相关论文: Modeling of High-Frequency Variability in X-ray Bi…
We examine in detail several aspects of the physics of accretion disks of possible relevance to the outburst mechanism of the black hole X-ray transients. We adopt the one dimensional, time dependent model described in detail by Cannizzo,…
This thesis investigates phenomena occurring in black-hole accretion discs which are likely to induce high-frequency quasi-periodic variability. Two classes of pseudo-relativistic theoretical models are studied. The first is based on the…
We study Compton upscattering of low-frequency photons in a converging flow of thermal plasma. The photons escape diffusively and electron scattering is the dominant source of opacity. We solve numerically and approximately analytically the…
Black hole X-ray binaries in their hard and hard-intermediate states display hard and soft time lags between broadband noise variations (high-energy emission lagging low-energy and vice versa), which could be used to constrain the geometry…
The nature and geometry of the accretion flow in the low/hard state of black hole binaries is currently controversial. While most properties are generally explained in the truncated disc/hot inner flow model, the detection of a broad…
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 variability in which the X-ray energy spectrum…
We analyzed the power density spectra of a sample of 9 neutron star and 9 black hole binaries in the low/hard spectral state. In the power density spectra of accreting neutron stars with a weak magnetic field a significant power is…
A jet model for Galactic black-hole X-ray binaries will be presented that appears to explain several observational characteristics. In particular, it explains the energy spectrum from radio to hard X-rays, the time-lags as a function of…
RXTE/PCA observations of several black hole X-ray binaries in the low spectral state revealed a tight correlation between spectral parameters and characteristic frequencies of variability of X-ray flux. In particular, the amplitude of…
Quasars emission is highly variable, and this variability gives us clues to understand the accretion process onto supermassive black holes. We can expect variability properties to correlate with the main physical properties of the accreting…
Understanding the dynamics behind black hole state transitions and the changes they reflect in outbursts has become long-standing problem. The X-ray reflection spectrum describes the interaction between the hard X-ray source (the power-law…
We propose a physical model for the peaked noise in the X-ray power density spectra of accreting X-ray binaries. We interpret its appearance as an interference of two Comptonization continua: one coming from the up-scattering of seed…
The spectra of black hole binaries in the low/hard state are complex, with evidence for multiple different Comptonisation regions contributing to the hard X-rays in addition to a cool disc component. We show this explicitly for some of the…
At luminosities below a few percent of Eddington, accreting black holes switch to a hard spectral state which is very different from the soft blackbody-like spectral state that is found at higher luminosities. The hard state is…
We propose a new model of the steep power law state of luminous black hole X-ray binaries. The model uses the fact that at high luminosities, the inner radii of radiation pressure dominated accretion discs are expected to i) become…
A framework for the interpretation of the spectral states of black hole X-ray transients based on the diversity of accretion disk models is introduced. Depending on the mass accretion rate, it is proposed that the accretion disk is…
We review the properties of 40 X-ray binaries that contain either a confirmed black hole or a black hole candidate. After discussing briefly the significance of these Galactic black holes to both astronomy and physics, we present basic data…
Black hole binaries exhibit dramatic changes in their X-ray spectral and timing properties over time, providing important clues about the physical processes that occur in these systems. Black holes and black hole candidates are prime…
The observed variability of X-ray binaries over a wide range of time-scales can be understood in the framework of a stochastic propagation model, where viscous fluctuations at different radii induce accretion rate variability that propagate…
The possibility that some of the observed X-ray and optical variability in active galactic nuclei and galactic black hole candidates is produced in accretion disks through the development of a self-organized critical state is reconsidered.…