Higher order nonlinearity in accretion disks: QPOs of black hole and   neutron star sources and their spin
  We propose a unified model to explain Quasi-Periodic-Oscillation (QPO), particularly of high frequency, observed from black hole and neutron star systems globally. We consider accreting systems to be damped harmonic oscillators exhibiting epicyclic oscillations with higher order nonlinear resonance to explain QPO. The resonance is expected to be driven by the disturbance from the compact object at its spin frequency. The model explains various properties parallelly for both types of the compact object. It describes QPOs successfully for ten different compact sources. Based on it, we predict the spin frequency of the neutron star Sco X-1 and specific angular momentum of black holes GRO J1655-40, XTE J1550-564, H1743-322, GRS 1915+105. 
Banibrata Mukhopadhyay