In this paper, we consider the effect of thermal fluctuations on the entropy of both neutral and charged black holes. We emphasize the distinction between fixed and fluctuating charge systems; using a canonical ensemble to describe the former and a grand canonical ensemble to study the latter. Our novel approach is based on the philosophy that the black hole quantum spectrum is an essential com...

Two-temperature spherical accretion flows produce ≈ 100 Mev gamma-rays from the decay of neutral pions created in proton-proton collisions close to the black hole; they also produce ∼ 10 keV X-rays by bremsstrahlung emission at large radii. The gamma-ray to X-ray luminosity ratio is nearly independent of black hole mass and accretion rate. It does depend sensitively on the radial density profil...

We have analyzed the soft X-ray emission from the nuclear source of the nearby spiral galaxy M81, using the available data collected with ROSAT, ASCA, BeppoSAX, and Chandra. The source flux is highly variable (sometimes dramatic: a factor of 4 in 20 days), showing variability at different timescales, from 2 days to 4 yr, and in particular a steady increase of the flux by a factor of k2 over 4 y...

It has been argued by several authors that the quantum mechanical spectrum of black hole horizon area must be discrete. This has been confirmed in different formalisms, using different approaches. Here we concentrate on two approaches, the one involving quantization on a reduced phase space of collective coordinates of a Black Hole and the algebraic approach of Bekenstein. We show that for non-...

We study phases of five-dimensional three-charge black holes with a circle in their transverse space. In particular, when the black hole is localized on the circle we compute the corrections to the metric and corresponding thermodynamics in the limit of small mass. When taking the near-extremal limit, this gives the corrections to the constant entropy of the extremal three-charge black hole as ...

In many astrophysical scenarios the charge of black hole is often neglected due to unrealistically large values required for Reissner-Nordstr\"om spacetime metric. However, holes may possess small electric various selective accretion mechanisms. this paper we investigate effect a hypothetical Schwarzschild on ionization freely falling neutral particle and subsequent escape ionized from hole. We...

We have analysed the soft X-ray emission from the nuclear source of the nearby spiral galaxy M 81, using the available data collected with ROSAT, ASCA, BeppoSAX and Chandra. The source flux is highly variable, showing (sometimes dramatic: a factor of 4 in 20 days) variability at different timescales, from 2 days to 4 years, and in particular a steady increase of the flux by a factor of 2 over 4...

We present evidence for a broad, ionized Fe Kα line in the XMM-Newton spectrum of the broad-line radio galaxy (BLRG) 4C+74.26. This is the first indication that the innermost regions of the accretion flow in BLRGs contain thin, radiatively efficient disks. Analysis of the 35 ks XMM-Newton observation finds a broad line with an inner radius close to the innermost stable circular orbit for a maxi...

Two-temperature spherical accretion flows produce ≈ 100 Mev gamma-rays from the decay of neutral pions created in proton-proton collisions close to the black hole; they also produce ∼ 10 keV X-rays by bremsstrahlung emission at large radii. The gamma-ray to X-ray luminosity ratio is nearly independent of black hole mass and accretion rate. It does depend sensitively on the radial density profil...