Astronomy Reports最新文献

Ultra-hot Jupiter Kelt9b impels to reconsider existing models of the upper atmospheres of hot exoplanets, which were previously developed using examples of G or M star systems such as HD209458b and GJ436b. The unique conditions of interaction between the radiation of an A-class star and the atmosphere necessitate kinetic modeling of excited levels of elements, primarily the hydrogen atom. Kelt9b shows the absorption for several Balmer lines and lines of a number of heavy elements, the quantitative interpretation of which is an urgent problem. In this study, for the first time, 3D modeling of the atmosphere of a planet with a close location of the Roche lobe is implemented with allowance for the aeronomy and kinetics of excited hydrogen.

A method for studying the secular evolution and stabilization of the shape of rings in small celestial bodies that do not have shepherd satellites is developed. A model of a compound ring consisting of two close, generally non-coplanar elliptical Gaussian rings is constructed. The self-gravitation of the ring is taken into account through the mutual gravitational energy of the boundary rings W_mut. The function W_mut is presented as a series with an accuracy of up to the 4th power of small eccentricities and mutual inclination of the rings. The secular evolution of a compound ring is described by differential equations in special (collective) variables. For rings without a central body (problem 1), a closed system of eight differential equations is obtained using the mutual energy function. The evolution of rings in the azimuthally averaged potential of a rotating triaxial body is also studied (problem 2), for which a second system of eight differential equations is derived. In both problems, besides the general case, two particular ones are considered: (i) the case of coplanar elliptical rings, and (ii) the case of circular rings with a tilt. The theory is applied to study the recently discovered ring of dwarf planet Haumea. It is shown that without taking into account self-gravity, the nodal precession time of the Haumea ring is equal to T_Ω = 12.9 ± 0.7d but taking into account the self-gravity of the ring can reduce this period. It is established that self-gravity does indeed contribute to the preservation of the ring shape without invoking the hypothesis of shepherd satellites. Criteria for the preservation of the ring shape are obtained, which made it possible to estimate the interval for the ratio of the ring mass to the mass of Haumea 10^–4 < m/M < 10^–3. Taking into account the optical thickness of the ring τ ≈ 0.5, it is shown that the Haumea ring with a mass m/M ≈ (1–2) × 10^–4 can consist of ice particles with a size of ({{d}_{0}} approx 0.7{-} 1) m.

Results of a study of physical parameters of stellar population in star formation regions in galaxies with signs of peculiarity NGC 3963 and NGC 7292 are presented. The study was carried out based on the analysis of photometric (UBVRI bands), H(alpha ) and spectroscopic data obtained by the authors, using evolutionary models of stellar population. Among 157 star formation regions identified in galaxies, the young stellar population mass estimates were obtained for 16 of them and the age estimates were obtained for 15. The age of star formation regions clearly correlates with the presence of emission in the H(alpha ) line: H II regions in the galaxies are younger than 6–8 Myr, and the regions without gas emission are older. The studied objects are included in the version 3 of our catalogue of photometric, physical and chemical parameters of star formation regions, which includes 1667 objects in 21 galaxies. Key aspects of the technique used to estimate the physical parameters and different relations between observational and physical parameters of the young stellar population in star formation regions are discussed.

Using a high-precision algorithm for interpreting transit light curves in a model of a classical eclipsing binary star-exoplanet system, we studied the possibility of determining the system parameters in the absence of a priori knowledge of the orbital eccentricity. It was shown that it is impossible to determine the exact value of the eccentricity and periastron longitude based on the main minimum of the transit light curve alone. Also, at an observational accuracy of ~1% of the eclipse depth, the uncertainty in the eccentricity and periastron longitude together causes a significant uncertainty in the values of the component radii (a two-threefold error relative to the true values) and the orbital inclination angle. However, the ratios of the system component radii and the limb darkening coefficients are determined with good accuracy. At an increase in the observational accuracy to 0.1% of the eclipse depth, it becomes possible to determine the component radii and the orbital inclination angle when interpreting the light curve with allowance for the eccentricity.

For the Tashanta point, 49°43(' )4('' ) N, 89°11(' )31('' ) E, Gorny Altai, data from continuous measurements of astroclimatic parameters of the surface layer, monthly average values of the total cloud cover, suspended water vapor from the Era5 atmospheric reanalysis database, and primary measurements of the altitude distribution of turbulence are presented. The results show unique astroclimatic and operational conditions, which probably make it one of the best places in the Russian Federation for submillimeter and optical range observatories.

The frame work of this study is the bi-elliptic restricted four body problem, where the largest primary ({{m}_{1}}) is assumed to be a radiating body and the other two massive bodies ({{m}_{2}}) and ({{m}_{3}}) are assumed to be oblate spheroids. The problem is restricted in the sense that the fourth body is assumed to be of infinitesimal mass. The goal of the paper is to study the so-called equilibrium points by generalizing R3BP to a non-coherent but highly practical R4BP model. The location of the planar equilibrium points according to this model is numerically studied for Sun–Earth–Moon system. The position of the triangular equilibrium points are also obtained analytically and graphically compared with numerically obtained values. Both the graphical and analytical studies confirms the high dependence of the position of the triangular equilibrium points on radiation pressure, however the collinear points were found to be less affected. The collinear points were found to be more affected by the oblateness of the second primary. The triangular equilibrium points were found to be stable for the third and fourth order resonance cases when the mass ratio is less than equal to a critical mass ratio. This critical mass ratio is also found to be dependent on the radiation pressure and phase angle ({{theta }_{0}}). The transition curve in the ((mu - {{epsilon }_{2}})) plane is plotted to find the value of ({{epsilon }_{2}}) for which the motion near triangular equilibrium points become unstable.

The results of the analysis of observational data of interplanetary scintillations obtained at the Big Synphasic Antenna radio telescope of the Lebedev Physical Institute (BSA LPI) before, during and after the magnetic storm that occurred on December 1–2, 2023. Observational data were compared with model calculations for corotating and propagating large-scale disturbances. The results of observations of scintillations of radio sources indicate that the magnetic storm that took place was caused by the superposition of two types of large-scale disturbances of the solar wind. On the day before the start of the magnetic storm, signs of interaction of the Earth’s magnetosphere with the corotating region of multi-velocity solar wind flows were observed, whereas later signs of disturbance of the magnetosphere by a coronal mass ejection propagating after the M9.8 flare on November 28, 2023 were observed.

Positional and multicolor photometric observations of near-Earth asteroids were carried out using the SBG telescope of the Kourovka Astronomical Observatory of Ural Federal University and the Zeiss-1000 telescope of the Simeiz Observatory of INASAN in 2022–2023. Based on the results of positional observations with the SBG telescope, improved orbital elements were obtained for seven asteroids. The periods of axial rotation of seven asteroids were estimated from photometric observations. Based on the results of photometric observations in the B, V, R, I filters, color indices were obtained for six asteroids.

The analysis of parameters of radio pulsars with periods (P > 5) s has been carried out. It was found that there is no clear dependence of (dP{text{/}}dt) on (P) on the ({ dP{text{/}}dt,P} ) diagram. The lack of dependence can be explained within the disk model. It is shown that the pulse width decreases with increasing period for the sample considered. It is the opposite of the dependence in the generally accepted pulsar model. It indicates that the distance from the surface of the neutron star to the radio emission generation region in the studied population depends on the period or that the magnetic field in the generation region has a non-dipolar structure. The possibility of explaining the longest intervals between successive pulses in pulsars J0901–4046 and J0250+5854 by the influence of drift waves at the periphery of the magnetosphere has been considered. Within the framework of the drift model, the calculated rotation periods in these pulsars turn out to be several times shorter than the observed intervals between successive pulses.

The rotation of the Milky Way halo in the solar vicinity is studied using kinematic data of the GAIA DR3 catalog for RR Lyrae variable stars with parallax errors of less than 20%. Two criteria were used for selecting halo stars: kinematic and spatial. In both approaches, we confirm the existence of weak rotation of the halo in the direction opposite to the rotation of the Galactic disk with velocities of (4.08 pm 2.19) km/s for the kinematic criterion and (9.49 pm 2.59) km/s for the spatial criterion.