Deterministic Chaos in Accreting Systems: Analysis of the X-Ray Variability of Herculis X-1

Abstract

The irregular X-ray variability of Her X-1 has been investigated in different phases of the 1.7 day orbital period of the binary system Her X-1/HZ Her. The analyzed data have been sampled by the Exosat satellite during two main-on states of the 35 day cycle of the system. Using new system theoretical methods, the attractors of different processes have been reconstructed which are responsible for the temporal evolution of the observed X-ray radiation. For the dynamics of the emission of X-ray radiation from Her X-1, an attractor has been established which is of intriguingly low fractal dimension. This fact provides evidence for a nonstochastic, deterministic chaotic origin of the irregular variability of the emitted X-ray radiation. Higher dimensional deterministic chaos has also been found to govern the dynamical processes in the accretion disk of the system. Corresponding attractors have been derived for those phases when the X-ray source is partially obscured by the accretion disk.