Status of the accretion flow solution in the Golden Jubilee year of the discovery of extra-solar X-ray sources

S. K. Chakrabarti1,2*
1S. N. Bose National Centre for Basic Sciences, JD Block, Salt Lake, Kolkata, 700098, India
2Indian Centre for Space Physics, 43 Chalantika, Garia Station Rd., Kolkata, 700084, India

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Fifty years have just passed since the first discovery of the extra-solar X-ray sources by Giacconi and his team which we know today to be some stellar mass black holes. By 1973, not only a catalog of these enigmatic objects were made, and their spectra were obtained. Today, forty years have passed since the revolutionary idea of the thin, axisymmetric, Keplerian, disk model by Shakura and Sunyaevwas published. Yet, the complete predictability of their radiative properties remains as illusive as ever. The only available and self-consistent solution to date is the generalized viscous transonic flow solutions where both heating and cooling effects are included. I demonstrate that the latest ‘Avatar’ of the accretion /outflow picture, the Generalized Two Component Advective Flow (GTCAF), is capable of explaining almost all the black hole observational results, when the results of the time dependent simulation of viscous and radiative processes are also taken into consideration. I also discuss the problems with predictability and argue that understanding companion’s behaviour in terms of its habit of mass loss, ellipticity of its orbit, magnetic properties, etc. is extremely important for the prediction of emission properties of the accretion flow.

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Keywords : black hole physics – accretion, accretion discs – hydrodynamics – X-rays: binaries