Study of Accretion processes Around Black Holes becomes Science: Tell Tale Observational Signatures of Two Component Advective Flows

摘要

An accretion flow around a black hole has a saddle type sonic point justoutside the event horizon to guarantee that the flow enters the black holesupersonically. This feature exclusively present in strong gravity limit makesits marks in every observation of black hole candidates. Another physical sonicpoint is present (as in a Bondi flow) even in weak gravity. Every aspect ofspectral or temporal properties of every black hole can be understood usingthis transonic or advective flow having more than one saddle type points. Thismost well known and generalized solution with viscosity and radiative transferhas been verified by numerical simulations also. Spectra, computed for variouscombinations of the standard Keplerian, and advective sub-Keplerian componentsmatch accurately with those from satellite observations. Standing, oscillatingand propagatory oscillating shocks are produced due to centrifugal barrier ofthe advective component. The post-shock region acts as the Compton cloudproducing the power-law spectra. Jets and outflows are also produced from thispost-shock region, commonly known as the CENtrifugal barrier supported BOundaryLayer or CENBOL. In soft states, the CENBOL is cooled down by soft photons fromthe Keplerian disk, and thus the outflow is absent. Type-C and Type-B QPOs aregenerated respectively due to strong and weak resonance oscillations of theCENBOL. Away from resonance, oscillation may be triggered when Rankine-Hugoniotconditions are not satisfied and Type-A QPOs could be seen.