MG15 - Talk detail

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Abstract

The class variable source GRS 1915+105 is different from the transient sources in the sense that it exhibits peculiar time variabilities in the range of a few seconds to days. Depending on cts/s in different energy bands and the conventional color-color diagram, the variabilities were classified into sixteen classes and were sequenced in ascending order based on the Comptonization Efficiency. It was obtained that the chi classes were the hardest among all classes, and have significantly lower variability. However, all such variational features across different classes should ultimately be related to the variation of accretion rates, which can be obtained from the TCAF fitting. This motivated us to do the spectral analysis on this object using TCAF solution. In the chi_{2,4} classes where the outflow contribution is minimum, the spectra could be fitted using TCAF solution only, and various fitted parameters were extracted. In the chi_{1,3} class, an additional cutoff power-law had to be used to account for the outflow. The normalization of this model along with the variation of photon index and exponential roll off factor could provide us important offshoots regarding the outflow. Similarly, the burst-off states of the intermediate phase could be fitted with the same TCAF normalization for the hard states, and in the burst on state, there is significant change in the disk rate. That gives a legitimate picture of the transition between hard to soft state vis-a-vis the accretion rate.

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