Related papers: Accretion disc variability in the hard state of bl…

(Abridged) Recent XMM-Newton studies of X-ray variability in the hard states of black hole X-ray binaries (BHXRBs) imply that the variability is generated in the 'standard' optically-thick accretion disc. The variability originates in the…

We report on the analysis of hard-state power spectral density function (PSD) of GX 339-4 down to the soft X-ray band, where the disc significantly contributes to the total emission. At any luminosity probed, the disc in the hard state is…

We use the XMM-Newton EPIC-pn instrument in timing mode to extend spectral time-lag studies of hard state black hole X-ray binaries into the soft X-ray band. We show that variations of the disc blackbody emission substantially lead…

Black hole accretion flows show rapid X-ray variability. The Power Spectral Density (PSD) of this is typically fit by a phenomenological model of multiple Lorentzians for both the broad band noise and Quasi-Periodic Oscillations (QPOs). Our…

The power spectral density (PSD) of the X-ray emission variability from the accretion disc-corona region of black hole X-ray binaries and active galactic nuclei has a broken power law shape with a characteristic break time-scale. If the…

The properties of the aperiodic variability in X-ray binaries with black holes are considered. The power spectra of the luminosity variability for a flat accretion disk that is an emission source with a power-law energy spectrum have been…

X-ray variability of active galactic nuclei (AGN) and black hole binaries can be analysed by means of the power spectral density (PSD). The break observed in the power spectrum defines a characteristic variability timescale of the accreting…

We analyze X-ray light curves of the blazar Mrk 421 obtained from the Soft X-ray Imaging Telescope and the Large Area X-Ray Proportional Counter instrument onboard the Indian space telescope $AstroSat$ and archival observations from…

After a careful analysis of the instrumental effects on the Poisson noise to demonstrate the feasibility of detailed stochastic variability studies with the Swift X-Ray Telescope (XRT), we analyze the variability of the black hole X-ray…

Black hole binary transients undergo dramatic evolution in their X-ray timing and spectral behaviour during outbursts. In recent years a paradigm has arisen in which "soft" X-ray states are associated with an inner disc radius at, or very…

Constraining the accretion flow geometry of black hole binaries in outburst is complicated by the inability of simplified multi-colour disc models to distinguish between changes in the inner disc radius and alterations to the emergent…

We report results obtained from a systematic analysis of X-ray lags in a sample of black hole X-ray binaries, with the aim of assessing the presence of reverberation lags and studying their evolution during outburst. We used XMM-Newton and…

We investigate the behaviour of the accretion discs in the outbursts of the low-mass black-hole X-ray binaries (BHXRB), an overview of which we have presented previously. Almost all of the systems in which there are sufficient observations…

We use global magnetohydrodynamic simulations, in a pseudo-Newtonian potential, to investigate the temporal variability of accretion discs around Schwarzschild black holes. We use the vertically-averaged magnetic stress in the simulated…

The high state of black hole candidates is characterized by a quasi- thermal emission component at $kT \sim 1$ keV. In addition, this state tends to have very low variability which indicates that it is relatively stable, at least on {\it…

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…

Variable features in black hole X-ray Binaries (BH-XRBs) are observed in different energy ranges and time scales. The physical origin of different spectral states in BH-XRBs and their relations with the underlying accretion disc are still…

Two component X-ray spectra (soft multicolor black body plus harder power law) are frequently observed from accreting black holes. These components are presumably associated with the different parts of the accretion flow (optically thick…

During the outbursts of black hole X-ray binaries (BHXRBs), their accretion flows transition through several states. The source luminosity rises in the hard state, dominated by non-thermal emission, before transitioning to the…

We study the outbursts of the black hole X-ray binaries MAXI J1659-152, SWIFT J1753.5--0127 and GX 339-4 with the Swift X-ray Telescope. The bandpass of the X-ray Telescope has access to emission from both components of the accretion flow:…