Publication date: Dec 2012
Abstract:
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
νU and νL 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 a and mass M of the neutron star located in
the atoll source 4U 1636-53 where two resonant points are observed at
frequency ratios νU:νL=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. The predicted
ranges of the neutron star parameters are strongly dependent on the twin
modes applied in the RS model. We demonstrate that for some of the
oscillatory modes used in the RS model the predicted parameters of the
neutron star are unacceptable. Among acceptable RS models the most
promising are those combining the Relativistic Precession and the Total
Precession frequency relations or their modifications.
Authors:
Stuchlík, Z.; Kotrlová, A.; Török, G.;