Acta Astrophysica Taurica最新文献

{"title":"Determination of supermassive black hole spins in active galactic nuclei","authors":"A. Mikhailov","doi":"10.31059/aat.vol3.iss1.pp44-47","DOIUrl":"https://doi.org/10.31059/aat.vol3.iss1.pp44-47","url":null,"abstract":"Abstract Black hole spin is a key to the relativistic jet generation. Existing models are based on the Blandford–Znajek and/or Blandford–Payne mechanisms. The jet power in these models is determined by the spin value, black hole mass, magnetic fields at the event horizon, and the accretion disc. Independent estimates of mass, jet power, and magnetic field give opportunity to constrain the supermassive black hole spin value. We present an application of this approach for supermassive black holes in different samples of active galactic nuclei (AGNs). We found that the assumption about equipartition between magnetic field energy density and accreting matter energy density is reasonable for the systems with thin accretion discs. The “mass-spin” diagrams were constructed for the samples of PG quasars and distant quasars at redshift z ≈ 4.8 and demonstrated the flattening region at masses MBH ≈ 108.5M☉. These diagrams can be used to study accretion onto supermassive black holes.","PeriodicalId":225286,"journal":{"name":"Acta Astrophysica Taurica","volume":"25 8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122078625","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Misalignments in NGC 1068","authors":"P. Vermot","doi":"10.31059/aat.vol3.iss1.pp23-26","DOIUrl":"https://doi.org/10.31059/aat.vol3.iss1.pp23-26","url":null,"abstract":"NGC 1068 is a nearby Active Galactic Nuclei (AGN) of type 2, meaning that its accretion disk is hidden behind a large amount of foreground extinction. Observations at several wavelengths have revealed various disk-like structures around the nucleus, all possibly part of the putative torus responsible for the obscuration of the AGN. I present results based on a GRAVITY/VLTI interferometric observation in the near-infrared, which provides very high angular resolution and gives insights into the geometry of the innermost region of this torus. The 3D orientation of the structure is surprising in several aspects, as it is misaligned with other disks present around the nucleus, and leaves a clear line of sight toward the central source.","PeriodicalId":225286,"journal":{"name":"Acta Astrophysica Taurica","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117165790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Looking at radio-quiet AGN with radio polarimetry","authors":"Silpa Sasikumar, P. Kharb","doi":"10.31059/aat.vol3.iss1.pp17-22","DOIUrl":"https://doi.org/10.31059/aat.vol3.iss1.pp17-22","url":null,"abstract":"The dominant radio emission mechanism in radio-quiet quasars (RQQs) is an open question. Primary contenders include: low-power radio jets, winds, star-formation and coronal emission. Our work suggests that radio polarization and emission-line studies can help to distinguish between these scenarios and determine the primary contributor. Our multi-frequency, multi-scale radio polarization study has revealed a composite jet and \"wind\" radio outflow in the radio-intermediate quasar, III Zw 2, as well as in the BALQSO, Mrk 231. Our radio polarization study in conjunction with the [O III] emission-line study of five type 2 RQQs have provided insights on the interplay of jets/winds and emission-line gas. These sources reveal an anti-correlation between polarized radio emission and [O III] emission. This is similar to that observed in some radio-loud active galactic nuclei (AGN) in the literature and suggests that the radio emission could be depolarized by the emission-line gas. Overall, our work suggests that a close interaction between the radio outflow and the surrounding gaseous environment is likely to be responsible for their stunted form in RQ and RI AGN.","PeriodicalId":225286,"journal":{"name":"Acta Astrophysica Taurica","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128159312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Morphology-dependent Black Hole–Host Galaxy Correlations: A Consequence of Physical Formation Processes","authors":"N. Sahu, A. Graham, Benjamin Lee Davis","doi":"10.31059/aat.vol3.iss1.pp39-43","DOIUrl":"https://doi.org/10.31059/aat.vol3.iss1.pp39-43","url":null,"abstract":"For decades, astronomers have been investigating how the central supermassive black hole (BH) may govern the host galaxy’s properties and vice versa. Our work adds another step to this study. We have performed state-of-theart 2D modeling and multi-component photometric decompositions of the largest-to-date sample of galaxies with dynamically-measured black hole masses (MBH). The multi-component decomposition allows us to accurately extract the bulge (spheroid) stellar luminosity/mass and structural parameters (also for other galaxy components) and provides detailed galaxy morphologies. We investigated the correlations between MBH and various host galaxy properties, including the bulge (M*,sph) and total galaxy (M*,gal) stellar masses discussed here. Importantly, we analyzed the role of galaxy morphology in these correlations. Our work reveals that the BH scaling relations depend on galaxy morphology and thus depend on the galaxy’s formation and evolution physics. Here we discuss that in the MBH–M*,sph diagram, early-type galaxies (ETGs) with a disk, ETGs without a disk, and late-type galaxies (LTG-spirals) define distinct relations, with quadratic slopes but different zero-points. We also review the MBH–M*,gal relation, where ETGs and LTGs define different relations. Notably, the existence of the MBH–M*,gal relations enables one to quickly estimate MBH in other galaxies without going through the multi-component decomposition process to obtain M*,sph. The final morphology-dependent black hole scaling relations provide tests for morphology-aware simulations of galaxies with a central BH and hold insights for BH-galaxy co-evolution theories based on BH accretion and feedback.","PeriodicalId":225286,"journal":{"name":"Acta Astrophysica Taurica","volume":"107 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132418878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determination of QW Ser and QZ Lib parameters from optical spectra","authors":"A. Dudnik, V. Shimansky, N. Borisov, Nail Sakhbullin, M. Gabdeev","doi":"10.31059/aat.vol3.iss1.pp12-16","DOIUrl":"https://doi.org/10.31059/aat.vol3.iss1.pp12-16","url":null,"abstract":"The paper investigates a new technique for determining dwarf nova parameters based on the analysis of their optical spectra with a signal-to-noise ratio S/N ≈ 80. We have determined parameters for the QW Ser and QZ Lib systems related to the SU UMa and WZ Sge dwarf novae. Moderate resolution spectra of both systems were obtained at BTA SAO during their low state with an optically thin accretion disk and the dominance of white dwarf radiation. As a result of the model analysis of the spectra, the parameters of the accretor atmosphere of QW Ser (Teff = 23500 ± 400 K and log g = 8.36 ± 0.05 dex) and constraints on the parameters for QZ Lib (Teff = 9500 ± 300 K and log g > 8.55 dex) were found. The presence of moderate noise in the studied spectra is not shown to affect the accuracy of determining parameters. The low temperature of the white dwarf does not allow to obtain a correct estimate of its surface gravity. Based on the determined parameters of the accretor atmospheres, a complete set of QW Ser parameters and estimates of QZ Lib parameters were found. The secondary components of both systems are defined to be red dwarfs of spectral type M.","PeriodicalId":225286,"journal":{"name":"Acta Astrophysica Taurica","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121386803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Studies of Active Galactic Nuclei in Kazakhstan","authors":"I. Izmailova","doi":"10.31059/aat.vol3.iss1.pp35-38","DOIUrl":"https://doi.org/10.31059/aat.vol3.iss1.pp35-38","url":null,"abstract":"This article presents an overview of works on the study of active galactic nuclei in Kazakhstan. The studies have been conducted at Fesenkov Astrophysical Institute (FAI) and still ongoing. Since the number of works carried out is large and it is not possible to review them in one article, the author limited herself to a review of the one object studies (Mrk 1095 = Ark 120) and a short description of the theoretical model of active galactic nuclei (AGN) developed at FAI. \u0000Spectral studies of Mrk 1095 revealed the presence of three emission objects near the galactic core. This made it possible to determine the orbits of these objects and to calculate the mass of the central body. In addition, from the observational data a possibility of the binary nature of the central body was established. \u0000At the end of the past century, scientists from FAI improved the unified AGN model. The theories put forward for this purpose made it possible to explain the presence of broad absorption lines (BAL) in the spectra of active galaxies","PeriodicalId":225286,"journal":{"name":"Acta Astrophysica Taurica","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131194183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic field of pulsating stars","authors":"V. Butkovskaya, S. Plachinda","doi":"10.31059/aat.vol3.iss1.pp1-5","DOIUrl":"https://doi.org/10.31059/aat.vol3.iss1.pp1-5","url":null,"abstract":"To date, magnetic fields have been detected in various types of pulsating stars. For several of these stars, the variability of the magnetic field with their radial pulsation period was confirmed. The physical mechanism of the pulsation variability of the magnetic field remains unknown. We discuss the current state of the problem of magnetic field variability over pulsation cycles in radially pulsating stars.","PeriodicalId":225286,"journal":{"name":"Acta Astrophysica Taurica","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116302566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A study of many-year spectral variability of the Ae Herbig star HD 36112","authors":"M.I. Fursyak, O. Kozlova","doi":"10.31059/aat.vol2.iss1.pp21-25","DOIUrl":"https://doi.org/10.31059/aat.vol2.iss1.pp21-25","url":null,"abstract":"We present the results of long-term high-dispersion spectral observations (R = 20000) of the Ae Herbig star HD 36112 in the regions of the Ha emission line and the NaI D resonance doublet lines. They show that parameters of the Ha emission line demonstrate complicated variability on several time scales: 1) variability from night to night caused by inhomogeneity of the circumstellar envelope; 2) variability on a time scale of about 1200d characterized by a variation of the equivalent width, intensity, and other emission parameters; 3) variability on a time scale of more than 4000d observed as a many-year trend in variations of parameters of the Ha emission line. \u0000We associate these results with variability of physical and kinematic conditions in the inner regions of the accretion disk and wind. The most probable mechanism of this variability is a process of planet formation in the circumstellar disk.","PeriodicalId":225286,"journal":{"name":"Acta Astrophysica Taurica","volume":"103 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124590319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Distributed electric current and its relation to ultraviolet radiation of the active region","authors":"Yu.A. Fursyak, A. S. Kutsenko","doi":"10.31059/aat.vol2.iss1.pp30-38","DOIUrl":"https://doi.org/10.31059/aat.vol2.iss1.pp30-38","url":null,"abstract":"We utilized full magnetic field vector magnetogramsacquired by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) to calculate vertical electric currents in the NOAA active region (AR) 12192. The AR was tracked between October 22, 2014 and October 25, 2014 with 720 s cadence. We revealed the presence of a large-scale electric current structure – distributed electric current – with the absolute magnitude varying in the range of (40–90)·1012 A. The distributed electric current is supposed to exist throughout the entire AR, and, extending to the upper layers of the solar atmosphere in one part of the AR, it closes through the chromosphere and corona in the remaining part of the AR. To test this assumption, we have compared the temporal variation of the distributed electric current value with the flare activity level (using GOES-15 data), as well as with intensity of ultraviolet radiation (UV) in the AR (using the Atmospheric Imaging Assembly (AIA/SDO) data in channels 94 Å, 193 Å, 304 Å, and 1600 Å). We found that: i) Time intervals of enhanced flare activity are co-temporal with intervals of increased values of the distributed electric current. The absence of rapid changes in the value of the distributed electric current during solar flares can be explained by high inductance of the current-carrying magnetic loops. ii) Rough estimates of the magnetic energy carried by the distributed electric current into the corona yield the values of about 1033–1034 erg for 12192. Onlya small amount of this energy is released during flare processes in the AR. Most of this energy seems to be consumed during other dissipative processes in the corona. iii) Comparison of the temporal variations of intensity in the 193 Å UV-radiation channel with dynamics of the distributed electric current in the AR reveals a good positive correlation between these values (Pearson’s R = 0.63). The absence of a correlation between the distributed electric current value and the intensity of UV radiation in channels 1600 Å, 304 Å and 94 Å might be explained by a low efficiency of the coronal loop heating by ohmic dissipation of electric currents in the corona due to the strong dependence of plasma conductivity on temperature. iv) Our results may support the concept of equivalent LRC circuit of a current-carrying coronal magnetic loop proposed by Alfven and Carlqvist in 1967 and developed by V.V. Zaitsev, A.V. Stepanov, and others. According to this model, the large-scale electric currents must exist in the upper layers of the solar atmosphere and take part in the coronal plasma heating.","PeriodicalId":225286,"journal":{"name":"Acta Astrophysica Taurica","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132581266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic fields of red giants and supergiants: a review of spectropolarimetric observations","authors":"S. Plachinda, V. Butkovskaya, D. Shulyak, N. Pankov, V. Tsymbal","doi":"10.31059/aat.vol3.iss1.pp6-11","DOIUrl":"https://doi.org/10.31059/aat.vol3.iss1.pp6-11","url":null,"abstract":"Today, magnetic fields have been reliably detected in many classes of stars with convective envelopes, from young T~Tauri stars to supergiants. We present an overview of the results obtained with high-precision spectropolarimetric observations of selected single F0-M0 giants and supergiants. The measurements of the magnetic field in these objects were started in 1989 at the 2.6-meter ZTSh telescope of the Crimean Astrophysical Observatory. To date, weak magnetic fields have been recorded in nearly four dozen of slowly rotating red giants. The longitudinal component of the field in several cases reaches a few tens of gauss. A spectropolarimetric survey of red supergiants includes three dozen objects. The magnetic field was detected in dozen of them. For one of these targets, $epsilon$~Gem, the magnetic field up to 10~G was reported. Because the magnetic field is frozen into the plasma, it is expected that the magnetic field of giants and supergiants should not exceed one gauss because stars have increased in size after the main sequence. Therefore, the main conclusion from the results of spectropolarimetric surveys of giants and supergiants with convective envelopes is that the most probable mechanism for the generation and amplification of the magnetic field in these objects is the dynamo action.","PeriodicalId":225286,"journal":{"name":"Acta Astrophysica Taurica","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125725726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}