Monte Carlo simulations of global Compton cooling in inner regions of hot accretion flows (2009)
Xie, Fu-Guo, Niedzwiecki, Andrzej, Zdziarski, Andrzej A., Yuan, Feng
Hot accretion flows such as advection-dominated accretion flows are generally optically thin in the radial direction. Thus photons generated at some radii can cool or heat electrons at other radii...
Orbital and superorbital variability and their coupling in X-ray binaries (2008)
Zdziarski, Andrzej A., Poutanen, Juri, Ibragimov, Askar, Gierlinski, Marek, Wen, Linqing
We review X-ray flux modulation from X-ray binaries on time scales corresponding to the orbital period and those at longer time scales (so called superorbital). Those modulations provide a powerful...
Poutanen, Juri, Zdziarski, Andrzej A., Ibragimov, Askar
We discover a pronounced dependence of the strength of the X-ray orbital modulation and the hardness in Cyg X-1 in the hard state on its superorbital phase. Our results can be well modelled as a...
Seyferts and Radio Galaxies (2007)
Neil Johnson Andrzej, W. Neil Johnson, Andrzej A. Zdziarski, Greg M. Madejski, William S. Paciesas, Ying-chi Lin
. Observations with Compton Gamma Ray Observatory have provided key insights to the high energy emission mechanisms in Active Galactic Nuclei (AGN) and clearly separate them into a class of Blazars,...
Fl-Ray Spectra, Andrzej A. Zdziarski, David Smith, Greg M. Madejski, W. Neil Johnson
We study X-ray and soft fl-ray spectral properties of nearby Broad-Line Radio Galaxies (BLRGs) using data from Ginga, ASCA, OSSE and EXOSAT. The X-ray spectra are well fitted by an intrinsic...
Dependence of the orbital modulation of X-rays from 4U 1820-303 on the accretion rate (2007)
Zdziarski, Andrzej A., Gierlinski, Marek, Wen, Linqing, Kostrzewa, Zuzanna
We report the discovery, using RXTE data, of a dependence of the X-ray orbital modulation depth on the X-ray spectral state in the ultracompact atoll binary \source. This state (measured by us by the...
The superorbital variability and triple nature of the X-ray source 4U 1820-303 (2007)
Zdziarski, Andrzej A., Gierlinski, Marek, Wen, Linqing
We perform a comprehensive analysis of the superorbital modulation in the ultracompact X-ray source 4U 1820-303, consisting of a white dwarf accreting onto a neutron star. Based on RXTE data, we...
Fiocchi, Mariateresa, Bazzano, Angela, Ubertini, Pietro, Zdziarski, Andrzej A.
We present data from INTEGRAL and BeppoSAX satellites showing spectral state transitions of the neutron-star, atoll-type, low-mass X-ray binary 1705-44. Its energy spectrum can be described as the...
Tarana, Antonella, Bazzano, Angela, Ubertini, Pietro, Zdziarski, Andrzej A.
We study the 4-200 keV spectral and temporal behaviour of the low mass X-ray binary 4U 1820-30 with INTEGRAL during 2003-2005. This source as been observed in both the soft (banana) and hard (island)...
Modeling the hard states of XTE J1550--564 during its 2000 outburst (2006)
Yuan, Feng, Zdziarski, Andrzej A., Xue, Yongquan, Wu, Xue-Bing
We study hard states of the black-hole binary XTE J1550--564 during its 2000 outburst. In order to explain those states at their highest luminosities, $L\sim 10%$ of the Eddington luminosity, $L_{\rm...
Periodic long-term X-ray and radio variability of Cygnus X-1 (2005)
Lachowicz, Pawel, Zdziarski, Andrzej A., Schwarzenberg-Czerny, Alex, Pooley, Guy G., Kitamoto, Shunji
We present a comprehensive analysis of long-term periodic variability of Cyg X-1 using the method of multiharmonic analysis of variance (mhAoV) applied to available monitoring data since 1969, in...
Bulk motion Comptonization in black-hole accretion flows (2005)
Niedzwiecki, Andrzej, Zdziarski, Andrzej A.
We study spectra generated by Comptonization of soft photons by cold electrons radially free-falling onto a black hole. We use a Monte Carlo method involving a fully relativistic description of...
Patterns of energy-dependent variability from Comptonization (2005)
Gierlinski, Marek, Zdziarski, Andrzej A.
We study fractional variability as a function of energy from black-hole X-ray binaries on timescales from milliseconds to hundreds of seconds. We build a theoretical model of energy-dependent...
Energy-dependent variability from accretion flows (2005)
We develop a formalism to calculate energy-dependent fractional variability (rms) in accretion flows. We consider rms spectra resulting from radial dependencies of the level of local variability (as...
GRS 1915+105: the distance, radiative processes and energy-dependent variability (2005)
Zdziarski, Andrzej A., Gierlinski, Marek, Rao, A. R., Vadawale, S. V., Mikolajewska, Joanna
We present an exhaustive analysis of five broad-band observations of GRS 1915+105 in two variability states, chi and omega, observed simultaneously by the PCA, HEXTE and OSSE. We find all the spectra...
Broad-band spectra of Cyg X-1 and correlations between spectral characteristics (2005)
Ibragimov, Askar, Poutanen, Juri, Gilfanov, Marat, Zdziarski, Andrzej A., Shrader, Chris R.
We present the results of spectral analysis of 42 simultaneous broad-band Ginga--OSSE and RXTE--OSSE observations of Cyg X-1 carried out in 1991 and 1996--1999. The hardest spectra in our sample in...
Radiative Processes, Spectral States and Variability of Black-Hole Binaries (2004)
Zdziarski, Andrzej A., Gierlinski, Marek
We review radiative processes responsible for X-ray emission in hard (low) and soft (high) spectral states of black-hole binaries. The main process in the hard state appears to be scattering of...
GX 339-4: the distance, state transitions, hysteresis and spectral correlations (2004)
Zdziarski, Andrzej A., Gierlinski, Marek, Mikolajewska, Joanna, Wardzinski, Grzegorz, Smith, David M., Harmon, B. Alan, ...
We study X-ray and variability and distance of GX 339-4. We derive d>7 kpc, based on recent determination of the binary parameters. We study data from the Ginga/ASM, the CGRO/BATSE, and the RXTE/ASM,...
Yuan, Feng, Zdziarski, Andrzej A.
We investigate accretion disc models for the X-ray emission of Seyfert-1 galaxies and the hard state of black-hole X-ray binaries. We concentrate on two hot accretion disc models: advection-dominated...
Discovery of powerful millisecond flares from Cygnus X-1 (2003)
Gierlinski, Marek, Zdziarski, Andrzej A.
We have found a large number of very strong flares in the available XTE PCA data of Cyg X-1 (also seen in available HEXTE and BATSE data) with 13 flares satisfying our chosen threshold criterion,...
Correlations between X-ray and radio spectral properties of accreting black holes (2002)
Zdziarski, Andrzej A., Lubinski, Piotr, Gilfanov, Marat, Revnivtsev, Mike
We study correlations betwen X-ray spectral index, strength of Compton reflection, and X-ray and radio fluxes in accreting black holes (Seyferts and black-hole binaries). We critically evaluate the...
Radiative Processes in Microquasars (2002)
Poutanen, Juri, Zdziarski, Andrzej A.
Recent advances in the X-ray and soft gamma-ray observations of accreting black holes and microquasars, in particular, are reviewed. The radiative processes responsible for the emission are discussed...
X-ray and gamma-ray spectra and variability of the black-hole candidate GX 339-4 (2002)
Wardzinski, Grzegorz, Zdziarski, Andrzej A., Gierlinski, Marek, Grove, J. Eric, Jahoda, Keith, Johnson, W. Neil
We analyse five observations of the X-ray binary GX 339-4 by the soft gamma-ray OSSE detector on board CGRO simultaneous with either Ginga or RXTE observations. The source was bright during four of...
A Chandra Observation of the Luminous NLS1 1H 0707-495 (2002)
Leighly, Karen M., Zdziarski, Andrzej A., Kawaguchi, Toshihiro, Matsumoto, Chiho
We present preliminary results from a long Chandra HETG observation of the luminous Narrow-line Seyfert 1 galaxy 1H 0707-495. We find a complex X-ray spectrum comprised of a two-component continuum...
Zdziarski, Andrzej A., Poutanen, Juri, Paciesas, William S., Wen, Linqing
We present an analysis of all observations of Cygnus X-1 by the BATSE (20-300 keV) and by ASM (1.5-12 keV) until 2002 June, including 1200 days of simultaneous data. We find a number of correlations...
NGC 4151: an intrinsically average Seyfert 1 (2001)
Zdziarski, Andrzej A., Leighly, Karen M., Matsuoka, Masaru, Cappi, Massimo, Mihara, Tatehiro
We present a detailed analysis of a long, 100 ksec, observation of NGC 4151 by ASCA, contemporaneous with an observation by the CGRO/OSSE. We fit the data with physical models including an Fe K line...
OSSE and RXTE Observations of GRS 1915+105: Evidence for Non-thermal Comptonization (2001)
Zdziarski, Andrzej A., Grove, J. Eric, Poutanen, Juri, Rao, A. R., Vadawale, S. V.
GRS 1915+105 was observed by the CGRO/OSSE 9 times in 1995-2000, and 8 of those observations were simultaneous with those by RXTE. We present an analysis of all of the OSSE data and of two RXTE-OSSE...
Wardzinski, Grzegorz, Zdziarski, Andrzej A.
We investigate how the presence of a non-thermal tail beyond a Maxwellian electron distribution affects the synchrotron process as well as Comptonization in plasmas with parameters typical for...
Observations of Seyferts by OSSE and parameters of their X-ray/gamma-ray sources (2000)
Zdziarski, Andrzej A., Poutanen, Juri, Johnson, W. Neil
We present a summary of spectra of Seyfert galaxies observed by the OSSE detector aboard Compton Gamma Ray Observatory. We obtain average spectra of Seyferts of type 1 and 2, and find they are well...
Radiative Processes and Geometry of Spectral States of Black-Hole Binaries (2000)
I review radiative processes responsible for X-ray emission in the hard (low) and soft (high) spectral states of black-hole binaries. The main process in the hard state appears to be thermal...
Thermal synchrotron radiation and its Comptonization in compact X-ray sources (1999)
Wardzinski, Grzegorz, Zdziarski, Andrzej A.
We investigate thermal synchrotron radiation at semi-relativistic and relativistic temperatures. We find an analytic expression for the angle-averaged emission coefficient, and show that it is...
X-rays and soft gamma-rays from Seyferts, radio galaxies, and black-hole binaries (1998)
Selected topics dealing with X-ray/soft gamma-ray emission from accreting black-hole sources are reviewed. The shape of soft gamma-ray spectra of Seyferts observed by OSSE can be well modelled by...
Accretion disk in Cyg X-1 in the soft state (1998)
Gierlinski, Marek, Zdziarski, Andrzej A.
We analyze the simultaneous ASCA/RXTE observation of Cyg X-1 in the soft state on 1996 May 30. We apply a multi-color disk model with a torque-free boundary condition in the pseudo-Newtonian...
Zdziarski, Andrzej A., Poutanen, Juri, Mikolajewska, Joanna, Gierlinski, Marek, Ebisawa, Ken, Johnson, W. Neil
We present X-ray/gamma-ray spectra of the binary GX 339-4 observed in the hard state simultaneously by Ginga and CGRO OSSE during an outburst in 1991 September. The Ginga spectra are well represented...
X-ray and soft gamma-ray spectra of Broad-Line Radio Galaxies (1998)
Wozniak, Przemyslaw R., Zdziarski, Andrzej A., Smith, David, Madejski, Greg M., Johnson, W. Neil
We study X-ray and soft gamma-ray spectral properties of BLRGs using data from Ginga, ASCA, OSSE and EXOSAT. The X-ray spectra are well fitted by an intrinsic power-law continuum with an energy index...
Hot accretion discs with thermal Comptonisation and advection in luminous black hole sources (1998)
We solve for the structure of a hot accretion disc with unsaturated thermal Comptonisation of soft photons and with advection, generalizing the classical model of Shapiro et al. The upper limit on...
Thermal/non-thermal model of Cyg X-1 in the soft state (1997)
Gierlinski, Marek, Zdziarski, Andrzej A., Coppi, Paolo S., Poutanen, Juri, Ebisawa, Ken, Johnson, W. N.
We analyze X-ray/gamma-ray observations of Cyg X-1 in the soft state. We find the hybrid thermal/non-thermal model fits the data very well. The significant contribution from the non-thermal electrons...
X-ray and gamma-ray spectra of Cyg X-1 in the soft state (1997)
Gierlinski, Marek, Zdziarski, Andrzej A., Dotani, Tadayasu, Ebisawa, Ken, Jahoda, Keith, Johnson, W. Neil
We present X-ray/gamma-ray observations of Cyg X-1 in the soft state during 1996 May-June. We analyze ASCA, RXTE and OSSE data. The spectrum consists of soft X-ray blackbody emission of an optically...
Thermal conduction in accretion disk coronae (1997)
Maciolek-Niedzwiecki, Andrzej, Krolik, Julian H., Zdziarski, Andrzej A.
We study the effects of thermal conduction in a hot, active corona above an accretion disk. We assume that all of the dissipative heating takes place in the corona. We find that the importance of...
X-rays and gamma-rays from accretion flows onto black holes in Seyferts and X-ray binaries (1996)
Zdziarski, Andrzej A., Johnson, W. Neil, Poutanen, Juri, Magdziarz, Pawel, Gierlinski, Marek
We review observations and theoretical models of X-ray/gamma-ray spectra of radio-quiet Seyfert galaxies and of Galactic black-hole candidates (in the hard spectral state). The observed spectra share...
Simultaneous X-ray and gamma-ray observations of Cyg X-1 in the hard state by Ginga and OSSE (1996)
Gierlinski, Marek, Zdziarski, Andrzej A., Done, Chris, Johnson, W. Neil, Ebisawa, Ken, Ueda, Yoshihiro, ...
We present four X-ray/gamma-ray spectra of Cyg X-1 observed in the hard ('low') state simultaneously by Ginga and GRO/OSSE on 1991 July 6. The 3-30 keV Ginga spectra are well represented by power...
The first simultaneous X-ray/gamma-ray observations of Cyg X-1 by Ginga and OSSE (1995)
Gierlinski, Marek, Zdziarski, Andrzej A., Johnson, W. Neil, Phlips, Bernard F., Ebisawa, Ken, Done, Chris
We present the results of 4 simultaneous observations of Cygnus X-1 by Ginga and OSSE. The X-ray/gamma-ray spectra can be described by an intrinsic continuum and a component due to Compton reflection...