Effects of Resonance in Quasiperiodic Oscillators of Neutron Star Binaries

Abstract

Using a large quantity of Rossi X-ray Timing Explorer data presented in the literature I offer a detailed investigation into the accuracy of quasiperiodic oscillations (QPO) frequency determination. The QPO phenomenon seen in X-ray binaries is possibly a result of the resonance of the intrinsic (eigen) oscillations and harmonic driving forces of the system. I show that the resonances, in the presence of the damping of oscillations, occur at the frequencies which are systematically and randomly shifted with respect to the eigenfrequencies of the system. The shift value strongly depends on the damping rate which is measured by the halfwidth of the QPO feature. Taking into account this effect I analyze the QPO data for four Z-sources: Sco X-1, GX 340+0, GX 5-1, GX 17+2 and two atoll sources: 4U 1728-34, 4U 0614+09. The transition layer model (TLM) predicts the existence of the invariant quantity: delta, an inclination angle of the magnetospheric axis with respect to the normal to the disk. I calculate delta and the error bars of delta using the resonance shift and I find that the inferred delta-values are consistent with constants for these four Z-sources, where horizontal branch oscillation and kilohertz frequencies have been detected and correctly identified. It is shown that the inferred delta are in the range between 5.5 and 6.5 degrees. I conclude that the TLM seems to be compatible with data.

9 pages and 2 figures. Accepted for publication in the Astrophysical Journal Letters 2002 August 22

References in corpus (1)

• Why is it Difficult to Detect a Millisecond Pulsar in Neutron Star X-ray Binaries?

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