abridged Extending the work of Czerny et al. (2004), we model the fractional variability amplitude due to distributions of hot spots co-orbiting on the accretion disk around a supermassive black ...hole. From defined radial distributions, our code samples random positions for the hot spots across the disk. The local spot emission is computed as reprocessed radiation coming from a compact primary source above the disk. The structure of the hot spot and the anisotropy of the re-emission are taken into account. We compute the fractional variability spectra expected from such spot ensembles and investigate dependencies on the parameters describing the radial spot distribution. We consider the fractional variability F_var with respect to the spectral mean and also the so-called point-to-point F_pp. Our method includes relativistic corrections for the curved space-time; the black hole angular momentum is a free parameter and subject to the fitting procedure. We confirm that the rms-variability spectra involve intrinsic randomness at a significant level when the number of flares appearing during the total observation time is too small. Furthermore, F_var is not always compatible with F_pp. For MCG -6-30-15, we can reproduce the short-timescale variability and model the suppressed variability in the energy range of the Kalpha line without any need to postulate reprocessing farther away from the center. An increasing rate of energy production by the flares toward the center of the disk, a fast rotation of the central black hole, and considerable suppression of the primary flare emission are required. The modeled line remains consistent with the measured equivalent width of the iron Kalpha line complex.
The authors investigate the transformation of the plasma oscillations excited by an electron beam into EMR during the nonlinear interaction of HF plasma with LF ion-sound waves in the magnetized ...plasma waveguide.
We discuss a model of X-ray variability of active galactic nuclei (AGN). We consider multiple spots which originate on the surface of an accretion disk following intense irradiation by coronal ...flares. The spots move with the disk around the central black hole and eventually decay while new spots continuously emerge. We construct time sequences of the spectra of the spotted disk and compute the corresponding energy-dependent fractional variability amplitude. We explore the dependence on the disk inclination and other model parameters. AGN seen at higher inclination with respect to the observer, such as Seyfert 2 galaxies, are expected to have fractional variability amplitude of the direct emission by a factor of a few higher than objects seen face on, such as the Seyfert 1s.
We have explored the ideas that parametric resonance affects nearly geodesic motion around a black hole or a neutron star, and that it may be relevant to the high frequency (twin) quasi-periodic ...oscillations occurring in some low-mass X-ray binaries. We have assumed the particles or fluid elements of an accretion disc to be subject to an isotropic perturbation of a hypothetical but rather general form. We find that the parametric resonance is indeed excited close to the radius where epicyclic frequencies of radial and meridional oscillations are in a 2:3 ratio. The location and frequencies of the highest amplitude excitation vary with the strength of the perturbation. These results agree with actual frequency ratios of twin kHz QPOs that have been reported in some black hole candidates, and they may be consistent also with correlation of the twin peaks in Sco X-1.
Astron.Astrophys. 272 (1993) 400-406 The Seyfert galaxy NGC 6814 is known to show periodic variation of its X-ray
luminosity. We found that the sequences of peaks (variability patterns) in the
folded ...X-ray light curves constructed from the {\it Exosat} and {\it Ginga}
data are remarkably similar when one ignores amplitudes of the peaks and
considers only their phases. The stable pattern consists of five peaks which
are present in the both curves. The phases of the corresponding peaks coincide
with an accuracy of about 10 degrees. The probability that this coincidence
occurs by chance is less than about 1\% according to the most conservative
estimate. The observed stable pattern of peaks may be produced by a stable
distribution of ``bright spots'' on the accretion disk surface, {\it e.g.} by
strong vortices or magnetic flux tubes.
One of the principle purposes is the research of the most effective method of extraction of energy of the oscillations excited by an electron beam from plasma into the outer space or high frequency ...(HF) tracks. The most attractive solution of this problem, is presented with hybrid plasma waveguides that combine advantages of the both plasma waveguides and the standard slow wave structures.
The Seyfert galaxy NGC 6814 is known to show periodic variation of its X-ray luminosity. We found that the sequences of peaks (variability patterns) in the folded X-ray light curves constructed from ...the {\it Exosat} and {\it Ginga} data are remarkably similar when one ignores amplitudes of the peaks and considers only their phases. The stable pattern consists of five peaks which are present in the both curves. The phases of the corresponding peaks coincide with an accuracy of about 10 degrees. The probability that this coincidence occurs by chance is less than about 1\% according to the most conservative estimate. The observed stable pattern of peaks may be produced by a stable distribution of ``bright spots'' on the accretion disk surface, {\it e.g.} by strong vortices or magnetic flux tubes.
The tasks of increase of the HF power under excitation and the microwave energy extraction into the outer space are the key problems of microwave electronics. In order to solve them, the authors ...proposed the application of hybrid plasma waveguides. The hybrid plasma waveguide is the slow-wave structure with its passage channel filled with plasma. (HPSWS). In such a waveguide, the principal advantages of plasma electronics characteristics are realizable.
It is shown that the distribution function of secondary electrons of ion-induced emission from frond and back surfaces of thin Ag, Cu, Ni foils can be approximated by the power-law function with ...different power indices in the corresponding energy ranges. The increases of ion energy losses caused the power index to growth in the first energy interval, while in the second energy interval the power index showed the trend to decrease.
