Variability Properties of Galactic Black Holes
In X-ray binaries, fast variability in X-ray emission on time-scales of milli-seconds to seconds is a common and very complex phenomenon. The variability of astronomical sources is usually expressed as a time series. The study of variability property implies the time series analysis of the light curve obtained from various sources. These study includes the study of Power Density Spectrum (PDS) and time/phase lag spectrum. Studies of energy dependent temporal properties (i.e.,variability properties) in different variability time scale for the nearly edge on (high inclination) and nearly face on (low inclination) compact binary sources could through-light the detail structure of the accretion geometry. Again, the evolutionary picture of variability parameters, such as QPO frequency, time lag and energy dependent lag for transient and persistent sources can be studied with the simplified framework of Two Component Advective Flow (TCAF) solution. However, even with this simplified model and employing Monte-Carlo simulation technique, the simulated spectral behavior can be tested with the observational results. Thus it is possible to answer the cause of hard and soft lag and their transitions in higher inclination sources within the framework of a single TCAF solution. Also the evolution of the low frequency quasi-periodic oscillations (LFQPOs) and associated time lag in transient and persistently variable black hole sources as a function of time can be explained by variation of the Compton cloud size in a Two Component Advective Flow solution (TCAF).
I like to thank Prof. S. K. Chakrabarti for his continuous advice and guidance during and as well as after the PhD work. I acknowledge T. Belloni for providing the timing analysis software GHATS.
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