Broadband spectro-temporal studies of burst-outburst phenomena of neutron star low mass X-ray binaries

Abstract

This thesis focuses on the spectro-timing studies of burst and outburst phenomena of compact objects in Low Mass X-ray Binaries (NS LMXBs). Neutron stars in LMXBs exhibit a plethora of interesting observational features like outbursts, bursts, quasi-periodic oscillations (QPOs), and jets that can address the physics of accretion dynamics, strong gravity, and ultra-dense degenerate matter. Theoretical predictions can be compared and tested with the observational signatures present in the surrounding environment of the central compact object of LMXBs, specifically in the accretion disc. The emission from the accretion disc is mainly in the X-ray band and can be highly variable on the dynamic time scale. NS LMXBs exhibit several extended and short-duration features depending on the spectral state of the source thought to be driven by the accretion properties. The variability properties of NS LMXBs are known to be highly dependent on their position within the hardness intensity diagrams (HIDs) and correlated with the spectral state of the source. Apart from the continuum properties, a surface phenomenon occurring for a short duration, such as Type-I X-ray bursts, provides a great platform to constrain NS parameters. Broadband spectro-timing studies of NS LMXBs can put unique constraints ontheevolutionofthebinarycomponentsduringanoutburstphasemanifestingthespectral state evolution and thereby unveiling underlying physical mechanisms, their geometry, and high-energy emission mechanisms.