Doughnut strikes sandwich: the geometry of hot medium in accreting black hole X-ray binaries

Poutanen, Juri; Veledina, Alexandra; Zdziarski, A. A.

doi:10.1051/0004-6361/201732345

Cited by 73 publications

(69 citation statements)

References 115 publications

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“…Including Comptonization of reflection very slightly reduces the value of χ 2 , to χ 2 ν ≈ 62.0/60, at f sc ≈ 0.30 +0.15 −0.30 , and yields very similar other parameters. The relatively low value of f sc can be reconciled with the relatively large τ T of the model in the geometry of a central hot flow surrounded by a truncated disc, in which relatively few reflected photons return into the hot flow, see, e.g., Zdziarski, Lubiński & Smith (1999), Poutanen, Veledina & Zdziarski (2018). S17 also considered models without the presence of a distant reflector.…”

Section: Models With Reflkerr (Incident Thermal Comptonization)mentioning

confidence: 94%

Comparison of spectral models for disc truncation in the hard state of GX 339–4

Dziełak

Zdziarski

Szanecki

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We probe models of disc truncation in the hard spectral state of an outburst of the well-known X-ray transient GX 339-4. We test a large number of different models of disc reflection and its relativistic broadening, using two independent sets of codes, and apply it to a Rossi X-ray Timing Explorer spectrum in the rising part of the hard state of the 2010/11 outburst. We find our results to be significantly model-dependent. While all of the models tested show best-fits consistent with truncation, some models allow the disc to extend close to the innermost stable circular orbit (ISCO) and some require substantial disc truncation. The different models yield a wide range in best-fit values for the disc inclination. Our statistically best model has a physical thermal Comptonization primary continuum, requires the disc to be truncated at a radius larger than or equal to about two ISCO radii for the maximum dimensionless spin of 0.998, and predicts a disc inclination in agreement with that of the binary. Our preferred models have moderate Fe abundance, 2 times solar. We have also tested the effect of increasing the density of the reflecting medium. We find it leads to an increase in the truncation radius, but also to an increase in the Fe abundance, opposite to a previous finding.

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Section: Models With Reflkerr (Incident Thermal Comptonization)mentioning

confidence: 94%

Comparison of spectral models for disc truncation in the hard state of GX 339–4

Dziełak

Zdziarski

Szanecki

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…For brevity, we display only the components inferred from the XMM fit, but the NuS-TAR components feature exactly the same parameters only with the Compton spectral indices swung by +0.18 (see Table 1). The simplicity, noting however that this would be an inaccurate assumption in the case of cyclo-synchrotron excitation in the inner flow (Poutanen, Veledina & Zdziarski 2018). We also assume that the solid angle subtended on the disc by both the soft and hard components is the same for model simplicity.…”

Section: Spectral Fitmentioning

confidence: 99%

Reverberation reveals the truncated disc in the hard state of GX 339-4

Mahmoud

Done

Marco

2019

Monthly Notices of the Royal Astronomical Society

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The nature and geometry of the hard state in black hole binaries is controversial. The broadband continuum spectrum and fast variability properties can be explained in a model where the inner disc evaporates into a geometrically thick, hot flow. However these models are challenged by the persistent detection of an extremely broad iron line, which requires that the disc extends down to the last stable orbit of a high spin black hole. This line width can be considerably reduced if the Comptonisation continuum is multi-component rather than single temperature, but such models are highly degenerate. Here we show a specific model of a radially stratified continuum coupled to a model of propagating fluctuations, fit to some of the best hard state data from GX 339-4. This full spectral-timing model can fit the time averaged spectrum, the power spectra in different energy bands, and the frequency dependent lags between these bands. For the first time we also include disc reverberation and show that this same spectral-timing successfully predicts the lag-energy spectra on all timescales. This gives a more robust method to determine the inner radius of the disc, which is of order 20 R g , i.e. significantly truncated. This opens up the way to use the fast variability spectral-timing data to trace the source geometry of black hole binaries in all states.

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“…Approximate values of the photon index Γ and energy cutoff E cut , derived by comparison with a simple cutoff power-law model in this energy range, are indicated on each plot. JED inside the disk will also naturally increase the SAD emission (Poutanen et al 2018). In our model, we only take into account the intrinsic disk emission, but X-ray reprocessing can be mimicked by increasing ω.…”

Section: Effect Of An External Illumination On the Jed Thermal Structurementioning

confidence: 99%

A unified accretion-ejection paradigm for black hole X-ray binaries

Marcel

Ferreira

Petrucci

et al. 2018

A&A

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Context. It has been suggested that the cycles of activity of X-ray binaries (XRB) are triggered by a switch in the dominant disk torque responsible for accretion. As the disk accretion rate increases, the disk innermost regions therefore change from a jet-emitting disk (JED) to a standard accretion disk (SAD). Aims. While JEDs have been proven to successfully reproduce X-ray binary hard states, the existence of an outer cold SAD introduces an extra nonlocal cooling term. We investigate the thermal structure and associated spectra of such a hybrid disk configuration. Methods. We use a two-temperature plasma code, allowing for outside-in computation of the disk local thermal equilibrium with self-consistent advection and optically thin-to-thick transitions in both radiation and gas supported regimes. The nonlocal inverse Compton cooling introduced by the external soft photons is computed by the BELM code. Results. This additional cooling term has a profound influence on JED solutions, allowing a smooth temperature transition from the outer SAD to the inner JED. We explore the full parameter space in disk accretion rate and transition radius, and show that the whole domain in X-ray luminosities and hardness ratios covered by standard XRB cycles is well reproduced by such hybrid disk configurations. Precisely, a reasonable combination of these parameters allows us to reproduce the 3–200 keV spectra of each of five canonical XRB states. Along with these X-ray signatures, JED-SAD configurations also naturally account for the radio emission whenever it is observed. Conclusions. By varying only the radial transition radius and the accretion rate, hybrid disk configurations combining an inner JED and an outer SAD are able to simultaneously reproduce the X-ray spectral states and radio emission of X-ray binaries during their outburst. Adjusting these two parameters, it is then possible to reproduce a full cycle. This will be shown in a forthcoming paper.

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Doughnut strikes sandwich: the geometry of hot medium in accreting black hole X-ray binaries

Cited by 73 publications

References 115 publications

Comparison of spectral models for disc truncation in the hard state of GX 339–4

Comparison of spectral models for disc truncation in the hard state of GX 339–4

Reverberation reveals the truncated disc in the hard state of GX 339-4

A unified accretion-ejection paradigm for black hole X-ray binaries

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