Related papers: Black Hole Accretion in Transient X-Ray Binaries
X-rays are a critical wavelength for understanding supermassive black holes (SMBHs). X-rays probe the inner accretion flow, closest to the event horizon, where gas inspirals, releasing energy and driving black hole growth. This region also…
Studies of the observed characteristics of black-hole (BH) X-ray binaries can be provide us with valuable information about the process of BH formation. In this paper I address some of the aspects of our current understanding of BH…
The radiative mechanism of the black hole X-ray transients (BHXTs) in their quiescent states (defined as the 2-10 keV X-ray luminosity $\le 10^{34}{\rm \,erg\,s^{-1}}$) remains unclear. In this work, we investigate the quasi-simultaneous…
Our X-ray study of the nuclear activity in a new sample of six quiescent early-type galaxies, and in a larger sample from the literature, confirmed (Soria et al., Paper I) that the Bondi accretion rate of diffuse hot gas is not a good…
We present X-ray properties of optically-selected intermediate-mass (~10^5--10^6 M_Sun) black holes (BHs) in active galaxies (AGNs), using data from the Chandra X-Ray Observatory. Our observations are a continuation of a pilot study by…
We have compiled and analysed reports from the literature of (quasi-)simultaneous observations of X-ray transients at radio and X-ray wavelengths and compared them with each other and with more unusual radio-bright sources such as Cygnus…
We have studied the nuclear activity in a sample of six quiescent early-type galaxies, with new Chandra data and archival HST optical images. Their nuclear sources have X-ray luminosities ~ 10^{38} - 10^{39} erg/s (L_X/L_Edd ~ 10^{-8} -…
Hard X-ray emission is ubiquitous in accreting black holes, both in Galactic binary systems and in Active Galactic Nuclei. I review the different spectra which can be seen from these systems, and possible ways of producing this emission.…
We present a new picture for the central regions of Black Hole X-ray Binaries. In our view, these central regions have a multi-flow configuration which consists in (1) an outer standard accretion disc down to a transition radius r_J, (2) an…
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…
Low-mass X-ray binaries (LMXBs) are systems in which a low-mass companion transfers mass via Roche-lobe overflow onto a black hole (BH) or a weakly magnetized neutron star (NS). It is believed that both the solid surface and the magnetic…
We report the discovery of hysteresis between the x-ray spectrum and luminosity of black-hole binary LMC X-3. Our observations, with the Proportional Counter Array on the Rossi X-ray Timing Explorer, took place entirely within the soft…
This is a general review on the observations and physics of black hole X-ray binaries and microquasars, with the emphasize on recent developments in the high energy regime. The focus is put on understanding the accretion flows and measuring…
Among the sample of Galactic transient X-ray binaries (SXTs) discovered to date, about 70 have been proposed as likely candidates to host a black hole. Yet, only 19 have been dynamically confirmed. Such a reliable confirmation requires…
This dissertation is written as an annotated collection of selected articles. The dissertation focuses on the modelling of accretion disks in X-ray binaries with a black hole or neutron star. The main objective is to use advanced numerical…
In the canonical understanding of transient X-ray sources the accretion during quiescence occurs via a geometrically thin disk in the outer part and via an advection-dominated hot coronal flow/ADAF in the inner part. The inner part…
A fundamental difference between a neutron star (NS) and a black hole (BH) is the absence of a physical surface in the latter. For this reason, any remaining kinetic energy of the matter accreting onto a BH is advected inside its event…
We present a new method to derive binary inclinations in quiescent black hole (BH) X-ray transients (XRTs), based on the depth of the trough (T) from double-peaked Ha emission profiles arising in accretion discs. We find that the…
Supergiant Fast X-ray Transients (SFXTs) represent the most extreme case of X-ray variability in High Mass X-ray Binaries hosting blue supergiant companions. Mainly discovered thanks to the INTEGRAL monitoring of the Galactic plane, these…
Before the launch of the Rossi X-ray Timing Explorer (RXTE) satellite, the differences in the rapid X-ray variability between the two main types of neutron star binaries (i.e., the Z and atoll sources) could be explained by invoking…