Deterministic chaos in the X-Ray sources

TL;DR

This paper investigates whether the variability in X-Ray binary systems is due to stochastic processes or deterministic chaos, using recurrence analysis on observational data from two sources to identify underlying nonlinear dynamics.

Contribution

It applies recurrence analysis to real X-Ray binary data to distinguish between stochastic and deterministic chaos in accretion disk variability.

Findings

Evidence of non-linear variability in observed data

Comparison of real data with surrogate series shows signs of chaos

Analysis suggests accretion disk instability may be chaotic in nature

Abstract

Hardly any of the observed black hole accretion disks in X-Ray binaries and active galaxies shows constant flux. When the local stochastic variations of the disk occur at specific regions where a resonant behaviour takes place, there appear the Quasi-Periodic Oscillations (QPOs). If the global structure of the flow and its non-linear hydrodynamics affects the fluctuations, the variability is chaotic in the sense of deterministic chaos. Our aim is to solve a problem of the stochastic versus deterministic nature of the black hole binaries vari- ability. We use both observational and analytic methods. We use the recurrence analysis and we study the occurence of long diagonal lines in the recurrence plot of observed data series and compare it to the sur- rogate series. We analyze here the data of two X-Ray binaries - XTE J1550-564, and GX 339-4 observed by Rossi X-ray Timing Explorer. In these sources, the non-linear variability is expected because of the global conditions (such as the mean accretion rate) leading to the pos- sible instability of an accretion disk. The thermal-viscous instability and fluctuations around the fixed-point solution occurs at high accretion rate, when the radiation pressure gives dominant contribution to the stress tensor.