Characterising anomalous transport in accretion disks from X-ray observations

Abstract

Whilst direct observations of internal transport in accretion disks are not yet possible, measurement of the energy emitted from accreting astrophysical systems can provide useful information on the physical mechanisms at work. Here we examine the unbroken multi-year time variation of the total X-ray flux from three sources: Cygnus X-1, the microquasar GRS1915+105, and for comparison the nonaccreting Crab nebula. To complement previous analyses, we demonstrate that the application of advanced statistical methods to these observational time-series reveals important contrasts in the nature and scaling properties of the transport processes operating within these sources. We find the Crab signal resembles Gaussian noise; the Cygnus X-1 signal is a leptokurtic random walk whose self-similar properties persist on timescales up to three years; and the GRS1915+105 signal is similar to that from Cygnus X-1, but with self-similarity extending possibly to only a few days. This evidence of self-similarity provides a robust quantitative characterisation of anomalous transport occuring within the systems.

8 pages, 15 figures; the following now added: reference to instabilities, power spectra, log-normal distributions, explicit connection between differencing/rescaling technique and turbulence/instability models, associated references

References in corpus (1)

• The disc instability model for X-ray transients: evidence for truncation and irradiation

Cited by in corpus (11)

• Recurrence plot statistics and the effect of embedding
• Polarized NIR and X-ray Flares from SgrA*
• Anomalous diffusion in the dynamics of complex processes
• Anomalous diffusion as a stochastic component in the dynamics of complex processes
• On the Nature of X-ray Variability in Ark 564
• Universal Probability Distribution Function for Bursty Transport in Plasma Turbulence
• Quantifying the Anisotropy and Solar Cycle Dependence of "$1/f$" Solar Wind Fluctuations Observed by Ace
• Coordinated multi-wavelength observations of Sgr A*
• Statistical characterisation of full-disk EUV/XUV solar irradiance and correlation with solar activity
• Identification of a 12-17 day timescale in X-ray observations of GRS 1915+105
• Coordinated mm/sub-mm observations of Sagittarius A* in May 2007