Publication date: Mar 2008
Relation between the lower and upper frequency mode of the twin peak
quasi-periodic oscillations observed in the neutron star X-ray binaries
is qualitatively well fitted by the frequency relation following from
the relativistic precession model. Assuming this model with no preferred
radius and the probability of an observable twin QPO excitation being
uniform across the inner edge of an accretion disk we compare the
expected and observed twin peak QPO distribution in the case of atoll
source 4U 1636-53. We find these two distributions highly incompatible.
We argue that the observed distribution roughly corresponds to the
expected one if an additional consideration of preferred resonant orbits
is included. We notice that our findings are relevant for some disk-
oscillation QPO models as well.
Torok, G.; Bakala, P.; Stuchlik, Z.; Cech, P.;