A physical model for the spectral-timing properties of accreting black holes

Mahmoud, Ra'ad; Done, Chris

doi:10.1093/mnras/sty2133

Cited by 48 publications

(36 citation statements)

References 66 publications

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“…Second, while the production of time lags is usually associated with a corona or lampost geometry (Uttley et al 2014, Fig. 1), very recent studies have shown that a radial stratification of the disk can be used to explain timing properties (Mahmoud & Done 2018;Mahmoud et al 2019). This is very promising and fits surprisingly well with our own framework.…”

Section: Open Questionssupporting

confidence: 74%

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

Marcel

Ferreira

Clavel

et al. 2019

A&A

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Context. Transient X-ray binaries (XrB) exhibit very different spectral shapes during their evolution. In luminosity-color diagrams, their behavior in X-rays forms q-shaped cycles that remain unexplained. In Paper I, we proposed a framework where the innermost regions of the accretion disk evolve as a response to variations imposed in the outer regions. These variations lead not only to modifications of the inner disk accretion rate ṁin, but also to the evolution of the transition radius rJ between two disk regions. The outermost region is a standard accretion disk (SAD), whereas the innermost region is a jet-emitting disk (JED) where all the disk angular momentum is carried away vertically by two self-confined jets. Aims. In the previous papers of this series, it has been shown that such a JED–SAD disk configuration could reproduce the typical spectral (radio and X-rays) properties of the five canonical XrB states. The aim of this paper is now to replicate all X-ray spectra and radio emission observed during the 2010–2011 outburst of the archetypal object GX 339-4. Methods. We used the two-temperature plasma code presented in two previous papers (Papers II and III) and designed an automatic ad hoc fitting procedure that for any given date calculates the required disk parameters (ṁin,rJ) that fit the observed X-ray spectrum best. We used X-ray data in the 3–40 keV (RXTE/PCA) spread over 438 days of the outburst, together with 35 radio observations at 9 GHz (ATCA) dispersed within the same cycle. Results. We obtain the time distributions of ṁin(t) and rJ(t) that uniquely reproduce the X-ray luminosity and the spectral shape of the whole cycle. In the classical self-absorbed jet synchrotron emission model, the JED–SAD configuration also reproduces the radio properties very satisfactorily, in particular, the switch-off and -on events and the radio-X-ray correlation. Although the model is simplistic and some parts of the evolution still need to be refined, this is to our knowledge the first time that an outburst cycle is reproduced with such a high level of detail. Conclusions. Within the JED–SAD framework, radio and X-rays are so intimately linked that radio emission can be used to constrain the underlying disk configuration, in particular, during faint hard states. If this result is confirmed using other outbursts from GX 339-4 or other X-ray binaries, then radio could be indeed used as another means to indirectly probe disk physics.

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Section: Open Questionssupporting

confidence: 74%

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

Marcel

Ferreira

Clavel

et al. 2019

A&A

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“…This seems to disagree with the assumption of the propagating fluctuations model that each independent annulus produces fluctuations with most of the variability power centred at the local viscous frequency. Moreover, it rules out the damping of propagating fluctuations (Arévalo & Uttley 2006;Rapisarda, Ingram & van der Klis 2017;Mahmoud & Done 2018b). Fig.…”

Section: Simulation Amentioning

confidence: 87%

Looking for the underlying cause of black hole X-ray variability in GRMHD simulations

Bollimpalli

Mahmoud

Done

et al. 2020

Monthly Notices of the Royal Astronomical Society

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ABSTRACT Long-term observations have shown that black hole X-ray binaries exhibit strong, aperiodic variability on time-scales of a few milliseconds to seconds. The observed light curves display various characteristic features like a lognormal distribution of flux and a linear rms–flux relation, which indicate that the underlying variability process is stochastic in nature. It is also thought to be intrinsic to accretion. This variability has been modelled as inward propagating fluctuations of mass accretion rate, although the physical process driving the fluctuations remains puzzling. In this work, we analyse five exceptionally long-duration general relativistic magnetohydrodynamic (GRMHD) simulations of optically thin, geometrically thick, black hole accretion flows to look for hints of propagating fluctuations in the simulation data. We find that the accretion profiles from these simulations do show evidence for inward propagating fluctuations below the viscous frequency by featuring strong radial coherence and positive time lags when comparing smaller to larger radii, although these time lags are generally shorter than the viscous time-scale and are frequency-independent. Our simulations also support the notion that the fluctuations in $\dot{M}$ build up in a multiplicative manner, as the simulations exhibit linear rms–mass flux relations, as well as lognormal distributions of their mass fluxes. When combining the mass fluxes from the simulations with an assumed emissivity profile, we additionally find broad agreement with observed power spectra and time lags, including a recovery of the frequency dependency of the time lags.

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“…The onset of this millennium has seen several ongoing efforts in the development of stochastic propagation models to explain energy dependent continuum variability observed in most X-ray binaries. Most of these models are built upon the fundamental idea that the perturbations originate at the outer annuli of the disk and propagate towards the central object (Kotov et al 2001;Ingram & Done 2011Ingram & van der Klis 2013;Rapisarda et al 2016Rapisarda et al , 2017Mahmoud & Done 2018;Axelsson & Done 2018). Primarily, these models are aimed at making quantitative predictions of PDS, energy dependent time-lags and rms variability.…”

Section: Stochastic Propagation Modelmentioning

confidence: 99%

Unveiling the Temporal Properties of MAXI J1820+070 through AstroSat Observations

Mudambi

Maqbool

Misra

et al. 2020

ApJL

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We present here the results of the first broadband simultaneous spectral and temporal studies of the newly detected black hole binary MAXI J1820+070 as seen by SXT and LAXPC on-board AstroSat. The observed combined spectra in the energy range 0.7−80 keV were well modeled using disk blackbody emission, thermal Comptonization and a reflection component. The spectral analysis revealed that the source was in its hard spectral state (Γ = 1.61) with a cool disk (kT in = 0.22 keV). We report the energy dependent time-lag and root mean squared (rms) variability at different frequencies in the energy range 3−80 keV using LAXPC data. We also modeled the flux variability using a single zone stochastic propagation model to quantify the observed energy dependence of time-lag and fractional rms variability and then compared the results with that of Cygnus X-1. Additionally, we confirm the detection of a quasi-periodic oscillation with the centroid frequency at 47.7 mHz.

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A physical model for the spectral-timing properties of accreting black holes

Cited by 48 publications

References 66 publications

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

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

Looking for the underlying cause of black hole X-ray variability in GRMHD simulations

Unveiling the Temporal Properties of MAXI J1820+070 through AstroSat Observations

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