| Abstract: X-ray binaries rank among the most luminous X-ray sources. They consist of a compact star (Neutron Star/Black-hole) gravitationally bound to a normal companion star. Due to their extreme gravity near the compact star and intense magnetic fields, in some cases, X-ray binaries serve as natural laboratories for studying extreme physical conditions. This thesis focuses on the timing, spectroscopy, and polarimetry studies of various X-ray binary systems to improve understanding of their accretion processes, emission mechanisms and reprocessing environment. The first study reports the discovery of transient quasi-periodic oscillations in the high-mass X-ray binary pulsar LMC X-4, enabling an indirect estimation of its magnetic field strength in the absence of Cyclotron Resonant Scattering Features. The second study investigates the reprocessing environment in high-mass X-ray binaries by analyzing eclipse flares in sources such as Vela X-1, LMC X-4, and 4U 1700-37. In 4U 1700-37, we detected a soft excess in the spectrum whose flux does not vary between eclipse flare and non-flare states. Our analysis suggests that this emission originates from the extremely thin shell of the stellar wind surrounding the photosphere of the companion star. The third study explores eclipse bursts in the low-mass X-ray binaries EXO 0748-676 and XTE J1710-281. We estimate the reprocessing efficiencies in both systems at various orbital phases by modeling the peculiar eclipse bursts, which exhibit tails extending beyond the eclipses. X-ray polarimetry is a relatively new area of research and offers unique insights into anisotropies within celestial systems. The thesis includes results from the Indian X-ray polarimeter (POLIX) onboard XPoSat, focusing on detector calibration, energy-dependent response, and data selection strategies to optimize the signal-to-noise ratio, particularly for faint X-ray sources. With results from timing and spectroscopy analyses, together with POLIX polarimetry data, this thesis aims to provide a comprehensive understanding of X-ray binary systems. |
