Communications of the Byurakan Astrophysical Observatory (ComBAO)
Volume 72, Issue 2, Dec 2025

Dynamics of clusters of galaxies in the presence of dark energy: Virgo cluster 0.1 MB
H. A. Harutyunian and E. H. Nikogosyan
Pages: 200-205
Abstract. It is shown that, owing to the interaction of baryonic matter with the carrier of dark energy, all configurations of baryonic matter acquire energy and inevitably must expand. This conclusion applies to all hierarchical levels of the baryonic universe, including galaxy clusters. We propose a simple statistical method for identifying possible radial motions of galaxies within clusters. To illustrate this method, we examined the structural features of the Virgo galaxy cluster and identified its substructure, comprising groups of galaxies of varying multiplicity. Galaxies in the substructure are somewhat brighter than those in the overall cluster, and each subgroup contains an active galaxy. Subgroups are considered to be the product of primordial ejections of matter from the central generator galaxy. It is shown that the average stellar magnitude of galaxies in subgroups positively correlates with their average velocity. This correlation can be interpreted as evidence of cluster expansion.



Quantum interference of a de Broglie wave of a Dirac particle beyond the 'hypothesis of locality'. Part I: Dirac equation 0.2 MB
G. Ter-Kazarian
Pages: 206-225
Abstract. This is the first of three articles that explore the possibility of quantum mechanical inertial properties of the Dirac particle beyond the `hypothesis of locality´. This is done within the framework of the Master Space-Teleparallel Supergravity ( - TSC) (Ter-Kazarian, 2025) theory, which we recently proposed to account for inertial effects (Ter-Kazarian, 2026). The `hypothesis of locality´ used for extension of the Lorentz invariance to accelerated observers within the Special Relativity. This hypothesis in effect bypasses acceleration and replaces the accelerated observer by a continuous infinity of hypothetical momentarily comoving inertial observers along its wordline. Despite the successes for the tiny accelerations we usually experience, when the curvature of the wordline could be ignored and that the differences between observations by accelerated and comoving inertial observers will also be very small, however, the basic conceptual framework of this assumption has been considered by many scientists to be unsatisfactory. In general case, this is actually untenable and represents strict restrictions, and that the hypothesis of locality will have to be extended to describe physics for arbitrarily accelerated observers. This immediately leads to the disturbing fact within the - TSC theory that the metric of a two-dimensional semi-Riemannian space, calculated in the non-inertial frame of reference of an accelerating and rotating observer, becomes incomplete. To recover the complete metric, therefore, our strategy in the latest paper (Ter-Kazarian, 2026) was to go beyond this hypothesis by invoking a general deformation of the flat master space, MS_p → . Continuing along this line, in present article, we compute the object of anholonomicity and connection defined with respect to the anholonomic frame. Based on these premises, we derive the explicit form of the Dirac equation for an observer in a reference frame that is accelerated and rotating.



Quantum interference of a de Broglie wave of a Dirac particle beyond the 'hypothesis of locality'. Part II. Hermicity and non-relativistic limit 0.2 MB
G. Ter-Kazarian
Pages: 226-246
Abstract. This is the second of three articles that explore the possibility of quantum mechanical inertial properties of the Dirac particle beyond the, so-called, `hypothesis of locality´, of standard approach. This is done within the framework of the Master Space-Teleparallel Supergravity ( - TSC) Ter-Kazarian (2025a) theory, which we recently proposed to account for inertial effects Ter-Kazarian (2026). Our strategy in Ter-Kazarian (2025b) (first article of three) is to compute the object of anholonomicity and connection defined with respect to the anholonomic frame. Based on this, we derived the general Dirac equation in an accelerated and rotating frame of reference beyond the`hypothesis of locality´. This equation, however, contains also residual imaginary terms, which are artifacts that due to coordinate transformations in the non-inertial frames. To eliminate these terms to all orders, in present article, at first, we apply the standard techniques used in relativistic quantum mechanics and quantum field theory, where non-Hermitian terms can be removed via suitable similarity transformations. This standard method allows us to choose a physically more suitable reference frame. We show that the expectation values of physical observables remain real. No imaginary contamination remains in physical quantities. Thus the energy, momentum, probability, etc., remain real and consistent. Secondly, we are interested in low-energy properties, avoiding solutions with negative energy. In the method employed for reducing the Dirac Hamiltonian to non-relativistic two-component form, in order to decouple the positive and the negative energy states, we use an approximate scheme of the Foldy-Wouthuysen canonical transformation of the Dirac Hamiltonian for a free particle. This is performed by an infinite sequence of FW-transformations leading to a deformed Hamiltonian, which is an infinite series in powers of (1/m). Evaluating the operator products to the desired order of accuracy, we derive the deformed, non-relativistic Hamiltonian. We then compute the inertial effects for a massive Dirac fermion in non-relativistic approximation, which are displayed beyond the `hypothesis of locality´ as extended (deformed) versions of the standard effects. The latter are well-known important inertial effects such as the redshift effect (Colella-Overhauser-Werner experiment), the Sagnac-type effect, the spin rotation effect (Mashhoon), the kinetic energy redshift effect, the new inertial spin-orbit coupling. Expanding further the deformation coefficients, several new effects will rather appeared involving spin, angular momentum, proper linear 3-acceleration and proper 3-angular velocity in various mixed combinations.



Quantum interference of a de Broglie wave of a Dirac particle beyond the 'hypothesis of locality'. Part III: Geometry 0.2 MB
G. Ter-Kazarian
Pages: 247-267
Abstract. This is the last of three articles that explore the quantum mechanical inertial properties of the Dirac particle beyond the `hypothesis of locality´. This is done within the framework of the Master Space-Teleparallel Supergravity ( - TSC) (Ter-Kazarian, 2025a) theory, which we recently proposed to account for inertial effects (Ter-Kazarian, 2026). In present article, we review the technical details of geometry beyond the `hypothesis of locality´, referred to the 4D background Minkowski space in noninertial frame of arbitrary accelerating and rotating observer (Ter-Kazarian, 2025b). Given the anholonomic frame and coframe members, the object of anholonomicity and connection (Ter-Kazarian, 2025b), we compute the connection 1-forms, the curvature 2-form and write it in terms of Riemann curvature tensor. Then we derive the Riemann tensor in an anholonomic frame and compute the Riemann tensor, Ricci tensor, Ricci scalar, Kretschmann scalar.



Dynamical Preconditions for Ice Formation in Supernova Remnant and Cloud Interactions: A 2D MHD Study 5.2 MB
A. Yeghikyan, M. Rah, S. Shamyar, S. Khachatryan
Pages: 268-278
Abstract. Water ice has been detected in several supernova remnants (SNRs) despite the highly excited and irradiated environment, challenging standard dust processing paradigms. Using two-dimensional magnetohydrodynamic (MHD) simulations with the PLUTO code, we model the early-time interaction between an SNR blast wave and a dense interstellar cloud to identify the physical conditions conducive to ice formation. Our adiabatic simulation (without radiative cooling) demonstrates that shock compression produces high-density regions (n ∼ 10⁴ to 10⁵ cm^-3) with compression factors of 4 to 10, comparable to observations in IC 443. Although adiabatic temperatures remain elevated (T ∼ 107 to 108 K), we estimate radiative cooling timescales of ∼650 yr (for n = 10⁴ cm^-3) to ∼65 yr (n = 10⁵ cm^-3), much shorter than typical SNR ages. These results establish that the SNR shock-cloud interactions create the necessary dynamical preconditions (high density and strong compression) for the formation of H₂O ice. Future simulations incorporating radiative cooling and grain surface chemistry will directly demonstrate ice mantle growth in these compressed clumps.



Pulsars and Millisecond Pulsars III: Tracing Compact Object Dynamics in Globular Clusters with NBODY6++GPU 0.4 MB
M. Rah, R. Spurzem, F. F. Dotti, A. Mickaelian
Pages: 279-293
Abstract. Neutron stars in globular clusters undergo complex evolutionary pathways involving binary interactions, mass transfer, and dynamical exchanges. While direct N-body simulations like NBODY6++GPU have successfully modeled stellar dynamics and compact object formation, the explicit tracking of pulsar spin evolution and magnetic field decay has historically been absent. In Papers I and II of this series, we identified this gap and proposed seven distinct evolutionary scenarios for pulsars in dense stellar environments. Here we present a comprehensive case study from an existing simulation with N=105,000 particles, demonstrating concretely where a neutron star forms and evolves for 200 Myr without pulsar physics tracking. We compare our approach with the recent implementation and detail our seven-scenario framework incorporating magnetic dipole spin-down, exponential field decay, environmental torques, accretion-driven spin-up, gravitational wave radiation, and merger dynamics. The neutron star Pulsar973 formed at t=800 Myr with an anomalous post-supernova mass of 5.35 M☉, evolved to 2.52 M☉ by t=1000 Myr, yet lacks all pulsar parameters: period P, period derivative 'P, magnetic field B, and scenario classification. We provide complete mathematical formulations with literature references for each scenario, demonstrating integration points within NBODY6++GPU’s Hermite scheme, Ahmad-Cohen neighbors, KS regularization, and BSE stellar evolution. Our framework enables scenario-based evolution, complementing population synthesis approaches.



Unveiling Long-Period Variables in M33’s Central Region: Insights into Stellar Evolution and Star-Formation via Near-Infrared Photometry 0.2 MB
M. Alizadeh, Yo. Abedini, and H. Abdollahi
Pages: 294-299
Abstract. We present an analysis of UKIRT observations obtained between 2003 and 2007 to investigate the evolved stellar populations within the central square kiloparsec of M33. Point-spread function (PSF) photometry is employed to mitigate the effects of stellar crowding and to ensure accurate measurements in this densely populated region. This method, applied to merged observations from UIST and WFCAM in the J, H, and K bands, extracts 211, 179 stars by cross-matching frame-by-frame across 39 observing nights in three bands. From this, we identify approximately 750 long-period variables (LPVs), predominantly Asymptotic Giant Branch (AGB) stars, by cross-matching PSF results with aperture photometry, focusing on the UIST field for robust variability confirmation. The PSF approach proves particularly effective for resolving blended sources and detecting faint, dusty variables that might remain undetected. We also examined aperture photometry data to validate our results; however, the PSF-derived measurements provide superior depth and completeness, particularly for obscured stellar populations. The resulting master catalog provides a basis for future analyses of variability amplitudes, periods, and star-formation history (SFH), paving the way for a deeper understanding of mass-loss and the dynamical evolution of the central region of M33.



IdentYS: A Python-Based Tool for Identifying Young Stars in Star-Forming Regions 0.3 MB
E. Nikoghosyan, D. Baghdasaryan, D. Andreasyan, N. Azatyan, A. Samsonyan, and A.Yeghikyan
Pages: 300-312
Abstract. Research on young stellar populations is essential to understand the properties of embedded clusters and advance theories of their formation. This has driven advancements in methodologies for star detection, leading to the development of valuable databases and software. We present the scientific justification and operating principles of the IdentYS tool, which is designed to identify young stellar objects (YSOs) in star-forming regions. The tool facilitates the identification of young stars with infrared (IR) excess in remote and embedded star-forming regions, focusing primarily on Class I and II YSOs. For this purpose, near- and mid-IR photometric data and five colour-colour diagrams (J - H) vs. (H - K), K - [3.6] vs. [3.6] - [4.5], [3.6] - [4.5] vs. [5.8] - [8.0], [3.6] - [4.5] vs. [8.0] - [24], and [3.4] - [4.6] vs. [4.6] - [12] are used. The purity of the YSOs sample is enhanced by excluding field contamination from stellar and extragalactic objects. As a result, we compile a list of YSO candidates displaying the source designation, astrometric, and photometric parameters, as well as information on the evolutionary stage determined by the presence of IR excess, as indicated by certain diagrams. The application of this program can greatly streamline the statistical analysis of young stellar populations across diverse star-forming regions, including distant and deeply embedded ones, which typically require processing large volumes of initial data.



The Potential Lunisolar Gnomonic Function of Pillars 18 and 19 in Enclosure D at Portasar (Göbekli Tepe) 1.1 MB
H. A. Malkhasyan
Pages: 313-329
Abstract. This study examines the possible gnomonic (shadow-measurement) function of Pillars 18 and 19 in Enclosure D at Portasar (Göbekli Tepe), based on precise architectural measurements, an analysis of the Sun’s and Moon’s culminations, and calculations of the astronomical conditions around 9500 BCE. Unlike previously proposed iconographic or symbolic interpretations, the present analysis is built exclusively on an empirical basis, without making prior assumptions about the meaning of the carved motifs.
The results show that the shadow boundaries produced by the mutual alignment of Pillars 18 and 19 correspond systematically to the winter solstice, the periods around the vernal and autumnal equinoxes, as well as to the Moon’s culminations during its major and minor standstills. Particularly significant is the fact that the arrangement of the seven birds carved on the pedestal of Pillar 18 coincides with the movement of Pillar 19’s midday shadow and reflects the period during which the seven stars of the Pleiades are not visible. This correspondence outlines a winter period of approximately 206.5 days, comprising seven synodic lunar months.
Overall, the findings suggest that Pillars 18 and 19 of Enclosure D may have functioned as elements of a shadow-based calendrical system capable of explaining the associated iconography. By contrast, the widely cited “roofed building” hypothesis faces substantial difficulties in accounting for the observed reliefs.



A New N-Type Carbon Star Identified in the Gaia DR3 Spectroscopic Database 0.1 MB
K. K. Gigoyan
Pages: 330-332
Abstract. The Gaia Source 6054499677907012352 is a carbon star of late N – sub-types. We present Gaia DR3 BP/RP spectra, G-band magnitude, BP – RP color, radial velocity (RV), and phased light curve in G – band for new discovered C star.



INTRODUCTION 0.1 MB
Editorial Board
Pages: 333



Website with interactive visualization of multivariate astronomical time series 0.2 MB
M. Volkov, M. Demianenko, D. Matveev, K. A. Grishin, and I. V. Chilingarian
Pages: 334-340
Abstract. Light curves represent astronomical time series of flux measured across one or more photometric bands. With the rapid growth of large-scale sky surveys, time-domain astronomy has become an essential area of modern astrophysical research. Interactive visualization of extensive light-curve datasets plays a key role in exploring transient phenomena and in planning large follow-up campaigns. In this work, we introduce two web-based platforms designed for interactive light-curve visualization: Fulu, for transient event studies, and VALC, for investigations of low-mass active galactic nuclei (AGNs). These tools provide a user-friendly interface for examining, comparing, and interpreting vast collections of astronomical light curves, supporting scientific discovery.



The Gaia All-Sky Stellar Parameters Service (GASPS) 0.2 MB
I. McDonald, A.A. Zijlstra, N.J. Cox, and J. Bernard-Salas
Pages: 341-350
Abstract. Temperature and luminosity are the two key diagnostics of a star, yet these cannot come directly from survey data, but must be imputed by comparing those data to models. SED fitting offers a high-precision method to obtain both parameters for stars where both their distance and extinction are well known. The recent publication of many all-sky or large-area surveys coincides the publication of parallaxes and 3D extinction cubes from the Gaia satellite, making it possible to perform SED fitting of truly large (> 108) numbers of Galactic stars for the first time. The analysis of this data requires a high level of automation. Here, we describe the ongoing Gaia All-Sky Stellar Parameters Service (GASPS): the fitting of 240 million SEDs from Gaia DR3 and the extraction of temperatures and luminosities for the corresponding stars using the PySSED code. We demonstrate the quality of the initial results, and the promise that these data show, from wavelength-specific information such as the ultraviolet and infrared excess of each star, to stellar classification, to expansion of the project beyond our own Galaxy, and mineralogical mapping of the Milky Way’s interstellar medium.



Systematic and Statistical Uncertainties in Cepheid PL Relations: Incorporating a Cross-Filter Random-Phase Mitigation Approach 0.1 MB
M. Abdollahi and A. Javadi
Pages: 351-357
Abstract. The Period–Luminosity (PL) relation of Cepheid variable stars is a fundamental tool for measuring extragalactic distances and constraining the Hubble constant (H₀). Achieving high precision in PL-based distances requires careful consideration of both systematic and statistical uncertainties. We review the main sources of these uncertainties in PL relations, highlighting the increasing impact of random-phase errors in single-epoch observations from limited temporal coverage, such as those obtained with the James Webb Space Telescope (JWST). We discuss mitigation strategies for systematic errors, including photometric calibration offsets, metallicity effects, blending, and parallax biases, and quantify key contributors to statistical errors, such as photometric noise, intrinsic scatter, and phase-sampling limitations. Special attention is given to a recently proposed cross-filter random-phase correction method (Abdollahi et al., 2025), which recovers mean magnitudes from single-epoch data by exploiting correlations between PL residuals in different bands. This technique reduces the dispersion in the infrared PL relation by 28%, equivalent to an order-of-magnitude increase in effective temporal sampling, demonstrating an efficient path to improving Cepheid-based distance measurements and the precision of H₀.



The Third Catalogue of the First Byurakan Survey of Late-Type Stars 0.2 MB
K. K. Gigoyan, K. S. Gigoyan, and G. R. Kostandyan
Pages: 358-362
Abstract. A new value-added catalogue of late-type stars (LTSs), including M dwarfs, M giants, as well as new C (carbon) stars of N and CH types, was published from the analysis of the Digitized First Byurakan Survey (DFBS) spectral database. 1091 LTSs have been confirmed (243 M giants, 834 M dwarfs, and 14 C stars). All these objects were selected as LTS candidates when analysing the DFBS plates. For spectral type confirmation, the Gaia DR3 low-resolution BP/RP spectroscopic database has been used. To clarify the nature of the newly confirmed objects, Gaia DR3 photometric data and transiting Exoplanet Survey satellite (TESS) Input Catalog (TIC) data (masses, radii, effective temperatures, colors, distances, etc.) have been used. Using distances derived from the parallax in Gaia DR3, BP-RP color versus G-band absolute magnitude diagram (color-absolute magnitude diagram-CaMD) were constructed. Part of the newly confirmed M dwarfs presents binary systems.



The Role of Thermal and Nonthermal Processes in Star Formation at the Galactic Center 0.3 MB
F. Mazoochi, F. Tabatabaei, C. Henkel, S. Longmore, and D. Walker
Pages: 363-368
Abstract. Centers of galaxies hosting supermassive black holes (SMBHs) drive extreme astrophysical processes that shape galaxy evolution. The circumnuclear region of the Galactic Center (GC) provides a unique laboratory to study these effects around Sgr A*. Using MeerKAT 1.3 GHz continuum and ALMA H40α data, we separate thermal free–free and nonthermal synchrotron emission at 18" (0.7 pc) resolution. The correlation between nonthermal radio and FIR emission reveals a balance between magnetic, cosmic ray, and gas pressures, with an equipartition magnetic field averaging 445±7 μG and increasing toward Sgr A*. We find that the nonthermal pressure imposed by turbulent gas almost balances that of the magnetic field/cosmic rays and is about two orders of magnitude larger than the thermal pressure. Mass-to-flux ratios suggest a generally subcritical state, implying that magnetic fields play a key role in stabilizing clouds against collapse.



SEDust: A Pipeline for Deriving Best-Fit Spectral Energy Distributions from DUSTY Outputs 0.2 MB
H. Mahani and A. Javadi
Pages: 369-374
Abstract. In this study, we introduce SEDust, a pipeline designed to identify the best-fitting spectral energy distributions from the outputs of the DUSTY code and compare them to observational data. The pipeline incorporates a grid of 24000 models, enabling robust fitting for both carbon- and oxygen-rich AGB stars. It calculates key physical parameters, including luminosity, optical depth, and mass-loss rate, and produces the corresponding best-fit SED plots. Using SEDust, we derived the specific mass-return rates for the galaxies NGC 147 and NGC 185. The specific mass-return rate of AGB stars in NGC 147 is 8.13 × 10⁻¹²yr⁻¹, while in NGC 185 it is 6.52 × 10⁻¹¹yr⁻¹. These results indicate that the mass loss from evolved stars alone cannot account for the total mass budget required to sustain these galaxies, highlighting the need for additional sources or mechanisms of mass replenishment to resolve the observed discrepancies.



Diversity of active phenomena created by dark energy 0.1 MB
H. A. Harutyunian
Pages: 375-380
Abstract. Activity phenomena are widespread at all hierarchical levels of baryonic structures. In the microcosm, they manifest as radioactive decay. In the planetary world, volcanic and seismic activity is observed. Stars exhibit a much greater diversity. But even more types of activity are observed in galaxies. For all activity phenomena, identifying the energy source is crucial. This paper presents a new concept: at all hierarchical levels of the universe, active phenomena utilize dark energy, which a baryonic object acquires through interaction with a dark energy carrier.



Dust Production by AGB stars in the NGC 6822 Galaxy 0.2 MB
N. Rostami and H. Mahani
Pages: 381-385
Abstract. Asymptotic Giant Branch (AGB) stars and Long-Period Variables (LPVs) represent the final evolutionary stages of low- to intermediate-mass (0.8–8 M☉) stars and play a crucial role in enriching the interstellar medium (ISM) with metals and dust, thereby influencing the chemical evolution of galaxies. In this study, AGB stars and LPVs in the dwarf irregular galaxy NGC 6822 were investigated using publicly available multi-wavelength photometric data spanning the near- to mid-infrared regime, including observations from JWST, Spitzer, and UKIRT. Candidate AGBs and LPVs were identified through cross-matching with available online catalogs, and a consolidated catalog of their multi-band photometry was compiled. The spectral energy distributions (SEDs) of these sources were modeled using the DUSTY and SEDust codes to derive mass-loss rates and other dust-related parameters. Both oxygen-rich (O-type) and carbon-rich (C-type) AGB and LPV populations were analyzed, and their combined contribution to the chemical enrichment of NGC 6822 was quantified, yielding a total mass-loss rate of 2.4 × 10^-4 M☉ yr^-1 for the modeled sample. Correlations between key parameters, such as optical depth and bolometric correction, were further examined to estimate mass-loss rates for AGBs and LPVs not modeled due to incomplete photometric coverage.



Computational estimates for magnetic fields of a variety of disks surrounding Be-stars 0.1 MB
E. N. Zhikhareva, E. A. Mikhailov, E. B. Ryspaeva, and A. F. Kholtygin
Pages: 386-389
Abstract. We study the decretion disks formed around Be stars and characterized by the outflow of matter, unlike accretion disks. It is shown that, despite the opposite direction of the mass flow, the evolution of a large-scale magnetic field in such disks can be described within the framework of a large-scale dynamo approach. Field generation is considered a result of the combined action of the alpha effect and differential rotation. Peaceman – Rachford method was used to numerically solve the dynamo equation in a thin disk. Based on the observational data, a module simulating periodic emissions of substance and frozen-in magnetic fields was integrated into the computational code. The simulation is quite similar to that for accretion disks. Its results confirm the possibility of magnetic field generation in decretion disks.



Metallicity Effects on Machine Learning Classification of Dusty Stellar Sources in the Magellanic Clouds 0.2 MB
S. Ghaziasgar, M. Abdollahi, A. Javadi, J. Th. van Loon, I. McDonald, J. Oliveira, and H. G. Khosroshahi
Pages: 390-395
Abstract. Differences in metallicity between the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) offer an opportunity to examine whether environmental metallicity affects the performance of machine learning models in classifying dusty stellar sources. The five stellar classes studied include young stellar objects (YSOs), red supergiants (RSGs), post-asymptotic giant branch stars (PAGBs), and oxygen- and carbon-rich asymptotic giant branch stars (OAGBs and CAGBs), which are key phases of stellar evolution involved in dust production. Using spectroscopically labeled data from the Surveying the Agents of Galaxy Evolution (SAGE) project, we trained and evaluated a probabilistic random forest (PRF) classifier with four approaches: (1) separate training on LMC and SMC, including all five classes, (2) excluding the underpopulated PAGB class, (3) combined LMC and SMC datasets, and (4) cross-galaxy training and testing. The model achieved 93% accuracy on the SMC and 88% on the LMC across all five classes. In the SMC, PAGB sources were misclassified as YSOs, mainly because of their small sample size (4 objects). When PAGB was excluded, both the LMC and the SMC reached 92% accuracy. A combined dataset produced the same accuracy, and cross-galaxy training yielded similar results, indicating that metallicity does not significantly impact model performance. A comparison of absolute CMDs for the LMC and SMC confirms their similarity in stellar populations. These findings suggest that environmental metallicity has little effect on ML-based classification of dusty stellar sources, supporting the use of combined datasets and cross-galaxy models in low-metallicity environments.



Recent results of studies of radio galaxies 0.2 MB
H. V. Abrahamyan, A. M. Mickaelian, G. A. Mikayelyan, and G. M. Paronyan
Pages: 396-400
Abstract. The investigation of the physical properties of Active Galactic Nuclei is one of the most important tasks in astronomy. Until now, the properties of AGN have not been fully studied. Therefore, we have studied a number of important properties of AGN. For example, one of the main properties of AGN is variability. We have studied samples of AGN derived from different methods. For these sources, we have identified some properties of activity in the radio and optical ranges. These properties provide us with insight into active galaxies.



Activity types of x-ray selected galaxies 0.3 MB
G. M. Paronyan, A. M. Mickaelian, H. V. Abrahamyan, G. A. Mikayelyan, A. G. Sukiasyan, V. K. Mkrtchyan, and A. A. Gasparyan
Pages: 401-408
Abstract. We have created a general catalogue of AGN selected from optical identifications of X-ray sources using two sources: Hamburg-ROSAT Catalogue (HRC) and Byurakan-Hamburg-ROSAT Catalogue (BHRC). Both contain optical identifications of X-ray sources from ROSAT catalogues based on low-dispersion spectra of Hamburg Quasar Survey (HQS). HRC used ROSAT Bright Source Catalogue (BSC) and BHRC used brighter sources of ROSAT Faint Source Catalogue (FSC), thus extending the sample to count rates (CR) of photons ≥ 0.04 ct/s in the area with galactic latitudes |b| ≥ 20^° and declinations δ ≥ 0^° (the area of HQS). However, HRC and BHRC contain a number of misidentifications, and by using the recent optical and multiwavelength (MW) catalogues we have revised both samples excluding false AGN and adding new genuine AGN. As a result, a new homogeneous complete sample of 4253 X-ray selected AGN was created (ROSAT BSC/FSC AGN).
For these sources we retrieved all multiwavelength data from recent catalogues and carried out statistical investigations. An attempt to find connections between the radiation fluxes in different bands for different types of sources, and identify their characteristics thus confirming candidate AGNs have been done. We have analyzed X-ray properties of these sources to find a limit between normal galaxies and X-ray AGN.
In this study we carry out detailed spectral classification of AGN candidates from the Joint HRC/BHRC sample. These objects were revealed as optical counterparts for ROSAT X-ray sources, however spectra of them are given in SDSS without definite spectral classification. We studied these objects using the SDSS spectra and revealed the detailed activity types for them. Three diagnostic diagrams and direct examination of the spectra were used to have more confident classification.



Recent results of studies of IR galaxies 0.1 MB
G. A. Mikayelyan
Pages: 409-415
Abstract. Infrared galaxies are among the most important extragalactic objects for studying the formation and evolution of galaxies, star formation and SFR in galaxies, morphology, interacting and merging galaxies, variety of types of active galaxies (many Seyferts, LINERs, Starbursts and Composites), the luminosity function of galaxies (at higher redshifts), radiation mechanisms / energy sources, cosmological role of active galaxies, interrelationship between Starburst, AGN and interaction/merging phenomena, etc. We have carried out several studies of IR galaxies, including their revelation by optical identifications of IR sources and creation of Byurakan-IR Galaxies (BIG) sample of 1179 galaxies, redshift survey, study of pairs and multiples among the BIG objects, compilation of a IRAS PSC/FSC Combined Catalogue of 345,163 IR sources and distinguishing extragalactic objects among them, study of IR luminosities and IR/opt flux ratios, search and discovery of 114 ULIRGs and HLIRGs in the mentioned sample, their activity types from SDSS, morphology and X-ray, UV, optical and radio properties of IR galaxies, study of SEDs of IR galaxies by 17 photometric measurements from 1.25μ to 160μ range using 2MASS, WISE, IRAS and AKARI IRC and FIS catalogues.



Half-Light Radius Measurements of Andromeda Dwarf Satellites from the Isaac Newton Telescope Survey Using Exponential, Plummer, and Sérsic Fits 0.2 MB
H. Abdollahi
Pages: 416-422
Abstract. We present half-light radius measurements for the dwarf satellites of Andromeda, based on multi-epoch imaging from the Isaac Newton Telescope (INT) Monitoring Survey of Local Group dwarf galaxies. This analysis is conducted within a larger study to identify long-period variable (LPV) stars in these galaxies. The survey was performed with the Wide Field Camera on the 2.5-m INT and covers multiple epochs obtained between 2015 and 2018 in the i (Sloan) and V (Harris) bands. To determine the half-light radii, we derived surface brightness and number density profiles for each system and fitted them with Exponential, Plummer, and Sérsic models. The resulting half-light radii are in good agreement with literature values but reveal subtle variations linked to differences in stellar distribution and morphology. Distances were independently estimated using the Tip of the Red Giant Branch (TRGB) method, yielding values consistent with previous determinations. The complete photometric and variability catalogs will be made publicly available through CDS/VizieR, providing a valuable resource and foundation for future studies of the structure, stellar populations, and evolution of Andromeda’s dwarf companions.



Optical Variability of Blazars 0.1 MB
V. Kh. Mkrtchyan, A. M. Mickaelian, and H. V. Abrahamyan
Pages: 423-426
Abstract. In this work, we compiled and cross-identified optical variability data for Roma-BZCAT blazars using nine major photometric surveys. Despite the inhomogeneous nature of these datasets, their integration provides a unique opportunity to statistically characterize blazar variability and identify extreme cases for detailed study.
Cross-identifications were performed between BZCAT and these nine catalogs, and variability parameters such as amplitude, periodicity, and light-curve morphology were analyzed across different blazar subtypes (BZB, BZG, BZQ, and BZU). Several objects exhibiting extreme variability were identified as candidates for detailed follow-up studies.



Dynamical Effect of Galactic Magnetic Fields on the HI Gas Rotation Curve 0.2 MB
M. Khademi, S. Nasiri, and F. S. Tabatabaei
Pages: 427-436
Abstract. Magnetic fields are known to influence the thermal and structural properties of galactic gas, yet their impact on the rotational dynamics of galaxies remains largely underexplored. In this study, we examine how the magnetic arms of the spiral galaxy NGC 6946 affect its HI-traced circular gas rotation, incorporating two dark matter density models: the pseudo-isothermal (ISO) and the Navarro-Frenk-White (NFW) profile. To assess the magnetic contribution, we employ a three-dimensional representation of the galaxy’s magnetic field and perform a χ² minimization to match the modeled rotation curve with observational data. Our results show that including magnetic effects yields a better fit to the HI rotation curve, particularly in the outer disk where magnetic forces become more significant. The typical amplitude of the regular magnetic field contribution to the rotation curve increases with galactocentric radius, reaching approximately 14 km s^-1 in the outer gaseous disk of the galaxy NGC 6946, which corresponds to about five percent of the observed rotational velocity. These findings suggest that large-scale magnetic fields play a non-negligible role in the global dynamics of spiral galaxies, especially at large radii.



Membership Analysis of Open Clusters Using Machine Learning on Gaia Data Release 3 0.3 MB
M. Noormohammadi and A. Javadi
Pages: 437-443
Abstract. The first and most important stage in studying open clusters is the detection of reliable members. Since open clusters form and evolve within the inner disk of the galaxy, they are surrounded by numerous field stars, making membership determination challenging. Because cluster members originate from the same molecular clouds, they exhibit similar physical parameters—such as proper motion and parallax—and align along a single main sequence in the color-magnitude diagram. For this reason, machine learning algorithms can identify cluster members as familiar data among field stars. In this work, we used a combination of unsupervised machine learning algorithms—DBSCAN and GMM—based on astrometric parameters, proper motion, parallax, and position from the latest Gaia data release (GDR3). After selecting reliable members within the tidal radius, we applied the Random Forest algorithm to detect members beyond the tidal radius, utilizing proper motion, parallax, G-band magnitude, and BP-RP color index as classification features. By leveraging accurate data and a suitable method capable of handling large datasets, we identified members both inside and beyond the tidal radius of clusters. We observed clusters with a comprehensive field of view and analyzed their morphology. All members outside the tidal radius fall within the range of proper motion, parallax, and the main sequence of members inside the tidal radius.



M type Periodic Variables from Catalina Sky Survey 0.1 MB
G. R. Kostandyan and K. S. Gigoyan
Pages: 444-446
Abstract. In this paper, we continue spectral class determinations for optically faint periodic variables from the Catalina Sky Survey (CSS) database. Based on Gaia Data Release 3 (DR3) BP/RP spectroscopic database, 169 objects are confirmed as G and K-type stars, while 78 objects are confirmed as M-type stars.



Investigating The Star Formation History of the Nearby Dwarf Irregular Galaxy, NGC 6822 0.1 MB
F. Khatamsaz and M. Abdollahi
Pages: 447-450
Abstract. NGC 6822 is an isolated dwarf irregular galaxy in the local group at a distance of ∼ 490 kpc. In this paper, we present the star formation history (SFH) within a field with a radius of ∼ 3 kpc, beyond the optical body of the galaxy (∼ 1.2 kpc). We utilized a novel method based on evolved asymptotic giant branch (AGB) stars. We collected the Near-infrared data of 329 variable stars, including long-period and -amplitude variables and Carbon-rich AGB stars. We used stellar evolutionary tracks and theoretical isochrones to obtain the birth mass, age, and pulsation duration of the detected stars to calculate the star formation rate (SFR) and trace the SFH of the galaxy.