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RXTE and Chandra observations of galactic microquasars GRO J1655-40 and GRS 1915+105

Bülbül, Gül Esra
In this thesis, RXTE timing analysis of Galactic Microquasars GRO J1655-40 and GRS 1915+105, the Chandra and RXTE joint spectral analysis of GRS 1915+105 are presented. We have investigated quasi periodic oscillations (QPOs) in the black hole binaries GRO J1655-40 and GRS 1915+105 observed in 99 and 122 observations made by the Proportional Counter Array (PCA) on board Rossi X-Ray Timing Explorer (RXTE) in both low energy band (2-12 keV) and high energy band (13-27 keV), respectively. Four different X-ray states are seen in the combined characteristics of power spectra, light curves extracted by using All Sky Monitor (ASM) and spectra during 1996 and 2005. Timing analysis of RXTE observations of both of two black hole binaries GRO J1655-40 and GRS 1915+105 displays twin high frequency quasi periodic oscillations (QPOs) which are sometimes simultaneous in high energy band. It is also shown that the time averaged 30 ksec Chandra grating spectrum analysis and RXTE spectrum analysis of recent observation of GRS 1915+105 in the very high state are consistent with the parameters which were mentioned before. We briefly discussed our results and the models on black hole spin and mass.