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Low angular momentum flow model of Sgr A* activity
B. Czerny, M. Moscibrodzka
Sgr A* is the closest massive black hole and can be observed with the highest angular resolution. Nevertheless, our current understanding of the accretion process in this source is…
Hot-spot model for accretion disc variability as random process
T. Pechacek, V. Karas, B. Czerny
Theory of random processes provides an attractive mathematical tool to describe the fluctuating signal from accreting sources, such as active galactic nuclei and Galactic black hol…
The nature of the intranight variability of radio-quiet quasars
B. Czerny, A. Siemiginowska, A. Janiuk +1
We select a sample of 10 radio-quiet quasars with confirmed intranight optical variability and with available X-ray data. We compare the variability properties and the broad band s…
High-frequency X-ray variability as a mass estimator of stellar and supermassive black holes
Marek Gierlinski, Marek Nikolajuk, Bozena Czerny
There is increasing evidence that supermassive black holes in active galactic nuclei (AGN) are scaled-up versions of Galactic black holes. We show that the amplitude of high-freque…
Low angular momentum accretion flow model of Sgr A* activity
B. Czerny, M. Moscibrodzka, D. Proga +2
Sgr A* is a source of strongly variable emission in several energy bands. It is generally agreed that this emission comes from the material surrounding the black hole which is eith…
Iron lines from transient and persisting hot spots on AGN accretion disks
R. W. Goosmann, M. Mouchet, B. Czerny +4
[abridged] We model the X-ray reprocessing from a strong co-rotating flare above an accretion disk in active galactic nuclei. We explore the horizontal structure and evolution of t…
Accretion of Low Angular Momentum Material onto Black Holes: Radiation Properties of Axisymmetric MHD Flows
Monika Moscibrodzka, Daniel Proga, Bozena Czerny +1
Numerical simulations of MHD accretion flows in the vicinity of a supermasssive black hole provide important insights to the problem of why and how systems -- such as the Galactic…
The Search for Primordial Black Holes Using Very Short Gamma Ray Bursts
D. B. Cline, C. Matthey, S. Otwinowski +2
We show the locations of the SWIFT short hard bursts (SHB) with afterglows on the galactic map and compare with the VSB BATSE events. As we have pointed out before, there is an exc…
Constraining global parameters of accreting black holes by modeling magnetic flares
R. W. Goosmann, M. Mouchet, M. Dovciak +3
We present modeling results for the reprocessed radiation expected from magnetic flares above AGN accretion disks. Relativistic corrections for the orbital motion of the flare and…
Accreting corona model of the X-ray variability in soft state X-ray binaries and active galactic nuclei
A. Janiuk, B. Czerny
We develop a two-flow model of accretion onto a black hole which incorporates the effect of the local magneto-rotational instability. The flow consists of an accretion disk and an…
Constraints on a strong X-ray flare in the Seyfert galaxy MCG-6-30-15
R. W. Goosmann, B. Czerny, V. Karas +3
We discuss implications of a strong flare event observed in the Seyfert galaxy MCG-6-30-15 assuming that the emission is due to localized magnetic reconnection. We conduct detailed…
Modeling time delays in the X-ray spectrum of the Seyfert galaxy MCG-6-30-15
R. W. Goosmann, B. Czerny, V. Karas +1
We propose a reflection model of the time delays detected during an exceptionally bright, single flare in MCG-6-30-15. We consider a scenario in which the delays of the hard X-rays…
Modeling the X-ray fractional variability spectrum of Active Galactic Nuclei using multiple flares
R. W. Goosmann, M. Dovciak, V. Karas +3
Using Monte-Carlo simulations of X-ray flare distributions across the accretion disk of active galactic nuclei (AGN), we obtain modeling results for the energy-dependent fractional…
Response of the warm absorber cloud to a variable nuclear flux in active galactic nuclei
L. Chevallier, B. Czerny, A. Rozanska +1
Recent modeling of the warm absorber in active galactic nuclei has proved the usefulness of constant total (gas plus radiation) pressure models, which are highly stratified in temp…
Extinction curves in AGN
B. Czerny
The presence of the dust in the circumnuclear region strongly affects our view of the nucleus itself. The effect is strong in type 2 objects but weaker effect is likely to be prese…
Black hole masses in NLS1 galaxies from the X-ray excess variance method
M. Nikolajuk, P. Gurynowicz, B. Czerny
We estimate black hole masses in Narrow Line Seyfert 1 (NLS1) galaxies at the basis of their X-ray excess variance. We apply the standard approach appropriate for Broad Line Seyfer…
Modeling the UBVRI time delays in Mrk 335
B. Czerny, A. Janiuk
We develop a model of time delays between the continuum bands in the Narrow Line Seyfert 1 galaxy Mrk 335 to explain the observed delays measured in this source. We consider two ge…
Magnetic flares in Active Galactic Nuclei: Modeling the iron Kalpha-line
R. W. Goosmann, B. Czerny, M. Mouchet +5
The X-ray spectra of Active Galactic Nuclei (AGN) are complex and vary rapidly in time as seen in recent observations. Magnetic flares above the accretion disk can account for the…
Comparison of VSB from BATSE, KONUS and Swift
D. B. Cline, C. Matthey, S. Otwinowski +2
We show the locations of the SWIFT short hard bursts (SHB) with afterglows on the Galactic map and compare with the very short bursts (VSB) BATSE events. As we have pointed out bef…
Wavelet analysis of MCG-6-30-15 and NGC 4051: a possible discovery of QPOs in 2:1 and 3:2 resonance
Pawel Lachowicz, Bozena Czerny, Marek A. Abramowicz
Following our previous work of Lachowicz & Czerny (2005), we explore further the application of the continuous wavelet transform to X-ray astronomical signals. Using the public arc…
Consistency of the black hole mass determination in AGN from the reverberation and the X-ray excess variance method
M. Nikolajuk, B. Czerny, J. Ziolkowski +1
Values of black hole masses are frequently determined with the help of the reverberation method. This method requires a specific geometrical factor related to the distribution of t…
The structure and X-ray radiation spectra of illuminated accretion disks in AGN. III. Modeling fractional variability
R. W. Goosmann, B. Czerny, M. Mouchet +5
[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 su…
The pattern of accretion flow onto Sgr A*
Monika Moscibrodzka, Tapas K. Das, Bozena Czerny
The material accreting onto Sgr A* most probably comes from the nearby stars. We analyze the pattern of this flow at distances of a fraction of a parsec and we argue that the net a…
The puzzle of the soft X-ray excess in AGN: absorption or reflection?
L. Chevallier, S. Collin, A. -M. Dumont +4
The 2-10 keV continuum of AGN is generally well represented by a single power law. However, at smaller energies the continuum displays an excess with respect to the extrapolation o…