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) was ob served by the Rossi X-ray Timing Explorer from April-July 1998. Strong quas i-periodical oscillations (QPO) with a central peak frequency around 9 Hz w as detected in one observation of the series performed by the PCA/RXTE expe riment. The 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. Statistically significant variability of the QPO pa rameters was detected, in short-term correlation with the flux variability. Fractional amplitudes of Very Low frequency Noise and the QPO component of the power density spectrum demonstrate a strong energy dependence, while o ther parameters do not change significantly.