Astronomy Letters-A Journal of Astronomy and Space Astrophysics最新文献

{"title":"Detection of the Gravitational-Wave Event GW 190425 with the BSA LPI Radio Telescope","authors":"A. E. Rodin,&nbsp;A. S. Pozanenko,&nbsp;V. A. Fedorova","doi":"10.1134/S1063773726700143","DOIUrl":"10.1134/S1063773726700143","url":null,"abstract":"<p>We present the results of our search for and detection of radio emission from the gravitational-wave event GW 190425 at a frequency of 111 MHz with the BSA LPI radio telescope. A new radio source was detected approximately at <span>(2^{circ})</span> from the center of the maximally probable localization region of GW 190425; its coordinates (J2000.0) are <span>(alpha=16^{textrm{h}}30^{textrm{m}}pm 1^{textrm{m}})</span> and <span>(delta=13^{circ}21^{prime}pm 15^{prime})</span>. We have constructed the light curve and estimated the peak flux density to be <span>({approx}2)</span> Jy. The peak of the light curve occurs on day 20–30 after the trigger. We have calculated the false alarm probability for an event of this kind, <span>(P_{fa}=5times 10^{-7})</span>.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"52 1","pages":"8 - 18"},"PeriodicalIF":0.9,"publicationDate":"2026-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148695604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Orbital Motion Control near the Designed Orbitin the Vicinity of a Collinear Libration Point","authors":"D. V. Shymanchuk,&nbsp;A. S. Shmyrov,&nbsp;V. A. Shmyrov","doi":"10.1134/S1063773726700118","DOIUrl":"10.1134/S1063773726700118","url":null,"abstract":"<p>The controlled motion of a spacecraft in the vicinity of a Sun–Earth collinear libration point is studied. The spacecraft motion is described by the model of the circular restricted three-body problem. An approach to constructing the orbital spacecraft motion control laws for a long stay in the designed orbits is proposed. The approach is based on the use of a special function of phase variables and time whose value characterizes the deviation of the spacecraft trajectory from the designed orbit. The results of numerical simulations are presented.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"51 11-12","pages":"734 - 743"},"PeriodicalIF":0.9,"publicationDate":"2026-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148292347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Eruptive Young Star IRAS 21204+4913","authors":"M. A. Burlak,&nbsp;A. V. Dodin,&nbsp;A. V. Zharova,&nbsp;S. G. Zheltoukhov,&nbsp;N. P. Ikonnikova,&nbsp;S. A. Lamzin,&nbsp;B. S. Safonov,&nbsp;I. A. Strakhov,&nbsp;A. A. Tatarnikov,&nbsp;A. M. Tatarnikov","doi":"10.1134/S1063773726700076","DOIUrl":"10.1134/S1063773726700076","url":null,"abstract":"<p>We present the results of photometric, polarimetric, and spectroscopic observations for the young star IRAS 21204+4913, whose visible brightness has increased by <span>({approx}5^{textrm{m}})</span> since October 2025. The star’s absorption spectrum in the range <span>(0.36textrm{--}0.75mu)</span>m resembles the spectra of A–F giants and supergiants, but at the same time there are molecular TiO bands in its spectrum. The brightening of the star was accompanied by an increase in the degree of polarization of its radiation (to <span>({approx}16%)</span> in the <span>(I)</span> band), probably due to its scattering by dust in an expanding circumstellar shell. The P Cyg H<span>(alpha)</span> line profile implies a dusty wind velocity of <span>({approx}300)</span> km s<span>({}^{-1})</span>. We believe that the outburst of IRAS 21204+4913 is caused by an increase in the accretion rate of protoplanetary disk matter onto the young star with a mass <span>({lesssim}0.5)</span> to <span>({gtrsim}3times 10^{-5})</span>\u0000 <span>(M_{odot})</span> yr<span>({}^{-1})</span>. At the same time, a number of peculiar features have been detected in IRAS 21204+4913: the dependence of the width and radial velocity of absorption lines on the excitation potential, the emission in the TiO molecular bands, and the outburst with a comparable amplitude occurred in 1948. Several T Tauri stars and a group of Herbig–Haro objects have been found in the vicinity of the star.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"51 11-12","pages":"692 - 707"},"PeriodicalIF":0.9,"publicationDate":"2026-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148292412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analysis of the Space Velocities of Several Samples of Open Star Clusters","authors":"V. V. Bobylev,&nbsp;A. T. Bajkova","doi":"10.1134/S1063773726700064","DOIUrl":"10.1134/S1063773726700064","url":null,"abstract":"<p>We have analyzed the kinematics of open star clusters (OSCs) with their characteristics from the new catalog of Hunt and Reffert. From 4003 OSCs younger than 200 Myr we have found the following parameters of the angular velocity of Galactic rotation: <span>(Omega_{0}=28.99pm 0.11)</span> km s<span>({}^{-1})</span> kpc<span>({}^{-1})</span>, <span>(Omega^{prime}_{0}={-}3.909pm 0.026)</span> km s<span>({}^{-1})</span> kpc<span>({}^{-2})</span>, and <span>(Omega^{primeprime}_{0}=0.662pm 0.018)</span> km s<span>({}^{-1})</span> kpc<span>({}^{-3})</span>, where <span>(V_{0}=234.8pm 3.0)</span> km s<span>({}^{-1})</span> for <span>(R_{0}=8.1pm 0.1)</span> kpc. We have established that a periodicity in the radial OSC velocities manifests itself for clusters younger than 600 Myr, while a wave in the residual tangential velocities manifests itself only for the youngest clusters younger than 40 Myr. Based on a spectral Fourier analysis of the radial velocities of three OSC samples with mean ages of 18, 72, and 143 Myr, we have obtained the following values of the wavelength <span>(lambda)</span> and the velocity perturbation amplitude <span>(f_{R})</span>: <span>(lambda=2.0)</span> kpc and <span>(f_{R}=4.3)</span> km s<span>({}^{-1})</span>, <span>(lambda=2.2)</span> kpc and <span>(f_{R}=8.2)</span> km s<span>({}^{-1})</span>, and <span>(lambda=2.1)</span> kpc and <span>(f_{R}=9.6)</span> km s<span>({}^{-1})</span>, respectively. We have established a systematic change in the positions of the wave maxima and minima in the radial OSC velocities as a function of the sample age. From our analysis of these shifts we have found the absolute value of the difference <span>(|DeltaOmega|)</span> of the spiral pattern speed <span>(Omega_{p})</span> and the angular velocity of Galactic rotation, <span>(|DeltaOmega|=2.0pm 0.5_{textrm{stat}}pm 2.3_{textrm{syst}})</span> km s<span>({}^{-1})</span> kpc<span>({}^{-1})</span>. On this basis, we have estimated two possible corotation radii, <span>(8.6pm 0.2)</span> and <span>(7.6pm 0.2)</span> kpc, suggesting that the Sun is very close to corotation.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"51 11-12","pages":"645 - 654"},"PeriodicalIF":0.9,"publicationDate":"2026-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148292413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analytical Approaches to Studying the Phase of the Visibility Function","authors":"S. V. Chernov","doi":"10.1134/S1063773726700088","DOIUrl":"10.1134/S1063773726700088","url":null,"abstract":"<p>In radio interferometric observations, the main source of information is the complex visibility function that includes the amplitude and the phase. In this paper, the dependence of the phase of the visibility function on the baseline projection is investigated when used in radio interferometry with space baselines up to six Earth diameters. An analytical expression is derived for the dependence of the phase of the visibility function on the baseline projection and direction. It is shown that for small baseline projections, this dependence is universal and is consistent with the numerical magnetohydrodynamic models for the distribution of an ideal fluid in the immediate vicinity of black holes.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"51 11-12","pages":"708 - 717"},"PeriodicalIF":0.9,"publicationDate":"2026-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148292264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characteristics and Geoeffectiveness of CME–Flare Events (({boldsymbol{geq}})M5.0) from December 2019 to July 2023","authors":"A. Kubera Raja,&nbsp;A. Mujiber Rahman","doi":"10.1134/S1063773726700106","DOIUrl":"10.1134/S1063773726700106","url":null,"abstract":"<p>We researched the slow, normal, and fast coronal mass ejections (CMEs) associated with solar flares (<span>({&gt;})</span>M5.0 X-ray class) from December 2019 to July 2023 (44 month period) in the early rising phase of solar cycle 25. This research aims to examine the features of slow, normal, and fast CMEs along with their associated Solar Flares, Type II Bursts, SEPs, and Geomagnetic Storms. This paper highlights CME-Flare pairs by grouping them based on speed and investigating their connection to DH type II bursts, solar energetic particle occurrences, and Dst indices. The locations of flares associated with the three types of CMEs, the number of events corresponding to different flare classes, as well as the flare rise times and durations, were thoroughly studied. During the study period, we analyzed the 57 CME events and the distribution of their angular widths. Using different electron density models, the start distance, end distance, drift rate, and shock speed were analyzed in detail. Solar energetic particles (SEPs) with intensities greater than 10 pfu, generated by shock waves and the geoeffectiveness of full halo CME, were discussed. In this statistical study, we conclude that the fast CMEs are associated with longer flare durations, and stronger geoeffectiveness compared to slow and normal CMEs. They are also significant drivers of type II radio bursts, SEP events, and geomagnetic storms.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"51 11-12","pages":"718 - 733"},"PeriodicalIF":0.9,"publicationDate":"2026-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148292249","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"X-ray and Gamma-ray Emission from a High-Temperature Plasma and the Spectra of Accreting Black Holes","authors":"S. A. Grebenev","doi":"10.1134/S106377372670009X","DOIUrl":"10.1134/S106377372670009X","url":null,"abstract":"<p>We present the results of our numerical computations of the broadband radiation spectra forming in a layer of high-temperature (<span>(kT_{textrm{e}}sim 50)</span> keV) semitransparent (with a Thomson optical depth <span>(tau_{textrm{T}}sim 1{-}3)</span>) plasma with an electron density <span>(N_{textrm{e}}sim 10^{17}{-}10^{19}textrm{ cm}^{-3})</span> typical for the accretion disk regions surrounding a black hole in X-ray binaries. In our computations we took into account the bremsstrahlung processes of the production (and absorption) of photons and their subsequent Comptonization. The intrinsic radiation from such a high-temperature plasma is shown to be enough to explain the X-ray spectra observed in the low (hard) state of Galactic black hole candidates and X-ray novae. No commonly assumed additional soft (with energies <span>(hnulesssim 1)</span> keV) photons to maintain Comptonization are required; moreover, their presence would lead to severe distortions of the spectrum compared to the observed one or would require a very fine tuning of plasma parameters. In the hard X-ray range the forming power-law radiation spectrum with a photon index <span>(alphasim 1.4{-}1.7)</span>, which has an exponential cutoff at energies <span>(hnugtrsim 100)</span> keV, exceeds considerably the bremsstrahlung flux that might be expected from such a plasma layer in the limit of an infinitely small optical depth. This is a result of the multiple inverse Compton scattering of bremsstrahlung photons. It is important that, according to our computations, the power-law radiation spectrum for such a high-temperature plasma should extend in an invariable form downward along the energy axis to the ultraviolet, optical, and infrared ranges (<span>(hnusim 1{-}3)</span> eV). At energies <span>(hnulesssim 1)</span> eV the optical depth for bremsstrahlung absorption grows rapidly and the radiation spectrum becomes the Rayleigh–Jeans one. To explain the steeper (<span>(alphasim 2.1{-}2.5)</span>) X-ray spectra observed from accreting black holes in their high (soft or two-component) state, it is indeed necessary that a large number of soft photons additional to the intrinsic plasma bremsstrahlung photons enter a hot cloud. Such photons could be emitted by the surface of an outer dense and cold accretion disk whose inner edge during these states characterized by a powerful soft component in the X-ray spectrum approaches the black hole maximally closely. The optical and infrared emission from systems in these states is associated precisely with the emission from the outer disk, whereas during their low state it can be produced directly in the hot central disk region bloated by instabilities. Under favorable conditions (disk size and inclination) the low-frequency emission from this region can noticeably exceed in flux and luminosity the emission from the outer cold accretion disk regions.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"51 11-12","pages":"655 - 691"},"PeriodicalIF":0.9,"publicationDate":"2026-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148292263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling the Nonequilibrium Kinetics and Spectra of Supernovae: The Rosenbrock Method with Solution Positivity Control","authors":"M. Sh. Potashov","doi":"10.1134/S1063773726700015","DOIUrl":"10.1134/S1063773726700015","url":null,"abstract":"<p>Computing the spectra of supernovae at the photospheric phase requires detailed modeling of nonequilibrium atomic level populations in a rapidly expanding envelope. We consider the fundamental problem of interpreting the observed spectra through the solution of a highly stiff system of time-dependent kinetic equations in an expanding envelope, where the characteristic time scales of atomic processes differ from the hydrodynamic time scale by many orders of magnitude. Based on the analysis of a singularly perturbed system, we introduce a heuristic rule for the selective deactivation of sparsely populated levels, reducing the dimension of the system and the computational cost without any loss of accuracy. An extremely large scatter of characteristic process time scales leads to a numerical instability that manifests itself as nonphysical negative populations and a ‘‘jump’’ to a false solution. We present a modified fourth-order Rosenbrock method supplemented by a correction procedure that guarantees the positivity of the solutions based on the works of Goldin and Kalitkin. This correction acts as a specialized step controller, automatically preventing the choice of too large integration steps that lead to an instability. The method is implemented in the <b>LEVELS</b> code and has been tested on the type II-P supernova SN 2018aoq. We show that the hybrid approach stably integrates a system of more than 1500 equations and allows the observed optical spectra to be satisfactorily reproduced, making it possible to refine the hydrodynamic explosion parameters based on spectroscopic data.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"51 10","pages":"587 - 603"},"PeriodicalIF":0.8,"publicationDate":"2026-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147738910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study of Massive OBA Stars with X-ray Emission","authors":"E. A. Nikolaeva,&nbsp;I. F. Bikmaev,&nbsp;E. N. Irtuganov,&nbsp;M. R. Gilfanov,&nbsp;R. A. Sunyaev,&nbsp;P. S. Medvedev","doi":"10.1134/S1063773726700027","DOIUrl":"10.1134/S1063773726700027","url":null,"abstract":"<p>We have studied the physical parameters of a group of 15 OBA stars from which X-ray emission was detected by the SRG/eROSITA telescope. Whereas the X-ray emission from cool FGKM stars is directly produced near their surface zones—in their chromospheres and coronae—the nature of the X-ray emission from OBA stars requires a separate study in each specific case, since single OBA stars are not intrinsic X-ray sources. We have determined the main physical characteristics of the stars under study, including their effective temperature <span>(T_{textrm{eff}})</span> and surface gravity <span>(log g)</span>, based on the spectral energy distribution and the optical spectra obtained with the 1.5-m Russian–Turkish RTT-150 telescope. An additional analysis of the H<span>({alpha})</span> line profiles has allowed the possible X-ray emission mechanisms to be assessed: generation in non-stationary stellar winds, collisional processes in circumstellar envelopes, and coronal emission of hidden cool companions. As a result of the analysis, we have concluded that the X-ray emission from eight stars with typical X-ray luminosities in the range <span>(log L_{textrm{X}}=28.5{-}30.0)</span> is determined by their hidden late-type companions.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"51 10","pages":"604 - 619"},"PeriodicalIF":0.8,"publicationDate":"2026-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147738813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Prospects for Measuring the Gravitational Time Dilation Effect Using Clocks in a Distant Retrograde Lunar Orbit","authors":"D. A. Litvinov,&nbsp;A. V. Alakoz","doi":"10.1134/S1063773726700040","DOIUrl":"10.1134/S1063773726700040","url":null,"abstract":"<p>The prospects for testing the Einstein Equivalence Principle by measuring the gravitational time dilation effect using clocks in a distant retrograde orbit around the Moon are investigated. To obtain estimates of the accuracy that can be achieved in such an experiment, we constructed a model that accounts for the colored nature of the clock noise, as well as a possible clock frequency bias and drift. This model is applied to the case of a lunar distant retrograde orbit (a <span>(2:1)</span> resonance) and three types of clocks characterized by qualitatively different stability and accuracy parameters: hydrogen masers (VCH-1010 and VCH-2021), a cesium fountain clock (PHARAO), and a strontium optical clock (I-SOC). Assuming 5 years of data accumulation, the following estimates for the achievable accuracy of the experiment were obtained: <span>(6times 10^{-4})</span> for VCH-1010, <span>(1times 10^{-5})</span> for VCH-2021, <span>(2times 10^{-5})</span> for PHARAO, and <span>(3times 10^{-7})</span> for I-SOC. These estimates show that an experiment with an optical clock would significantly improve upon both the current best result (<span>((2{-}3)times 10^{-5})</span>, GREAT project) and the anticipated results of experiments on the ISS and Tiangong orbital stations. A comparison of our results with previous studies that do not account for clock drift and frequency bias is provided.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"51 10","pages":"631 - 639"},"PeriodicalIF":0.8,"publicationDate":"2026-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147738909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}