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Seminars and Colloquia


Numerical Studies of sub-Keplerian Accretion Disk around Black Holes 
Wed, Jan 23, 2019,   04:00 PM at Physics Seminar Room 31, 2nd Floor, Main Building

Dr Sudip Garain
University of Notre Dame, USA

Abstract :

Two component advective flow (TCAF) model is quite successful in explaining the spectral and timing properties of the accretion disks around black holes. According to this model, the most general structure of an accretion disk consists of a Keplerian and a sub-Keplerian component. Theoretical calculations predict that as the sub-Keplerian matter approaches the black holes, it slows down due to centrifugal force and sometimes, a shock may form. In the post-shock region, the sub-Keplerian matter mixes up with a Keplerian component and an optically slim (optical depth ~ 1) disk is formed. Because of the shock, this region becomes hotter too. It is believed that the soft photons from the Keplerian disk get inverse-Comptonized in this post-shock region and leave the system as hard radiations (Chakrabarti & Titarchuk 1995). In this talk, I shall mainly present results of our numerical experiments of the sub-Keplerian component showing that the formation of the shock is indeed possible under various circumstances. I shall also present some simulation results showing how such disk can explain the observed radiations from the black hole binaries. Finally, I shall present our new simulation technique on Geodesic Mesh and present a few 3D simulation results of the sub-Keplerian disk.

In the later part of my presentation, I shall present some results of my research activities associated with the studies of turbulent dynamo and computational electrodynamics.