bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of the dynamic masses of open star clusters
Authors: Kulesh M. , Seleznev A.
Published: December 2024

The determination of star cluster masses is crucial for the study of cluster dynamics, the evaluation of gravitational binding, and the assessment of star formation efficiency. Traditional photometric approaches face challenges such as incompleteness, the problem of evaluating the uncertainty in the mass-luminosity relation, contamination by binaries, and so on. Dynamic (virial) approaches, which provide an estimate of the total cluster mass, have a difficulty in estimating the velocity dispersion. This study proposes a method to calculate the dynamic masses by using proper motions, taking into account for their observational errors. Using modern data for open clusters and samples of their probable members, we estimate dynamic masses of 833 open clusters. The resulting dynamic mass distribution is nearly log-normal with the mode of $2400\,M_\odot$.
Analysis of data on lopsided galaxies and theories of their formation
Authors: Nuritdinov S. , Mirtadjieva K. , Omonov A.
Published: December 2024

Ground-based and space observations show that the nuclei of many disk-shaped galaxies are significantly offset from their geometric center. This can lead to the excitation of the lopsided mode m=1. To determine the dependence of this effect on the geometry of the system, in this work we have compared a non-stationary disk model with respect to the gravitational instabilities of the lopsided mode N=3; m=1 perturbation. In this work we have also compiled a summary catalog of lopsided disk-shaped galaxies and conducted a statistical analysis of their physical parameters.
Behavior of sectorial instabilities depending on the parameters of the generalized model of a self-gravitating disk
Authors: Nuritdinov S. , Mirtadjieva K.
Published: December 2024

In this work we study the problem of gravitational instability in the generalized model of a nonlinearly radially pulsating disk with an anisotropic velocity diagram relative to sectoral perturbation modes. This model is a nonstationary generalization of the equilibrium self-gravitating disk of Bisnovatyi-Kogan and Zeldovich. Nonstationary analogues of dispersion equations (NADE) are obtained on the background of this generalized model for sectoral modes of perturbations. Based on the results of numerical calculations of NADE, graphs comparing the increments of instability as a function of the initial virial ratio of the system for different values of the parameters and , characterizing the difference and the degree of anisotropy of the nonlinearly nonstationary generalized model of the self-gravitating disk, are constructed. In particular, it is found that the development of the bar-like perturbation mode will be the same for all anisotropic models, since the NADE of this mode does not depend on these parameters and .
The evolution of the fossil large-scale magnetic field in turbulent accretion disks of young stars
Authors: Orlov A. , Khaibrakhmanov S.
Published: December 2024

We study the fossil large-scale magnetic field evolution in a turbulent accretion disk of young T Tauri star. The coefficient of turbulent viscosity is calculated according to the Shakura and Sunyaev model. The modeling is performed taking into account the weakening of the turbulence in the region of low ionization fraction (``dead" zone). The ionization structure is calculated taking into account thermal ionization, cosmic rays and radioactive elements, radiative recombinations and recombinations on dust grains. The magnetic field is calculated taking into account ambipolar diffusion. The simulations show that the magnetic field is frozen in gas and its strength is proportional to the gas surface density in the inner region of the disk, $R<0.2$ AU. The magnetic field strength increases from $10^2$ G to $10^3$ G in this region within 5 Myr. The outer boundary of the ``dead" zone depends on the dust grain size and ranges from 30 AU for $a_g=0.1$ $\mu$m to 3 AU for $a_g=10^3$ $\mu$m. The size of the ``dead" zone decreases with time. The magnetic field strength inside the ``dead" zone remains practically constant at around $10^{-3}$–$10^{-4}$ G during the disk evolution.
Random force distribution for fractal stellar medium in the solar neighborhood based on Gaia DR2 data
Authors: Ostashova M. , Rastorguev Alexei
Published: December 2024

We examine the law of the distribution of the magnitude of random force in the nearest-neighbor approximation (the generalized Holtsmark distribution) and asymptotics of the Holtsmark distribution for large random forces for the fractal stellar medium in the Solar neighborhood with fractal dimension $D \approx 2.41$. Our investigation is based on the study of 200 000 stars of all spectral types at a distance of 1 to 100 pc from the Sun. We demonstrate that for fractal stellar medium slower decreasing random force distribution takes place. It indicates an important role of strong fields in the kinetics of gravitating medium in comparison with a classical uniform stellar medium.
Radial profiles of systematic velocities in massive protostellar cores
Authors: Pirogov L. , Zemlyanukha P.
Published: December 2024

The knowledge of systematic velocity radial profiles in the star-forming cores is important for theoretical models. We analyzed the HCO$^+$(1-0) spectral maps of five massive cores from the MALT90 database associated with the regions of high-mass star formation at different stages of evolution. We fitted the maps calculated in the framework of spherically symmetric model into observed ones. An approach based on the principal component analysis and the k-nearest neighbors method was used to find minimum of the error function between model and observed spectral maps. Radial profiles of density, turbulent and systematic velocity are obtained. Densities in the cores decrease with radial distance with power-law indices ranging from 1.5 to 2.5, turbulent velocities decrease with power-law indices ranging from 0.3 to 0.45. Systematic (infall) velocity profiles in the cores are close to $r^{-0.1}$ which differs from what is expected for free fall. Analysis of the $^{13}$CO (2-1) SEDIGISM data for three sample objects has revealed the V-shape features on the position-velocity profiles which implies motions from surrounding gas to the cores. Taken together, the results support the scenario of globally contracting cores which interact with their surroundings.
Periodic changes in the orientation of orbits and the age of the Galactic bar
Authors: Podzolkova E. , Melnik A.
Published: December 2024

We studied the model of the Galaxy that reproduces the observed median velocity distribution derived from Gaia DR3 data along the Galactocentric distance, $R$. The model profiles of radial velocity, $V_R$, demonstrate an increase with a period of $P = 2.1 \pm{0.1}$ Gyr and form humps at $R = $ 6-7 kpc. The average amplitude of variation in the radial velocity is $A = 1.76 \pm{0.20}\, \rm km\, s^{-1}$. The humps are supported by orbits changing orientation relative to the major axis of the bar within the range of $[-45, \;45]$$^{\circ}$. The median period of variation in the angular momentum of hump-supporting orbits is $P = 1.85 \pm{0.17}$ Gyr, and 71.6 % of them support ring $R_2$. The observed profile does not show any humps. In the model profile, humps disappear during the times $2.5 \pm{0.3}$ and $4.5 \pm{0.5}$ Gyr, indicating that the age of the Galactic bar must be close to one of these values. The model disk forms outer resonance rings $R_1$ and $R_2$, which demonstrate periodic changes in their morphology with a period of $P = 2.0\pm{0.1}$ Gyr, supported by orbits trapped by the Outer Lindblad Resonance.
Evolution of large-scale magnetic fields of chemically peculiar stars
Authors: Romanyuk I. , Semenko E. , Yakunin I. , Moiseeva A. , Kudryavtsev D. , Korchagina E. , Aitov V.
Published: December 2024

We studied the magnetic field of chemically peculiar stars in the young Orion OB1 association and in other five older clusters. We have found new evidence of the validity of the relic origin of the magnetic field. In the Orion OB1 association, the magnetic field values and the occurrence frequency of magnetic stars are systematically higher than in older groups. There is no magnetic field generation during the life of a star on the main sequence. The observations were carried out using the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. We studied the magnetic field of about 80 stars. More than 1000 spectra were obtained with the circular polarization analyzer on the BTA Main Stellar Spectrograph.
Spectroscopy of B stars in the very young open star cluster IC 1805
Authors: Tarasov A.
Published: December 2024

Based on moderate-resolution spectra in the range 4200–5200 Å, we have studied late O and early B stars in the very young open star cluster IC 1805. The temperatures of the stars under the study have been derived by the differential method, in which simple parameters were chosen for a number of spectral lines and were then compared with the analogous parameters from an extensive sample of O–B stars. Accurate $T_{\rm eff}$ estimates have been obtained for them from model atmospheres. Applying this method for the sample of objects under the study has allowed the cluster age $t = 2 \pm 0.5$ Myr and distance modulus $(v$–$V)_{0} = 11.\!\!^{\rm m}5$ to be determined with confidence.
Formation of quasi-periodic oscillations in the solar corona
Authors: Derteev S. , Sapraliev M. , Shividov N. , Mikhalyaev B.
Published: December 2024

The dispersion of acoustic waves in the rarefied high-temperature plasma of the solar corona and its role in the propagation of disturbances occurring in the corona are analyzed. We believe that the quasi-periodic oscillations (QPOs) that are recorded when observing propagating disturbances in coronal holes and loops are formed as a result of the combined effect of dispersion and damping of compressive waves. Observations and wavelet analysis show that their spectra are continuous, where the periods are distinguished by corresponding maxima. The shape of spectrum is characteristic of localized disturbances. The study is based on the simple model of non-adiabatic waves in high-temperature plasma, taking into account the properties of thermal conductivity, radiative cooling and constant heating.
Magnetic reconnection flux in eruptive and confined solar flares
Authors: Gopasyuk O.
Published: December 2024

The magnetic properties of 59 flare events (38 eruptive and 21 confined) of GOES class M5.0 and above between February 2011 and December 2022 were analyzed. To identify the statistical properties of magnetic reconnection fluxes, we used the observational data from Solar Dynamics Observatory. The flare durations were analyzed using data from the GOES. The correlation between the GOES peak X-ray flux of a flare and magnetic reconnection flux is strong both for confined and eruptive flares. Eruptive flares show statistically larger magnetic reconnection flux and ribbon area than confined flares. The magnetic reconnection flux is strongly correlated with the flare duration. There is an approximately linear relationship between rise and decay times: the longer the rise time, the longer the decay time. We found a relation between the fraction of active regions (ARs) involved in reconnection process and the eruptive character of large flares.
The probability that AR-induced flares will be associated with a coronal mass ejection (CME) increases with the fraction of ARs involved in the reconnection.
Diversity and similarity of linear polarization among low-albedo NEAs: extremely high polarization of NEA 25330 (1999 KV4)
Authors: Kiselev N. , Shcherbina M. , Busarev V. , Zhuzhulina E. , Karpov N. , Shein A.
Published: December 2024

This study explores the diversity and similarity of linear polarization among low-albedo Near-Earth Asteroids (NEAs), focusing on the exceptionally high polarization of NEA 25330 (1999 KV4). Polarimetric observations are essential for understanding the physical properties of NEAs, providing insights into the nature of scattering particles and ambient physical processes that cannot be achieved using other observational methods.
Fire-hose instability of the torsional Alfven oscillation as a mechanism of plasma layering in an experimental coronal solar loop-type magnetic arch
Authors: Koryagin S. , Viktorov M.
Published: December 2024

The compact experimental setup ``Solar Wind'' (IAP RAS) is designed for modeling plasma processes in a magnetic arch of the coronal solar loop type. Arc discharges at the bases of the arch create plasma with a significantly increased ionic temperature along the magnetic force line. Optical images show that the plasma rope is stratified into two belts along the upper and lower vaults of the arch or as a near-wall cylindrical layer. The system stratifies when the longitudinal ionic pressure at the top of the loop is 2 times the magnetic pressure. The indicated pressure ratio coincides with the threshold value for the development of the fire-hose instability of the Alfven wave in a plasma with temperature anisotropy. We propose a variant of the growing torsional Alfven oscillation as a mechanism for the formation of a cylindrical layer along the plasma tube wall.
Interpretation of polarimetric observations of hyperbolic comets
Authors: Petrov D. , Zhuzhulina E. , Kiselev N.
Published: December 2024

Polarimetric observations of comet C/2013 X1 (PANSTARRS) were compared with polarimetric data taken from the Polarimetric Comet Observations Database. To obtain a synthetic phase dependence of the degree of linear polarization of hyperbolic comets, the data were interpreted using computer simulations. In this case, computer simulation means calculating the characteristics of light scattered by particles of irregular shape and a certain chemical composition. Simulations showed that the dust ball would have to be 74 % amorphous carbon, 25 % magnesium-rich silicates, and 1 % water ice to reproduce the observed linear polarization values.
Investigation of the dynamics of the magnetic field and vertical electric current during the precursors of the M6.5 class solar flare of June 22, 2015 using vector 135-second HMI magnetograms
Authors: Sharykin I. , Zimovets I.
Published: December 2024

This paper considers the M6.5 eruptive solar flare occurred on June 22, 2015, for which ultraviolet preflare emission sources in the 1600 Å chromospheric channel have been analyzed using AIA/SDO data. Magnetic fields at the photospheric level are also analyzed using HMI/SDO vector magnetograms with a time resolution of 135 seconds. Since the selected flare has a long preflare phase (about one hour), the available time resolution of vector magnetograms is sufficient to study the flare and preflare dynamics of magnetic fields at the photospheric level. It can be noted that the literature mainly considers the change in currents during solar flares, while insufficient attention is paid to precursors. Our main goal is to provide continuous monitoring of the dynamics of electric current during the preflare period, at the beginning of the flare and during the main phases of the flare. We determined the magnetic flux (and its time derivative) in the preflare sources at the chromospheric level in comparison with the magnetic fluxes of the flare ribbons. Analysis of 135-second HMI photospheric vector magnetograms showed that there was an increase in the total vertical electric current about 1 hour before the flare. During this hour, there were variations of the mean vertical electric current density and its subsequent drop during the flare. We probably see an intermittent increase and dissipation of currents due to individual bursts in the preflare region. Also, the analysis of magnetic fluxes showed that, despite the weak preflare soft X-ray fluxes, the variations in magnetic flux during precursors are comparable in order of magnitude to what we see during the main phase of the solar flare. The difference between the time derivatives of the magnetic flux for precursor radiation sources and flare ribbons does not exceed a factor of 3.
Using UBVRI-photometry to detect signs of asteroid activity
Authors: Shcherbina M. , Busarev V.
Published: December 2024

This paper focuses on the application of UBVRI-photometry to detect signs of sublimation-dust activity in Main Belt asteroids. Survey observations have been conducted at the Caucasian Mountain Observatory of Moscow State University since 2021, using the RC600 telescope, which has provided data for 133 asteroids. Special attention is given to primitive-type asteroids (with low-temperature mineralogy), many of which may still retain water ice in their interiors. Numerical models of light reflection by active C-type asteroids with a dust exosphere have confirmed spectral differences depending on particle composition. A qualitative criterion for the activity of a primitive asteroid was established, based on the occurrence of a negative gradient in its reflection spectrum in an active state due to ice sublimation and the formation of a dust exosphere. As a result of observations and data analysis, spectral signs of dust activity were detected in 14 primitive asteroids, confirming the effectiveness of the method used.
Gaia Data Release 3: analysis of reflectance spectra of near-Earth asteroids and Mars-crossers
Authors: Shcherbina M. , Kovaleva D.
Published: December 2024

Since July 2014, the European Space Agency (ESA) Gaia mission has been observing objects in the Solar System as part of its various scientific missions. The third data release (DR3) includes observations of more than 150,000 objects, including asteroids. Analysis of Gaia asteroid reflectance spectra has allowed for the first time to determine spectral types for many objects and to confirm or refine previously determined classes. The distribution of spectral groups coincides with the analysis of ground-based observations performed by other authors, with a sample overlap of less than 20 %. The main groups include the S-group ($\sim$60 %) and the C-group ($\sim$20—25 %). Mars-crossing objects are slightly more likely to have mixed mineralogy. This distribution remains constant over different ranges of object diameters. Analysis of the distribution of spectral groups by semi-major axis and perihelion distance may serve as indirect evidence for the prevalence of sublimation-dust activity in primitive asteroids.
Differential rotation of sunspots of different magnetic polarity
Authors: Tlatova K. , Tlatov A.
Published: December 2024

The rotation rate was analyzed depending on the latitude of individual sunspots of different magnetic polarity. To identify sunspots, we used observations of the SDO/HMI space observatory in the period 2010-2024 in the continuum and observations of magnetic fields at the same time. It was found that the rotation rate of sunspots depends on the magnetic polarity in the 22-year Hale magnetic cycle. The dependence of the rotation rate of sunspots on latitude can be written for sunspots of leading polarity, the rotation rate can be approximated by the formula: $\omega_{\rm ld}(\theta)=14.574-2.225 \rm{sin}^{\rm 2}\theta-0.02 \rm{ sin}^{\rm 4}\theta$ deg/day. For sunspots of trailing polarity $\omega_{\rm tr}(\theta)=14.216-2.60 \rm{sin}^{\rm 2}\theta-0.01 \rm{ sin}^{\rm 4}\theta$ deg/day. Thus, sunspots of leading polarity rotate more than $\sim2\%$ faster than sunspots of trailing polarity. For sunspots with magnetic flux $\Phi>2\cdot 10^{20}$ Mx, the rotation rate practically does not change with increasing magnetic flux.
Electric currents in the solar corona and the kink instability of magnetic flux rope
Authors: Tsap Yu. , Stepanov A. , Kopylova Yu.
Published: December 2024

We found the dispersion equation for magnetohydrodynamic kink oscillations of a force-free magnetic flux rope with uncompensated longitudinal electric current under the conditions of the solar corona using the energy method and the thin magnetic flux tube approximation. It is shown that the eigenfunctions, along with the eigenvectors, impose additional restrictions on the stability conditions of the kink instability of a flux rope. This allows us to obtain not only the necessary, but also a sufficient condition for stability. The observed weak twist of coronal loops with a small (< 2–3) number of the turns of magnetic field lines around the axis indicates the dominance of unshielded magnetic flux rope in the corona of the Sun, in which the longitudinal electric currents do not exceed $10^{11}$–$10^{12}$ A.
Determination of the exoplanet HD 189733 b atmospheric structure based on the multicolor photometric transit observations obtained with the HST and at the Caucasian Mountain Observatory
Authors: Bekesov E.
Published: December 2024

The paper presents a study of the exoplanet HD 189733 b based on the multicolor photometric observations obtained by the Hubble Space Telescope as well as on the equipment of the Caucasian Mountain Observatory. It is shown that with all other parameters fixed, the radius of the planet obtained from the interpretation of the light curves varies, which may be a consequence of the presence of an extended Rayleigh atmosphere.
Measurement of the metastable helium atomic rates important for astrophysical observations
Authors: Golubovsky M. , Shaikhislamov I. , Rumenskikh M.
Published: December 2024

We present an experimental setup for measurement of the collisional rates relevant for the population of the triplet level of metastable helium. To estimate and verify the theoretical values, the absorption in helium plasma in the 1083 nm line will be measured. We are going to use plasma consisting of helium ions generated by $\theta$-pinch, filling in a 6 m$^3$ volume of a vacuum chamber at concentrations of $10^{12}$–$10^{13}$ cm$^{-3}$. Based on the expected parameters, the optical depth $\tau = 1$ is going to be achieved with a path length $L = 1$ km. To increase the effective path length in the plasma, an optical scheme based on a concave resonator is proposed.
Migration of planetesimals and dust particles in the Proxima Centauri exoplanetary system
Authors: Ipatov S.
Published: December 2024

The motion of the planetesimals and dust particles from the vicinity of the orbit of planet c in the Proxima Centauri exoplanetary system was studied. The computer simulations of planetesimal motion showed that during the growth of the mass of planet c by a factor of 2, the semimajor axis of its orbit could decrease by at least a factor of 1.5. After hundreds of millions of years, some planetesimals could still move in elliptical resonant orbits inside the feeding zone of planet c that had been mainly cleared from planetesimals. The amount of water delivered to the inner planet Proxima Centauri b probably exceeded the mass of water in Earth’s oceans. It is difficult to expect the existence of such a massive analogue of the Oort cloud around Proxima Centauri as around the Sun. The probability of the collisions of the dust particles with a diameter of about 100 microns migrated from the feeding zone of planet c with planet b could exceed 0.1, and it could be much greater than for the planetesimals from the same zone. More particles with diameters of the order of 10 and 100 microns can be delivered from the feeding zone of planet c to planet b than to planet c.
Migration of planetesimals in the TRAPPIST-1 exoplanetary system
Authors: Ipatov S.
Published: December 2024

The calculations of the motion of planetesimals at the late stages of accumulation of planets in the TRAPPIST-1 system were made. In each calculation variant, initial orbits of planetesimals were near one of the planets. The number of collisions of planetesimals with the planets were calculated. The calculations has shown that the outer layers of neighboring exoplanets in the TRAPPIST-1 system can include similar material if there were a lot of planetesimals near their orbits at the late stages of the accumulation of the exoplanets.
Simulation of the H$\alpha$ absorption for the hot Jupiter HAT-P-32 b
Authors: Sharipov S. , Miroshnichenko I. , Shaikhislamov I. , Rumenskikh M.
Published: December 2024

The paper presents the results of modeling the absorption spectrum in the H$\alpha$ and He 10830 Å lines for the hot Jupiter HAT-P-32 b. The simulation was carried out using a 3D hydrodynamic model coupled to a Monte Carlo model of Ly$\alpha$ photon transfer. It was determined that to explain the absorption in both lines at a ratio ${\rm H}/{\rm He}=99/1$, high values of the XUV flux and stellar Ly$\alpha$ flux are required: $F_{\rm XUV}=100$ erg cm$^{-2}$ s$^{-1}$ and $I_{\rm Ly\alpha}=600$ erg cm$^{-2}$ s$^{-1}$, which may indicate high activity of the star. New parameters were also found that describe the absorption at ${\rm H}/{\rm He}=97/3$ while requiring less extreme $F_{\rm XUV}=25$ erg cm$^{-2}$ s$^{-1}$ and $I_{\rm Ly\alpha}=600$ erg cm$^{-2}$ s$^{-1}$. Monte Carlo modeling showed that the absorption in the H$\alpha$ line is formed by stellar photons producing H(2) concentrations at a level of $10^2$–$10^3$ cm$^{-3}$ in the atmospheric layer up to $2R_{\rm p}$, where the absorption occurs.
Orbital dynamics of the superactive comets 46P/Wirtanen and 103P/Hartley
Authors: Chernetenko Yu. , Pavlov S.
Published: December 2024

Comets 46P/Wirtanen and 103P/Hartley are Jupiter-family short-period comets. They passed very close to the Earth in 2018 and 2010, respectively, resulting in radar observations and a large number of positional observations and, thus, they caught our attention. Radar observations have revealed the presence of ice grains in the comas surrounding comets, ejected by streams of more volatile compounds during sublimation, which allowed them to be classified as hyperactive. So far, we have not seen the results of combining positional and radar observations of comet 103P in one orbit. We managed to overcome this assuming the presence of offset between the center-of-light and the center-of-mass in positional observations of the apparition with the radar observations by the value of ${S = S_0/r^2}$. The components of the vector ${S_0} (R, T, N)$ in the orbital coordinate system associated with the comet were: $R$ = 264$\pm$6 km, $T$ = 7$\pm$5 km, $N$ = $-116\pm$5 km. In addition, the residuals, $(O-C)$, of both comets revealed systematic deviations that could not be explained by systematic errors of individual observatories. In addition, the light curves of these comets showed peculiarities matching with $(O-C)$ behavior. To eliminate systematic deviations in the positional observations, they were divided into four intervals according to the light curves. We determined a set of parameters of non-gravitational acceleration $A_1, A_2, A_3$ at each interval simultaneously with the determination of the orbit from all observations. This approach allowed us to get rid of deviations in $(O-C)$. The results obtained for these comets may indicate a truly complex nature of the non-gravitational acceleration acting on these comets.
Length of day multifractal dynamics
Authors: Denisenko S. , Petrov S.
Published: December 2024

In this work, the power spectral densities (PSD) of several combined and instrumental length of day (LOD) multifractal time series are computed. As a result, a stable power spectrum, practically independent of the type of time series, of multifractal structure is obtained. The power spectrum of the duration of the day can be divided into three frequency bands. For periods of less than three months, the LOD behaves like a power noise with a score close to $-1.5$. Over periods of three months to three years, LOD behaves almost like white noise. Finally, over periods of more than three years, the LOD also exhibits power noise behavior with a score of about $-1.5$. It turns out that the revealed structure practically does not depend on the type of time series (combined or instrumental), its length, and the parameters of the method for assessing PSD.
On the issues of estimating the accuracy of Earth rotation parameters
Authors: Gayazov I. , Kurdubov S. , Skurikhina E.
Published: December 2024

Earth rotation parameters (ERP) are determined at the Institute of Applied Astronomy (IAA) by processing the following types of observations: Very Long Baseline Interferometry (VLBI), Global Navigation Satellite Systems (GNSS) and Satellite Laser Ranging (SLR). The IAA also carries out special sessions of VLBI observations on radio telescopes of the Quasar network for ERP determination in various modes. The accuracy of the obtained series is estimated by comparison with the combined results of the International Earth Rotation and Reference Systems Service (IERS) usually accepted as reference. The accuracy of various ERP series has been analyzed also using a method based on the assumption that there can be no abrupt changes in ERP and after removing the intra-day variations the series should be sufficiently smooth. In this method the evaluation is performed without calculating the differences of two independent series and is related only to the internal properties of the series. The article presents an overview of the results of the analysis and concludes that the proposed technique can be used to estimate the accuracy of the ERP series.
Detecting low signal-to-noise meteor images in the astronomical camera video stream
Authors: Izmailov I. , Khovrichev M. , Tolstoy A. , Pavlov S. , Bikulova D.
Published: December 2024

The analysis of space mission data, such as Long Duration Exposure Facility (LDEF), reveals that the majority of meteor particles fall within the microgram to milligram range. This range corresponds to meteor absolute magnitudes from 5-6 mag to 10-11 mag. Global Meteor Network (GMN) and Mini-MegaTORTORA (MMT) database analysis shows a noticeable decrease in the number of detected meteors fainter than threshold ``limiting magnitude minus about 2 mag''. This implies that there may be a loss of faint meteors at low signal-to-noise ratios. Therefore, it is crucial to improve the methods for detecting faint meteor events. We present a technique focused on real-time data processing. The key components of the pipeline involve rapidly identifying local peaks and then projecting the chosen points from a series of frames onto a reference frame within a sub-series of several images for analysis using the Hough transform. Initial test observations indicate an increasing trend in the number of faint meteor detections.
Determination of the mass of asteroid (16) Psyche and masses of other asteroids of the taxonomic class M by the dynamic method
Authors: Kuznetsov V. , Chernetenko Yu.
Published: December 2024

We use the dynamical method of estimation of the mass of perturbing asteroid by its gravitation influence on test asteroids. The positional observations of test asteroids from Minor Planet Center database and Focus Product Release of Gaia cosmic telescope are employed. The calculation of coordinates of perturbing planets is based on the ephemeris DE440. The set of test asteroids is used for estimation of perturbing mass. This set was collected by error of the mass of the perturbing asteroid for each test object. The number of test asteroids was selected particularly for each estimated mass. For the mass of asteroid (16) Psyche a value equal to \mbox{$(1.1868\pm0.0092) 10^{-11} M_{\odot}$} was obtained. The masses of sixteen asteroids with numbers 55, 69, 75, 77, 83, 92, 97, 110, 129, 135, 201, 325, 441, 498, 516, and 739, that are from the taxonomic class M were estimated also. The estimated masses more than twice exceed their errors.
The influence of uncertainty in the shape of an asteroid on the estimate of perturbation magnitudes in its rotational dynamics when approaching the Earth
Authors: Lobanova K. , Melnikov A.
Published: December 2024

The shape of the vast majority of small asteroids is unknown. There are only estimates of the average diameter obtained for them on the basis of absolute magnitude and albedo under a number of assumptions. To estimate the magnitude of perturbations in the rotational dynamics of an asteroid that arise when approaching the Earth by means of numerical modeling, it is necessary to know its moments of inertia, determined, among other things, by the shape of the asteroid. By conducting massive numerical experiments to simulate a close approach of an asteroid to the Earth, the influence of the figure's parameters on the magnitude of perturbations in the rotational dynamics of the asteroid was studied. It has been established that with very fast rotation (period $P < 1$ hour), even significant errors in knowledge of the asteroid's figure do not have a significant effect on the estimate of the magnitude of the perturbations. On the contrary, with a relatively slow rotation of the asteroid ($P > 5$ hours), inaccurate specification of the parameters of the asteroid's figure can lead to a significant underestimation of the perturbation values in numerical experiments. For example, for the asteroid Apophis ($P = 30.6$ hours), the error in the estimation of the rotational period after its close approach to the Earth in 2029 can be several hours, and the uncertainty in knowledge of the orientation of the rotational axis can be tens of degrees.
Tidal changes in the rotational state of asteroids asevolution factor of the magnitude of the Yarkovsky effect
Authors: Melnikov A. , Khovrichev M. , Balyaev I. , Lobanova K.
Published: December 2024

We examined possible tidal-induced leaps in the rotational state parameters of the asteroids during their planet approaches. These dramatic changes in the rotational period and obliquity lead to significant changes in orbital dynamics due to the corresponding Yarkovsky acceleration $A_2$ leap. Our numerical simulations of asteroid rotational parameters evolution due to their planet encounters support the conclusion that significant $A_2$ changes can happen when planetocentric distance is less than ten planetary radii. We have found nine asteroids with anomalous $A_2$ values. However, there is no exact evidence that these$A_2$ discrepancies can be explained by tidal effects only.
Perturbations in the rotational dynamics
Authors: Melnikov A. , Lobanova K.
Published: December 2024

Using numerical modeling, perturbations that occur in the rotational motion of small (10--50 m in diameter) asteroids during their close approaches to the Earth (at distances of the order of several Earth radii) are considered. For a number of asteroids (Duende, 2012\,TC4 and 2023 BU), estimates of possible changes in the rotational period $P$ and the orientation of the rotational axis due to approach to the Earth were obtained. It has been established that in the case of fast rotation of an asteroid ($P < 1$~h), perturbations in its rotational motion that arise during approach are negligible. With a relatively slow rotation of the asteroid ($P > 5$~h), perturbations can be significant: changes in $P$ may reach several hours, and deviations of the rotation axis from the initial position may amount to tens of degrees. Such perturbations influence further orbital dynamics of a slowly rotating asteroid by changing the magnitude of the Yarkovsky effect.
Accuracy of orbits of small celestial bodies obtained using different software
Authors: Pavlov S. , Medvedev Yu. , Galushina T. , Baturin A.
Published: December 2024

The threat of a collision with a potentially hazardous object (PHO) and smaller asteroids requires the ability to reliably calculate the orbits of celestial bodies. The quality of the determined orbit depends on both the accuracy and intervals of observations and on the method of their processing: the completeness of the dynamic model, the method of numerical integration, calculation errors, etc. The practical implementation of the orbit determination algorithm is associated with the peculiarities of taking into account the above factors. To assess the accuracy of motion prediction using orbits obtained with the help of different software packages, we compared the deviations in observed and calculated values of observations, i.e. $O$–$C$, that were not included in the orbit improvement. The $O$–$C$ comparison was carried out for orbits obtained using software developed in leading Russian scientific organizations with teams working on asteroid-comet dynamics: Pulkovo, Tomsk State University (TSU) and Institute of Applied Astronomy of RAS (IAA), as well as orbits presented on the Jet Propulsion Laboratory's (JPL) Horizons website. The asteroids Apophis and Phaethon were chosen as objects for which the $O$–$C$ comparison was performed. Observations of each asteroid were divided into two samples by time. The asteroid's orbit was improved using the earlier sample, and the later sample was used to access the accuracy of the prediction. The $O$–$C$ distribution profile for orbits obtained using different software turned out to be very similar, indicating the proximity of predictions. The most accurate orbits were obtained using the Improvement and IDA software developed at the IAA and TSU, respectively.
Identification of a new asteroid family 3854 George in the Hungaria group
Authors: Vinogradova T.
Published: December 2024

A search for asteroid families was performed in the Hungaria group. Proper elements needed for this procedure were calculated by the empirical method using distributions of osculating elements. All, more than 30000 multi-opposition asteroids, discovered in this region to date, were used for this aim. An approach similar to the hierarchical clustering method was applied for the identification of families. As a result, two asteroid families were found: 434 Hungaria and 3854 George. 434 Hungaria family is a well known one, it includes a large fraction of asteroids in this region. A new family 3854 George was identified in the high inclination region $24^{\circ}$–$26^{\circ}$. It is composed by small asteroids with diameters less than 1 km and includes about 400 members now.
Precise two-stage deployment of a petal space antenna
Authors: Bujakas V. , Glotov M.
Published: December 2024

One of the directions in modern radio astronomy is observing in the centimeter and millimeter ranges of the electromagnetic spectrum. The reflectors of radio telescopes operating in these ranges are generally parabolic mirrors. The sensitivity and angular resolution of a radio telescope depend on the mirror surface area. At the same time, due to the short wavelengths, high precision of the reflecting surface is required. This paper discusses a new design for a solid-state petal mirror. To enhance the accuracy of the reflecting surface, a two-stage deployment scheme of the petal antenna is proposed. In the first stage, a preliminary unstressed low-precision deployment of the antenna is performed. In the second stage, a high-precision fixation of the deployed reflector final state takes place. It is proposed to use self-adjusting locks to fix the final state of the deployed antenna. The results of computer and physical modeling of the new mirror design are presented. The method for controlling the deployment repeatability of the transformable reflector model is discussed.
RadioAstron project: calibration of the space radio telescope during the flight in 2011–2018 in the 1.35, 6.2, 18, 92 cm bands using improved primary calibration scales
Authors: Ermakov A. , Vasilkov V. , Voitsik P. , Kovalev Yu. , Lisakov M. , Kovalev Yu.
Published: December 2024

We summarize the results of processing calibration telemetry sessions for the four known primary calibrators of spectral radio flux density—Cassiopeia A, Crab Nebula, Cygnus A, and Virgo A—in the autonomous observation mode with the space radio telescope (SRT) in flight. A new system of automated data processing was used, previously successfully tested in similar processing of the measurements with the SRT in 2015–018 in the 6.2, 18, and 92 cm bands. The calibration of the SRT intrinsic noise and the internal artificial generators of the noise signal (NG) was performed for two versions of the primary scale of spectral radio flux density: the generally accepted original scale by Baars et al. suggested in 1977 and its improved version based on the results from newer publications. The main differences between the versions are related to the fact that the actual rate of secular variation in the fluxes of astronomical calibrators differs from the extrapolated values in the previously accepted scale. Preliminary results for the SRT calibration with the improved scale coincide within 10–15 percent with the results published earlier.
The impact of technical constraints on the possibility of resolving the pulsar magnetosphere by observing its scintillations
Authors: Fadeev E. , Andrianov A. , Burgin M. , Popov M. , Rudnitskiy A. , Smirnova T. , Soglasnov V.
Published: December 2024

Variation in the pulsar dynamic spectra with pulse longitude had in the past been interpreted as a result of the spatial motion of the pulsar emission region and led to some conclusions about the altitude of the emission regions or the magnetosphere structure. Motivated by this research, we used the VLBI observations of PSR B1237+25 with the Arecibo and Green Bank radio telescopes at 324 MHz, performed as part of a RadioAstron observing program, and analyzed scintillations at separate longitudes of the pulse profile. We have found that the fringe phase characteristics of the visibility function vary quasi-sinusoidally as a function of longitude. Also, the dynamic spectra from each of the telescopes shift in frequency as a function of longitude. However, we have found that these shifts arise from the low-level digitizing of the pulsar signal. After correcting for these digital effects, the frequency shifts have largely disappeared. The residual effects may be of instrumental origin or indicate the pulse emission altitudes well below the pulsar light cylinder radius.
New panoramic camera for SAO RAS BTA
Authors: Fokin M. , Komarov V. , Shaldyrvan I. , Komarova V.
Published: December 2024

The development of a new multifunctional panoramic sky-viewing system for the 6-m optical telescope BTA at the Upper Scientific Site (VNP) of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) is described. The new viewing system based on an IP camera with a CMOS detector is being created to replace the panoramic system of the previous generation. The multifunctional online operating mode of the new system will provide remote monitoring of the sky over the VNP both at night and in the daytime (in color mode) with a variable field of view ranging from $5^\circ$ to $87^\circ$ and the ability of $360^\circ$ scanning in azimuth and $90^\circ$ by elevation angle. It is also possible to obtain not only the images of the night sky with stars and/or the Moon but also images of the Sun in daytime with sunspots resolved.
The new 50-cm multipurpose telescope of the Russian-Cuban Observatory
Authors: Ibrahimov M. , Nalivkin M. , Naroenkov S. , Shugarov A. , Ponce-Rodriguez O. , Barcenas-Fonseca Z.
Published: December 2024

The international collaboration between Russia and Cuba in astronomical research first began in 2017. The first 20-cm robotic telescope of the Russian-Cuban network has been operating since 2021 in Havana. The construction of the second 50-cm telescope has been underway since 2023, and it is expected to be finished and installed in 2025 near Kislovodsk (Russia). By 2030, the plan is to build the third 1-m telescope at Valle de Picadura (Cuba). We describe the main parameters and scientific equipment of the new 50-cm telescope and discuss its role in the Russian-Cuban distributed global telescope network.
Tomo-V: a new tool for Doppler tomography
Authors: Kaygorodov P.
Published: December 2024

The paper presents a new tool for constructing Doppler tomograms: Tomo-V (https://tomo-v.inasan.ru), developed on the basis of the Algebraic Reconstruction Technique (ART). Previously, the ART method was not widely used in tomography since its direct implementation had high computational complexity. The author developed a fast version of this algorithm, which made it possible to implement it as a web application that runs at an acceptable speed in a browser on a personal computer. Using this method, it is possible to obtain sharp tomographic images from blurred profiles; in addition, the method has shown good results in restoring images from noisy data, from a small number of profiles, and from profiles contaminated with absorption lines and the emission of an expanding envelope. Tomo-V also includes tools for analysing the obtained tomograms, allowing one to display accretion disks and Roche lobes on the tomogram as well as the back projection of the tomographic image onto the flow elements in spatial coordinates.
Methods for analyzing the light curves of the non-thermal radiation in active galactic nuclei
Authors: Khabibullina M. , Stolyarov V. , Mikhailov Alexander , Kudryavtsev D. , Vlasyuk V. , Sotnikova Yu. , Mufakharov T. , Morozova D.
Published: December 2024

We present different methods for analyzing the light curves of active galactic nuclei (AGNs). Based on the example of AGN multiwavelength measurements, features of the following methods are considered: (1) structure functions (SFs)—to search for variability timescales; (2) discrete correlation functions (DCFs)—to search for connections between processes; (3) the Lomb–Scargle (L–S) periodogram—to search for periodicity. We analyze advantages and disadvantages of the methods and discuss their constraints and interpretation.
Universal viewing camera for SAO RAS BTA
Authors: Komarov V. , Shaldyrvan I. , Komarova V. , Fokin M.
Published: December 2024

The development, creation, and implementation of highly sensitive observing systems both for the observing complexes and round-the-clock monitoring of sky transparency and cloudiness, are carried out at the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS). The latest development is the universal viewing camera presented in this work, mounted on the outside of the 6-meter telescope (BTA) prime focus cage (CPF) and monitoring a $4^\circ$ field. This system looks at the sky area where an object under study in BTA observations is located, i.e., the CPF viewing camera is always directed to the same sky field at which the BTA is pointed. And the images are obtained in real time, regardless of the BTA observing program and the complexes in one of the three foci involved.
Testing the DiFX VLBI correlator in a cloud service infrastructure
Authors: Kononov A. , Bezrukov I. , Melnikov A.
Published: December 2024

This study explores the possibility of using cloud infrastructure to deploy the DiFX software correlator for creating a backup system in case of emergencies. The proposed approach involves running DiFX on virtual servers provided by a cloud service, allowing the reduction of financial and time resources. The DiFX software correlator is a primary tool for processing data obtained through Very Long Baseline Interferometry (VLBI). Running such software on cloud provider servers will enable the scaling of the data correlation system. For the experiment, the automation tools Ansible (written in Python) and Terraform were used. Ansible was utilized to deploy the necessary software on a pre-created virtual machine (VM) with Linux, while Terraform managed the provisioning of the virtual machine in the cloud environment. The study analyzes the performance and scalability of DiFX in the cloud. Additionally, the advantages and limitations of deploying DiFX in the cloud in terms of cost, flexibility, and ease of use were evaluated. This paper presents the results of testing and using cloud technologies for running DiFX and justifies the relevance of developing such software.