Unraveling certain high energy astrophysical features based on advective accretion disks

Abstract

The presence of an accretion disk around a neutron star (NS) or a black hole (BH) is mainly responsible for the observed X-rays from the night sky. NS or BH is a part of the binary systems, and matter flows from a companion star to them. That is why they are categorized as X-ray binaries (XRBs). However, accretion flow around an astrophysical object is not only restricted to XRBs. They are ubiquitous in different astrophysical sites e.g., around a white dwarf (WD), supermassive black hole, young stellar object etc. Nevertheless, the hard X-rays present in the observed spectral energy distribution of XRBs cannot be explained by the so-called standard, geometrically thin, optically thick, Keplerian Shakura-Sunyaev disks (SSDs), which is responsible for the softer spectrum. The hard X-rays are responsible for optically thin, geometrically thick, hot advective accretion disks around the central accretor. Till now, the outer region of XRB and active galactic nucleus (AGN) disks is understood to be colder SSD and inner region to be advective accretion disk, together forming a disk-wind system. Although we try to explore different scientific objectives, throughout this thesis work, our study is centered around hot advective accretion flows around WD, NS and BH.