Black Hole Accretion: From Quasars to Nano-Quasars

In this review we shall comment on a few recent findings which strengthen the view that the black hole accretion has substantial amount of sub-Keplerian component. The manifestation of this component is many fold. We discuss some of them. A general outline of the complex structure that emerges from the multitude of observations is presented. A detailed outline of what might be going on in outburst sources is also discussed. The relationship amount the spectral and timing properties can be best understood by this picture. We claim that the sub-Keplerian advective disk paradigm is a complete package. Since signatures of sub-Keplerian motion is already increasing in the literature, the whole package must be correct.Comment: 7 Pages, 2 Figures, Proceeding of the 2nd Kolkata Conference on "Observational Evidence for the Black Holes in the Universe", Published in AIP, 200

Universal canonical black hole entropy

Non-rotating black holes in three and four dimensions are shown to possess a canonical entropy obeying the Bekenstein-Hawking area law together with a leading correction (for large horizon areas) given by the logarithm of the area with a {\it universal} finite negative coefficient, provided one assumes that the quantum black hole mass spectrum has a power law relation with the quantum area spectrum found in Non-perturbative Canonical Quantum General Relativity. The thermal instability associated with asymptotically flat black holes appears in the appropriate domain for the index characterising this power law relation, where the canonical entropy (free energy) is seen to turn complex.Comment: Revtex, 5 pages, no figures. Typos corrected and a footnote and some references adde

Spectral Properties of M87 Using Two-Component Flow

We fit the observational data for M87 using two-component advective disk model. We show that the flat spectrum from the nucleus of M87 is due to synchrotron radiation produced by non-thermal electrons in the CENBOL. The non-thermal distribution is produced due to acceleration of electrons across the shock in a sub-Keplerian flow.Comment: 4 Pages, 1 Figures, Proceeding of the 2nd Kolkata Conference on "Observational Evidence for the Black Holes in the Universe", Published in AIP, 200

Black hole mass measurements using ionized gas discs: systematic dust effects

Using detailed Monte Carlo radiative transfer simulations in realistic models for galactic nuclei, we investigate the influence of interstellar dust in ionized gas discs on the rotation curves and the resulting black hole mass measurements. We find that absorption and scattering by interstellar dust leaves the shape of the rotation curves basically unaltered, but slightly decreases the central slope of the rotation curves. As a result, the "observed" black hole masses are systematically underestimated by some 10 to 20% for realistic optical depths. We therefore argue that the systematic effect of dust attenuation should be taken into account when estimating SMBH masses using ionized gas kinematics.Comment: 4 pages, 2 figures, to appear in "Observational Evidence for Black Holes in the Universe", AIP Conference Proceeding