Spectral properties of two component advective flows around black holes with standing shock in presence of Comptonization

P. S. Pal1* and S. K. Chakrabarti1,2
1Indian Centre for Space Physics, Chalantika 43, Garia Station Rd., Kolkata, 700084, India
2S. N. Bose National Centre for Basic Sciences, Salt Lake, Kolkata, 700098, India

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We study a self-consistent solution for the spectral properties of a general class of steady state accretion disks in presence of Comptonization. We couple both the hydrodynamics and the radiative transfer process analytically to calculate the emitted spectrum. In our work, we consider a two-component accretion flow, where one component (Keplerian) supplies soft photons, which are reprocessed by the electrons in the halo (sub-Keplerian). We show how the boundary changes as the shock moves inward in presence of Compton cooling. Due to the radiative loss, some energy is removed from the accreting matter and the shock moves towards the black hole to maintain the pressure balance condition. We solve the two-temperature equations with Coulomb energy exchange between the protons and the electrons, and the radiative processes such as the bremsstrahlung and Comptonization. We modify Rankine-Hugoniot relation to obtain the shock-locations when the post-shock region suffers energy loss due to Comptonization. We compute the radiated spectrum from the disk and study the variation of the hydrodynamical and spectral properties as functions of the accretion rates of the Keplerian and sub-Keplerian components. Ours is the most self consistent transonic solution of an inviscid flow around a black hole till now.

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Keywords : black holes – accretion, accretion discs – shock waves – hydrodynamics