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

{"title":"Increase in the Brightness of the Cosmic Radio Background toward Galaxy Clusters","authors":"S. A. Grebenev, R. A. Sunyaev","doi":"10.1134/S1063773724700063","DOIUrl":"10.1134/S1063773724700063","url":null,"abstract":"<p>We explore the possibility of detecting the excess of the cosmic radio background toward galaxy clusters due to its Compton scattering by electrons of the hot intergalactic gas. When mapping the background fluctuations at frequencies below <span>({lesssim}800)</span> MHz, this effect gives rise to a radio source at the location of the cluster. At higher frequencies, where the microwave (relic) radiation dominates in the cosmic background, a ‘‘negative’’ source (a ‘‘shadow’’ on the map of background fluctuations) is observed at the location of the cluster due to the transfer of some of the relic photons upward along the frequency axis upon their scattering (into the range <span>(nugtrsim 217)</span> GHz; Sunyaev and Zeldovich 1970, 1972). We have computed the spectra of the expected radio background distortions for various parameters of clusters and show that in many cases in the wide frequency range <span>(30 textrm{MHz}lesssimnulesssim 3 {textrm{GHz}})</span> the measurement of the distortions will be hindered by the intrinsic thermal (bremsstrahlung) radiation from the intergalactic gas and the scattered radio emission from cluster galaxies associated with their past activity, including the synchrotron radiation from ejected relativistic electrons. Below <span>({sim}20)</span> MHz the scattering effect always dominates over the thermal gas radiation due to the general increase in the intensity of the cosmic radio background, but highly accurate measurements at such frequencies become difficult. Below <span>({sim}5)</span> MHz the effect is suppressed by the induced scattering. We have found the frequency ranges that are optimal for searching for and measuring the Compton radio background excess. We show that hot (<span>(kT_{textrm{e}}gtrsim 8 {textrm{keV}})</span>) clusters at high (<span>(zgtrsim 0.5)</span>) redshifts are most promising for its observation. Because of the strong concentration of the bremsstrahlung to the cluster center, the peripheral observations of the Compton excess must be more preferable than the central ones. Moreover, owing to the thermal radiation of the gas and its concentration to the center, the above-noted transition from the ‘‘negative’’ source on the map of background fluctuations to the ‘‘positive’’ one when moving downward along the frequency axis must occur not gradually but through the stage of a ‘‘hybrid source’’—the appearance of a bright spot surrounded by a dark ring. This form of the source in projection is explained by its unusual three-dimensional shape in the form of a narrow radio bremsstrahlung peak rising from the center of a wide deep hole associated with the Compton scattering of the cosmic microwave background. The scattered radiation from an active central cluster galaxy in the past can amplify the effect. An analogous ‘‘hybrid source’’ also appears on the map of background fluctuations near a frequency of <span>(217.5)</span> GHz—when passing from the deficit of the cosmic microwave backgr","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"50 3","pages":"159 - 185"},"PeriodicalIF":1.1,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141610710","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":"Clumpy Accretion As a Possible Cause of Prolonged Eclipses in UX Ori Stars","authors":"V. P. Grinin,&nbsp;T. V. Demidova","doi":"10.1134/S1063773724700075","DOIUrl":"10.1134/S1063773724700075","url":null,"abstract":"<p>We propose a model of deep and prolonged eclipses in young UX Ori stars. Some of these events last for decades and existing models cannot explain them. We show that such eclipses can be caused by the infall of gas and dust clumps from the remnants of the protostellar cloud onto the protoplanetary disk. The perturbation in the disk caused by the infall of a clump leads to a burst of accretional stellar activity and, as a consequence, to a strengthening of the disk wind. If the circumstellar disk is tilted at a small angle to the line of sight, then the dust raised by the wind from the disk surface can cause a dramatic decrease in the stellar brightness that can last for decades.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"50 3","pages":"194 - 202"},"PeriodicalIF":1.1,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141614659","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 Method of Periodic Principal Components for the Dynamic Spectrum of Radio Pulsars and Faraday Rotation of Nine Pulse Components of PSR B0329+54","authors":"V. V. Kocharovsky,&nbsp;V. V. Vdovin,&nbsp;A. S. Gavrilov,&nbsp;E. R. Kocharovskaya,&nbsp;S. V. Logvinenko,&nbsp;E. M. Loskutov,&nbsp;V. M. Malofeev","doi":"10.1134/S1063773724700051","DOIUrl":"10.1134/S1063773724700051","url":null,"abstract":"<p>We have developed the method of periodic principal components for signals with a quasi-periodic dynamic spectrum characteristic of radio pulsars. The method is based on an analysis of the eigenvectors and eigenvalues of the signal frequency–time correlation matrix averaged over many pulsar rotation periods. Using the observations of PSR B0329<span>(+)</span>54 with the radio telescope at Pushchino Radio Astronomy Observatory near a frequency of 111 MHz in a 2.5 MHz band as an example, we show that even for short data intervals (a few minutes) the developed method allows one to identify up to nine pulse components of the pulsar, to estimate the correlation between them, and to find the period of Faraday modulation for each component as well as its relative phase and frequency–time chirp rate, i.e., it allows the structure of the emission source to be judged.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"50 2","pages":"120 - 137"},"PeriodicalIF":1.1,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141172517","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 the Components of the Double Star ADS 15571 by Speckle Interferometry","authors":"E. N. Sokov,&nbsp;D. L. Gorshanov,&nbsp;I. S. Izmailov,&nbsp;N. A. Shakht,&nbsp;I. A. Sokova,&nbsp;A. S. Beskakotov,&nbsp;V. V. Dyachenko,&nbsp;A. F. Maksimov,&nbsp;A. A. Mitrofanova,&nbsp;D. A. Rasstegaev","doi":"10.1134/S1063773724700038","DOIUrl":"10.1134/S1063773724700038","url":null,"abstract":"<p>Based on the speckle observations of the wide double star ADS 15571 with the 6-m BTA telescope at the Special Astrophysical Observatory of the Russian Academy of Sciences in 2014, we have confirmed the existence of a close companion to component A that was previously detected from astrometric observations at the Pulkovo Observatory. An extension of the BTA observations from 2014 to 2022 has allowed 28 positions of the companion relative to the primary star to be obtained. From this series we have constructed the relative orbit of the companion and determined the sum of the masses of subsystem A (<span>(1.686pm 0.014)</span>\u0000 <span>(M_{odot})</span>). A comparison of this orbit with the orbit of the photocenter of component A constructed from Pulkovo photographic observations has also allowed the mass ratio of the primary star and the companion and their individual masses to be estimated: <span>(M_{textrm{Aa}}=(1.10pm 0.07))</span>\u0000 <span>(M_{odot})</span> and <span>(M_{textrm{Ab}}=(0.59pm 0.07))</span>\u0000 <span>(M_{odot})</span>. Based on the estimates of the magnitude difference between the two stars of the system ADS 15571A, we have estimated the spectral types of the components: ADS 15571Aa—F8V; ADS 15571Ab—K5V–K5.5V. The speckle observations of component B have shown that it has no resolvable companions.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"50 2","pages":"138 - 147"},"PeriodicalIF":1.1,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141172550","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":"Passage of a Gamma-Ray Burst through a Molecular Cloud: Cloud Ionization Structure","authors":"A. V. Nesterenok","doi":"10.1134/S1063773724700014","DOIUrl":"10.1134/S1063773724700014","url":null,"abstract":"<p>We have constructed a model for the passage of gamma-ray burst radiation through a dense molecular cloud. In our calculations we take into account the main radiation–cloud material interaction processes: the ionization of H and He atoms, the ionization of metal ions with the emission of Auger electrons, the ionization and photodissociation of H<span>({}_{2})</span> molecules, the absorption of ultraviolet radiation in the H<span>({}_{2})</span> lines of the Lyman and Werner bands, and the vaporization of dust grains. The ionization of metal ions by X-ray radiation determines the gas ionization fraction in the region where the gas is predominantly neutral. The photoionization of the inner electron shells of ions is accompanied by the emission of Auger electrons, giving rise to metal ions in a high ionization state. In particular, the column densities of Mg, Si, and Fe ions in the ionization states I–IV are much lower than the column densities of these ions in the ionization state V or higher. The photoionization of metal ions by ultraviolet radiation occurs only at distances smaller than the dust vaporization radius and for neutral atoms with an ionization threshold below 13.6 eV. The results of our calculations have confirmed the previously made assumption that the ionization of He atoms plays an important role in the absorption of radiation in the X-ray wavelength range. For a low metallicity, <span>(textrm{[M/H]}leq{-}1)</span>, the role of helium atoms is dominant.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"50 2","pages":"99 - 119"},"PeriodicalIF":1.1,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141172974","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":"Magnetic Field Structures of the Stars HD 94660, HD 75049, and HD 154708","authors":"Yu. V. Glagolevskij","doi":"10.1134/S106377372470004X","DOIUrl":"10.1134/S106377372470004X","url":null,"abstract":"<p>Based on published data, we have constructed models for the magnetic structures of three stars with a relatively strong magnetic field. They all have a dipolar structure and do not differ in their properties from the bulk of the magnetic stars. However, they, as well as some other objects with a strong magnetic field, do not obey the direct dependence of the rotation period on the stellar magnetic field strength that is expected from the hypothesis about the loss of angular momentum by its transfer to the surrounding protostellar clouds through magnetic field lines.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"50 2","pages":"148 - 158"},"PeriodicalIF":1.1,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141172488","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":"On the Flare Activity of the H({}_{2})O Maser in DR21OH","authors":"A. V. Lapinov,&nbsp;A. M. Tolmachev,&nbsp;A. K. Kiselev,&nbsp;N. I. Lapin,&nbsp;S. A. Lapinova,&nbsp;I. A. Startseva,&nbsp;A. S. Loginova","doi":"10.1134/S1063773724600140","DOIUrl":"10.1134/S1063773724600140","url":null,"abstract":"<p>An H<span>({}_{2})</span>O maser flare detected in July 2023 in the star-forming region DR21OH when monitoring the continuum emission in DR21 with PRAO RT22 is reported. These observations were part of a program to study the characteristics of the antenna and the atmospheric absorption at a wavelength of 1.35 cm. Subsequent access to archival data and new measurements have shown that the detected flare in 2023 was not the only one in the source, and DR21OH is highly variable in the H<span>({}_{2})</span>O line at 22 GHz with a rather unpredictable character. Based on continuum measurements in DR21, we have estimated the effective area of RT22.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"50 1","pages":"62 - 69"},"PeriodicalIF":1.1,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140935141","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":"Radar Images of the Candidate Spacecraft Landing Sites on the Moon","authors":"Yu. S. Bondarenko,&nbsp;D. A. Marshalov,&nbsp;B. M. Zinkovsky,&nbsp;A. G. Mikhailov","doi":"10.1134/S1063773724600127","DOIUrl":"10.1134/S1063773724600127","url":null,"abstract":"<p>We present new radar images and polarimetric data for the candidate landing sites of the Russian Luna-25 spacecraft near the Manzinus and Boguslawsky craters in the south polar region of the Moon. The images were obtained with the 64-m TNA-1500 antenna at the Bear Lakes Satellite Communications Center of the Special Design Bureau of the Moscow Power Engineering Institute and the 13.2-m RT-13 radio telescope at the Svetloe Observatory of the Institute of Applied Astronomy of the Russian Academy of Sciences in a bistatic configuration at a wavelength of 4.2 cm. At this wavelength the radar signals can penetrate into the lunar regolith to a depth up to 1 m and are sensitive to surface and suspended rocks with a diameter of about 1 cm or more. A spatial resolution <span>({sim}80)</span> m per pixel was achieved through the focused processing algorithm that avoids the radar image smearing at a long integration time. The receiving-system noise temperature measurements during the entire observation session provided a reliable estimate of the circular polarization ratio (CPR) of the echo signal. Analysis of the radar images obtained revealed regions with high radar backscatter and CPR. The number and distribution of rocks and irregularities with sizes comparable to the radar wavelength on the surface and in the near-surface layer of regolith were estimated. As a result of the radar data analysis, we conclude that the surface and the near-surface regolith layer of the main site are smoother than those of the reserved site, which makes it preferable for landing. Thus, the resulting new radar images and CPR maps can be used in planning future lunar missions.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"50 1","pages":"92 - 97"},"PeriodicalIF":1.1,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140934799","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":"Deep Hard X-ray Survey of the M81 Field Based on INTEGRAL1 Data","authors":"R. A. Krivonos,&nbsp;I. A. Mereminskiy,&nbsp;S. Yu. Sazonov","doi":"10.1134/S1063773724600115","DOIUrl":"10.1134/S1063773724600115","url":null,"abstract":"<p>We have carried out a deep survey of the M81 field in the 25–60 keV energy band based on long-term (2003–2023) INTEGRAL observations. A record sensitivity of 0.16 mCrab at a detection significance of <span>(4sigma)</span> has been achieved in the central part of the field owing to the long accumulated exposure (19.2 Ms). The total area of the survey is 1004 deg<span>({}^{2})</span> at a sensitivity level better than 0.72 mCrab. We have produced a catalog of sources detected at a significance level higher than <span>(4sigma)</span>. It contains 51 objects most of which are active galactic nuclei (AGNs). The median redshift of the Seyfert galaxies in the catalog is <span>(z=0.0366)</span>. Six sources have not been detected previously in any of the X-ray surveys. According to the available indirect data, all of them and two more sources that have already been entered previously into the INTEGRAL survey catalogs can also be AGNs, including those with strong internal absorption.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"50 1","pages":"25 - 33"},"PeriodicalIF":1.1,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140934791","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":"Estimation of the Accuracy of Stellar Atmosphere Parameters and Interstellar Extinction from Highly Accurate Broadband Photometry","authors":"Yu. V. Pakhomov","doi":"10.1134/S1063773724600164","DOIUrl":"10.1134/S1063773724600164","url":null,"abstract":"<p>We analyze the accuracy of estimating the stellar parameters (effective temperature <span>(T_{textrm{eff}})</span>, surface gravity log <span>(g)</span>, metallicity [Fe/H], angular diameter <span>(theta)</span>) and the color excess <span>(E(B-V))</span> obtained by the <span>(chi^{2})</span> minimization method from broadband photometry using the Johnson–Cousins, 2MASS photometric systems, and ATLAS9 model stellar atmospheres as an example. The method has been tested for the internal accuracy and with real objects: isolated stars and stars from clusters. A high photometric accuracy (<span>(sigma_{m}leq 0.01ldots 0.015^{m})</span>), at which the errors are <span>({sigma}T_{textrm{eff}}approx 2{-}5{%})</span>, <span>(sigma)</span> log <span>(gapprox 0.6)</span>, <span>(sigma[textrm{Fe/H}]approx 1)</span>, <span>(sigmathetaapprox 2%)</span>, and <span>({sigma}E(B-V)approx 0.02{-}0.07^{m})</span> for stars with <span>(T_{textrm{eff}}lesssim 8000)</span> K, is required to obtain acceptable results. For hotter stars <span>({sigma}T_{textrm{eff}})</span> reaches <span>(10%)</span>, <span>(sigma)</span> log <span>(gapprox 0.6)</span> dex, <span>(sigmathetaapprox 3%)</span>, and <span>({sigma}E(B-V)approx 0.02{-}0.07^{m})</span>, but the determination of the metallicity becomes impossible. We show that the method can be used to estimate the color excess in stellar fields. The limitations of the method are discussed.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"50 1","pages":"34 - 52"},"PeriodicalIF":1.1,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140934871","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}