Temporal study of GRS 1915+105 with rms-flux relation: The importance of magnetic activities in the corona

The rms-flux relations for some observations of GRS 1915+105 are studied. The rms-flux relations of the light curves in only one state, state C or state A, can be described by the simple non-linear model provided Zhang; we thus interpret that such a linear relation reflects the relative importance of magnetic instability for X-ray emission in the corona of the system, compared to the thermal viscous instability for the X-ray emission in the accretion disk. The rms-flux relations for state B are very scattered, possibly because of the dominance of thermal viscous instability for the X-ray emission in the accretion disk. The complex rms-flux relations for the observations of transitions between two or three states are caused by the combination of the different rms-flux relations of these states. The underlying physical processes are the combination of magnetic topology in the corona and thermal viscous instability in the accretion disk.