Whither TCAF?

Sandip K. Chakrabarti1,2*
1S.N. Bose National Centre for Basic Sciences, Block-JD, Salt Lake, Kolkata, India
2Indian Centre for Space Physics, Chalantika 43, Garia Station Road, Kolkata, India

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Two Component Advective Flow is the only complete solution that incorporates outcomes of actual theoretical solutions to explain spectral and timing properties of radiation emitted from the vicinity of black holes. It redefined the subject of black hole astrophysics by upgrading it from some sort of ‘climatology’ and making it a precision science. Today any good spectral and temporal data could be fitted with TCAF with ease using as few as four parameters, totally un-heard of by the plethora of models which are rat-racing to fit gross properties of data. TCAF addresses most of the issues of observations from both galactic and extra-galactic black holes while keeping the underlying framework (equations, assumptions) unchanged. We discuss some of these points in this short review. As such, it concentrates on our group’s work to develop the subject till the present day. Most interestingly, these success of TCAF were accomplished without explicitly using any magnetic field. The magnetized disk solutions or simulated results in the literature till date are in the dark of how these issues could be addressed, indicating that magnetic fields in the accretion flow are either not implemented properly or may not be as important as they are thought and made out to be. Other models of hot accretion flow are either special cases of TCAF or are simply wrong and can explain some special features on special occasions. We claim that any observation that can be fitted by any of the multitude of models can be most certainly fitted with TCAF using far fewer number of parameters.

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Keywords : black hole physics - accretion disks - hydrodynamics - shock waves - radiative transfer