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Full-Text Articles in Astrophysics and Astronomy
Ion Viscosity Mediated By Tangled Magnetic Fields: An Application To Black Hole Accretion Disks, P. Subramanian, P. A. Becker, Menas Kafatos
Ion Viscosity Mediated By Tangled Magnetic Fields: An Application To Black Hole Accretion Disks, P. Subramanian, P. A. Becker, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
We examine the viscosity associated with the shear stress exerted by ions in the presence of a tangled magnetic field. As an application, we consider the effect of this mechanism on the structure of black hole accretion disks. We do not attempt to include a self-consistent description of the magnetic field. Instead, we assume the existence of a tangled field with coherence length λcob• which is the average distance between the magnetic "kinks" that scatter the particles. For simplicity, we assume that the field is self-similar, and take λcob to be a fixed fraction ξ of the local disk height …
Shock Study In Fully Relativistic Isothermal Flows. Ii, Ruixin Yang, Menas Kafatos
Shock Study In Fully Relativistic Isothermal Flows. Ii, Ruixin Yang, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
The isothermal shocks and their stabilities in fully relativistic accretion wedge flows onto black holes are studied. The jump condition across the shock is modified by the relativistic effects when the sound speed is comparable to the speed of light. With a new kind of instability analysis, it is found that only one of the two possible shocks is stable. The results are applied to the QPO behavior in galactic black hole candidates such as Cygnus X-1.
The High-Energy Spectrum Of Hot Accretion Disks, J. A. Eilek, Menas Kafatos
The High-Energy Spectrum Of Hot Accretion Disks, J. A. Eilek, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
A hot, two-temperature accretion disk can be a strong γ-ray and relativistic particle source. This occurs when the accretion rate is high enough -- M/ M ≥ 3 X 10^-9 α γr^-1 for a canonical Kerr black hole-due to the high ion temperature in the inner disk. We present detailed photon and particle spectra for specific disk models. The predicted γ-ray flux is as high as 10% of the bolometric luminosity in sub-Eddington models. Most of the γ-radiation is continuous, due to the π^0 decay, emitted around 100 MeV but degraded to a few MeV in optically thick models. Spectral …
Gamma Rays From Penrose Powered Black Holes In Centaurus A, 3c 273, And Ngc 4151, Menas Kafatos
Gamma Rays From Penrose Powered Black Holes In Centaurus A, 3c 273, And Ngc 4151, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
Gamma-ray observations of active galaxies have important consequences for theories of the activity in their nuclei. The observations of Cen A, 3C 273, and NGC 4151 are examined under the assumption that Penrose collision processes in the ergospheres of massive black holes power their nuclei. The observed sharp break in the MeV region of the NGC 4151 spectrum cannot be due to the γ-γ pair production process. We attribute this break to the Penrose Compton scattering (PCS), in which γ-rays escape from the ergosphere as a result of Penrose processes involving electrons and lower energy X-ray photons in the ergosphere …
Penrose Pair Production As A Power Source Of Quasars And Active Galactic Nuclei, Menas Kafatos, D. Leiter
Penrose Pair Production As A Power Source Of Quasars And Active Galactic Nuclei, Menas Kafatos, D. Leiter
Mathematics, Physics, and Computer Science Faculty Articles and Research
In this paper we propose a new mechanism, Penrose pair production in massive, canonical (with a/M = 0.998) Kerr black holes, as a power source in quasars, Seyfert galaxies, radio galaxies, and BL Lac objects (i.e., what one usually refers to as active nuclei). As a working hypothesis, we postulate that massive (10^8 M0 or around this value) Kerr black holes reside in the centers of these objects. We also postulate that an accretion disk is formed. In a variety of models, hot, inner disks are expected. If the temperature is sufficiently high-as, for example, in the two-temperature model-then MeV …
Penrose Pair Production In Massive, Extreme Kerr Black Holes, D. Leiter, Menas Kafatos
Penrose Pair Production In Massive, Extreme Kerr Black Holes, D. Leiter, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
We show that in the case of very massive (M > 108 M0 ) Kerr black holes with extreme ranges of angular momentum 1 ≥ a/M > 0.998, the possibility of photon-induced Penrose pair production (PPP) in the ergosphere is very plausible. The pairs that escape the ergosphere are very high energy and on the order of the GeV rest mass of the Penrose accreted protons which participate in the photon-induced pair production process. Application of this model to the case of quasistellar objects (QSOs) is shown to lead to reasonable predictions about their masses, lifetimes, and luminosities. The physical mechanism is …