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We investigate the transition of a radiatively inefficient phase of a viscoustwo temperature accreting flow to a cooling dominated phase and vice versaaround black holes. Based on a global sub-Keplerian accretion disc model insteady state, including explicit cooling processes self-consistently, we showthat general advective accretion flow passes through various phases during itsinfall towards a black hole. Bremsstrahlung, synchrotron and inverseComptonization of soft photons are considered as possible cooling mechanisms.Hence the flow governs a much lower electron temperature ~10^8 - 10^{9.5}Kcompared to the hot protons of temperature ~10^{10.2} - 10^{11.8}K in the rangeof the accretion rate in Eddington units 0.01 - 100. Therefore, the solutionsmay potentially explain the hard X-rays and the gamma-rays emitted from AGNsand X-ray binaries. We finally compare the solutions for two different regimesof viscosity and conclude that a weakly viscous flow is expected to be coolingdominated compared to its highly viscous counterpart which is radiativelyinefficient. The flow is successfully able to reproduce the observedluminosities of the under-fed AGNs and quasars (e.g. Sgr A*), ultra-luminousX-ray sources (e.g. SS433), as well as the highly luminous AGNs andultra-luminous quasars (e.g. PKS 0743-67) at different combinations of the massaccretion rate and ratio of specific heats.

Transition from radiatively inefficient to cooling dominated phase in two temperature accretion discs around black holes