SPECTRA OF QUASI-PERIODIC OSCILLATIONS OF GALACTIC-X-RAY SOURCES - DYNAMICAL REGIMES FROM A SIMPLE-MODEL

We suggest that the dynamical regime(s) underlying quasiperiodic oscil lations observed in the spectra of bright galactic-bulge X-ray sources are nonlinear with a mixed phase space. The important feature of such regimes is that they are generic among nonlinear Hamiltonian and near ly Hamiltonian systems of more than two degrees of freedom. We give a simple example of such chaotic (deterministic) systems whose spectra s hare a number of features with those observed for quasiperiodic oscill ations of such sources.