Related papers: Black Hole and Neutron Star Transients in Quiescen…
The mass and radius of the neutron star (NS) in low-mass X-ray binaries can be obtained by fitting the X-ray spectrum of the NS in quiescence, and the mass and radius constrains the properties of dense matter in NS cores. A critical…
Recurring outbursts associated with matter flowing onto compact stellar remnants (black-holes, neutron stars, white dwarfs) in close binary systems, provide strong test beds for constraining the poorly understood accretion process. The…
Recently, it has been shown that soft-state black hole X-ray binaries and active galactic nuclei populate a plane in the space defined by the black hole mass, accretion rate and characteristic frequency. We show that this plane can be…
We report the discovery of a new hysteresis effect in black hole X-ray binary state transitions, that of the near-infrared (NIR) flux (which most likely originates in the jets) versus X-ray flux. We find, looking at existing data sets, that…
We consider a class of models for the redshift evolution (between $0\lsim z \lsim 4$) of the observed optical and X-ray quasar luminosity functions (LFs), with the following assumptions: (i) the mass-function of dark matter halos follows…
The accretion of the stellar wind material by a compact object represents the main mechanism powering the X-ray emission in classical supergiant high mass X-ray binaries and supergiant fast X-ray transients. In this work we present the…
I review observational data on X-ray energy spectra and variability of Seyfert 1 and Narrow Line Seyfert 1 galaxies, and compare them to black hole binary (BHB) systems. There seems to be greater similarity of time averaged properties (i.e.…
We consider ultraluminous X-ray sources (ULXs) where the accretor is a neutron star rather than a black hole. We show that the recently-discovered example (M82 X-2) fits naturally into the simple picture of ULXs as beamed X-ray sources fed…
We explore possible systematic errors in the mass measurements of stellar mass black holes. We find that significant errors can arise from the assumption of zero or constant emission from the accretion flow, which is commonly used when…
To date more than half a dozen X-ray dim isolated neutron stars are known. Their X-ray spectra are characterized by soft blackbody-like emission (kT about 50-120 eV) without indication for harder, non-thermal components. These stars…
The dynamical and radiative properties of the quiescent state (X-ray luminosity $<10^{34}\ {\rm erg s^{-1} cm^{-2}}$) of black hole X-ray transients (BHXTs) remains unclear, mainly because of low-luminosity and poor data quantity. We…
Recently, several accreting neutron stars (NSs) in X-ray binary systems inside supernova remnants have been discovered. They represent a puzzle for the standard magneto-rotational evolution of NSs, as their ages ($\lesssim 10^5$ years) are…
We compare all the available observational data on the redshift evolution of the total stellar mass and star formation rate density in the Universe with the mass and accretion rate density evolution of supermassive black holes, estimated…
This review summarizes the observational constraints on the mass spectrum of compact objects in X-ray binaries. We currently have 20 X-ray binaries with confirmed black holes, based on dynamical information (i.e. mass in excess of 3 Msun).…
High resolution X-ray spectra of accreting stellar mass Black Holes reveal the presence of accretion disc winds, traced by high ionisation Fe K lines. These winds appear to have an equatorial geometry and to be observed only during disc…
We present high time-resolution multicolour observations of the quiescent soft X-ray transient XTE J1118+480 obtained with ULTRACAM. Superimposed on the double-humped continuum g' and i'-band lightcurves are rapid flare events which…
We present models of the soft X-ray transients, A0620-00, V404 Cyg, and X-ray Nova Mus 1991, in quiescence. In each source, we postulate that there is an outer region, extending outward from about 3000 Schwarzschild radii, where the…
We study the effect of physics input on thermal evolution of neutron stars in soft X-ray transients (SXTs). In particular, we consider different modern models of the sources of deep crustal heating during accretion episodes and the effects…
Recent observations show that supergiant fast X-ray transients (SFXTs) spend most of their lifetime at an intermediate level luminosity $\sim 10^{33}-10^{34}$ ergs$^{-1}$, and, when a blackbody model for the spectra is adopted, the…
We study the thermal and viscous stability of accretion flows in Low Mass Black Hole Binaries (LMBHBs). We consider a model in which an inner advection-dominated accretion flow (ADAF) is surrounded by a geometrically thin accretion disk,…