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Space Sciences Seminar

Theoretical and Observational Constraints on Accretion Flows on Black
Hole: The Case of sub-Keplerian Motion

Friday, May 23, 2008 - 11:00am
Speaker:
Sandip K. Chakrabarti, Senior Professor, S.N. Bose National Centre for Basic Sciences
Location:
Research I, Room 302

Abstract

Theoretically, matter enters into a black hole with velocity of light
and thus every flow, independent of its past history, must be
supersonic on the horizon. Not surprisingly, the transonic flow
solutions respect such a boundary condition, even when it allows very
exciting possibility that flows should pass through shocks and slow
the matter down at a few Schwarzschild radii before the horizon. It is
thus no surprise that ALL the observations (ranging from spectral
state transition, Quasi-periodic oscillations, jets and outflows and
non-thermal spectra from black holes) agree to the fact that such a
Centrifugal Pressure Dominated Boundary Layer (CENBOL) should exist.
There are several post-facto cartoon models in the literature which
apparently have no knowledge of such beautiful behaviour of the flow
and surprisingly come up with cartoon diagrams having the same
behaviour. In our advective disk paradigm, jets are produced when
CENBOL is present. Thus it no surprise that some post-facto models
include the base of the jet (which is nothing but CENBOL in our
picture) in explaining outgoing spectrum from disk surface and thereby
creating a confusion that X-rays from the jets are also serious
contestants. We show that for every observation that has been a
pre-facto prediction of our paradigm of two component advective flow
(TCAF). These are re-discovered by many in the literature under new
names, pictures and models. What is more important, however, is that
the theoretical solutions and the cartoons from fitting observational
data are finally converging. This paves the way of further progress in
the subject.

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