Timing analysis of the X-ray transient source XTE J1806--246 (2S1803--245)

An outburst of the X-ray transient source XTE J1806--246 (2S1803--245) has been observed by Rossi X-ray Timing Explorer in April-July 1998. Strong quasi-periodical oscillations (QPO) with a central peak frequency around 9 Hz was detected in one observation of the series performed by PCA/RXTE experiment. X-ray flux from the source during the observation with QPO was maximal. The energy spectrum of XTE J1806--246 at this time was softer than for other observations. A sufficient variability of the QPO parameters has been detected, in short-term correlation with the flux variability. Fractional amplitudes of Very Low frequency Noise and QPO component of power density spectrum demonstrate strong energy dependence, while other parameters do not change significantly.