共查询到20条相似文献，搜索用时 31 毫秒
1.
Mikhailov A. G. Piotrovich M. Yu. Buliga S. D. Natsvlishvili T. M. Gnedin Yu. N. 《Astronomy Reports》2019,63(6):433-444
Astronomy Reports - Hybrid models for the generation of relativistic jets are used to place constraints on the spins of supermassive black holes (SMBHs) in active galactic nuclei at redshifts z... 相似文献
2.
A. M. Cherepashchuk 《Astronomy Reports》2017,61(4):265-274
After 50 years of observational studies of black holes, great progress has been achieved in this branch of astrophysics. Several dozen stellar-mass black holes have been discovered in X-ray binaries, and several hundred supermassive black holes in galactic nuclei. The remarkable recent discovery of gravitational waves from merging black holes in a binary system by LIGO marks the beginning of a new stage in black-hole research. It is quite possible that gravitational-wave studies will provide definitive evidence for the existence of event horizons in black holes in the near future. On the other hand, the development of methods for space and ground-based radio-interferometry observations provides hope that it will be possible to obtain images of “shadows” of supermassive black holes in galactic nuclei, and to observe directly processes occurring in the vicinities of the event horizons of supermassive black holes. This is important for tests of general relativity in extremely strong gravitational fields. 相似文献
3.
Acceleration of spatial motions of stars by close-binary supermassive black holes in galactic nuclei
The conditions for the acceleration of the spatial motions of stars by close-binary supermassive black holes (SMBHs) in galactic nuclei are analyzed in order to derive the velocity distribution for stars ejected from galaxies by such black holes. A close binary system consisting of two SMBHs in circular orbits was subject to a spherically symmetrical “barrage” of solar-mass stars with various initial velocities. The SMBHs were treated as point objects with Newtonian gravitational fields. Models with binary component-mass ratios of 1, 0.1, 0.01, and 0.001 were studied. The results demonstrate the possibility of accelerating neutron stars, stellar-mass black holes, and degenerate dwarfs to velocities comparable to the relative orbital velocities of the binary-SMBH components. In the stage when the binary components are merging due to the action of gravitational-wave radiation, this velocity can approach the speed of light. The most massive binary black-holes (M ? 109M⊙) can also accelerate main-sequence stars with solar or subsolar masses to such velocities. 相似文献
4.
A. E. Vol’vach A. M. Kutkin M. G. Larionov L. N. Vol’vach A. Lakhteenmaki M. Tornikoski J. Tammi P. Savolainen M. F. Aller H. D. Aller M. Sasada 《Astronomy Reports》2014,58(2):71-77
Flux-density variations of the quasar S0528+134 (Nimfa) are analyzed based on long-term monitoring at five radio frequencies between 4.8 and 37 GHz, performed at the Crimean Astrophysical Observatory, the Metsähovi Radio Observatory of Aalto University, and the University of Michigan Radio Astronomy Observatory. The dynamics of a powerful flare in 1996 are analyzed using gamma-ray (0.1–300 GeV), X-ray (2–10 keV, 15–50 keV), and radio observations. The delays of the flare between different spectral ranges and between different radio wavelengths have been measured. The dependence for the delays at different radio wavelengths relative to the X-ray and optical flares is established based on long-term observations in the X-ray, optical, and radio obtained from 2004 to 2013. Multi-frequency monitoring in the radio is used to estimate the orbital and precession periods in the binary supermassive black hole system S0528+134 and the physical characteristics of this system. 相似文献
5.
A review of our current understanding of the physics and evolution of close binary stars with various masses under the influence of the nuclear evolution of their components and their magnetic stellar winds is presented. The role of gravitational-wave radiation by close binaries on their evolution and the loss of their orbital angular momentum is also considered. The final stages in the evolution of close binary systems are described. The review also notes the main remaining tasks related to studies of the physics and evolution of various classes of close binaries, including analyses of collisions of close binaries and supermassive black holes in galactic nuclei. Such a collision could lead to the capture of one of the components by the black hole and the acceleration of the remaining component to relativistic speeds. 相似文献
6.
Astronomy Reports - Stars located closely to supermassive black holes (SMBHs) can, under certain conditions, form close binary systems with the SMBHs, in which the star may fill the Roche lobe and... 相似文献
7.
A model for the formation of supermassive black holes at the center of a cluster of primordial black holes is developed. It is assumed that ～10?3 of the mass of the Universe consists of compact clusters of primordial black holes that arose as a result of phase transitions in the early Universe. These clusters also serve as centers for the condensation of dark matter. The formation of protogalaxies with masses of the order of 2 × 108 M ⊙ at redshift z = 15 containing clusters of black holes is investigated. The nuclei of these protogalaxies contain central black holes with masses ～105 M ⊙, and the protogalaxies themselves resemble dwarf spherical galaxies with their maximum density at their centers. Subsequent merging of these induced protogalaxies with ordinary halos of dark matter leads to the standard picture for the formation of the large-scale structure of the Universe. The merging of the primordial black holes leads to the formation of supermassive black holes in galactic nuclei and produces the observed correlation between the mass of the central black hole and the bulge velocity dispersion. 相似文献
8.
We list and analyze the main currently known mechanisms for accelerating the space motions of stars. A high space velocity
of a star can be a consequence of its formation in the early stages of the evolution of a massive galaxy, when it was spheroidal
and non-stationary, so that stars were born with velocities close to the escape velocity for the galaxy. Another possibility
is that the star arrived from another galaxy with a velocity that is high for our Galaxy. The decay of unstable close multiple
stars or supernova explosions in close binaries can also provide velocities of up to several hundreds of km/s to main-sequence
stars and velocities of up to ∼1000 km/s to degenerate stars, neutron stars, and stellar-mass black holes. The merger of components
of a binary system containing two neutron stars or a neutron star and a black hole due to gravitational-wave radiation can
accelerate the nascent black hole to a velocity∼1000 km/s. Hypervelocity relativistic stars can be born due to asymmetric
neutrino ejection during a supernova explosion. Stars can be efficiently accelerated by single and binary supermassive black
holes (with masses from several millions to several billions of solar masses) in the nuclei of galaxies. Thanks to their gravitational
field and fast orbital motion (in the case of binary objects), supermassive black holes are able to accelerate even main-sequence
stars to relativistic velocities. 相似文献
9.
The possible influence of galactic interaction on the formation and growth of supermassive black holes in their nuclei and
the dynamics of their circumnuclear regions are considered, based on new data from the updated Vorontsov-Velyaminov catalog
of interacting galaxies and modern estimates of the masses of supermassive black holes. A sample of interacting galaxies with
known black-hole masses is created, and the dependence of the masses of the central black holes on the absolute B magnitudes and central stellar velocity dispersions in the host galaxy derived for this sample. A statistical analysis of
the sample shows that the black-hole masses in interacting galaxies satisfy the same mass-velocity dispersion relation as
non-interacting galaxies. A higher mass dispersion is characteristic of merging pairs than for galaxies that interact in other
ways. The maximum masses of the central black holes are observed in radio galaxies. 相似文献
10.
A complete sample of 104 bright active galactic nuclei (AGNs) from the “Planck” catalog (early results) were observed at 36.8 GHz with the 22-m radio telescope of the Crimean Astrophysical Observatory (CrAO).Variability indices of the sources at this frequency were determined based on data from theWMAP space observatory, theMetsa¨ hovi RadioObservatory (Finland), and the CrimeanAstrophysical Observatory. New observational results confirm that the variability of these AGNs is stronger in the millimeter than at other radio wavelengths. The variability indices probably change as a result of the systematic decrease in the AGN flux densities in the transition to the infrared. Some radio sources demonstrate significant flux-density variations, including decreases, which sometimes cause them to fall out of the analysed sample. The change of the variability index in the millimeter is consistent with the suggestion that this variability is due to intrinsic processes in binary supermassive black holes at an evolutionary stage close to coalescence. All 104 of the sources studied are well known objects that are included in various radio catalogs and have flux densities exceeding 1 Jy at 36.8 GHz. 相似文献
11.
A. E. Volvach L. N. Volvach M. G. Larionov H. D. Aller M. F. Aller 《Astronomy Reports》2007,51(6):450-459
Variations in the radio flux of 3C 454.3 on various time scales from decades to a year are analyzed using long-term monitoring data at five frequencies from 4.8 to 36.8 GHz obtained at the University of Michigan Radio Astronomy Observatory and the Crimean Astrophysical Observatory. A spectral analysis of the light curves at the various frequencies reveals the presence of five periodic components. The long-and short-period components of the variability are compared using models for the precessional and orbital periods for motion in the system. The parameters for the supposed binary black-hole system are determined: the dimensions of the orbit and masses of the central black holes. The dynamics of the powerful flare in 2005–2006 are examined, and the time delays for its development from the optical to the radio and between radio frequencies are determined. The different frequency spectra of different individual flares can be explained in a model with a moving, expanding cloud that is first optically thick, then becomes optically thin at successively lower frequencies as it expands. 相似文献
12.
A. E. Vol’vach A. M. Kutkin M. G. Larionov L. N. Vol’vach A. Lahteenmaki M. Tornikoski J. Tammi J. Léon-Tavares E. Järvelä M. F. Aller H. D. Aller 《Astronomy Reports》2013,57(1):46-51
We present an analysis of data from multi-frequency monitoring of the blazar 3C 454.3 in 2010–2012, when the source experienced an unusually prolonged flare with a duration of about two years. This corresponds to the orbital period of the companion in a scenario in which two supermassive black holes are present in the nucleus of 3C 454.3. The flare’s shape, duration, and amplitude can be explained as a result of precession, if the plane of the accretion disk and the orbital plane of the binary are coincident. We detected small-scale structure of the flare, on time scales of no more than a month. These features probably correspond to inhomogeneities in the accretion disk and surrounding regions, with sizes of the order of 1015 cm. We estimated the size of the accretion disk based on the dynamical and geometrical parameters of this binary system: its diameter is comparable to the size of the orbit of the supermassive binary black hole, and its thickness does not exceed the gravitational radius of the central black hole. The presence of characteristic small-scale features during the flare makes it possible to estimate the relative time delays of variations in different spectral ranges: from gamma-ray to millimeter wavelengths. 相似文献
13.
A. A. Kisselev Yu. N. Gnedin E. A. Grosheva N. A. Shakht D. L. Gorshanov M. Yu. Piotrovich 《Astronomy Reports》2007,51(2):100-108
We have used two astrometric methods developed at the Main Astronomical Observatory of the Russian Academy of Sciences—the method of apparent-motion parameters (AMP) and a direct geometrical method (DGM)—to derive the orbit of the star S2 around the Galactic center, and thereby the mass of the supermassive black hole at the Galactic center. The AMP method, which is based on measurements of the curvature of a fairly short orbital arc, is efficient if observational data on the relative radial velocity are available. The mass of the supermassive black hole was also estimated using astrophysical methods, based on the empirical relation between the masses of the supermassive black holes at the centers of galaxies and quasars and the radio and X-ray luminosities of these regions. We estimate the magnetic-field strength near the event horizon of the supermassive black hole at the Galactic center using a synchrotron self-absorption model. 相似文献
14.
This is the first paper in a project aimed at analyzing relations between the masses of supermassive black holes or nuclear
clusters in galaxies and the kinematic features of the host galaxies. We present long-slit spectroscopic observations of galaxies
obtained on the 6-m telescope of the Special Astrophysical Observatory using the SCORPIO focal reducer. Radial profiles of
the line-of-sight velocities and velocity dispersions of the stellar populations were obtained for seven galaxies with known
masses of their supermassive black holes (Mkn 79, Mkn 279, NGC 2787, NGC 3245, NGC 3516, NGC 7457, and NGC 7469), and also
for one galaxy with a nuclear cluster (NGC 428). Velocity profiles of the emitting gas were obtained for some of these galaxies
as well. We present preliminary galactic rotation curves derived from these data. 相似文献
15.
A. E. Volvach V. S. Bychkova M. G. Larionov N. S. Kardashev L. N. Volvach V. V. Vlasyuk O. I. Spiridonova A. Lähteenmäki M. Tornikoski M. F. Aller H. D. Aller G. Pooley L. Carrasco A. Porras E. Recillas 《Astronomy Reports》2016,60(12):1035-1045
Data from long-term multi-frequency monitoring are used to analyze variations in the flux density of the active galactic nucleus S4 0954+658. These data were obtained at the CrimeanAstrophysical Observatory, the Metsähovi Radio Observatory of Aalto University, the University of Michigan Radio Astronomy Observatory, the Cavendish Laboratory of Cambridge University, the Special Astrophysical Observatory, and the National Institute of Astrophysics, Optics, and Electronics; 0.1–300-GeV data from the Fermi space gamma-ray observatory were also used. Radio data at 4.8, 8, 14.5, 15, 22.2, and 36.8 GHz are considered together with optical and near-infrared data in the R, J, H, and K filters. 相似文献
16.
We present the results of monitoring of the integrated fluxes of variable extragalactic sources at 4.8 and 8.6 GHz at the Svetloe Radio Astronomy Observatory (Institute of Applied Astronomy, Russian Academy of Sciences) from 1999 up to the present. More than 1000 observations of 36 sources have been carried out over this monitoring interval. We describe some of the most interesting flares detected in a number of sources, including the well-known objects 0851+202, 3C 345, and BL Lac. Even observations of variability at two frequencies can be very useful for planning astrophysical and astrometric observations. We briefly discuss the possibility of enhancing the effectiveness of the monitoring by expanding the range of frequencies to 22 GHz and adding polarization observations. 相似文献
17.
V. S. Beskin 《Astronomy Reports》2011,55(7):660-664
We present a brief account of lectures presented at the nuclear astrophysics school that took place on June 5–16, 2010 at
the Pushchino Radio Astronomy Observatory of the Astro Space Center of the Lebedev Physical Institute (Russian Academy of
Sciences). 相似文献
18.
Yu. N. Gnedin V. L. Afanasiev N. V. Borisov M. Yu. Piotrovich T. M. Natsvlishvili S. D. Buliga 《Astronomy Reports》2012,56(8):573-577
Strong constraints are obtained for the spins of supermassive black holes in a number of Active Galactic Nuclei. These estimates are based on spectropolarimetric data, obtained mainly on the 6-m telescope of the Special Astrophysical Observatory, as well as data on the kinetic power of relativistic jets. The magnetic fields at the innermost stable Keplerian orbit in the accretion disk and at the event horizon of the supermassive black hole are estimated. These data are used to place strong constraints on the spins of supermassive black holes in Active Galactic Nuclei. 相似文献
19.
We present the observations of the H2O maser in S140 with the 22-m radio telescope of the Pushchino Radio Astronomy Observatory in 1992–1999. The H2O maser emission is mainly concentrated in three symmetrically placed narrow radial-velocity intervals. In contrast to our earlier observations (1981–1991), we did not detect emission simultaneously in all three intervals; instead, the emission appeared successively in each. We discuss possible origins for this behavior. To explain the flux variability and radial-velocity drift of the main components, we propose a model with Keplerian orbital motion of clumps (protoplanets) and calculate their orbital parameters. 相似文献
20.
Yu. I. Neshpor N. N. Chalenko A. A. Stepanian O. R. Kalekin N. A. Jogolev V. P. Fomin V. G. Shitov 《Astronomy Reports》2001,45(4):249-254
The active galactic nucleus BL Lac was observed with the GT-48 atmospheric Cherenkov detector of the Crimean Astrophysical Observatory from July 23–September 1, 1998, in order to search for ultrahighenergy gamma-ray (>1 TeV) emission. The object was in the field of view of the detector for more than 24 hours. The source was detected with a high level of confidence (7.2 σ) with a flux equal to (2.1±0.4)×10?11 photons cm?2 s?1. 相似文献