Resonant switch model of twin peak HF QPOs applied to the source 4U 1636-53

Understand

Resonant Switch (RS) model of twin peak high-frequency quasi-periodic oscillations (HF QPOs) assumes switch of twin oscillations at a resonant point where frequencies of the upper and lower oscillations become commensurable and the twin oscillations change from one pair of the oscillating modes (corresponding to a specific model of HF QPOs) to some other pair due to non-linear resonant phenomena.

• The RS model is used to determine range of allowed values of spin and mass of the neutron star located at the atoll source 4U 1636-53 where two resonant points are observed at frequency ratios $nu_{U}$ : $nu_{L}$ = 3:2, 5:4.
• We consider the standard specific models of the twin oscillations based on the orbital and epicyclic geodetical frequencies.
• The resonant points are determined by the energy switch effect exhibited by the vanishing of the amplitude difference of the upper and lower oscillations.