Chingis Omarov

This paper presents the architecture of the Kazakhstani National Virtual Observatory (KazVO)—an International Virtual Observatory Alliance (IVOA) compliant node that unifies the heterogeneous observational datasets of the Fesenkov Astrophysical Institute (FAI). The architectural foundation of the system is built upon a partitioned Data Lake, a German Astrophysical Virtual Observatory (GAVO) Data Center Helper Suite (DaCHS) publishing backend, and a PostgreSQL database in which metadata for published observational products are mapped to IVOA ObsCore, while catalogs and simulation grids use dedicated relational tables. We follow Open Science principles by introducing a metadata-only showcase model based on a four-class data embargo mechanism. Machine-to-Machine services deployed via IVOA protocols are exposed through the KazVO publishing registry registered in the global Registry of Registries (RofR), enabling analysis of Kazakhstani observational assets within external clients such as Tool for OPerations on Catalogues And Tables (TOPCAT), Aladin, and PyVO. The current implementation combines operational VO publication services and targeted photometric processing with scheduled, batch-mode data ingestion, supporting access to published historical and modern observational holdings. Replication has been validated on pilot datasets, while routine deployment at the observing sites and automated reduction of modern spectroscopic streams remain under development. The architecture provides a framework for progressively integrating these components into a complete data lifecycle.

We present empirical effective temperature ( T _eff ) calibrations for Galactic supergiants of spectral types B5–A5 based on optical spectra. The relationships were derived from a reference sample with adopted literature temperatures and use equivalent widths, central line depths, and ratios of selected spectral features as temperature indicators. Quadratic relationships are established for individual diagnostics and their ratios. Collectively, the calibrations span a T _eff interval from 8400 to 14,700 K, while the validity range of each relationship is individually specified. Detailed quantitative atmospheric analyses remain indispensable for deriving physically consistent stellar parameters. However, their application to extensive spectroscopic samples is observationally and computationally demanding. The empirical relationships presented here provide a homogeneous and readily applicable temperature scale for the characterization of Galactic BA supergiants. The complete calibration tables, including fitted coefficients and uncertainty information, together with an interactive Python tool to apply the relationships, are publicly available through Zenodo. The reduced continuum-normalized spectra and associated metadata are published through a Virtual Observatory–compliant service of the Kazakhstan National Virtual Observatory.

The results of direct N-body simulations of three Milky Way bulge globular clusters – Terzan 2, Terzan 4, and Terzan 5 – evolving in a time-varying galactic potential derived from the IllustrisTNG-100 cosmological database over 8 Gyr are presented. Incorporating full stellar evolution and compact remnant formation, we quantify the probability and efficiency of stellar accretion onto the Galactic nuclear star cluster (NSC) during close pericentre passages of these three clusters. To parametrize the effect of dynamical friction in the dense central environment, we introduce a velocity reduction factor (Vred) ranging from 1.00 to 0.10. It was found that all three clusters contribute stars to the NSC even in the absence of velocity reduction, with a combined bound stellar count of ~730 stars and a total accreted mass of ~278 M☉ at Vred = 1.00, growing to ~5420 stars and ~1175 M☉ at Vred = 0.10. Terzan 4 is the dominant contributor across all velocity reduction factors, reflecting its more frequent and closer pericentre passages near the Galactic centre. The mass distribution of accreted stars reveals a bimodal structure: a low-mass component below ~1 M☉ whose capture is independent of Vred, and a prominent high-mass tail extending to ~20 M☉ corresponding to neutron stars and black holes, which grows with decreasing Vred. Notably, Terzan 4 is the only cluster for which white dwarfs are also captured by the NSC at every Vred value. Our results suggest that the Terzan family represents a more significant source of compact remnants for the Galactic NSC than previously studied clusters, while confirming that tidal stripping of surviving globular clusters alone cannot account for the total NSC mass.

We establish the multimessenger mechanics of episodic mass transfer in supermassive black hole binaries stalled within circumbinary discs. Utilizing continuous wavelet transforms, we isolate localized gas clumps at the cavity edge and track their evolution. By regularizing the forced fluid equations at Lindblad resonances via the inhomogeneous Airy differential equation, we bypass linear Wentzel–Kramers–Brillouin singularities to extract the finite wave amplitudes that trigger nonlinear shock formation. These shocks produce bounded accretion bursts. We model the time-domain thermal luminosity, utilizing the Fourier shift theorem to derive an analytical power spectral density that forms an extended harmonic cascade. The superposition of the accretion streams generates a spectral beat frequency, providing a theoretical diagnostic template to estimate the binary mass ratio, though sensitive to intrinsic cavity shape. The radiative cooling of shock-accelerated electrons produces a multiwavelength spectral energy distribution from a synchrotron radio continuum to an inverse-Compton gamma-ray tail, regulated by pair-production thermostats. We identify a relativistic signature: a discontinuous, high-frequency gravitational wave sideband termed the “background gas humming.” We analytically differentiate this from steady spiral pattern speeds, showing it arises from the physical advection of highly localized, transient fluid hot spots following accretion shocks. Evaluating the asymptotic properties of the Airy regularization, we show that this humming manifests as a sequence of discrete high-frequency bursts with temporal quiescence gaps that systematically compress as the cavity shrinks. We show that the instantaneous accretion rate of the gas actively trapped within the cavity violently amplifies prior to decoupling, culminating in a terminal burst near 4 mHz (normalized to a 10 ⁶ M _⊙ system) that serves as a multimessenger precursor to the final vacuum inspiral.

We investigate the orbital eccentricity evolution of supermassive black hole binaries (SMBHBs; 10 ⁴ –10 ⁷ M _⊙ ) within galactic environments. Merger timescales depend on eccentricity when gravitational-wave (GW) emission dominates. We analyze the dynamics in triaxial merger remnants and subsequent interactions with geometrically thick nuclear disks. Gravitational torques in triaxial potentials extract angular momentum ( T _J ≪ T _E ), resulting in binary formation with high initial eccentricities ( e > 0.95). We analyze the binary–disk interaction using a 3D analytical framework incorporating the Airy formalism and present a self-consistent derivation demonstrating that the 3D suppression of high-order torques leads to distinct scalings with disk thickness ( h ), with migration rates τ a − 1 ∝ h − 3 and eccentricity damping rates τ e − 1 ∝ h − 5 , which establish a timescale hierarchy, τ _e / τ _a ∝ h ² . For typical parameters, eccentricity damping is significantly faster than orbital decay ( τ _e ≈ 0.04 τ _a ). We further develop a wavelet-based formalism to quantify the impact of disk inhomogeneities arising from accretion feedback and turbulence. We derive the stochastic torque variance in the wavelet domain and employ a Fokker–Planck analysis to determine the equilibrium eccentricity distribution. While stochastic fluctuations counteract deterministic damping, the strong damping imposed by the thick disk geometry ensures the equilibrium eccentricity remains small unless the fluctuations are highly nonlinear. Hence, highly eccentric born SMBHBs are rapidly circularized. This “circularization trap” forces binaries to approach the GW-dominated regime on nearly circular orbits, prolonging the total merger timescale. This introduces a cosmological delay (0.3–2.5 Gyr) governed by stellar relaxation.

We present a modification of the original GalIC code, which is designed to generate equilibrium initial conditions for numerical $N$-body models of collisionless, gravitationally bound systems. The proposed approach focuses on improving the procedure for assigning initial particle velocities, which is crucial for ensuring the stability and physical consistency of equilibrium models. Instead of drawing trial velocities from a uniform distribution bounded by the local escape velocity, we introduce a Gaussian-like distribution with compact support. Its dispersion is adapted to the local properties of the system and is derived from the Jeans equations. This choice provides a more physically motivated sampling of velocity space while preserving the bound nature of the system. A detailed comparison with the original GalIC method is performed using isotropic Hernquist models. We demonstrate that the modified algorithm converges significantly faster and produces well-resolved time-averaged mass profiles and velocity distributions. The resulting models show improved convergence toward the target distribution function while maintaining a comparable computational cost per iteration. Overall, the proposed modification provides a more efficient and physically realistic framework for generating equilibrium $N$-body initial conditions in collisionless stellar dynamical systems.

We present the conceptual framework of the Astronomical Hub (AstroHub), a unified platform combining various optical instruments at a single observatory. Its major approach lies in arranging conditions for research groups to install telescopes and equipment and participate in joint projects. AstroHub is planned to integrate Virtual Observatory (VO) tools, FAIR data principles, and a telescope network to create a powerful and attractive ecosystem for both robust near-Earth object (NEO) monitoring and diverse deep space research. We provide an overview of the AstroHub development directions in the case study of the Assy-Turgen Observatory.

Objects with the B[e] phenomenon, whose defining features are the presence of forbidden emission lines and infrared excess coming from circumstellar dust, represent a broad range of evolutionary stages from pre-main-sequence to planetary nebulae. They are important for understanding mechanisms of the circumstellar matter formation and evolution. However, it is not easy to discover them, especially among faint stars, as forbidden emission lines are usually weak and hardly noticeable in low-resolution spectra. We developed photometric criteria to search for candidate objects with this phenomenon based on a combination of optical and near-infrared color indices and found nearly 40 objects that satisfy these criteria. Spectroscopy of the candidates allows us to make more confident conclusions on their classification. We present the results of our photometric and spectroscopic observations of six objects, which are part of a large list of ∼40 objects that satisfy our photometric selection criteria for candidate objects with the B[e] phenomenon. Forbidden lines of neutral oxygen were clearly detected in the optical spectrum of one object (VES 683) and suspected in three others. One object, AS 415, is most likely a binary system with components that exhibit partial eclipses but without the B[e] phenomenon, while IRAS 20402 + 4638 may be a luminous member of the FS CMa objects group.