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.;