Astronomy Reports最新文献

An analytical model of a parabolic screen illuminating a black hole is proposed. This allows to avoid naturally the appearance of edge effects associated with photons moving along the plane of the screen illuminating the black hole. The temperature distribution along the radius of the screen corresponds to that for a relativistic disk (Novikov–Thorne disk). It is shown that the structure of the emerging black hole shadow differs significantly from the case when the photon source is a remote screen, since in the model considered, the photons subjected to strong gravitational lensing of the black hole are emitted by the “back side” of the screen, which would not be visible in the absence of a black hole. In the thin screen approximation, the shadow of a Schwarzschild black hole has been constructed in cases when the angle between the axis of symmetry of the illuminating screen and the direction towards the observer is 5°, 30°, 60°, and 80°. The images for the Kerr black hole are shown for the angles of 60° and 80°.

In this study, we expand on White’s model proposed in [1], which explores the post-collapse evolution of density peaks while incorporating the influence of angular momentum. Within a time scale smaller than the peak collapse, denoted as ({{t}_{0}}), the inner regions of the peak reach an equilibrium state, forming a cuspy profile, consistent with White’s findings. However, the power-law density profile is slightly flatter, specifically (rho propto {{r}^{{ - 1.52}}}), due to the incorporation of the specific angular momentum (J) obtained from theoretical models of its evolution in CDM universes, represented as (J propto {{M}^{{2/3}}}). The outcome above demonstrates the impact of angular momentum on the slope of the density profile, allowing us to reproduce a slightly flatter profile similar to the one observed in high-resolution numerical simulations, where (rho propto {{r}^{alpha }}) with (alpha simeq - 1.5). Notably, our model, like the simulations, does not account for adiabatic contraction. Therefore, conducting more comprehensive simulations may yield different values for the slope of the density profile, presenting an opportunity to enhance and refine our model.

Three light curves of the V1059 Cep eclipsing binary obtained in 2012, 2013, and 2021 were analyzed. We found the rapid apsidal motion in this system at the rate (domega {text{/}}dt = 7.2^circ ) per year. Assuming the equality of observed and theoretical apsidal motion rates we estimated physical characteristics of the components based on the data on their temperatures from the literature. According to our calculations the components are two very similar stars of the B7V–B7.5V spectral type with masses ( approx {kern 1pt} (3.4 pm 0.3){kern 1pt} {{M}_{ odot }}) and age (180 pm 30) million years.

A statistical study on the statements of the Gnevyshev–Ohl rule (GOR) and some of its interpretations has been carried out. The original formulation of the GOR states that for the summary index of solar activity over the 11-year cycle (Sigma W), there is a close connection in pairs of even and subsequent odd cycles (EO), while opposite pairs (OE) exhibit no such connection. This statement strictly holds with the significance level (alpha = 0.01) for the new version of the sunspot index SN 2.0 (Wolf numbers). In this case, an even cycle is followed by an odd cycle with a greater (Sigma W). For amplitudes of cycles, the GOR is observed only as a trend, and the difference of connections in EO and OE pairs of cycles is statistically insignificant. The alternation of the cycle magnitude, both for the (Sigma W) parameter and the amplitudes, is also not statistically confirmed. It has been found that various aspects of the GOR are statistically better fulfilled for the new version of the sunspot index SN 2.0, which speaks in favor of further use of this index in solar physics.

The changes in the orbital periods of the Algol-type eclipsing binaries RW Cap, BG Peg, and CU Peg have been studied. The changes in the orbital period of RW Cap and BG Peg can be well represented by cyclic variations with large amplitude. It has been shown, that these changes cannot be explained by the presence of a third body. They can be a consequence of the magnetic activity of the secondary components having a convective zone. The changes in the orbital period of CU Peg can be represented by a superposition of a secular period increase due to exchange of matter between the components and cyclic variations. These cyclic variations can occur due to the presence of a third body in the system or they can be a consequence of the magnetic activity of the secondary component.

The magnetospheric model of the HAT-P-11b magnetic field has been constructed based on the available data on the magnetic field of the star HAT-P-11 and its closest exoplanet HAT-P-11b, as well as the information on the stellar wind in this system. It has been shown how the magnitude and orientation of the interplanetary magnetic field control the magnetospheric structure. Each component of the stellar wind’s magnetic field creates a specific type of reconnection with the exoplanet’s magnetic field.

We perform numerical magnetohydrodynamic (MHD) simulations of the gravitational collapse and fragmentation of a cylindrical molecular cloud with the help of the FLASH code. The cloud collapses rapidly along its radius without any signs of fragmentation in the simulations without magnetic field. The radial collapse of the cloud is stopped by the magnetic pressure gradient in the simulations with parallel magnetic field. Cores with high density form at the cloud’s ends during further evolution. The core densities are (n approx 1.7 times {{10}^{8}}) and (2 times {{10}^{7}}) cm^–3 in the cases with initial magnetic field strengths (B = 1.9 times {{10}^{{ - 4}}}) and (6 times {{10}^{{ - 4}}}) G, respectively. The cores move toward the cloud’s center with supersonic speeds (left| {{{{v}}_{z}}} right| = 3.6) and (5.3) km/s. The  sizes of the cores along the filaments radius and filament’s main axis are ({{d}_{r}} = 0.0075) pc and ({{d}_{z}} = 0.025) pc, ({{d}_{r}} = 0.03) pc and ({{d}_{z}} = 0.025) pc, respectively. The masses of the cores increase during the filament evolution and lie in range of ( approx {kern 1pt} (10{-} 20){kern 1pt} {{M}_{ odot }}). According to our results, the cores observed at the edges of molecular filaments can be a result of the filament evolution with parallel magnetic field.

The results of measurements of background brightness in the near-infrared range (J, H, K bands), carried out in 2016–2023 at the Caucasus Mountain Observatory of Moscow State University was analyzed. It is shown that the instrumental background associated with the thermal radiation of the telescope is noticeable only in the (K) band, and at operating temperatures its contribution mainly determines the level of the overall background in this band. The coefficients of a polynomial taking into account the contribution of instrumental and extra-atmospheric backgrounds are presented. It is shown that the brightness of the sky background does not depend on air temperature, but a weak dependence on the water vapor content is observed, close to that expected from model calculations: in the (J) and (H) bands, the background brightness decreases at a rate of ( approx {kern 1pt} 1% {text{/}}1) mm, and in the (K) band it grows at a rate of ( approx {kern 1pt} 2.5% {text{/}}1) mm. The maximum amplitude of background brightness variability on short time scales (( sim {kern 1pt} 30) min) has been estimated: ( approx {kern 1pt} 10)% in the (J) and (K) bands and ( approx {kern 1pt} 30)% in the (H) band. The maximum contribution of Moon’s radiation scattered in the atmosphere to the overall background level has been determined. It is shown that this contribution can be ignored at an angular distance from the Moon greater than ( sim {kern 1pt} 10^circ ) even during a full moon. The average background surface brightness mag/arcsec² in the J, H, and (K) bands was calculated: ({{m}_{J}} = 15.7), ({{m}_{H}} = 13.9), and ({{m}_{K}} = 13.1).

This paper investigates the dynamical behavior of the effects of perturbations on the motion of infinitesimal body in the restricted three-body problem (R3BP) with logarithmic potential where both spherical primaries are taken as source of radiation pressure and third infinitesimal body is considered as variable mass according to Jeans law. We also have taken the effects of coriolis and centrifugal forces. For further investigations, we derive the equations of motion of the infinitesimal body where we get the effective variation due to parameters. Furthermore, we numerically illustrate some analysis of potential function, the locations of equilibrium points, trajectories allocations, surfaces of section, regions of motion and basins of attraction. Finally, the stability examination is done for the equilibrium points using Meshcherskii space-time inverse transformations.

Among the diverse progenitor channels leading to Type Ia Supernovae (SNe Ia), there are explosions originating from white dwarfs with sub-Chandrasekhar masses. These white dwarfs undergo detonation and explosion triggered by primary detonation in the helium shell, which has been accreted from a companion star. The double-detonation model predicts a correlation between the age of the progenitor system and the near peak brightness: the younger the exploding progenitors, the brighter the SNe. In this paper, we present our recent achievements on the study of SNe Ia properties in different locations within host galactic discs and the estimation of their progenitor population ages. Observationally, we confirm the validity of the anticipated correlation between the SN photometry and the age of their progenitors.