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On the kHz QPO frequency correlations in bright neutron star X-ray binaries

T. Belloni·M. Mendez·J. Homan
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Abstract

We re-examine the correlation between the frequencies of upper and lower kHz quasi-periodic oscillations (QPO) in bright neutron-star low-mass X-ray binaries. By including the kHz QPO frequencies of the X-ray binary Cir X-1 and two accreting millisecond pulsars in our sample, we show that the full sample does not support the class of theoretical models based on a single resonance, while models based on relativistic precession or Alfven waves describe the data better. Moreover, we show that the fact that all sources follow roughly the same correlation over a finite frequency range creates a correlation between the linear parameters of the fits to any sub-sample.

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T. Belloni, M. Mendez, J. Homan. 2007-02-06. On the kHz QPO frequency correlations in bright neutron star X-ray binaries. https://doi.org/10.1111/j.1365-2966.2007.11486.x

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