The MHD Alfven wave oscillation model of kHz Quasi Periodic Oscillations of Accreting X-ray binaries

National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China e-mail: zhangcm@bao.ac.cn Research Center for Theoretical Astrophysics, School of Physics, The University of Sydney, NSW 2006, Australia

Received: 4 December 2003
Accepted: 19 April 2004

Abstract

We ascribe the interpretation of the twin kilohertz Quasi Periodic Oscillations (kHz QPOs) of X-ray spectra of Low Mass X-Ray Binaries (LMXBs) to MHD Alfvén wave oscillations in the different mass density regions of the accreted matter at the preferred radius, and the upper kHz QPO frequency coincides with the Keplerian frequency. The proposed model concludes that the kHz QPO frequencies depend inversely on the preferred radius, and that theoretical relation between the upper frequency () and the lower frequency () is , which is similar to the measured empirical relation. The separation between the twin frequencies decreases (increases) with increasing kHz QPO frequency if the lower kHz QPO frequency is more (less) than ~400 Hz.