Modelling aperiodic X‐ray variabiity in black hole binaries as propagating mass accretion rate fluctuations: A short review

Ingram, Adam

doi:10.1002/asna.201612318

Cited by 28 publications

(27 citation statements)

References 35 publications

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“…XRPs commonly show fast aperiodic variability of X-ray flux over a broad frequency range (similar variability is shown by accreting black holes, see Ingram 2016). The variability is explained by the propagating fluctuations model (Lyubarskii 1997).…”

Section: Power Spectra Affected By Closed Envelopementioning

confidence: 71%

Optically thick envelopes around ULXs powered by accreating neutron stars

Mushtukov

Suleimanov

Tsygankov

et al. 2017

Mon. Not. R. Astron. Soc.

109

175

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Magnetized neutron stars power at least some ultra-luminous X-ray sources. The accretion flow in these cases is interrupted at the magnetospheric radius and then reaches the surface of a neutron star following magnetic field lines. Accreting matter moving along magnetic field lines forms the accretion envelope around the central object. We show that, in case of high mass accretion rates 10 19 g s −1 the envelope becomes closed and optically thick, which influences the dynamics of the accretion flow and the observational manifestation of the neutron star hidden behind the envelope. Particularly, the optically thick accretion envelope results in a multi-color black-body spectrum originating from the magnetospheric surface. The spectrum and photon energy flux vary with the viewing angle, which gives rise to pulsations characterized by high pulsed fraction and typically smooth pulse profiles. The reprocessing of radiation due to interaction with the envelope leads to the disappearance of cyclotron scattering features from the spectrum. We speculate that the super-orbital variability of ultra-luminous X-ray sources powered by accreting neutron stars can be attributed to precession of the neutron star due to interaction of magnetic dipole with the accretion disc.

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Section: Power Spectra Affected By Closed Envelopementioning

confidence: 71%

Optically thick envelopes around ULXs powered by accreating neutron stars

Mushtukov

Suleimanov

Tsygankov

et al. 2017

Mon. Not. R. Astron. Soc.

109

175

View full text Add to dashboard Cite

show abstract

“…Within the model that associates the low-frequency QPO with Lense-Thirring precession of the inner part of the accretion flow (see Ingram & Done 2011;Ingram 2016, and references therein) the QPO frequency is related to the size of the inner flow portion that precesses. With increasing accretion rate this region becomes smaller and the frequency increases.…”

Section: Discussionmentioning

confidence: 99%

Spectro-timing analysis of MAXI J1535–571 using AstroSat

Bhargava

Belloni

Bhattacharya

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We report the results of the analysis of an AstroSat observation of the Black Hole candidate MAXI J1535−571 during its Hard Intermediate state. We studied the evolution of the spectral and timing parameters of the source during the observation. The observation covered a period of ∼5 days and consisted of 66 continuous segments, corresponding to individual spacecraft orbits. Each segment was analysed independently. The source count rate increased roughly linearly by ∼30%. We modelled the spectra as a combination of radiation from a thermal disk component and a power-law. The timing analysis revealed the presence of strong Quasi Periodic Oscillations with centroid frequency ν QPO fluctuating in the range 1.7-3.0 Hz. We found a tight correlation between the QPO centroid frequency ν QPO and the power-law spectral index Γ, while ν QPO appeared not to be correlated with the linearly-increasing flux itself. We discuss the implications of these results on physical models of accretion.

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“…The power spectrum of fluctuations stirred up in each ring of the hot flow is a broad Lorentzian with most of the variability power concentrated at the local viscous frequency. This assumption follows the fact that fluctuations with characteristic frequency higher than the local viscous frequency are strongly damped, so they never reach the inner part of the accreting system, where most of the emission comes from (Ingram 2016). This effect was analytically demonstrated by Churazov et al (2001) for an optically thick geometrically thin disc, and in general it depends on the Green's function of the diffusion equation of the accreting system.…”

Section: The Damping Factormentioning

confidence: 92%

Cross-spectral modelling of the black hole X-ray binary XTE J1550-564: challenges to the propagating fluctuations paradigm

Rapisarda¹,

Ingram²,

Klis³

2017

Monthly Notices of the Royal Astronomical Society

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Timing properties of black hole X-ray binaries in outburst can be modeled with mass accretion rate fluctuations propagating towards the black hole. Such models predict time lags between energy bands due to propagation delays. First application of a propagating fluctuations model to black hole power spectra showed good agreement with the data. Indeed, hard lags observed from these systems appear to be in agreement with this generic prediction. Our PROPFLUC code allows to simultaneously predict power spectra, time lags, and coherence of the variability as a function of energy. This was successfully applied to Swift data on the black hole MAXI J1659-152, fitting jointly the power spectra in two energy bands and the cross-spectrum between these two bands. In the current work, we attempt to to model two high signal to noise Rossi X-ray Timing Explorer (RXTE) observations of the black hole XTE J1550-564. We find that neither observation can be adequately explained by the model even when considering, additionally to previous PROPFLUC versions, different propagation speeds of the fluctuations. After extensive exploration of model extensions, we tentatively conclude that the quantitative and qualitative discrepancy between model predictions and data is generic to the propagating fluctuations paradigm. This result encourages further investigation of the fundamental hypotheses of the propagating fluctuations model. We discuss some of these hypotheses with an eye to future works.

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Modelling aperiodic X‐ray variabiity in black hole binaries as propagating mass accretion rate fluctuations: A short review

Cited by 28 publications

References 35 publications

Optically thick envelopes around ULXs powered by accreating neutron stars

Optically thick envelopes around ULXs powered by accreating neutron stars

Spectro-timing analysis of MAXI J1535–571 using AstroSat

Cross-spectral modelling of the black hole X-ray binary XTE J1550-564: challenges to the propagating fluctuations paradigm

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