We analyzed the temporal behavior of GRS 1915+105 using the set of 9 RXTE /PCA observations representing typical patterns of the source X-ray evolution during the periods of flaring activity.
1. For all individual observations the tight correlation between the duration of a hard episode and the minimal QPO frequency was found.
2. For half of the observations this correlation is satisfactory described by the standard radiation pressure dominated disk theory assuming that the QPO frequency and the duration of a hard episode are proportional to the Keplerian frequency and the viscous time on the inner edge of the disk respectively. The derived values of the mass accretion rate for these observations are in the range . Not all observations fit this dependence. In fact for the large fraction the relation breaks. It should be noted, that for these observations the correlation (Belloni et al. 1997b ) also fails.
3. The temporal evolution of the QPO frequency during the rise
phase of the hard episodes can be explained as a change of the
Keplerian frequency at the inner edge of optically thick accretion
disk caused by its viscous motion.
© European Southern Observatory (ESO) 1999
Online publication: November 3, 1999