Article

# A Global Spectral Study of Black Hole X-ray Binaries

AIM – Unité Mixte de Recherche CEA – CNRS – Université Paris VII – UMR 7158, CEA-Saclay, Service d'Astrophysique, F-91191 Gif-sur-Yvette Cedex, France
(Impact Factor: 5.11). 02/2010; 403(1):61 - 82. DOI: 10.1111/j.1365-2966.2010.16114.x
Source: arXiv

ABSTRACT

(Abridged) We report on a consistent and comprehensive spectral analysis of
the X-ray emission of 25 Black Hole X-ray Binaries. All publicly available
observations of the black hole binaries in the RXTE archive were analysed.
Three different types of model were fitted to investigate the spectral changes
occurring during an outburst. For the population, as well as each binary and
each outburst from each binary, we construct two diagnostic diagrams. The
Hardness Intensity/Luminosity Diagram (HID/HLD) is most useful when studying a
single binary. However, to compare between different binary systems, the Disc
Fraction Luminosity diagram (DFLD) is more useful. We discuss the limitations
of both diagnostic diagrams for the study of the X-ray binary outbursts, and we
clearly illustrate how the two diagrams map onto each other for real outburst
data. We extract the peak luminosities in a single outburst, as well as the
luminosities at the transitions away from- and returning to the powerlaw
dominated state for each outburst. The distribution of the luminosities at the
transition from the powerlaw to the disc dominated state peaks at around
0.3L_Edd, the same as the peak of the distribution of the peak luminosities in
an outburst. Using the disc fraction to calculate the transition luminosities
shows that the distributions of the luminosities for the transitions away from-
overlap. Finally we compare the measured X-ray luminosities with a small number
of contemporaneous radio measurements. Overall this is the most comprehensive
and uniform global study of black hole X-ray binaries to date.

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Available from: Robert J H Dunn, May 28, 2015
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• "In general, four basic spectral states (Hard, Hard − Intermediate, S o f t − Intermediate, S o f t) are observed during the outburst of a transient BHC (McClintock & Remillard, 2006; Belloni et al., 2005; Nandi et al., 2012). One can find detailed discussions about these spectral states and their transitions in the literature (Homan & Belloni, 2005a; Belloni, 2010c; Dunn et al., 2010; Nandi et al., 2012). It was also reported by several authors (Fender et al., 2004; Homan & Belloni, 2005a; Belloni, 2010c; Nandi et al., 2012) that the observed spectral states form a hysteresis loop during their outbursts. "
##### Article: Evolution of the temporal and the spectral properties in 2010 and 2011 outbursts of H 1743-322
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ABSTRACT: The Galactic black hole candidate H~1743-322 exhibited two X-ray outbursts in rapid succession: one in August 2010 and the other in April 2011. We analyze archival data of this object from the PCA instrument on board RXTE (2-25 keV energy band) to study the evolution of its temporal and spectral characteristics during both the outbursts, and hence to understand the behavioral change of the accretion flow dynamics associated with the evolution of the various X-ray features. We study the evolution of QPO frequencies during the rising and the declining phases of both the outbursts. We successfully fit the variation of QPO frequency using the Propagating Oscillatory Shock (POS) model in each of the outbursts and obtain the accretion flow parameters such as the instantaneous shock locations, the shock velocity and the shock strength. Based on the degree of importance of the thermal (disk black body) and the non-thermal (power-law) components of the spectral fit and properties of the QPO (if present), the entire profiles of the 2010 and 2011 outbursts are subdivided into four different spectral states: hard, hard-intermediate, soft-intermediate and soft. We attempt to explain the nature of the outburst profile (i.e., hardness-intensity diagram) with two different types of mass accretion flow.
Advances in Space Research 09/2013; 52(12). DOI:10.1016/j.asr.2013.09.002 · 1.36 Impact Factor
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##### Article: An additional soft X-ray component in the dim low/hard state of black hole binaries
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ABSTRACT: We test the truncated disc models using multiwavelength (optical/ultraviolet/X-ray) data from the 2005 hard state outburst of the black hole Swift J1753.5−0127. This system is both fairly bright and has fairly low interstellar absorption, so gives one of the best data sets to study the weak, cool disc emission in this state. We fit these data using models of an X-ray illuminated disc to constrain the inner disc radius throughout the outburst. Close to the peak, the observed soft X-ray component is consistent with being produced by the inner disc, with its intrinsic emission enhanced in temperature and luminosity by reprocessing of hard X-ray illumination in an overlap region between the disc and corona. This disc emission provides the seed photons for Compton scattering to produce the hard X-ray spectrum, and these hard X-rays also illuminate the outer disc, producing the optical emission by reprocessing. However, the situation is very different as the outburst declines. The optical is probably cyclo-synchrotron radiation, self-generated by the flow, rather than tracing the outer disc. Similarly, limits from reprocessing make it unlikely that the soft X-rays are directly tracing the inner disc radius. Instead they appear to be from a new component. This is seen more clearly in a similarly dim low/hard state spectrum from XTE J1118+480, where the 10 times lower interstellar absorption allows a correspondingly better view of the ultraviolet/extreme ultraviolet (EUV) emission. The very small emitting area implied by the relatively high temperature soft X-ray component is completely inconsistent with the much larger, cooler, ultraviolet component which is well fit by a truncated disc. We speculate on the origin of this component, but its existence as a clearly separate spectral component from the truncated disc in XTE J1118+480 shows that it does not simply trace the inner disc radius, so cannot constrain the truncated disc models.
Monthly Notices of the Royal Astronomical Society 11/2009; 403(3). DOI:10.1111/j.1365-2966.2009.16129.x · 5.11 Impact Factor
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##### Article: On the nature of the X-ray corona of black hole binaries in the hard state
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ABSTRACT: We discuss the nature of the X-ray emitting plasma of black hole binaries. It is well known that the temperature and optical depth of the Comptonising electrons of the X-ray corona of black hole binaries can be measured using spectroscopy in the 1 keV-1 MeV energy band. We emphasize recent developments in the modeling of high energy radiation processes which allow us to constrain other important physical parameters of the corona, such as the strength of magnetic field, or the temperature of the ions. The results appear to challenge current accretion models. In particular, standard advection dominated accretion flow do not match the observed properties of bright hard state X-ray binaries such as Cygnus X-1 or GX 339-4. On the other hand, we find that all the data would be consistent with a multi-zone magnetically dominated hot accretion flow model. We also emphasize that besides the usual spectral state transitions observed at luminosities above a few percent of Eddington, there is observational evidence for at least two additional, more subtle, radiative transitions occuring at lower luminosities.
01/2010; DOI:10.1142/S2010194512004448