The preliminary results of spectralpolarization observations of a large sunspot on August 17, 2024, observed on the Echelle spectrograph of the horizontal solar telescope of the Astronomical Observatory of Taras Shevchenko National University of Kyiv are presented. Direct measurements of the magnetic field in this spot were performed by splitting the bisectors of the profiles of ten spectral lines, mainly the Fe I lines, as well as three lines of Fe II, Cr II, and Sc II ions. The magnetic field, measured by splitting the sigma components of the Fe I 5250.2 line, reached 3400 G, however, the field magnitude by other lines with smaller Landé factors was significantly smaller, apparently reflecting the longitudinal component BLOS of the magnetic field, rather than its intensity modulus. The shape of the bisectors of the I ± V profiles generally corresponds to a homogeneous field only for the Fe I lines, while for the ion lines these bisectors have a rather peculiar appearance, with a minimum splitting at approximately half the depth of the profiles and a maximum in the core of such lines or in their wings. If the magnetic field averaged over the entire profile is determined based on the average splitting of the bisectors at different depths of each spectral line, the following main effects are revealed: (a) the ion lines show 300–1200 G weaker magnetic fields than the neutral atom lines, (b) the measured BLOS value increases with the Landé factor for the neutral atom lines, but for ions, the corresponding dependence is obviously the opposite, (c) for the neutral atom lines the BLOS value decreases with increasing excitation potential EP of the lower term of the line. Effect (b) for the neutral atoms can be explained by the significant inclination of the field lines to the line of sight, while effects (a) and (c) indicate that the magnetic field strength in the spot decreased with depth. However, it remains unclear what role thermodynamic effects and the subtelescopic structure of the magnetic field might play here.

The Unistellar eVscope2 represents a new generation of compact astronomical instruments that combine portability, automation, and digital networking to empower both professional and citizen astronomers. This study evaluates the telescope’s technical performance, educational potential, and scientific applications, particularly in exoplanet transit photometry. Based on the comparison of our observational data obtained within the Unistellar global network and professional OGLE data, we showed the great possibility of this approach. Our results demonstrate that high-quality light curves can be produced even under sub-optimal conditions, and compact digital telescopes can play an essential role in expanding observational coverage and in training the next generation of astronomers. The Unistellar network model, combining technological innovation, social participation, and data integrity, stands as a powerful example of how future astronomy will operate at the intersection of professional and citizen science.

Spectral features of single Type III burst observed by PSP on 4 June 2020 in the frequency range 1.4–19 MHz are studied. This burst was also observed by radio telescopes URAN-2 and GURT in the frequency band 10–70 MHz (Melnik et al., 2024). At the first time the velocity spectrum of electrons, which responsible for the radio emission of different bursts levels, was found in the wide frequency band because this Type III burst was fairly powerful. The duration dependence as well as the flux dependence on frequency was analyzed in the frequency band of 10–70 MHz. This paper is the extension of the previous paper with the aim to expand essentially the frequency band using PSP observations. The discussed burst is also fairly powerful one at the frequencies 1.4–19 MHz so the analyzing procedure can be repeated for these frequencies as well. Comparing the obtained results with previous ones shows that the velocity spectrum is practically unchanged. The duration-frequency dependence is almost the same too. At the same time behavior of the burst flux at the frequencies of 1.4–19 MHz is essentially differed of it in the common band of 10–19 MHz even. According to PSP data the burst flux is decreased with decreasing frequency in this band, but not increased as follow to URAN-2 – GURT data. We associate it with the fact that PSP and URAN-2 – GURT observed this burst from different directions.

This paper includes the results of the studies of the orbital variability of the emission and absorption components of the Hα line of the eclipsing symbiotic system EG And. We used medium-resolution amateurs about 30 spectra (R = 9,000–11,000) taken from the Astronomical Ring for Access to Spectroscopy (ARAS) database obtained during 2020–2025. Radial velocity curves of the cool component were derived from the mean of the measured radial velocities of selected absorption lines forming in the atmosphere of a M-type red giant. The system’s orbital period is approximately 483.3 days (Kenyon & Garcia, 2016). It is assumed that the emission lines, and in particular the Hα line, are formed in the vicinity of a hot white dwarf. We have established that the intensity of the emission component of the Hα line has the greatest value at an orbital phase of about 0.5 (corresponding to the eclipsing of the cold primary component by the white dwarf) and the lowest at about 0.1 (the red giant eclipses the hot secondary component and the region of formation of strong emission lines), and an average at about a phase of 0.8.

We present a three-dimensional model of the positions of 20 stars in the field of the Cepheid UMi (Polaris) – 18 main sequence stars (spectral types A0–G0 V), the K-giant HD 6319 (K2 III) and Polaris itself (F8 Ib) – which was created using the 3D calculator Desmos 3D, based on the calculated U, V and W components of the full velocity vector of the stars in the Galactic coordinate system. In this paper, stellar radial velocity estimates from Usenko et al. (2023) were used. Two versions of the U, V, and W components were calculated based on Gaia DR3 parallaxes and photometric parallaxes. The resulting 3D image showed that, in both scenarios, 15 main-sequence stars, a K-giant, and Polaris form a noticeable clamp, while three stars (HD 14718, HD 90162, and HD 11696) are located outside of it. HD 14718 and HD 90162 belong to the thick disk, while HD 11696 is a remnant of a possible open cluster in Polaris’s field. The K-giant HD 6319 is located inside the clamp and quite close to the Cepheid, and it is quite possible that this clamp is part of the main component of the probable open cluster Polaris, dissolved in the field of the Cepheid. Using a 3D calculator to construct a spatial image of stars may serve as a good tool for studying the structure and dynamics of open clusters in the future.

Subject and purpose of the work. During the development and testing of radio engineering devices, in particular the active antenna sections of the GURT radio telescope, there is a need for prompt and efficient processing of experimental data. Large volumes of measurements obtained from vector network analyzers require tools for fast interpretation and statistical analysis. The purpose of this work is to create software that ensures high-quality processing and visualization of such data, contributing to improved accuracy in the evaluation of antenna system parameters. Methods and methodology. To achieve this goal, the Graphics v.1.9 software was developed, functioning in the Windows environment on the .NET Framework 4.8 platform. The program employs the ScottPlot library for building interactive plots and ClosedXML for handling Excel data. The architecture of the solution is designed according to a modular principle, which facilitates the integration of new functionality. The main methods include parsing data from the Obzor-103 analyzer, generating plots, performing statistical averaging of results, and exporting data into formats suitable for publications and presentations. Results of the work. The Graphics v.1.9 program enables advanced visualization of measurements, the creation of high-quality graphical reports, as well as the averaging of data of the same type to detect statistical deviations and assess the repeatability of results. This makes it possible to obtain generalized characteristics of the studied devices, quickly detect instabilities in individual elements, and perform comparative analysis within a series of identical components. Practical application of the program in the testing of GURT antenna sections has confirmed its efficiency and feasibility for scientific research. Conclusions. The developed software significantly increases the efficiency of experimental data analysis in radio astronomy and radio engineering. Graphics v.1.9 not only reduces the time required for data processing but also provides deeper insight into system characteristics and contributes to its optimization. Prospects for further development of the program include support for new input data formats, expansion of processing tools, and the implementation of advanced visualization features, making it a universal tool for a wide range of scientific and applied tasks.

The fundamental parameters – effective temperatures (Teff) and surface gravities (g) – have been determined for of A-type stars: HD 6364 (A5/7III), HD 6365 (A3III/IV), HD 6492 (A9V), HD 6723 (A8V), HD 25093 (A7II/III), HD 123798 (A8/9V), HD 129175 (A6V), HD 129433 (A0IV), HD 129660 (A7V), and HD 209124 (A0III-IV). In order to determine the chemical composition of stars using the model or synthetic spectrum method, it is essential to know their fundamental parameters – effective temperatures (Teff) and surface gravity (g). Teff and log g are the basic parameters of stellar atmosphere models – determining these parameters is necessary to compute stellar atmosphere models. On the other hand, by knowing the effective temperature (Teff) and surface gravity (g), it is possible to calculate the evolutionary parameters of stars – their masses (M), luminosities (L), radii (R), and ages (t). Thus, the accurate determination of the chemical composition of stars through the model or synthetic spectrum method depends on the precision of the Teff and log g parameters. The effective temperatures (Teff) and surface gravities (log g) of stars were determined using photometric method. The method employed is based on comparing observed and theoretical values of the photometric indices [c₁], Q, and β. This method is a simple and accurate method. The Q index in the UBV photometric system is defined as Q = (U – B) - 0.72(B – V), while the [c₁] index in the uvby photometric system is defined as [c₁] = c₁ - 0.2(b - y). These indices are free from the effects of absorption in the interstellar medium. The following values of Teff and log g were obtained for the studied stars: HD 6364: Teff = 7610 K, log g = 4.25; HD 6365: Teff = 7880 K, log g = 4.35; HD 6492: Teff = 7390 K, log g = 3.70; HD 6723: Teff = 7380 K, log g = 4.00; HD 25093: Teff = 7780 K, log g = 4.10; HD 123798: Teff = 7090 K, log g = 3.65; HD 129175: Teff = 8220 K, log g = 4.35; HD 129433: Teff = 9960 K, log g = 4.00; HD 129660: Teff = 7710 K, log g = 3.65; HD 209124: Teff = 9820 K, log g = 3.80.

The distribution patterns of chemical elements in the Galactic disc remain insufficiently described. In particular, despite considerable attention to the enrichment of disc stars with neutron-capture elements, several questions remain unresolved and warrant further investigation. In this study, we examine the enrichment of disc stars with first- and second-peak slow neutron-capture (s-process) elements using a sample of 150 Galactic disc giants. Their spectra were obtained with the 1.93-m telescope at the Observatoire de Haute-Provence (France), using the ELODIE echelle spectrograph. Elemental abundances of the first-peak (Sr, Y, Zr) and second-peak (Ba, La, Ce) s-process elements were determined using synthetic spectrum fitting under the assumption of Local Thermodynamic Equilibrium (LTE). The results were compared with predictions from Galactic Chemical Evolution (GCE) models. Our findings confirm that the enrichment in both first- and second-peak s-process elements is driven by contributions from both the s-process and r-process, with a possible additional input from other nucleosynthesis sources.

Active space debris removal operations require a priori knowledge of the target objects’ rotation parameters, i.e., information on their rotation speed and current orientation in space. This can be achieved through appropriate observations designed to determine these parameters. Recording and subsequent analysis of light curves is the most common method for monitoring space objects’ rotation using optical means. This paper examines the results of long-term photometric observations of a large space debris object — the third stage of the SL-14 rocket (international COSPAR number 1987-074G, USSTRATCOM ID 18340). It shows how this resident space object’s (RSO) rotation speed around its center of mass repeatedly changed between 2006 and 2025. To understand the cause of this behavior of RSO 18340, it is necessary to study the relationship between its different rotation speed states and the corresponding orientation of its rotation axis in inertial space. In paper, we consider the observed light curves of RSO 18340, recorded in 2024 at different observatories, analyze their structure and identify similar photometric patterns in different light curves. These photometric patterns are used to determine the spatial direction of the object’s rotation axis in two short (1–3 days) time intervals in late February – early March 2024. As a result of this analysis of the light curves, four estimates of the average direction of the rotation axis and its evolution over a two-week interval were obtained. Using two light curves obtained during flybys over different observing points on February 27, 2024, we obtained the current direction of the rotation axis in the inertial coordinate system: RA = 10°, Decl. = -66°. And based on six light curves obtained on March 9, 10 and 11, 2024, the following average coordinates were determined: RA = 06°, Decl. = -39°. We estimate the internal error of these results to be ±(5–10)°. Based on these results, we hypothesize that there are no rapid shifts in the rotation axis of RSO 18340.

We present a new spectroscopic study of HR 4049, a post-AGB star in a binary system, based on échelle spectra obtained between 2019/03/19 and 2025/04/08 with the 0.81 m telescope of the Three College Observatory (North Carolina, USA) at a resolution of R ≈ 12,000. A cross-correlation analysis of 83 spectra in the 4760–4780 Å range yielded the following orbital parameters: period P = 428.47 ± 0.01 days, eccentricity e = 0.29 ± 0.01, argument of periastron ω = 242.3° ± 0.3°, epoch of periastron T₀ = 2,458,383.2 ± 0.6, systemic radial velocity γ = -30.12 ± 0.09 kms⁻¹, and semi-amplitude K₁ = 15.52 ± 0.13 kms⁻¹. Using the Gaia DR3 parallax (d = 1397⁺¹⁷⁶₋₁₆₈ pc) and the average maximum brightness (mᵥ = 5.35 mag), the luminosity was estimated as log(L/L⊙) = 4.22 ± 0.12, consistent with an initial mass of 3–4 M⊙. The mass function combined with likely orbital inclinations implies current masses of ∼ 0.75 M⊙ for the primary and 0.70–0.82 M⊙ for the secondary. These results confirm the long-term orbital stability of HR 4049 and provide new constraints on the properties of post-AGB binaries.