arXiv subjects

Gulnara Suliyeva

Publications and source records attributed to Gulnara Suliyeva.

9 recordsLinked to original sources

arXiv2026

FAIR-Compliant Architecture for Heterogeneous Astronomical Data: KazVO Framework

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 that maps heterogeneous metadata to the unified IVOA ObsCore standard. We follow Open Science by introducing metadata-only model featuring based on a four-class data embargo mechanism. Machine-to-machine services deployed via IVOA protocols are listed in the global Registry of Registers, enabling analysis of Kazakhstani observational assets within external clients such as Tool for OPerations on Catalogues And Tables (TOPCAT), Aladin, and PyVO. As a result, KazVO framework provides a scalable platform driven by a developed end-to-end pipeline that bridges two fundamentally distinct data types - digitized historical glass-plate heritage (1950-1997) and live operational photometric and spectroscopic digital streams from telescopes at the Assy-Turgen and Tien-Shan Observatories - opening FAI's combined data datasets to the global scientific and time-domain astrophysics community.

astro-ph.IM↗

arXiv2026

Testing dark matter density profiles based on Padé approximants of different orders

We investigate whether low-order Padé rational functions can be used as empirical density profiles for modeling dark matter halos from galaxy RCs. We introduce three parameterizations determined from Padé series, denoted Padé 02, Padé 12 and Padé 03, and compare them with pseudo-isothermal, Burkert, Beta, Brownstein, exponential-sphere and Persic models. The analysis is performed for eight galaxies under the assumption that RCs are dark matter dominated. The parameters are inferred from RC data and the relative statistical performance of the models is obtained through the Bayesian Information Criterion. We find that the Padé profiles perform well, being comparable with the other profiles, albeit not universally preferred. In most galaxies, conventional two parameter profiles provide fits of comparable or better statistical quality, whereas the clearest improvement occurs for one particular galaxy, where the Padé 03 profile gives the lowest BIC. Even though the Padé profiles are often statistically less strong than other models, they appear plausible in explaining the dark matter nature. Hence, their empirical construction can therefore be used to reconstruct RCs phenomenologically.

astro-ph.GA↗

arXiv2026

Testing Scalar Field Dark Matter models in M31 galaxy through the Rotation Curve analysis

We explore the viability of scalar field dark matter halo models through the rotation curve analysis of the Andromeda galaxy (M31), taking into account a realistic description of its baryonic structure. The mass model includes a stellar disk described by the Freeman profile and two alternative bulge configurations: a classical single de Vaucouleurs bulge and a two-component structure consisting of inner and main bulges modeled by exponential sphere profiles. The dark matter halo is modeled using three scalar field motivated models: fuzzy dark matter (FDM), Bose-Einstein condensate and multistate scalar-field dark matter. The model parameters are determined through the Levenberg-Marquardt nonlinear least-squares fitting, and the relative performance of the models is evaluated using the Bayesian Information Criterion which allows a direct comparison with previous phenomenological halo studies performed for the same galaxy. We find that the two-bulge baryonic configuration ensures a better statistical description of the M31 rotation curve, independently of the adopted halo model. The results also suggest that, within scalar field dark matter scenarios, smooth cored halos, such as FDM, provide the most consistent description of the M31 kinematics.

astro-ph.CO↗

arXiv2026

The exponential metric: traversable wormhole and possible identification of scalar background

The static antiscalar solution of the Einstein-Klein-Gordon equations in the form of the Papapetrou exponential metric had been interpreted as a traversable wormhole with a throat at \textit{r=M}. We aim to search for the effects which could be associated with this scale and only find that the topological Gauss-Bonnet invariant swaps sign, and the value of the Keplerian frequency for circular geodesics becomes singular. At the same time, the geometric invariants of the curvature tensor have extremal values at the scale twice less than that of the throat, revealing new physical effects. In particular, the Ricci scalar at \textit{r=M/2} (rather than \textit{r=M}) is associated with the extremal values of thermodynamic characteristics of the scalar background. This approach in combination with the antiscalar static limit of the Einstein-Maxwell equations suggests the interpretation of the scalar background as a stable medium with a stiff equation of state, formed by the neutral superposition of ambient quasistatic electric fields.

gr-qc↗

arXiv2025

Geometric properties versus particle motion in the Fan-Wang spacetime

In this work, we explore general relativistic effects and geometric properties of the Fan-Wang spacetime, one of the simplest regular solutions that can be obtained in nonlinear electrodynamics. In particular, we investigate the motion of test particles, the capture cross-section of neutral massive and massless particles, such as neutrinos and photons, and the gravitational redshift. Additionally, using a perturbative approach, we derive analytical expressions for the perihelion shift and gravitational deflection of massless particles. By identifying the one-parameter corrections to the Schwarzschild spacetime, induced by the magnetic charge contained in the Fan-Wang metric, we show that this spacetime can be falsified, since it modifies classical general relativity predictions even at the local level. Moreover, we argue that these modifications could be experimentally tested with advanced observational instrumentation.

gr-qc↗

arXiv2024

Accretion disks properties around regular black hole solutions obtained from non-linear electrodynamics

We investigate a family of spherically symmetric, static, charged regular black hole solutions derived within the framework of Einstein-nonlinear electrodynamics. Our study focuses on examining the characteristics of accretion disks in the spacetimes described by the Dymnikova and Fan-Wang solutions. We explore circular geodesics of test particles and calculate various properties, including the radius of the innermost stable circular orbit, radiant energy, temperature, and conversion efficiency of accretion mass into radiation. We employ the Novikov-Thorne-Page thin accretion disk model as a background. By comparing our findings with those obtained in the Schwarzschild black hole case, we reveal significant modifications in the overall spectral properties. Specifically, we observe an increase in the energy emitted from the disk surface, resulting in higher temperatures for the accretion disks under certain values of the free parameters. Consequently, we note an enhanced efficiency of mass conversion into radiation compared to the Schwarzschild spacetime.

gr-qc↗

arXiv2024

On the weak and strong field effects in antiscalar background

The triumph of general relativity under the banner "gravity is geometry" began with confirming the crucial effects within the Solar system and proceeded recently to the strong-field shadow effect for the compact object in the center of the Milky Way. Here, we examine some of those phenomena for the Einstein-scalar equations in the antiscalar regime to reveal the difference from vacuum both in weak and strong fields. As a result, we find that for week-field perihelion shift the difference between vacuum and antiscalar cases proves to be observationally imperceptible in practice, even for S-cluster stars with high eccentricities, and even if accumulated over a century. In strong-field case, we reconsider the shadow effect (this time without involving complex-valued scalar field) as the most perspective from an observational viewpoint. Even though the resulting difference is quite appreciable (about 5%), no conclusion can be made until the mass of the central object is known with the accuracy an order of magnitude higher than the currently available.

gr-qc↗

arXiv2024

Circular geodesics in the field of double-charged dilatonic black holes

A non-extreme dilatonic charged (by two ``color electric'' charges) black hole solution is examined within a four-dimensional gravity model that incorporates two scalar (dilaton) fields and two Abelian vector fields. The scalar and vector fields interact through exponential terms containing two dilatonic coupling vectors. The solution is characterized by a dimensionless parameter $a$ $(0 < a < 2)$, which is a specific function of dilatonic coupling vectors. The paper presents solutions for timelike and null circular geodesics that may play a crucial role in different astrophysical scenarios, including quasinormal modes of various test fields in the eikonal approximation. For $a = 1/2, 1, 3/2, 2$, the radii of the innermost stable circular orbit are presented and analyzed.

gr-qc↗

arXiv2023

Adiabatic theory in Kerr spacetimes

We present the main aspects of the adiabatic theory and show that it can be used to study the motion of test particles in general relativity. The theory is based upon the use of vector elements of the orbits and adiabatic invariants. To prove the applicability of the adiabatic theory in Einstein's gravity, we derive a particular representation of the Kerr metric in harmonic coordinates, which allows us to obtain a general formula for the perihelion shift of test particles orbiting on the non-equatorial plane of a rotating central object. We show that the principle of superposition is fulfilled for the individual effects of the gravitational source mass and angular momentum up to the second order. We demonstrate that the adiabatic theory, along with its simplicity, leads to correct results, which in the limiting cases correspond to the ones reported in the literature.

gr-qc↗