Publication date: Mar 2014
Abstract:
Resonant Switch (RS) model has recently been proposed as an alternative
to the standard models of twin-peak high-frequency quasi-periodic
oscillations (HF QPOs) observed in low-mass X-ray binaries containing a
neutron star. The model assumes switch of twin oscillations at a
resonant point, where frequencies of the upper and lower oscillations
νU and νL become commensurable and one pair
of the oscillating modes (corresponding to a specific model of HF QPOs)
changes to some other pair due to non-linear resonant phenomena. We test
the RS model for the atoll source 4U 1636-53, where we assume two
resonant points observed at frequency ratios
νU:νL=3:2, 5:4, by fitting the pairs of the
oscillatory modes to the observed data in the regions related to the
resonant points. Among acceptable variants of the RS model the most
promising are those combining the relativistic precession (RP) and the
total precession (TP) frequency relations or their modifications. The
precision of the fits is shown to be strongly increased in comparison to
fits realized by individual pairs along the whole data range. We
demonstrate that the χ2 test is significantly improved.
Fitting of the HF QPO data in the source 4U 1636-53 by the RP1-RP
variant of the RS model gives the best results and implies that the
neutron star mass and dimensionless spin are M≍2.2 Msun
and a≍0.27.
Authors:
Stuchlik, Z.; Kotrlova, A.; Torok, G.; Goluchova, K.;