A self-consistent hybrid Comptonization model for broad-band spectra of accreting supermassive black holes

Veledina, Alexandra; Vurm, Indrek; Poutanen, Juri

doi:10.1111/j.1365-2966.2011.18635.x

Cited by 57 publications

(82 citation statements)

References 77 publications

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“…Merloni & Fabian 2001), the corona must be magnetically dominated. An underlying strong magnetic field means that the synchrotron boiler dominates the energy exchange between low-energy electrons and the photon field (Ghisellini, Guilbert & Svensson 1988;Ghisellini, Haardt & Svensson 1998;Belmont, Malzac & Marcowith 2008;Veledina, Vurm & Poutanen 2011). Taking these issues further is beyond the scope of this paper.…”

Section: Discussionmentioning

confidence: 99%

Properties of AGN coronae in theNuSTARera

Fabian

Lohfink

Kara

et al. 2015

Mon. Not. R. Astron. Soc.

360

433

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The focussing optics of NuSTAR have enabled high signal-to-noise spectra to be obtained from many X-ray bright Active Galactic Nuclei (AGN) and Galactic Black Hole Binaries (BHB). Spectral modelling then allows robust characterization of the spectral index and upper energy cutoff of the coronal power-law continuum, after accounting for reflection and absorption effects. Spectral-timing studies, such as reverberation and broad iron line fitting, of these sources yield coronal sizes, often showing them to be small and in the range of 3 to 10 gravitational radii in size. Our results indicate that coronae are hot and radiatively compact, lying close to the boundary of the region in the compactness -temperature (Θ − ℓ) diagram which is forbidden due to runaway pair production. The coincidence suggests that pair production and annihilation are essential ingredients in the coronae of AGN and BHB and that they control the shape of the observed spectra.

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Section: Discussionmentioning

confidence: 99%

Properties of AGN coronae in theNuSTARera

Fabian

Lohfink

Kara

et al. 2015

Mon. Not. R. Astron. Soc.

360

433

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“…We note that the origin of seed photons are different in alternative scenarios, i.e. they can be from the inner small cold disc in the disc -corona model ), or from the outer cold disc in the truncated disc model (Veledina et al 2011;Sobolewska et al 2011;Gardner & Done 2013). In order to quantitatively examine the above analysis on the Comptonized spectrum, we investigate emission at R = 5R S in the BHB case (see Section 4), with δ = 0.5.…”

Section: Underlying Physics Of the γ -L X /L Edd Correlationmentioning

confidence: 99%

“…4 & 5), locates at L X /L Edd ∼ 10 −3 (e.g., Yuan et al 2007;Constantin et al 2009;Veledina et al 2011;Trichas et al 2013). If we take the correction factor between the 2-10 keV X-ray luminosity and the bolometric luminosity L bol to be ∼ 1/16 (Ho 2008), then the turning point is at L bol /L Edd ∼ (1 − 2)%.…”

Section: Turning Point At L X ∼ 10 −3 -Location Of the Transition In mentioning

confidence: 99%

“…Note that in the specific model of Veledina et al (2011), see also Poutanen & Veledina (2014) for a review, the bulk of synchrotron emission is produced by non-thermal rather than thermal electrons. Such electrons might exist in hot accretion flows (Malzac & Belmont 2009;Poutanen & Vurm 2009;Niedźwiecki, Xie & Stepnik 2014;Niedźwiecki, Stepnik & Xie 2015) and then are likely to dominate the synchrotron emission (Wardziński & Zdziarski 2001).…”

Section: Introductionmentioning

confidence: 99%

“…The first type of works is based on the truncated thin disc plus hot accretion flow model (hereafter abbreviated as the truncated disc model), see, e.g., Veledina, Vurm & Poutanen (2011), Sobolewska et al (2011) and Gardner & Done (2013). In this model, the thin disc is truncated at a radius which decreases with the increasing accretion rate.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Correlation between the photon index and X-ray luminosity of black hole X-ray binaries and active galactic nuclei: observations and interpretation

Yang

Xie

Yuan

et al. 2014

Monthly Notices of the Royal Astronomical Society

121

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We investigate the observed correlation between the 2-10 keV X-ray luminosity (in unit of the Eddington luminosity; l X ≡ L X /L Edd ) and the photon index (Γ) of the X-ray spectrum for both black hole X-ray binaries (BHBs) and active galactic nuclei (AGNs). We construct a large sample, with 10 −9 < ∼ l X < ∼ 10 −1 . We find that Γ is positively and negatively correlated with l X when l X > ∼ 10 −3 and 10 −6.5 < ∼ l X < ∼ 10 −3 respectively, while Γ is nearly a constant when l X < ∼ 10 −6.5 . We explain the above correlation in the framework of a coupled hot accretion flow -jet model. The radio emission always come from the jet while the X-ray emission comes from the accretion flow and jet when l X is above and below 10 −6.5 , respectively. More specifically, we assume that with the increase of mass accretion rate, the hot accretion flow develops into a clumpy and further a disc -corona two-phase structure because of thermal instability. We argue that such kind of two-phase accretion flow can explain the observed positive correlation.

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Modelling Spectral and Timing Properties of Accreting Black Holes: The Hybrid Hot Flow Paradigm

Poutanen

Veledina

2013

The Physics of Accretion Onto Black Holes

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The general picture that emerged by the end of 1990s from a large set of optical and X-ray, spectral and timing data was that the X-rays are produced in the innermost hot part of the accretion flow, while the optical/infrared (OIR) emission is mainly produced by the irradiated outer thin accretion disc. Recent multiwavelength observations of Galactic black hole transients show that the situation is not so simple. Fast variability in the OIR band, OIR excesses above the thermal emission and a complicated interplay between the X-ray and the OIR light curves imply that the OIR emitting region is much more compact. One of the popular hypotheses is that the jet contributes to the OIR emission and even is responsible for the bulk of the X-rays. However, this scenario is largely ad hoc and is in contradiction with many previously established facts. Alternatively, the hot accretion flow, known to be consistent with the X-ray spectral and timing data, is also a viable candidate to produce the OIR radiation. The hot-flow scenario naturally explains the power-law like OIR spectra, fast OIR variability and its complex relation to the X-rays if the hot flow contains non-thermal electrons (even in energetically negligible quantities), which are required by the presence of the MeV tail in Cyg X-1. The presence of non-thermal electrons also lowers the equilibrium electron temperature in the hot flow model to 100 keV, making it more consistent with observations. Here we argue that any viable model should simultaneously explain a large set of spectral and timing data and show that the hybrid (thermal/non-thermal) hot flow model satisfies most of the constraints.

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A self-consistent hybrid Comptonization model for broad-band spectra of accreting supermassive black holes

Cited by 57 publications

References 77 publications

Properties of AGN coronae in theNuSTARera

Properties of AGN coronae in theNuSTARera

Correlation between the photon index and X-ray luminosity of black hole X-ray binaries and active galactic nuclei: observations and interpretation

Modelling Spectral and Timing Properties of Accreting Black Holes: The Hybrid Hot Flow Paradigm

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