Is a black hole accretion disk in a self-organized critical state?

Mineshige, Shin; Takeuchi, Mitsuru; Nishimori, Hiraku

doi:10.1086/187610

Cited by 131 publications

(120 citation statements)

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“…In Figure 5 we show power-law fits to the power spectra. For the systems in our sample, except for GS 2000+25, we find the power-law index ( ) to be roughly À1, similar to what is observed at X-ray wavelengths (Mineshige et al 1994). For GS 2000+25 we find a higher value of À0.28 (see Fig.…”

Section: The Power Spectrasupporting

confidence: 83%

“…The optical light curves of cataclysmic variables (Bruch 1992) and the X-ray light curves of galactic black hole candidates and AGNs generally have power spectra with an index of À1. These power spectra have been successfully reproduced by a cellular automaton model (Mineshige, Ouchi, & Nishimori 1994). In this model matter is randomly injected into an accretion disk surrounding a black hole.…”

Section: The Power Spectramentioning

confidence: 91%

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Evidence for Optical Flares in Quiescent Soft X‐Ray Transients

Zurita

Casares

Shahbaz

2003

ApJ

120

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We present the results of high time resolution optical photometry of five quiescent soft X-ray transients (SXTs): V404 Cyg, A0620À00, J0422+32, GS 2000+25, and Cen X-4. We detect fast optical variations superposed on the secondary star's double-humped ellipsoidal modulation. The variability resembles typical flare activity and has amplitudes ranging from 0.06 to 0.6 mag. Flares occur on timescales of minutes to a few hours, with no dependency on orbital phase, and contribute $19%-46% to the total veiling observed in the R band. We find that the observed level of flaring activity is veiled by the light of the companion star, and therefore, systems with cool companions (e.g., J0422+32) exhibit stronger variability. After correcting for this dilution, we do not find any correlation between the flaring activity and fundamental system parameters. We find no underlying coherent periods in the data, only quasi-periodic variations ranging between 30 and 90 minutes for the short-period SXTs and longer than 1 hr for V404 Cyg. The power-law index of the power spectra is consistent with what is observed at X-rays wavelengths, i.e., a 1/f distribution, which is compatible with the cellular automaton model. Our observed R 0 -band luminosities, which are in the range 10 31 -10 33 ergs s À1 , are too large to be due to chromospheric activity in the rapidly rotating companions. Since the typical timescale of the flares increases with orbital period, they are most likely produced in the accretion disk. The associated dynamical (Keplerian) timescales suggest that flares are produced at $0.3R d -0.7R d . Possible formation mechanisms are magnetic loop reconnection events in the disk or, less likely, optical reprocessing of X-ray flares. In the former scenario, the maximum duration of the flares suggests that the outer disk is responsible for the flare events and so allows us to constrain the sharing timescale to $ 5 6 ð Þ À1 K .

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Section: The Power Spectrasupporting

confidence: 83%

Section: The Power Spectramentioning

confidence: 91%

Evidence for Optical Flares in Quiescent Soft X‐Ray Transients

Zurita

Casares

Shahbaz

2003

ApJ

120

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“…The light curve, PDS, phase, and autocorrelation function (ACF) of the output from the model in Figures 1a, 1b, and 1c resemble the results of BTW88, Mineshige et al (1994), Scargle et al (1993), and Stern & Svensson (1997). As in BTW88, self-organization is achieved independently of initial conditions because the system quickly evolves to a state in which perturbations of above-average energy shock the plasma.…”

Section: Resultsmentioning

confidence: 53%

“…For low and flat geometry, the addeḋ m L60 SIVRON Vol. 503 parameter is expected to yield results similar to those of Mineshige et al (1994), since the random input and output for each disk cell are correlated. A second parameter, analogous to the parameter associated with the time profile of shots (Takeuchi, Mineshige, & Negoro 1995), is related to the profile of radiation events from each shock (SL98).…”

Section: Discussion and Concluding Remarksmentioning

confidence: 92%

“…CAs are tables of rules that describe how to model a nonlinear system with identical elements, commonly used when the partial differential equations for a nonlinear system are not easily solvable (Jackson 1989;Kaplan & Glass 1995). Using a CA, Mineshige, Takeuchi, & Nishimori (1994) assumed that the accreting material in BHBs is in the form of an accretion disk and that the avalanches are analogues to those in the self-organized criticality CAs for sand piles (Bak, Tang, & Wiesenfeld 1988, hereafter BTW88). Scargle et al (1993) assumed that the material in BHBs is in the form of a ring, as in the dripping hand model of Crutchfield & Kaneko (1988).…”

Section: Introductionmentioning

confidence: 99%

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Self-organized Criticality in Compact Plasmas

Sivron

1998

The Astrophysical Journal

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Compact plasmas, which exist near black hole candidates and in gamma-ray burst sources, commonly exhibit self-organized nonlinear behavior. A model that simulates the nonlinear behavior of a compact radiative plasma is constructed directly from the observed luminosity and variability. The simulation shows that such a plasma self-organizes and that the degree of nonlinearity as well as the slope of the power density spectrum increases with compactness. The simulation is based on a cellular automaton table that includes the properties of the hot (relativistic) plasma and the magnitude of the energy perturbations. The plasma cools, or heats up, depending on whether it releases more or less energy than that of a single perturbation. The energy released depends on the plasma density and temperature and the energy of the perturbations. Strong perturbations may cool the previously heated plasma through shocks and/or pair creation. New observations of some active galactic nuclei and gamma-ray bursts are consistent with the simulation.

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Power spectral distribution of the BL Lacertae object S5 0716+714

Mocanu

Marcu

2012

Astron Nachr

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Observational data in the BVRI bands of the variable BL Lacertae object S5 0716+714 are discussed from the point of view of its power spectral distribution (PSD). A model of the type P (f ) = βf −1 1 + (f/δ) α−1 −1 + γ is fitted to the data for four null hypothesis and the Bayesian p parameter for the fits is calculated. Spectral slopes with values ranging from 1.083 to 2.65 are obtained, with medium values for each band of αB = 2.028, αV = 1.809, αR = 1.932 and αI = 1.54 respectively. These values confirm conclusions of previous studies, namely that the source is turbulent. Two disk models, the standard prescription of the Shakura-Sunyaev disk and magnetized disks exhibiting magneto-rotational instabilities, were discussed. We found that it is unlikely that they explain this set of observational data.

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Is a black hole accretion disk in a self-organized critical state?

Cited by 131 publications

References 0 publications

Evidence for Optical Flares in Quiescent Soft X‐Ray Transients

Evidence for Optical Flares in Quiescent Soft X‐Ray Transients

Self-organized Criticality in Compact Plasmas

Power spectral distribution of the BL Lacertae object S5 0716+714

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