Timing analysis of the X - ray transient source XTE J 1806 – 246 ( 2 S 1803 – 245 )

An outburst of the X-ray transient source XTE J1806–246 (2S1803–245) was observed by the Rossi X-ray Timing Explorer from 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 the PCA/RXTE experiment. 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 parameters 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 other parameters do not change significantly.