Evolution of Flow Properties Around Black Holes from Observations: Developments over the Past Decades

Abstract

To find direct observational evidences of accretion flows around black holes, one needs to study them with a physical model. Although there are many phenomenological and theoretical models available in the literature, observational astronomy of black holes has changed significantly after the successful implementation of the two component advective flow solution (TCAF) into XSPEC as an additive table model to fit energy spectra. Accretion flow dynamics around black holes are now more transparent, since a spectral fit with this most generalized accretion flow solution directly provides us information about the flow parameters. Prediction of quasi-periodic oscillation frequencies, which is a timing feature, is also a reality from the TCAF model fitted shock parameters. One can also estimate black hole mass, spin, etc., which are intrinsic source parameters from spectral analysis with the TCAF solution. Estimation of X-ray contribution from jets or outflows are also possible from spectral analysis with the TCAF solution.