Astronomy Reports最新文献

At present, there is little doubt that accretion discs surrounding compact astrophysical objects such as black holes, white dwarfs, and neutron stars may have magnetic field structures. Thus, they explain the transfer of angular momentum between different parts of the disc and some other processes. There are various ways to explain the occurrence of these magnetic fields. In this paper, we study the possibility of generation of magnetic fields due to the Biermann battery mechanism. It is associated with radial flows of protons and electrons. Due to their different masses, they interact differently with the rotating medium, producing circular currents that generate magnetic fields. Previously, a similar process was studied for galactic discs and it was shown that the battery mechanism can generate initial magnetic fields in such objects. Here, we discuss the action of the Biermann battery for accretion disks. This requires solving an integral equation of the second kind, which arises if we take into account the self-interaction of the magnetic field. It is shown that co-rresponding fields are quite significant and can play an important role in the evolution of magnetic fields in discs.

In the present research work, we have carried out an analysis of the non-linear stability of the circular restricted three-body problem (CR3BP) with Kerr-like primaries. The model discussed here includes three bodies, two of which are Kerr primaries that spin on their axes and at the same time, revolve around the mutual center of mass (origin) and the third is an infinitesimal mass. We take here, the parameter (epsilon ) which represents the transition from Newtonian dynamics to beyond-Newtonian dynamics. With this perturbation, we evaluate the equation of motion of infinitesimal mass and then discuss the nonlinear stability of triangular stationary points ({{mathbb{L}}_{4}}) and ({{mathbb{L}}_{5}}). We use the KAM Theorem for the stability analysis and obtained some meaningful conclusions numerically. Further, these obtained results on stability and other dynamical properties like the location of ({{mathbb{L}}_{4}}) and ({{mathbb{L}}_{5}}), potential surfaces, and regions of motions have been discussed graphically.

Depending on the distance of the exoplanet from the central star and the properties of this star, different regimes of stellar wind flow around it arise. If the exoplanet is located at a distance up to the Alfvén radius, where the wind speed is equal to the Alfvén speed, or the Alfvén Mach number ({{M}_{{text{A}}}} = 1), the exoplanet generates Alfvén wings. If it is situated beyond the Alfvén radius, a comet-like magnetosphere appears, similar to that of the planets of the Solar System. The paper examines how the transition from one flow regime to another can be described on the base of a paraboloid model of the magnetospheric magnetic field using the example of exoplanet HD 209458b.

The problem of motion of a zero-mass point under the influence of attraction to the central body and a small perturbing acceleration ({mathbf{P}}{kern 1pt} ' = {mathbf{P}}{text{/}}{{r}^{2}}) is considered, where (r) is the distance to the attracting center, and components of vector ({mathbf{P}}) are assumed to be constant in a reference system with axes directed along the radius vector, the transversal, and the angular momentum vector. Previously, for this problem, we found equations of motion in the mean elements and formulas for the transition from the osculating elements to the mean elements in the first order of smallness; second-order quantities were neglected. In this study, the Euclidean (root-mean-square over the mean anomaly) displacement norm ({{left| {d{mathbf{r}}} right|}^{2}}) is obtained, where (d{mathbf{r}}) represents the difference between the position vectors on the osculating and mean orbit. It turned out that ({{left| {d{mathbf{r}}} right|}^{2}}) depends only on the components of vector ({mathbf{P}}) (positive definite quadratic form), the semimajor axis (proportional to the second power), and the eccentricity of the osculating ellipse. The norm ({{left| {d{mathbf{r}}} right|}^{2}}) is obtained in the form of series in powers of (beta = e{text{/}}(1 + sqrt {1 - {{e}^{2}}} )) and in powers of the eccentricity (e). The results are applied to the problem of the motion of asteroids under the influence of a perturbing acceleration inversely proportional to the square of the heliocentric distance, in particular, under the influence of the Yarkovsky effect.

The restricted circular three-body problem is studied. All global families of periodic orbits adjacent to the libration points are found. A scenario for the evolution of orbits in the family is given. Chains of global families are highlighted; the chain begins at the triangular libration point, contains global families for the triangular and all collinear libration points, and ends with a family whose orbits are pressed against the main bodies. The evolution of global families in the chain associated with changes in the energy of the system is described. Planar and spatial orbits are studied.

We explore the possibility of using measurements of the gravitational redshift effect as a means to constrain wave dark matter—a class of models in which the dark matter is accounted for by light scalar particles that behave like classical waves. We construct a mathematical framework that is appropriate for clock comparison experiments with remote clocks and can be used to determine the values of the coupling constants of such dark matter with particles of the Standard Model. Using this framework, we consider an experiment to detect dark matter of the Galactic halo using two satellites equipped with accurate and stable atomic clocks and placed into elliptical heliocentric orbits. We demonstrate that, in most cases, the accuracy of this experiment turns out to be not better than that of ground-based experiments with colocated clocks. The limitation of the accuracy of the space-based experiment is found to be due to the non-relativistic Doppler compensation system, required when using moving clocks, which decreases the amplitude of the useful signal. Possible solutions to this problem are discussed.

The kinematics of the ϵ Cha young stellar association close to the Sun has been studied based on a list of candidate stars from the Dickson-Vandervelde et al. work. The working sample consists of 26 stars with parallaxes, proper motions from the Gaia DR3 catalog and radial velocities taken from literary sources. The orbits of the stars back to the past were constructed, and the moment when the association had a minimum spatial size was determined, as well as an analysis of the dependencies of the velocities (U,;V,;W) on the coordinates (x,;y,;z) was carried out. It is shown that the initial sample is divided into two parts with different kinematic properties. The first sample included 9 stars. Based on the construction of the orbits of these 9 stars, an age estimate of (t = 4.9 pm 0.8) million years was obtained. An expansion coefficient in the (xz) plane with the value ({{K}_{{xz}}} = 135 pm 19) km/s/kpc was also found for them, on the basis of which another age estimate (t = 7.2 pm 1.0) Ma was obtained. The second sample included 17 stars. The construction of their orbits gave an estimate of age (t = 0.2 pm 0.3) Ma, and based on the gradient (dW{text{/}}dz = 707 pm ) 248 km/s/kpc, a second estimate of their age (t = 1.4 pm 0.5) Ma was obtained. This suggests that the (epsilon ) Cha association either consists of two groupings of different ages, or a younger one arose as a result of a recent outbreak of star formation within a common star system. The question of the gravitational connection of the groupings has not been considered in the framework of this work.

Geomagnetic storms have a significant impact on the performance of technical systems both in space and on Earth. The sources of strong geomagnetic storms are most often interplanetary coronal mass ejections (ICMEs), generated by coronal mass ejections (CMEs) in the solar corona. The ICME forecast is based on regular optical observations of the Sun, which make it possible to detect CMEs at the formation stage. It is known that the intensity of geomagnetic storms correlates with the magnitude of the southern component of the magnetic field (B_z) of the ICME. However, it is not possible yet to predict the sign and magnitude of B_z from solar observations for the operational forecast of an arbitrary CME. Under these conditions, a preliminary forecast of the magnetic storm probability can be obtained under the assumption that the strength of the storm is related to the magnitude of the magnetic flux from the eruption region, observed as dimming. In this paper, we examine the relationship between the integral magnetic flux from the dimming region and the probability that CMEs associated with them will cause geomagnetic storms, using a series of 37 eruptive events in 2010–2012. It is shown that there is a general trend toward an increase in the ICMEs geoefficiency with an increase in the magnitude of the magnetic flux from the dimming region. It has been demonstrated that the frequency of moderate and severe storms observation increases in cases of complex events associated with the interaction of CMEs with other solar wind streams in the heliosphere.

We investigate unresolved binary systems with components of main sequence star (MS) and white dwarf (WD) in nine open clusters. These systems are located below and to the left of the main sequence on the color-magnitude diagram. We compare the number of cluster stars that have likely evolved into white dwarfs with the number of candidates for unresolved binary systems with WD. The number of probable cluster members lying below the main sequence, is generally less than the expected number of WDs. The observations in the ultraviolet could detect WDs and unresolved binary WD+MS systems more confidently than the observations in the visible range.

The B1133+16 pulsar was observed at a frequency of 111 MHz with the BSA radio telescope of the Pushchino Radio Astronomy Observatory from October 2022 to March 2023. Observations were conducted twice a week for two consecutive days. In total, 38 measurements of the scintillation parameters were carried out with a high frequency resolution (up to 65 Hz). We used continuous signal recording in the frequency band of 2.5 MHz. The signal was reconstructed using the coherent dedispersion method. The pulsar’s dynamic spectra (DSP) were analyzed using the two-dimensional autocorrelation function (2DACF). The fine frequency structure of the pulsar’s scintillation was investigated both through the analysis of time and frequency sections of 2DACF from DSP and through the spectra of individual pulses. The analysis of the frequency sections of the 2DACF showed that the true form of diffractive frequency distortions can be represented by a generalized exponential function with a characteristic frequency width of 1.2 kHz and an index of 0.57. Comparison of scintillation parameters separately for two components of the average profile showed that they are identical for both components.