Evidence for local mass accretion rate variations in the disc of GRS 1915+105
We have analysed 16 observations of class beta of GRS 1915+105 performed with the Rossi X-ray Timing Explorer. We show the time-resolved evolution (every 16 seconds) of the X-ray spectral parameters during these observations. The three model independent states (A, B, C) identified in the color-color diagrams are described here in terms of the more physical (and model dependent) quantities of the disc and power law components. As in the color analysis, we observe specific and time-asymmetric transitions between states. Within a single observation, we identified a loop-like cycle of the power law spectral index that starts and ends with the ending of state C. There is evidence of local mass accretion rate variations and mass loss during the long instability intervals (long state C). This is consistent with simultaneous radio and X-ray observations that show a one-to-one relation between the long state C and the radio flares, that occur shortly after it: a loss of disc mass is followed by an ejection of matter in the jet.