman equation describing the expansion of the Universe, modified Friedman–Robertson–Walker equations have been constructed in the context of the entropic formalism, designed for modelling various dynamical aspects of the evolution of the Universe taking into account adiabatic creation of matter. Several forms of exchangeable phenomenological non-extensive entropies associated with the region of the apparent cosmological horizon were used in their derivation. The obtained evolutionary model, consistent with the standard Λ-model for cold dark matter, is intended to describe without introducing new fields the accelerated expansion of the late Universe, providing its cosmological history.

Since the first automatic missions to the Moon, the activity of dust particles from atmosphereless bodies has been recorded. Since then, a lot of theoretical and experimental studies of this effect have been carried out, but at present there is no clear understanding of the influence of external actions on the dynamics of this phenomenon. This paper presents the results of experiments to determine the effect of hard UV radiation on the activity of dust particles, which makes a significant contribution to particle dynamics. The result of determining the conditions for particle removal from the surface is in accordance with theoretical calculations.

The results of experimental research of the dynamics of current sheets, which are formed in laboratory experiments at the GPI RAS, are presented as a brief review. It is shown that the most significant features of phenomena like solar flares can be reproduced in laboratory conditions. These features include the relatively slow accumulation of the magnetic energy in the course of the current sheet formation, the rapid release of the energy during the disruption of the current sheet, acceleration of plasma flows, ultrafast plasma heating, and effective particle’s acceleration. A qualitative similarity has been established between the basic characteristics of current sheets in the tail region of the Earth’s magnetosphere and in laboratory conditions. A comparison of a number of fundamental dimensionless parameters indicates the possibility of quantitative laboratory modeling of processes occurring in the magnetosphere. It is concluded that experimental research of the dynamics of current sheets and magnetic reconnection processes represent one of the promising areas of the laboratory astrophysics.