Publication date: Dec 2007
Abstract:
The kHz quasiperiodic oscillations (QPOs) observed in low-mass X-ray neutron star binaries are most likely connected to the orbital motion in the accretion disc and show datapoint clustering of frequency ratio between the upper and lower QPOs in small natural numbers. It is shown for the atoll source 4U 1636-53 that using the Hartle-Thorne metric to describe the neutron star spacetime, the data clustered around the frequency ratios 3/2 and 5/4 could be fitted by three models (Relativistic Precession, Vertical Precession and Total Precession) involving the hot spot orbital motion with Keplerian, radial epicyclic and vertical epicyclic frequencies. We demonstrate that with taking into account the hotspots interaction with the neutron star magnetic field the discussed three models can provide good fits implying reasonable values of the neutron star mass and angular momentum. Therefore the hypothesis of more instances of one orbital resonance has the potential to explain the kHz QPO nature in the source 4U 1636-53.
Authors:
Török, Gabriel; Bakala, Pavel; Stuchlík, Zdeněk; Šrámková, Eva;