MG12 - Talk detail
 

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Abstract

Seeing is believing -- Do we see black holes?

Astrophysical black holes, those residing in Quasars to nano-quasars, cannot be 'seen' in conventional sense. However, the circumstantial evidences are piling up to show that they must exist. Based on very robust studies of hydrodynamic and radiative transfer processes specific to black hole space time, we are now pretty certain about the paradigm of the black hole accretion and formation of jets and outflows. We discuss this in the context of the stellar mass (nano-quasar), intermediate mass (micro-quasar), massive (milli-quasar) and super-massive (quasars) black holes.

Evidence of two component flows in the evolution of QPOs in Outburst sources

There seems to be a universality in the way the QPOs evolve in the outburst sources. We present examples of several such cases and follow how the QPOs evolve. Our conclusions are (a) The shock waves propagate towards the black holes during the rising phase and away from the black hole during the decline phase; (b) The oscillation of the shock causes the QPOs; (c) The QPO frequency variation can be modeled very accurately using very small propagation velocity (d) At the beginning of the outburst phase even the Keplerian disk is found to be in a formative stage.

Standing, Oscillating and Propagating Shocks in relativistic flows around black hole

A surprising feature of the curved spacetime around a black hole is that the flow may have multiple sonic points with higher entropy solutions passing through the inner sonic points. This enable a formation of a shock wave in the flow. Detail study shows that the shock formed in between the sonic points could be standing, oscillating or propagating. We present examples of these solutions. Just like a hard surface on a neutron star allows the formation of the shock and the consequent boundary layer, the shock around a black hole is centrofugal pressure dominated and also behaves like a boundary layer, enabling dissipation of heat and formation of jet in this region. We also discuss whether we actually see these boundary layers of a black hole!

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