The restoration of three subarrays of the Ukrainian radio telescope GURT, damaged as a result of military hostilities, marked an important milestone in the continuation of astronomical research under challenging conditions. In 2023, two of them were successfully restored and equipped with autonomous power supplies at the site of S. Braude Radio Astronomical Observatory. This enabled the resumption of systematic solar observations and the implementation of a two-element interferometer for studying cosmic radio sources. The third subarray was relocated and restored at the site of Poltava Gravimetric Observatory, where the primary challenge for its operation was strong radio-frequency interference (RFI) caused by the uninterruptible power supply system of the observatory. This issue was effectively resolved through the development and installation of a custom external mains filter. The restoration efforts of these instruments demonstrate that scientific work can continue even under war time adverse conditions, thanks to innovative engineering solutions and the perseverance of the research team.
We present the result of the analysis of the FI Sge individual light curves constructed on Transiting Exoplanet Survey Satellite (TESS) observations. FI Sge the RR Lyrae pulsating variable star with bicyclicity effects and possible Blazhko effect. In the present study, we analyzed 3603 photometric data obtained by the Transiting Exoplanet Survey Satellite (TESS) in the special TESS IR bandpass with a time resolution of about 10 minutes. The observations covered a 27-day interval (BJD 2459769.90 − 2459796.12) with a small gap of about a day. The full data set contains 52 minima and 51 maxima of the seasonal light curve. We suppose that for this data set, the analysis of the light curve shapes in minima provides more reliable results. We studied the variations of the minima’ shapes of the individual light curves at common and for the separate affinity groups. The last one allowed us to detect not only classical bicyclicity, but also secondary bicyclicity for FI Sge. This result was obtained at first and it is atypical behavior of light curves for pulsating variable stars.
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.
We discuss the problem of singularity crossing in isotropic and anisotropic universes. First, we consider the so called soft or sudden singularities and, in particular the Big Brake singularity. This singularity was discovered in a particular tachyon cosmological model and it was also shown that this kind of singularity arises in a very simple model, where matter is represented by the anti-Chaplygin gas. At the the encounter with the Big Brake singularity the universe has a finite scale factor, a vanishing expansion velocity and an infinite deceleration. The Christoffel symbols also vanish the geodesics are regular and the universe easily can cross such a singularity. Adding to the anti-Chaplygin gas or to the tachyon matter some amount of dust we see that the Big Brake singularity is substituted by a more general soft singularity, its crossing implies a certain transformation of the properties of matter. The crossing of the Big Bang – Big Crunch singularity is more counter-intuitive. However, we describe it for both Friedmann universe and Bianchi-I universe using the field reparametrization of the variables present in models (a scalar field and the metric). Then we consider the Wheeler-DeWitt equation and show that the probability for the universe to find itself at the soft singularity is different from zero, while the encounter with the Big Bang – Big Crunch singularity is suppressed. We analyze the possibility to construct Fock spaces of quantum particles at the vicinity of different cosmological singularities and see when it is possible and when it is not possible. Finally, we present some attempts to develop general approach to the connection between the field reparametrization and the elimination of singularities.
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.
Background. In light of recent discoveries, in particular the appearance in the literature of strong evidence in favor of a binary supermassive black hole (SMBH) in the core of OJ 287, interest in the search for such objects has revived. Therefore, the issue of detecting candidates has gained considerable relevance. The variability of the radio flux of Active Galactic Nuclei (AGN) in the optical, radio and spatial dimensions provides significant insights into the complex structure of physical phenomena in the immediate vicinity of the black hole and the conditions for launching jets. In particular, these manifestations may indicate the presence of a binary SMBH in the center of such a system. Data & methods. The paper uses multi-filter optical observations (aggregated by AAVSO) and radio observations of the MOJAVE project at 15 GHz, given in Lister et al. (2019), in the form of radio fluxes and bright component positions (obtained from the VizieR database). Time-frequency analysis methods (including wavelet analysis, LombScargle, and cross-correlation) as well as clustering and regression methods of machine learning and analysis are used for processing. Results. The intersections of the accretion disk by the companion black hole in the core of OJ 287 cause characteristic optical flares and affect the jet morphology. The latter is manifested in the change in the angles of the bright features (components). It is found that these changes in the case of OJ 287 exhibit noticeable patterns that can be used as indicators for binary black hole candidates (SMBBHs) in active nuclei. Conclusions. The established connection between optical flares (with potential X-ray verification) and changes in the orientation of jet components with a characteristic pattern can serve as a criterion for detecting binary black hole candidates in AGN.
This study investigates the gravitational influence of the major planets and the Moon on the orbital dynamics and mechanical energy of near-Earth asteroid 2024 PT5 during its temporary capture by Earth. Discovered on 7 August 2024 by the ATLAS Sutherland survey, the asteroid transitioned onto an elliptical geocentric orbit in late September 2024 and returned to a heliocentric trajectory in mid-November 2024. The primary objective is to determine which massive bodies of the Solar System specifically the Moon and the nearest planets facilitated the capture process, induced changes in the asteroid’s total mechanical energy during the capture phase, and provided the key perturbations leading to its escape from Earth’s gravitational field. High-precision geocentric ephemerides and osculating orbital elements were obtained from the JPL Horizons service. Numerical analyses of the time series for kinetic, potential, and total mechanical energy, as well as eccentricity, were performed to characterize both the capture and release phases. Particular attention was given to the temporal correlations between the asteroid’s close approaches to the Moon and to the major planets, and the corresponding variations in its orbital elements. This approach isolates the intervals during which 2024 PT5 experienced the most pronounced dynamical changes, thereby informing targeted numerical simulations. The methodology includes a detailed statement of the problem and computational procedure, including the criteria used to define the start and end of the temporary satellite phase and efforts to identify the bodies exerting the strongest gravitational influence. The results lay the groundwork for developing a general algorithm to assess the probability of capture for any near-Earth object, and to evaluate its potential hazard or scientific value for future sample-return missions. Application of these techniques promises to enhance the precision of asteroid trajectory forecasts and to support ongoing planetary defense initiatives.
Eclipsing binary stars have intrigued astronomers for centuries. To study them is to journey through discoveries and innovations. One of the earliest significant insights came in 1783 when 18-year-old John Goodricke boldly proposed that the periodic dimming of the star Algol, which he and his friend and mentor Edward Pigott had carefully studied, was due to an eclipse by a large dark body revolving about Algol. The communication so impressed the Royal Society of London that Goodricke was awarded the prestigious Copley medal that same year. As observational techniques evolved and photographic photometry developed, the quality as well as the quantity of data increased and by the early 20th century, gravitational physics had matured sufficiently that Henry Norris Russell and Harlow Shapley could provide quantitative procedures for finding the properties of stars in eclipsing systems to capitalize on them, an example of a path characterized by Russell (1948) as the Royal Road of Eclipses. Over the following decades, deeper understanding of the physics governing systems of short-period binary stars led to more sophisticated treatments. Zdenêc Kopal and other researchers expanded the analytical framework and initiated more rigorous studies of the internal and orbital dynamics of these systems. The advent of high-speed computing in the 1970s revolutionized the field by enabling simulations of increasing complexity. Continued computational and analytical improvements, coupled with the explosive growth in observational data from wide-field surveys culminating in the Gaia mission, are propelling eclipsing binary research into a new era. We have now both the computational power and the observational depth to probe stellar structure and evolution with unprecedented precision. This presentation highlights key milestones in the study of eclipsing binaries, innovative capabilities in data acquisition and modeling, and the promising role of high-precision infrared photometry. Particular attention will be paid to the enhanced precision attainable through the use of improved passbands for ground-based infrared photometry at local observatories, and to the extended functionalities of the Wilson-Devinney modeling framework, and complementary analytical tools and programs.
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.
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.
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.
The pre-equatorial Marcia crater on asteroid (4) Vesta represents one of the youngest and best-preserved impact structures on the body, distinguished by its complex morphology and strong spectral variability. Within the Av-8 Marcia quadrangle, two spectrally and morphologically distinct surface units — pitted impact deposits (PIDs) and orange material patches (OMPs) — dominate the region and provide valuable insights into post-impact surface evolution. Using calibrated Framing Camera (FC) images from NASA’s Dawn mission obtained during HAMO and LAMO phases, we analyzed the spectral characteristics of these units through color-ratio imaging (C(438 nm/749 nm) and C(749 nm/917 nm)) and reflectance spectra derived from Level 1b datasets. Results show that both PIDs and OMPs display higher albedo, redder spectral slopes, and deeper 0.9 μm pyroxene bands relative to surrounding materials, yet their spectral signatures differ markedly. PIDs generally exhibit deeper 0.9 μm absorption bands and broader reflectance variability, while OMPs display consistently redder slopes and lower reflectance at 438 nm. Spatially, OMPs and PIDs frequently co-occur in the southwestern vicinity of Marcia crater, where lobate, flowlike morphologies also appear. Our findings confirm that simultaneous examination of C(438 nm/749 nm) and C(749 nm/917 nm) color-ratio maps is an effective approach to discriminate between OMPs and PIDs.
We present the results of a detailed spectroscopic investigation of the supergiant HD 207260 (A2 Iae), based on high-resolution echelle spectra obtained in 2018 with the 2-meter telescope at the Shamakhi Astrophysical Observatory. The focus is on the variability of the Hα line, which exhibits a complex and variable profile, consisting of both an absorption and an emission component. The intensity of the emission component and its radial velocity were found to vary significantly across different epochs. These changes were accompanied by synchronous variations in the radial velocity of the absorption and in the equivalent width of the line. Such behavior suggests a dynamical origin for the emission component, possibly related to instabilities in the upper atmosphere or episodic mass loss processes. Fourier analysis of the radial velocity variations reveals with an approximate of 35–40 days. This periodicity is consistent with the presence of radial or non-radial pulsations, which may drive structured outflows in the upper layers of the stellar atmosphere. It is assumed that the change in the Hα line profile, the change in the radial velocity and the equivalent width of the absorption and emission components of the Hα line profile occur as a result of the interaction of the stellar atmosphere with the circumstellar envelope as a result of the pulsation of the star.
In order to understand significant meteorological processes occurring in Jupiter’s atmosphere, studies were carried out on ammonia NH₃ absorption lines, whose relative amount is small but whose influence could be comparable to water vapor in Earth's atmosphere. These observations were performed using a high spectral resolution échelle spectrometer installed at the Cassegrain focus of the 2-meter telescope at Shamakhi Astrophysical Observatory. Variations in the intensity of NH₃ absorption lines in the NH₃ λ 6475Å band were studied in different regions of Jupiter’s disk and at the center of Saturn’s disk. In this spectral region, 20 lines were selected for the center, 14 lines for the northern zone, and 11 lines for the southern zone. The obtained data were processed using the DECH 95 and DECH 30 programs. The spectrophotometric characteristics of these spectral lines, including their equivalent widths and half-widths, were determined. Based on the observational data obtained, Jupiter’s rotational temperature was determined from different line pairs. The calculated temperatures vary between approximately 180 K and 80 K. The observed variations in temperature could be attributed to lightning events within these layers. Summarizing the obtained results, the average temperature in the details of Jupiter’s disk was determined to be approximately 127 K, aligning well with findings reported by other authors.
An important key to studying the impact of solar activity variations on the Earth’s climate is the Maunder Minimum (late 17th century), during which extremely little sunspots were observed. Applying the rare event analysis method to these observations led the researchers to conclude that the appearance of sunspots during the Maunder minimum had a weak amplitude 22-year cycle. The concept of continuity of magnetic cycles at this time is also confirmed by measurements of cosmogenic radionuclides in natural terrestrial archives. Therefore, today it is believed that during the Maunder Minimum, the cyclic magnetic activity of the Sun did not stop, although the amplitude of the cycles was quite low. In the αΩ dynamo model, this may be due to the fact that the magnitude of the magnetic induction of the toroidal field, excited by radial differential rotation in the solar convection zone (SCZ), at this time did not reach the threshold value required for lifting magnetic power tubes to the solar surface (nonlinear dynamo mode). Possible physical mechanisms describing the suppression of the dynamo process at time intervals, when no sunspots were observed, are analysed. A scenario for explaining the north-south asymmetry of magnetic activity during the Maunder Minimum is proposed. A key role in the proposed scenario is played by the special nature of the internal rotation of the Sun, revealed in the helioseismological experiments. According to helioseismology data, the SCZ is naturally divided into polar and equatorial domains with opposite signs of the radial angular velocity gradient. In addition, the radial angular velocity gradient penetrates into the deep layers of the stable radiant zone below the SCZ. It is shown that, taking into account these helioseismology data, the αΩ dynamo excites two harmonics (dipole and quadrupole) of the toroidal magnetic field in the SCZ, which cyclically change their direction. The αΩ dynamo excites two harmonics (dipole and quadrupole) of the toroidal field in the RMS, which cyclically change their direction. At the same time, the deep Ω effect in the radiant zone creates the toroidal field of stationary orientation. The summary toroidal magnetic field (the dynamo-field of the SCZ + the field of the radiant zone) rising to the Sun’s surface due to magnetic buoyancy may contribute to the north-south asymmetry in sunspot activity.
In our detailed study of the inner structure of PF galaxy clusters, we found different kinds of substructures in these objects. Most of the detected substructures are quite common. In addition to the classical filamentary features described by Rood and coauthors’ papers, we include complex cross-shaped substructures and short dense chains of galaxies as regular. We suppose that regular substructures are connected with the Large-Scale Structure of the Universe elements, which form the parent cluster node. Our previous studies were based on the list of galaxies of the Muenster Red Sky Survey, which has no redshifts. It allowed us to study only the 2D distribution of galaxies inside the cluster. Modern data, such as the Sloan Digital Sky Survey, the VIMOS Public Extragalactic Redshift Survey, the Euclid Wide Survey, and others, give us the opportunity for 3D studies of these objects. We improved the base online version of the “Cluster Cartography 2D” tool (https://clustercartography.github.io/) into the “Cluster Cartography 2D+” tool. It allows to apply the algorithms developed for 2D version to the detection of regular substructures on a statistically significant level for the 3D distribution of galaxies in the rectangular projections. We tested this opportunity on artificial galaxy clusters with different kinds of substructures. We have shown that using 2D projections allows us to detect the 3D regular substructures, and to restore their real shapes and directions.
The results of the study of orbital spectral variability due to binary nature of the symbiotic star AG Peqasi are presented. We used high-resolution spectra (R = 28,000) taken by 2-m telescope of the Shamakhi Astrophysical Observatory during 2016–2019, and medium-resolution amateurs’ spectra (R = 9,000–11,000) taken from the Astronomical Ring for Access to Spectroscopy (ARAS) database obtained during 2020–2024. The system’s orbital period is approximately 815 days, and its spectral changes are correlated with this period. In this paper we present the radial velocity curve of the cold component (M3III), as well as the emission lines Hα, Hβ, and the HeII lines λ4686 Å and λ5412 Å formed around the hot component of the AG Peg system, constructed according to our measurements. We determined the mass function of the cool component, f₁ ≈ 0.023 M⊙.
This study examines the consequences of high-energy radiation interactions from X-ray sources with extended astrophysical objects. A comparative analysis is conducted between the spectra of primary radiation sources and those of irradiated absorbing and scattering regions. The limitations of current diagnostic methods are identified, and strategies for enhancing both the sensitivity and informational value of the resulting data are proposed. Signal-to-noise ratios are derived for a gamma-ray detector prototype developed by the authors, under various geometric configurations of emitting and scattering structures. Necessary modifications to the radiation transport equations are suggested, along with instrumental techniques for identifying and registering previously unrecognized astrophysical entities.
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.
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.
