Astronomy Reports最新文献

This study explores the existence and stability of equilibrium points in the restricted three-body problem, where the more massive primary is treated as a radiating body, and the less massive primary is modeled as a heterogeneous spheroid with four distinct layers. The analysis identifies five equilibrium points, three collinear and two non-collinear. While the collinear equilibrium points are linearly unstable, the non-collinear points exhibit linear stability under specific conditions, specifically when the mass parameter (μ) falls within the interval 0 < μ ≤ μ_c, where μ_c represents a critical threshold beyond which instability arises. Applying these findings to the Sun–Earth system, where Earth is represented as a four-layered heterogeneous body consisting of the crust, mantle, outer core, and inner core, we find that the density parameter is nearly negligible (λ ≈ 0.938911 × 10⁻²⁴), meaning that it has no significant impact on the existence and stability of equilibrium points. Instead, their behavior is entirely dictated by the radiation factor (α). The collinear equilibrium points remain unstable across the entire range of α, while non-collinear equilibrium points maintain linear stability only within a narrow interval of α ∈ [0, 0.00780552], emphasizing the limited range in which stability is preserved. These results enhance our understanding of the dynamical behavior of equilibrium points in planetary systems where the smaller primary possesses a layered structure and the bigger one is a source of radiation.

We investigate the basins of convergence associated with the equilibrium points in the Sitnikov five-body problem with oblate primaries using Newton’s iteration method. Initially, we analyze the equilibrium positions as a function of the oblateness factor (sigma ), finding that the nature of these equilibria changes with varying (sigma ). Various cases are considered to study the behavior of these equilibrium positions. Subsequently, we graphically illustrate the effect of the oblateness factor (sigma ) on the basins of convergence related to the equilibrium positions in the complex plane. Specifically, for a given oblateness factor (sigma ), the convergence region around the equilibrium points ({{E}_{i}}) ((i = 0,1,2,3,4)) is finite. When (sigma < 0), the convergence region around these points decreases as (sigma ) increases. Conversely, when (sigma > 0), the convergence region increases with (sigma ). We develop a series solution to the problem using the Green’s function approach. For ({{sigma }_{1}} < sigma < sigma _{2}^{*}), ({{sigma }_{2}} < sigma < {{sigma }_{3}}) and (sigma > {{sigma }_{3}}), the infinitesimal mass exhibits perpetual periodicity with consistent cyclic behavior over time. In contrast, for (sigma < {{sigma }_{1}}) and (sigma _{2}^{*} < sigma < {{sigma }_{2}}), the motion of the infinitesimal mass grows exponentially. Our comprehensive examination aims to provide valuable insights to enhance scientific understanding in these areas. Ultimately, this study may support future research on convergent systems influenced by factors such as oblateness.

The results of multicolor (B), (Rc), and (Ic) photometric observations of eight exoplanets have been presented. Using a single-parameter transit model, in which the only sought parameter is the exoplanet radius, the exoplanet radii have been determined as functions of wavelength. For the HD 189733 system, the dependence of the exoplanet radius on wavelength that is derived from an analysis of ground-based observations is consistent with the dependence obtained by interpreting high-precision satellite observations. For the Qatar-1 system, the exoplanet radius determined from ground-based (B), (Rc), and (Ic) observations increases with decreasing wavelength, possibly indicating the presence of an atmosphere scattering light according to Rayleigh’s law. For the TOI-2046 system, ground-based multicolor photometric observations propose an increase in the mean exoplanet radius with decreasing wavelength, suggesting the presence of a Rayleigh atmosphere, but not conclusively. No significant dependence of the exoplanet radius on wavelength has been detected for the HAT-P-16 system. The radii of the exoplanets WASP-12b, HAT-P-32b, WASP-33b, and Gaia-2b have also been determined.

Observational data on 86 pre-main sequence double-lined spectroscopic binaries (SB2s) were collected. Among them there are Herbig Ae/Be stars, T Tauri stars, and red dwarfs. Distributions of pre-main sequence (young) stars by masses and mass ratios of the components have been constructed, both observed and corrected for observational selection effects. The mass distributions of the components are approximated with a power law dN ~ M^–Γ((dlog M)), the exponent of which is ({{Gamma }} = 1.52 pm 0.44) for the observed distribution and ({{Gamma }} = 0.94 pm 0.19) for the distribution corrected for the effects of observational selection on an interval from the distribution maximum to the highest mass value, which is close to the Salpeter mass function. The most probable values of masses are M_prob = (0.76 ± 0.05) ({{M}_{ odot }}) and M_prob = (0.93 ± 0.02) ({{M}_{ odot }}), respectively. Both the observed and the corrected for the effects of observational selection distributions of young SB2 systems in terms of the mass ratio have a maximum in the interval q = 0.9–1.0. In systems with (P < {{10}^{{text{d}}}}) this maximum is more pronounced, and there is a secondary maximum at q = 0.5–0.6. For young SB2 stars with (P > {{10}^{{text{d}}}}) the mass-ratio distribution is flatter.

A method for pulsar timing based on monitoring data from the 3-th beam of the Large Phase Array (LPA LPI) radio telescope is proposed. In our observations, recorders with quartz clock generators were used as local clocks. Such recorders initially had an accuracy and hardware reference to the UTC time scale insufficient for pulsar timing. We have developed a method for referencing such clocks to the UTC based on observations of known pulsars used as intermediate reference clocks. This allowed us to improve dramatically the accuracy of determining the Time of Arrivals (TOAs) of pulsars’ pulses. We applied this method to the results of our observations of 24 second period pulsars over a time interval of 10 years. It was shown that the accuracy of the pulsar period, its first derivative ((P) and (dot {P})) and their coordinates in right ascension and declination ((alpha ), (delta )) allow us to predict the pulsar phase within ( pm 0.5{kern 1pt} P) during several years. The accuracy of determining the coordinates by right ascension and declination was typically better than (10'' ) with an angular resolution of the radio telescope of about (30' ). That makes it possible to use these parameters for timing using radio telescopes with narrow beam patterns. The accuracy of the calculated period was typically better than ({{10}^{{ - 8}}}) s.

Solar activity is a process driven by many independent but interconnected phenomena. Although the 11-year cycle is the result of operation of the dynamo mechanism, the cause of longer secular variations is not clear. In search of such a cause, it was proposed to take into account the influence of the planetary system. In order to verify the idea, we consider the action of all planets in the solar system reduced to the effect of a single barycenter. The tidal force is decomposed into radial and meridional components. The radial tidal force is too small compared to the powerful radial gravity of the Sun. The meridional force is not compensated for by solar gravity and depends on latitude. As the latitude of the barycenter changes quite slowly, the sign of this component changes over a characteristic time scale of about 5 years, during which the meridional acceleration constantly acts on the surface of the Sun. This could ultimately lead to speeds of several meters per second and, in principle, could significantly change the speeds of the meridional currents involved in generating the magnetic field. However, it turned out that the calculated speed variation does not agree with the observed periodicity of solar activity. Earlier, the relation was analyzed between the activity periods on solar-type stars and the rotation periods of exoplanets, and no correspondence was observed either. Thus, the planetary hypothesis as a cause of long-term modulation of solar activity is not confirmed.

We present the results of a study of maser emission in the OH 1665 and 1667 MHz lines in the W51M star-forming region. The observations were carried out in 2022 and 2024 at the Large Radio Telescope in Nançay (France). The research results on the evolution of the flux density and the degree of circular polarization of individual spectral features are presented. The spectral features were spatially identified. It has been found that the degree of linear polarization ({{m}_{{text{L}}}}) in five strongest features (55.92, 57.18, 57.72, 58.27, and 59.5 km/s) in the 1665 MHz line does not exceed 5%. For these features, the vector of the transverse magnetic field is oriented within an angular range of 19.6°–39.2°. Thus, it can be supposed that in this region there is a spatially organized magnetic field, which is of large scale for W51M (e1 and e2).

In this paper, the results of observations of the magnetar SGR 1935+2154 at a frequency of 111 MHz with the BSA LPI radio telescope in the period from April 2021 to November 2024 have been presented. To search for both periodic and single pulses, data from six frequency channels with a time resolution of 0.1 s, which are recorded in the reception band of ((110.25 pm 1.25)) MHz, have been used. During data processing for the specified period, the upper limit, 250 mJy, of radio emission of the magnetar SGR 1935+2154 at a frequency of 111 MHz has been estimated.

In order to study the Stark broadening of recombination radio lines in Orion A at a wavelength of 13.5 mm, observations of the H93γ, H94γ, H95γ and H65α lines were carried out at the RT22 (FIAN) radio telescope. An excess of the Stark broadening from the theoretical predictions was found for levels with the main quantum number (n) in the range of 93–95 with ∆n = 2, 3. The recombination radio line H82β was also observed together with the H145(12) and H152(14) lines, the latter also showed an excess of the Stark broadening from the theoretical predictions. It is shown that the Stark broadening data of different frequencies can be consistently described in units of velocities by the dependence ~n^4–4.5 in the range of n values from 70 to 174. For the first time, the density gradient estimates in this HII region were obtained using the Stark broadening. The electron density of the nebula center turned out to be ≈2 times higher than at a distance of 2(' )–3(' ) from the center.

The parameters of an axisymmetric model for the gravitational potential of the Galaxy have been refined. The basic curve of the Galaxy’s rotation in a distance interval of R ~ 0–190 kpc was constructed using the velocities of masers, classical Cepheids, Red Clump stars, Blue Horizontal Branch stars, halo stars, globular clusters, and dwarf satellite galaxies of the Milky Way. The rotation curve was selected in such a way that there would be no dominant burst of circular velocities in the central ((R < 2) kpc) region of the Galaxy. As a result, we constructed two two-component models of the galactic potential, which include contributions from the disk and the halo of invisible matter, as well as a three-component model with a small-mass bulge added in advance. These models can be useful in studying the long-term orbital evolution of stars and open and globular star clusters in the central ((R < 4) kpc) region of the Galaxy. The constructed models were tested for self-consistency by comparing their rotation curves with a set of model curves generated with the Illustris TNG50 software package.