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

{"title":"What Can We Learn about Compton-Thin AGN Tori from Their X-ray Spectra? *","authors":"F. Melazzini,&nbsp;S. Sazonov","doi":"10.1134/S106377372306004X","DOIUrl":"10.1134/S106377372306004X","url":null,"abstract":"<p>We have developed a Monte Carlo code for simulation of X-ray spectra of active galactic nuclei (AGN) based on a model of a clumpy obscuring torus. Using this code, we investigate the diagnostic power of X-ray spectroscopy of obscured AGN with respect to the physical properties and orientation of the torus, namely: the average column density, <span>(langle N_{textrm{H}}rangle)</span>, the line-of-sight column density, <span>(N_{textrm{H}})</span>, the abundance of iron, <span>(A_{textrm{Fe}})</span>, the clumpiness (i.e., the average number of gas clouds along the line of sight), <span>(langle Nrangle)</span>, and the viewing angle, <span>(alpha)</span>. In this first paper of a series, we consider the Compton-thin case, where both <span>(langle N_{textrm{H}}rangle)</span> and <span>(N_{textrm{H}})</span> do not exceed <span>(10^{24})</span> cm<span>({}^{-2})</span>. To enable quantitative comparison of the simulated spectra, we introduce five measurable spectral characteristics: the low-energy hardness ratio (ratio of the continuum fluxes in the 7–11 and 2–7 keV energy bands), the high-energy hardness ratio (ratio of the continuum fluxes in the 10–100 and 2–10 keV energy bands), the depth of the iron K absorption edge, the equivalent width of the Fe K<span>(alpha)</span> line, and the fraction of the Fe K<span>(alpha)</span> flux contained in the Compton shoulder. We demonstrate that by means of X-ray spectroscopy it is possible to tightly constrain <span>(langle N_{textrm{H}}rangle)</span>, <span>(N_{textrm{H}})</span>, and <span>(A_{textrm{Fe}})</span> in the Compton-thin regime, while there is degeneracy between clumpiness and viewing direction.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 6","pages":"301 - 319"},"PeriodicalIF":0.9,"publicationDate":"2023-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138454535","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":"Determination of the Parameters of a Nonlinear Kinematic Galactic Rotation Model Based on the Proper Motions and Radial Velocities of Stars from the Gaia DR3 Catalogue","authors":"A. S. Tsvetkov,&nbsp;F. A. Amosov","doi":"10.1134/S1063773723060051","DOIUrl":"10.1134/S1063773723060051","url":null,"abstract":"<p>We have solved the Ogorodnikov–Milne stellar-kinematics equations in the Galactic rectangular coordinate system based on the total velocities for a special sample of stars with radial velocities from the final Gaia Data Release 3 catalogue. We have found the region of applicability of the linear model and the regions that it describes poorly. We have constructed a second-order model that takes into account the peculiarities of stellar kinematics more accurately and showed its applicability for stars at distances up to 5 kpc.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 6","pages":"331 - 344"},"PeriodicalIF":0.9,"publicationDate":"2023-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138454563","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":"Azimuthal Patterns in Planetesimal Circumstellar Disks","authors":"T. V. Demidova,&nbsp;I. I. Shevchenko","doi":"10.1134/S1063773723060026","DOIUrl":"10.1134/S1063773723060026","url":null,"abstract":"<p>Ways of formation of azimuthal resonant patterns in circumstellar planetesimal disks with planets are considered. Our analytical estimates and massive numerical experiments show that the disk particles that initially reside in zones of low-order mean-motion resonances with the planet may eventually concentrate into potentially observable azimuthal patterns. The structuring process is rapid, usually taking <span>(sim)</span>100 orbital periods of the planet. It is found that the relative number of particles that retain their resonant position increases with decreasing the mass parameter <span>(mu)</span> (the ratio of masses of the perturbing planet and the parent star), but a significant fraction of the particle population is always removed from the disk due to accretion of the particles onto the star and planet, as well as due to their transition to highly elongated and hyperbolic orbits. Expected radio images of azimuthally structured disks are constructed. In the considered models, azimuthal patterns associated with the <span>(2:1)</span> and <span>(3:2)</span> resonances are most clearly manifested; observational manifestations of the <span>(1:2)</span> and <span>(2:3)</span> resonances are also possible.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 6","pages":"345 - 357"},"PeriodicalIF":0.9,"publicationDate":"2023-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138454562","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":"SRGz: Machine Learning Methods and Properties of the Catalog of SRG/eROSITA Point X-ray Source Optical Counterparts in the DESI Legacy Imaging Surveys Footprint","authors":"A. V. Meshcheryakov,&nbsp;V. D. Borisov,&nbsp;G. A. Khorunzhev,&nbsp;P. A. Medvedev,&nbsp;M. R. Gilfanov,&nbsp;M. I. Belvedersky,&nbsp;S. Yu. Sazonov,&nbsp;R. A. Burenin,&nbsp;R. A. Krivonos,&nbsp;I. F. Bikmaev,&nbsp;I. M. Khamitov,&nbsp;S. V. Gerasimov,&nbsp;I. V. Mashechkin,&nbsp;R. A. Sunyaev","doi":"10.1134/S1063773723070022","DOIUrl":"10.1134/S1063773723070022","url":null,"abstract":"<p>We describe the methods of the SRGz system for the physical identification of eROSITA point X-ray sources from photometric data in the DESI Legacy Imaging Surveys footprint. We consider the models included in the SRGz system (version 2.1) that have allowed us to obtain accurate measurements of the cosmological redshift and class of an X-ray object (quasar/galaxy/star) from multiwavelength photometric sky surveys (DESI LIS, SDSS, Pan-STARRS, WISE, eROSITA) for 87<span>({%})</span> of the entire eastern extragalactic region (<span>(0^{circ}&lt;l&lt;180^{circ})</span>, <span>(|b|&gt;20^{circ})</span>). An important feature of the SRGz system is that its data handling model (identification, classification, photo-z algorithms) is based entirely on heuristic machine learning approaches. For a standard choice of SRGz parameters the optical counterpart identification completeness (recall) in the DESI LIS footprint is <span>(95{%})</span> (with an optical counterpart selection precision of <span>(94{%})</span>); the classification completeness (recall) of X-ray sources without optical counterparts in DESI LIS is <span>(82{%})</span> (<span>(85{%})</span> precision). A high quality of the photometric classification of X-ray source optical counterparts is achieved in SRGz: <span>({&gt;}99{%})</span> photometric classification completeness (recall) for extragalactic objects (a quasar or a galaxy) and stars on a test sample of sources with SDSS spectra and GAIA astrometric stars. We present an analysis of the importance of various photometric features for the optical identification and classification of eROSITA X-ray sources. We have shown that the infrared (IR) magnitude <span>(W_{2})</span>, the X-ray/optical(IR) ratios, the optical colors (for example, <span>((g-r))</span>), and the IR color (<span>(W_{1}-W_{2})</span>) as well as the color distances introduced by us play a significant role in separating the classes of X-ray objects. We use the most important photometric features to interpret the SRGz predictions in this paper. The accuracy of the SRGz photometric redshifts (from DESI LIS, SDSS, Pan-STARRS, and WISE photometric data) has been tested in the Stripe82X field on a sample of 3/4 of the optical counterparts of eROSITA point X-ray sources (for which spectroscopic measurements are available in Stripe82X): <span>(sigma_{NMAD}=3.1{%})</span> (the normalized median absolute deviation of the prediction) and <span>(n_{&gt;0.15}=7.8{%})</span> (the fraction of catastrophic outliers). The presented photo-z results for eROSITA X-ray sources in the Stripe82X field are more than a factor of 2 better in both metrics (<span>(sigma_{NMAD})</span> and <span>(n_{&gt;0.15})</span>) than the photo-z results of other groups published in the Stripe82X catalog.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 7","pages":"359 - 409"},"PeriodicalIF":0.9,"publicationDate":"2023-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138438414","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":"Extreme Values of Sunspot Activity on a Long Time Scale","authors":"Yu. A. Nagovitsyn,&nbsp;A. A. Osipova","doi":"10.1134/S1063773723070034","DOIUrl":"10.1134/S1063773723070034","url":null,"abstract":"<p>The extreme levels of solar activity on time scales of 300–400 and 9000 years are considered. The total sunspot area <span>(AR)</span>, a physical index of solar activity, has been estimated using the sunspot number reconstruction from Wu et al. (2018). The main study has been carried out precisely in terms of this index. The variations in solar activity at the epoch of the last 300–400 years represent fairly well its variations on time scales of the order of nine millennia. The maximum level of solar activity for the yearly averages is <span>(AR_{M}=2930pm 400)</span> m.s.h. (millionths of the solar hemisphere). The upper limit for the daily values is <span>(AR_{M}=7500pm 2200)</span> m.s.h. for the traditional sunspot areas corrected for the perspective distortion and <span>(AR_{OM}=11,400pm 3300)</span> m.s.d. (millionths of the solar disk) for the so-called ‘‘observed’’ areas—the sunspot projections onto the visible solar disk. The maximum yearly averages of the sunspot number <span>(SN_{M}=258pm 38)</span> and the sunspot group number <span>(GN_{M}=12.3pm 2.4)</span> have also been estimated; 11.3<span>({%})</span> of the time the solar activity is at an extremely high level; 8.5 and 4.5<span>({%})</span> of the time its level corresponds to the Dalton minimum or lower and an extremely low one, respectively. Thus, extremely high levels are more likely for solar activity than extremely low ones.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 7","pages":"421 - 429"},"PeriodicalIF":0.9,"publicationDate":"2023-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138438367","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":"Peculiarities of Open Star Clusters with High Vertical Velocities from the Region of the Sco–Cen OB Association","authors":"V. V. Bobylev,&nbsp;A. T. Bajkova","doi":"10.1134/S1063773723070010","DOIUrl":"10.1134/S1063773723070010","url":null,"abstract":"<p>We have studied the kinematics of a unique sample of young open star clusters (OSCs) with high vertical velocities, <span>(15&lt;W&lt;40)</span> km s<span>({}^{-1})</span>. The characteristics of these clusters were taken from the catalogue by Hunt and Reffert (2023), where their mean proper motions, line-of-sight velocities, and distances were calculated using Gaia DR3 data. These OSCs are located within 0.6 kpc of the Sun and form two clumps: one in the region of the Sco–Cen OB association and the other one in the region of the Per OB3–Per OB2 associations. The OSC group of 47 members in the region of the Sco–Cen association is shown to expand along the <span>(y)</span> axis, <span>(partial V/partial y=51pm 12)</span> km s<span>({}^{-1})</span> kpc<span>({}^{-1})</span>. This group also has a positive rotation around the <span>(z)</span> axis with an angular velocity of <span>(71pm 11)</span> km s<span>({}^{-1})</span> kpc<span>({}^{-1})</span> and a negative rotation around the <span>(x)</span> axis with an angular velocity of <span>(-35pm 5)</span> km s<span>({}^{-1})</span> kpc<span>({}^{-1})</span>. Based on the velocities of 27 OSCs from the region of the Per OB3–Per OB2 associations, we have found no gradients differing significantly from zero. We have studied the kinematics of more than 1700 stars selected by Luhman (2022) as probable members of the Sco–Cen OB association. These stars are shown to have no high vertical velocities. The expansion coefficient of the stellar system in the <span>(xy)</span> plane has been found from all stars to be <span>(K_{xy}=43.2pm 2.2)</span> km s<span>({}^{-1})</span> kpc<span>({}^{-1})</span>. Based on stars from the three UCL, LCC, and V1062 Sco groups with a mean age <span>({sim}20)</span> Myr, for the first time we have found a volume expansion coefficient of the stellar system differing significantly from zero, <span>(K_{xyz}=43.2pm 3.4)</span> km s<span>({}^{-1})</span> kpc<span>({}^{-1})</span>.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 7","pages":"410 - 420"},"PeriodicalIF":0.9,"publicationDate":"2023-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136104888","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":"Investigation of the Flaring Activity of BL Lac in July–November 2021","authors":"L. S. Ugol’kova,&nbsp;M. S. Pshirkov,&nbsp;V. P. Goranskij,&nbsp;N. P. Ikonnikova,&nbsp;B. S. Safonov,&nbsp;A. M. Tatarnikov,&nbsp;E. V. Shimanovskaya,&nbsp;M. A. Burlak,&nbsp;M. D. Afonina","doi":"10.1134/S1063773723050067","DOIUrl":"10.1134/S1063773723050067","url":null,"abstract":"<p>The source BL Lac exhibited an enhanced activity from August 2020 to July 2022. This activity peaked in July–August 2021. In this period the source reached historic brightness maxima in various energy ranges. Observations of this nonstandard maximum were carried out by the SAI staff of the Crimean Station of SAI and with the telescopes of the Caucasus Mountain Observatory (CMO SAI MSU). Optical and near-infrared photometric data as well as optical polarimetric data were obtained. When investigating the correlation between the optical and gamma-ray fluxes and between the optical and infrared fluxes, its high degree with an almost zero lag was confirmed—this means that the emission regions spatially coincide or are very close together. The degree of linear polarization in the investigated period changed in a wide range, reaching 20<span>({%})</span>, with an anticorrelation between the degree of linear polarization and the brightness of the object having been observed. A similar pattern of variation was also observed in the preceding flares of this object. The changes in the electric vector position angle (EVPA) show a dependence on the rate of change of the object’s brightness. The EVPA changed greatly during flares and slowly at the times of a slow change in the intensity.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 5","pages":"216 - 228"},"PeriodicalIF":0.9,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50447187","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":"Counter-Rotating Gaseous Disk and Star Formation in the S0 Galaxy NGC 934","authors":"O. K. Sil’chenko,&nbsp;A. V. Moiseev,&nbsp;D. V. Oparin,&nbsp;D. V. Zlydneva,&nbsp;D. V. Kozlova","doi":"10.1134/S1063773723050043","DOIUrl":"10.1134/S1063773723050043","url":null,"abstract":"<p>Using long-slit and panoramic spectroscopy at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences and by mapping emission lines in a narrow passband of 13 Å with the MaNGaL instrument at the 2.5-m telescope of the Caucasus Mountain Observatory of the Sternberg Astronomical Institute of the Lomonosov Moscow State University, we have investigated the gaseous component of the giant lenticular galaxy NGC 934. The gas kinematics in the galaxy has turned out to disagree completely with the stellar kinematics, suggesting recent accretion of a large amount of cold gas by the galaxy. Weak star formation proceeds in the accreted gas on the periphery of the galaxy, mainly in a ring of radius 26 kpc, which may promise the buildup of a giant low-surface-brightness stellar disk in this early-type galaxy. The gas metallicity in the star formation ring is nearly solar: the accretion source is most likely the swallowing of a massive gas-rich satellite.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 5","pages":"229 - 239"},"PeriodicalIF":0.9,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50447188","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":"Cosmic Abundance of Iron","authors":"N. N. Chugai","doi":"10.1134/S1063773723050018","DOIUrl":"10.1134/S1063773723050018","url":null,"abstract":"<p>I explore the possibility of estimating an upper limit for the present-day iron abundance in the baryonic matter at which the gamma-ray background from the decay of <span>({}^{56})</span>Ni synthesized in the Universe to date comes into conflict with the observed MeV gamma-ray background. I calculate the brightness of the gamma-ray background from SNe Ia and SNe II by taking into account the gamma-ray scattering and absorption in supernova ejecta. The model brightness of the gamma-ray background is shown to be consistent with the observed MeV gamma-ray background if the iron abundance in the baryonic matter is less than 15<span>({%})</span> of the solar one.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 5","pages":"209 - 215"},"PeriodicalIF":0.9,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50447189","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":"Spectral and Temporal Analysis of the Supergiant Fast X-ray Transient IGR J16195–4945 with SRG/ART-XC","authors":"M. N. Satybaldiev,&nbsp;I. A. Mereminskiy,&nbsp;A. A. Lutovinov,&nbsp;D. I. Karasev,&nbsp;A. N. Semena,&nbsp;A. E. Shtykovsky","doi":"10.1134/S106377372305002X","DOIUrl":"10.1134/S106377372305002X","url":null,"abstract":"<p>We present the results of the analysis of the SRG/ART-XC observation of the Supergiant Fast X-ray Transient IGR J16195-4545 performed on March 3, 2021. Six bright flares are present in the light curve, with no significant change in hardness occuring during these flares. The spectrum is described with an absorbed power law model with a high energy exponential cutoff showing heavy absorption, with <span>(N_{textrm{H}}=(12pm 2)times 10^{22}text{ cm}^{-2})</span> and <span>(Gamma=0.56pm 0.15)</span>, <span>(E_{textrm{cut}}=13pm 2)</span> keV. Adopting the Bayesian block decomposition of the light curve, we measured the properties of the observed flares (duration, rise time, waiting time, released energy and pre-flare luminosity), which are consistent with the quasi-spherical subsonic accretion model. The stellar wind velocity of the supergiant is estimated to be <span>(v_{w}approx 500)</span> km s<span>({}^{-1})</span>. Additionally, the system was found to have an unusual near-IR variability.</p>","PeriodicalId":55443,"journal":{"name":"Astronomy Letters-A Journal of Astronomy and Space Astrophysics","volume":"49 5","pages":"249 - 256"},"PeriodicalIF":0.9,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50447185","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}