We present the results of a comprehensive study of four spectroscopic binary Cepheids with long orbital periods. The study makes use of all the available photometric, spectroscopic and astrometric information, and previously developed analysis techniques. The paper is based on a new catalog containing 702 radial velocity measurements of V496 Aql (232 measurements), V1344 Aql (194 measurements), V1334 Cyg (138 measurements), and AW Per (138 measurements). All the measurements were obtained over 1997$\!-\!$2021 on the Zeiss-1000 telescope of the Institute of Astronomy of the Russian Academy of Sciences Simeiz Observatory using the correlation Radial Velocity Meter (RVM) designed by A.A. Tokovinin. Using other published observations, the orbital periods and other orbital parameters were significantly refined: V496 Aql: $P_{\rm orb} \approx 1351\,.\!\!^{\rm d}3\pm0\,.\!\!^{\rm d}7$; V$1344$ Aql: $P_{\rm orb} \approx 6358\pm30{\rm ^d}$; V1344 Cyg: $P_{\rm orb} \approx 1934\,.\!\!^{\rm d}4\pm0\,.\!\!^{\rm d}8$; AW Per: $P_{\rm orb} \approx 13\,663\pm128{\rm ^d}$. Using the mass function, we have found additional constraints on the companion masses and the orientation of the orbital plane. For V496\,Aql and V1344\,Aql, a complete set of astrophysical parameters was found, including the color excess, pulsational radii, luminosity, and mass estimates based on the evolutionary tracks (for V496 Aql, $M \sim 5.6\!-\!5.8 M_\odot$; for V1334 Aql, $M \sim 5.8\!-\!6.0 M_\odot$). For the V1334 Cyg Cepheid with a massive companion, a strong constraint $i \sim 56^\circ\!-\!60^\circ$ on the inclination of its orbital plane was found based on the high mass function. AW Per, with an orbital period of over 37 years and a high mass function, has a companion of a comparable mass. The calculated pulsational radius and luminosity of the Cepheid are in good agreement with the evolutionary mass estimate of $M \sim 5.6\!-\!5.9\,M_\odot$. We show that at inclination angles smaller than $63^\circ\!-\!65^\circ$, the companion can only be a close binary system consisting of two hot stars near the main-sequence turnoff point.
Forecasts of economic indices are important for mitigating the risks of unexpected stresses in the global or local economy. However, the numerous factors that influence the resulting economic index create a complex picture that complicates determining a cyclical pattern. We studied the relationship between solar activity and the Dow Jones Industrial Average from 1896 to 2021. We used correlation and cross-correlation methods with a sliding time window and a wavelet coherency approach to analyze the data. The study revealed that the relationship between the events is not simple and evolves over time. Various synchronization periods, as well as variation in the coherence of these synchronizations over time, were identified. We discovered that the correlation with the 11-year periodicity is greater than 0.5 during the 1906–1936 and 1964–2000 time periods and is visible with a 95 % confidence level during the 1910–1930 and 1990–1994 time periods. This correlation is supported by the found 95 % confidence in the coherence between the cosmic ray data and the Dow Jones index during the same time periods (1964–2000), when the correlation between the sunspot number and this index is high, albeit with other phase differences. Furthermore, the correlation between the cosmic ray data and the Dow Jones is stronger. This could imply that the influence of solar activity on global economy fluctuations is mediated by the Sun’s modulation of cosmic rays.
This paper estimates the kinetic parameters of the fractal stellar medium in the vicinity of the Sun. In this regard, the main stages in the development of ideas about fractal structures in the stellar medium of galaxies are presented. This study is based on investigation of the spatial distribution of 200 000 stars of all spectral types at distances from 1 to 100 pc from the Sun based on the Gaia DR2 data. The results indicate the presence of fractal structures in the solar neighborhood with the fractal dimension D≈ 2.41 . Based on these data, the kinetic properties of the fractal stellar medium are studied. The role of irregular forces and paired stellar encounters in the collisional kinetics of stellar systems is considered. It has been shown that kinetic parameters such as the effective interparticle (interstellar) distance, correlation length, dynamic friction coefficient, and impact parameter for a fractal stellar medium differ significantly from the corresponding parameters for a quasi-homogeneous medium with limited density fluctuations and depend on the fractal dimension. It has been found that the fractal structure of the stellar medium leads to shortening the relaxation time in the Galaxy.
General relativity predicts the existence of an infinite number of nested photon rings around black holes, each containing information about the properties of curved space-time. In this paper, analytical models of a thick Gaussian asymmetric photon ring are developed and the visibility function with baselines up to six Earth diameters is calculated.
During the period of 2023–2026, the scientists of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) are implementing a project to create a millimeter-wave observatory based on the BTA optical telescope. The project involves the installation of subterahertz receivers at the Nasmyth focus and the performance of test observations. This paper discusses scientific objectives that can be addressed both at the initial stage of the project using bolometric receivers for continuum observations and, in the future, using receiver systems based on HEMT and SIS technologies for molecular line observations.
We present the results of a comprehensive study of four spectroscopic binary Cepheids with long orbital periods. The study makes use of all the available photometric, spectroscopic, and astrometric information and previously developed analysis techniques. The paper is based on a new catalog containing 702 radial velocity measurements of V496 Aql (232 measurements), V1344 Aql (194 measurements), V1334 Cyg (138 measurements), and AW Per (138 measurements). All the measurements were obtained over 1997–2021 with the Zeiss-1000 telescope of the Institute of Astronomy of the Russian Academy of Sciences Simeiz Observatory using the correlation Radial Velocity Meter (RVM) designed by A.A. Tokovinin. Using other published observations, the orbital periods and other orbital parameters were significantly refined: V496 Aql: P_orb≈ 1351d.3± 0d.7 ; V1344 Aql: P_orb≈ 635d.8± 30^d ; V1344 Cyg: P_orb≈ 1934d.4± 0d.8 ; AW Per: P_orb≈ 13 663± 128^d . Using the mass function, we have found additional constraints on the companion masses and the orientation of the orbital plane. For V496 Aql and V1344 Aql, a complete set of astrophysical parameters was found including the color excess, pulsational radii, luminosity, and mass estimates based on the evolutionary tracks (for V496 Aql, M∼ 5.6-5.8M_⊙ ; for V1334 Aql, M∼ 5.8-6.0M_⊙ ). For the V1334 Cyg Cepheid with a massive companion, the strong constraint i∼ 56^∘-60^∘ on the inclination of its orbital plane was found based on the high mass function. AW Per, with an orbital period of over 37 years and a high mass function, has a companion of a comparable mass. The calculated pulsational radius and luminosity of the Cepheid are in good agreement with the evolutionary mass estimate M∼ 5.6-5.9 M_⊙ . We show that at inclination angles smaller than 63^∘-65^∘ , the companion can only be a close binary system consisting of two hot stars near the main-sequence turnoff point.
During the implementation of the program of photometric studies of variable stars, 215 variable stars were studied in selected fields. Variability parameters were refined for 48 of them, and variability was discovered and studied for the first time for 42 of them. A description of the Small Photometric Telescope, installed in the 4th pavilion of the Caucasian Mountain Observatory (CMO) of the Sternberg Astronomical Institute of Moscow State University (SAI MSU), is provided. Particular attention is given to the installed instruments and technical aspects of the observation organization.
This study is devoted to the investigation of pre-flare processes preceding the eruptive X3.2-class solar flare that occurred on May 14, 2013. This event was selected because of its favorable position near the solar limb, the presence of a well-pronounced pre-flare phase, and the availability of high-quality observed data from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA), Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), Nobeyama Radio Heliograph (NoRH), and Siberian Solar Radio Telescope (SSRT). The main objective of this work is to identify possible eruption triggers and to perform a detailed multiwavelength analysis of the pre-flare energy release properties. In this study, we consider a pre-flare time interval of about one and a half hours. From the point of view of temporal evolution, the pre-flare phase of the selected event consists of two stages. During the first stage, a quasi-stationary compact X-ray source is observed in the 5–25 keV energy range. The radio sources are also relatively stable, and their centroids coincide with the X-ray brightness center. This is followed by a sharp burst (nonthermal emission up to 100 keV is detected) and a subsequent increase in emission intensity over a broad spectral range. The observed sources become nonstationary. The second stage, following the burst, lasts for about one hour. During this period, the sources expand, and the growth of a coronal loop system is observed. Afterward, the eruption and the main flare take place. It is noteworthy that the trigger burst (TB) between the first and second pre-flare stages was associated with a very compact X-ray source and a strong brightening in all available ultraviolet (EUV and UV) channels. To determine the magnetic field structure at the photospheric level, vector magnetograms obtained by the Helioseismic and Magnetic Imager/Solar Dynamics Observatory (HMI/SDO) were used. These data showed that the pre-flare energy release and the TB were localized near the magnetic neutral line. Estimates of the thermodynamic parameters of the flare plasma, the energy of accelerated electrons, and the thermal energy of the pre-flare plasma were obtained based on the analysis of microwave and X-ray spectra. The observed microwave spectra are well explained by a gyrosynchrotron model consisting of an extended source associated with high coronal loops and the plasma temperature T≈ 5-7 MK, a compact source in lower loops ( T≈ 10-20 MK), and bremsstrahlung emission at frequencies of 17–34 GHz. In general, the X-ray data from the compact source are in good agreement with the observed radio emission.
Results of infrared photometric observations of RW LMi in the JHKLM bands are presented. The observations were carried out from 1994 to 2024. Based on the observations of 17 pulsation cycles of the star, new brightness ephemerides were established: JD_max=2459677d.0+610d.9 E . A sinusoidal trend of the average brightness level was found. Its period is about 7300 days and its amplitude is approximately 1^m in the JHK bands. From the energy distribution in the spectrum in the wavelength range of 0.5–100 μ m, an estimate of the bolometric flux at the maximum brightness was obtained: F_bol=2.6× 10^-6 erg s ^-1 cm ^-2 . This corresponds to the luminosity L_max≈ 8500 L_⊙ . Modeling the RW LMi circumstellar envelope radiation was performed with the RAMDC-3D program. The simulation was carried out in the approximation of a spherically symmetric envelope shape with a constant mass-loss rate. The main envelope parameters are: the optical depth τ_V≈ 12.7 , the inner radius R_in≈ 8 AU, the outer radius R_out≈ 17 000 AU, and the mass-loss rate Ṁ=6× 10^-6M_⊙ yr ^-1 .
The paper estimates the average components of the velocities $V_R$, $V_{\theta}$, $V_z$, specific kinetic energies $T_k$, and dispersions $\sigma_V^2$ of the velocities of open star clusters (OSCs) in the solar neighborhood based on the Gaia\,DR3 data. The dependences of the dispersions of the $T_k$ values and the velocities of the open-clusters on the distance $R$ of the clusters to the Galactic rotation axis are constructed. A number of local maxima and minima in these dependences are noted. Numerical modeling of the trajectories of the OSC motions in the force field of the axisymmetric part of the Galaxy (the three-component model of Miyamoto, Nagai) and a four-armed spiral pattern was performed. Comparison of the values $T_k$, the amplitudes of $T_k$ oscillations and the cylindrical galactocentric coordinates ($R,\theta,z$) of the OSCs with time and kinematic data on the motion of clusters results in estimating the ratio of the potentials of the spiral arms and the axisymmetric part of the Galaxy $Q=0.0010$--$0.0012$. Within the framework of the considered model of the Galaxy, the following was obtained: (1) the ratio of the disk mass to the total mass of the three components of the Galaxy (in the range of distances from its center from 0 to $r$) equal to $0.4$ is achieved with $r = r_b\simeq 14.69$~kpc; (2) the contribution of the halo potential to the total potential of the Galaxy is equal to 0.778, 0.708, and 0.667 with $r=r_b$, 9, and 7~kpc, respectively. In this range of $r$ values, the influence of the halo on the motion of OSCs in the Galaxy is approximately three times greater than the influence of the disk. Therefore, radial oscillations of the halo can make a significant contribution to the motion of OSCs in the Galaxy; (3) a formula for the frequency of small oscillations of the halo was obtained, the period of such oscillations is $7.135\times 10^9$~yrs; (4) a formula for the free-fall time $\tau_{\rm ff}$ of a star from a distance $r_0$ to the halo center was obtained; (5) using $\tau_{\rm ff}$ and the data obtained in 2022 by Bird et al. on the velocities $\sigma_V$ of Galactic halo stars, an estimate of the Jeans radius was obtained for the halo: $r_J=26.7^{+4.1}_{-2.9}$~kpc. For the central part of the Galaxy, enclosed within a sphere of the radius $r_0=35$~kpc, using $\tau_{\rm ff}$ from our 2024 work for a homogeneous gravitating sphere, we obtained the estimate $r_J=33.83\pm 1.41$~kpc indicating the gravitational instability of regions of the Galaxy with the distances $r$ from $r=0$ to $r>r_J$.
Stellar photometry of 70 irregular galaxies was performed using archival Hubble Space Telescope images. The resulting Hertzsprung--Russell diagrams were used to distinguish the red supergiant and giant branches. The distances to the galaxies and the metallicity of the red giants were determined using the TRGB method. The \mbox{$(V-I)$} color index of the supergiant branch at the luminosity level \mbox{$M_I = -7\,.\!\!^{\rm m}0$} was chosen as the metallicity index of red supergiants. The measurements showed that no galaxy exhibits a metallicity inversion between young and old stars, which would occur if clouds of the low-metallicity intergalactic gas fall onto the galaxy. This means that the infall of intergalactic clouds, if it occurred, did not significantly affect the evolution of the stellar population of galaxies over the past billion years. Over billions of years of evolution, each galaxy underwent random processes that could alter the metallicity of its interstellar medium and stars. However, the linear relationship we have found between the metallicities of young and old stars in galaxies of different masses indicates that the bulk of galaxies' metal accumulation has occurred in the distant past. Modern processes are increasing the metallicity of galaxies but at a significantly slower rate than during galaxy formation. Otherwise, the linear relationship between the metallicities of stars of different ages in galaxies of different masses and star formation histories would not be observed.
The paper analyzes formation conditions for globular clusters (GCs) in circumgalactic clouds. The similarity between the metallicity distributions of GCs in the nearby Universe and of circumgalactic clouds is substantiated in detail over a wide range of redshifts: from 0.2 to 5.9. The distributions of the number of circumgalactic clouds and GCs both contain a sequence of four local maxima at the metallicity values: [X/H]≃-2.6,-2.0,-1.4,-0.5 . The sequential enrichment of a circumgalactic cloud with a mass of 10^8 M_⊙ is calculated starting the extremely low metallicity [X/H]<-2.3 , then following through the stages of -2.3≤[X/H]<-1.7 and -1.7≤[X/H]<-0.9 to the high metallicity [X/H]≥-0.9 , where the boundaries of these ranges coincide with the local minima of the number of objects in the distributions. It is shown that for the reproduction of such distributions, it is sufficient that at each stage of enrichment of a part of a cloud in metals, one or more GCs with a total mass of 3× 10^6 M_⊙ are formed. It is shown that the maximum mass of stars capable of leading to supernova explosions increases with the increase of metallicity. Possible values of this mass are calculated for the metallicities corresponding to the maxima in the distributions of clouds and GCs.
An Erratum to this paper has been published: https://doi.org/10.1134/S1990341326550018
We continue to search for luminous blue variables (LBVs) in the Local Volume galaxies to further study their fundamental parameters in relation to the age of their stellar environments and the metallicity of the gas in their host galaxies. In this paper, we report the discovery of the luminous star J022237.31+422234.2 ( M_Vmax<-10m.2 ) in the galaxy NGC 891 located at a distance of about 10 Mpc. The study involves data from ground-based and space telescopes (HST, JWST). Over the period from 1997 to 2024, the star exhibited the photometric variability Δ V=1m.12± 0m.06 . A statistical analysis of the broadband photometric data revealed a direct correlation between the (V-I_c) color index and the V -band brightness of the star, while no significant variability was observed in (B-V) and (V-R_c) . Based on a comparison of the optical spectrum obtained with the 6-m BTA telescope with a grid of extended atmosphere models, we estimated the photospheric temperature ( 8000≲ T_eff≲ 10100 K ) and the mass-loss rate ( 8× 10^-5≲Ṁ≲ 5× 10^-4M_⊙ yr^-1 ). Fitting the observed optical spectral energy distribution with models of extended atmospheres, accounting for interstellar extinction, yielded a bolometric luminosity estimate of 1.1× 10^6L_⊙≲ L≲ 2.6× 10^6L_⊙ . In the infrared range, a significant excess emission was detected at 1.5–8 μ m, which may indicate the presence of a warm dust with a temperature of 1300 K. The observed properties of J022237.31+422234.2 suggest its classification as a yellow hypergiant or an LBV in a cold state.
The paper presents spectropolarimetric monitoring of three chemically peculiar stars, HD 13404, HD 225114, and BD +64^∘ 325, whose peculiarity has been discovered during the SDSS/APOGEE IR survey. Observations were carried out with the 6-m BTA telescope equipped with a circular polarization analyzer. For the first time, the longitudinal magnetic field phase curves were constructed for these stars, and their rotational periods were refined using the TESS photometry. Significant differences in the nature of their magnetic variability were discovered: HD 13404 shows a weak modulation, probably due to the observation geometry, while HD 225114 and BD +64^∘ 325 were revealed to have a complex magnetic field topology associated with the non-uniform surface chemical distributions.
In this work, we present the program MOLLId (MOLecular Line Identification) for automated molecular line approximation with a Gaussian profile. Molecular identification was performed using multi-level comparison of the lines’ center frequencies and rest frequencies from the spectroscopic database. The program was tested in the identification of molecular lines in observed spectra of young stellar objects RCW 120 YSO S1 and RCW 120 YSO S2 located near the border of the RCW 120 PDR. In the spectra of the RCW 120 YSO S1 source, 100 lines of 41 molecules were identified over the level of 4–6 σ . In the spectra of the RCW 120 YSO S2 source, 407 lines of 79 molecules were identified over the 3–5 σ level. Using the Intel Core i7-12700K CPU, identification time is equal to 6 and 8 minutes per spectral range for the YSOs S1 and S2, respectively. From the analysis of CH _3 OH, CH _3 CN, CH _3 CCH molecules identified in RCW 120 YSO S2, we found a two-component structure and estimated the physical parameters in the LTE approximation for each of the components.
In this paper, we continue our research on constructing the optimal fundamental plane (FP) of galaxy groups and clusters for measuring their distances. This work was carried out using archival data from the SDSS and 2MASX catalogs. We present the fundamental planes (scaling relations of dynamical and photometric parameters) of 205 galaxy groups and clusters ( z<0.15 ). We found that in the near infrared ( K -filter), the distribution of galaxy clusters is well approximated by three-parameter planes of the form R_e∝σ^1.01± 0.05⟨ I_e⟩^-0.32± 0.03 and R_e∝ N^0.43± 0.01⟨ I_e⟩^-0.40± 0.02 and a four-parameter plane of the form R_e∝σ^0.15± 0.06⟨ I_e⟩^-0.39± 0.02N^0.38± 0.02 . The fundamental planes have logarithmic standard deviations of 0.060, 0.036, and 0.035. If we use the fundamental planes to measure distances of galaxy systems, these deviations correspond to 14 % and 8 % errors in the distance of a single cluster. Using the four-parameter fundamental plane, we obtained the scatter of the Hubble constant H_0=70± 5.6 km s^-1 Mpc ^-1 . Using three fundamental planes of galaxy clusters, it was found that the velocity of the average drift motion in the three-degree cosmic microwave background (CMB) system of five superclusters of galaxies from the SDSS region is ⟨ V_pec⟩=+241± 180 km s^-1 .
The paper presents methods for analyzing multiwavelength light curves of active galactic nuclei with uneven time sampling, including the use of the structure functions, autocorrelation and cross-correlation functions, Lomb–Scargle periodograms, and weighted wavelet analysis. The structure functions allow quantitative estimation of the temporal scales of variations, correlation functions provide detection of temporal delays between different frequencies, Lomb–Scargle periodograms detect periodicities in nonuniform data, and wavelet analysis makes it possible to localize variable processes in time and to study the evolution of the signal frequency composition. The comprehensive use of these methods allows detailed investigation of the temporal and frequency structure of physical processes in active galactic nuclei, taking into account the influence of the unevenness of experimental data. The advantages and limitations of each method are considered using examples of analyzing specific sources, and their practical significance for studying the variability of active galactic nuclei is demonstrated.
Massive stars that form the Gould Belt OB associations are known to have higher multiplicity than solar-type stars. Due to their luminosity and close vicinity, they are optimal targets for speckle interferometry. Among the members of the Cas–Tau OB association, observed with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (BTA SAO RAS), a binary system, HI P10944 (B9VpSi, G=5m.53 ), was discovered for the first time. We present the results of speckle interferometry monitoring of the star from 2007 to 2025, covering almost the entire orbital period ( P_orb=20.90 yrs). Based on the measured positional parameters, an orbit was constructed and the sum of the masses of the system’s components was determined ( M_*=4.26± 0.06M_⊙ ).
S H_0 ES (Supernovae and H_0 for the Equation of State of dark energy) 2016–2022 HVI data for classical Cepheids in the keystone galaxy NGC 4258 yield doubly discordant Wesenheit Leavitt functions: Δ W_0,H-VI=-0m.13± 0m.02 ( -0m.17 unweighted) and that is paired with the previously noted Δ W_0,I-VI≃-0m.3 , which in concert with complimentary evidence suggest the 2016 S H_0 ES NGC 4258-anchored H_0±σ_H_0 warrants scrutiny (i.e., σ_H_0/H_0≳ 6% ). Cepheid distance uncertainties are further exacerbated by extinction law ambiguities endemic to such Leavitt relations (e.g., NGC 4258), particularly for comparatively obscured variables (e.g., Δ d≳ 4% , reddened Cepheid subsamples in the Milky Way, M 31, NGC 2442, NGC 4424, NGC 5643, NGC 7250). Lastly, during the analysis it was identified that the 2022 S H_0 ES database relays incorrect SMC Cepheid photometry.
