2. Observations and data analysis
The observations used for the analysis are listed in Table 1. For the timing analysis in the keV energy range the RXTE /PCA (Bradt, Swank & Rothschild 1993) data in the `binned' and `event' modes containing X-ray events below and above 13 keV respectively were used. We generated power density spectra (PDS) in the Hz frequency range accumulated in the 4 s time intervals (Leahy et al. 1983). The PDS were linearly rebinned into 0.25 Hz bins. The white-noise level due to Poissonian statistics corrected for the dead-time effects was subtracted. For the determination of the QPO centroid frequencies the PDS were fitted to the analytic model consisting of a Lorentzian profile and a power law continuum in the Hz frequency range (typical error of the derived value of the QPO frequency is Hz).
© European Southern Observatory (ESO) 1999
Online publication: November 3, 1999