Dr. Santanu Mondal

Material captured by a black hole forms a differentially rotating disk that is known as an accretion disk,due to the inward transport of mass. Accreted material releases copious amounts of energy in the form of radiation,relativistic jets, and outflows, yet the causal connection between accretion and ejection is a jigsaw puzzle. The phenomenology of X-ray observations of these objects is very rich and has been exhaustively studied. To date, however, there is little agreement on the physics behind different accretion states and their transitions. To go beyond the standard model of a stable accretion flow, with no corona and only a parametric viscosity of unknown origin,it is necessary to rely on a promising physical solution. In this talk, I will discuss the spectral and timing properties of black hole binaries and what they tell us about the accretion-ejection flows. The efforts on probing the disk-corona-jet connection during black hole outbursts using observational data and detailed theoretical modeling will also be discussed. Finally, I will introduce some of my recent works to understand the powering mechanism of ultraluminous X-ray sources, changing look phenomena in active galactic nuclei, and the origin of the Fermi Bubbles.