[en] The effects of the feedback of e(+)-e(-) pair reinjection in a plasma due to photon photon absorption of its own radiation are examined. A mechanism is presented which can produce an electron distribution function that can account for the overall spectral distribution of radiation of AGNs and QSOs and the specific slopes observed in the IR to UV and 2-50 keV bands. It is interesting to note that the necessary condition for this mechanism to work (i.e., most of energy injected at e(M sub e)(C sup 2) is realized in the accretion shock model of Kazanas and Ellison. This mechanism involves only one free parameter the compactness of the sources, L/R, whose mean value can also account for the diffuse gamma ray background in terms of AGNs

[en] A model for active galactic nuclei (AGN), employing quasi-spherical accretion onto a black hole, when scaled down to solar mass objects, provides a straightforward account of the bimodal spectral behavior of Cyg X-1 and the other galactic black hole candidates. It is argued that the change in the spectrum is due to the drastic increase of the source compactness (L/R) with the accretion rate m and the subsequent conversion of most of the energy released by accretion into e(+)e(-) pairs. It is also argued that similar changes may be observed in active galactic nuclei

[en] The effects of the feedback of e(+)-e(-) pair reinjection in a plasma due to photon-photon absorption of its own radiation was examined. Under the assumption of continuous electron injection with a power law spectrum E to the minus gamma power and Compton losses only, it is shown that for gamma 2 the steady state electron distribution function has a unique form independent of the primary injection spectrum. This electron distribution function can, by synchrotron emission, reproduce the general characteristics of the observed radio to optical active galactic nuclei spectra. Inverse Compton scattering of the synchrotron photons by the same electron distribution can account for their X-ray spectra, and also implies gamma ray emission from these objects. This result is invoked to account for the similarity of these spectra, and it is consistent with observations of the diffuse gamma ray background

[en] The general properties of Active Galactic Nuclei (AGN) and quasars are reviewed with emphasis on their continuum spectral emission. Two general classes of models for the continuum are outlined and critically reviewed in view of the impending GRO (Gamma Ray Observatory) launch and observations. The importance of GRO in distinguishing between these models and in general in furthering the understanding of AGN is discussed. The very broad terms the status of the current understanding of AGN are discussed

[en] A model for a class of quasars and active galactic nuclei is described in which a shock around a massive black hole randomizes the infall kinetic energy of spherically accreting matter producing a nonthermal spectrum of high energy protons. These protons may be responsible for the secondary production (via tau + or - decay) of the radio emitting high energy electrons and also of high energy gamma rays (via pi decay and inverse Compton interactions of the electrons). The correlation between radio and gamma ray emission implied by the model is in good agreement with observations of 3C273. Observation of the flux of high energy neutrinos from quasars may provide a test for the model

[en] It is proposed that the fireballs invoked to explain the Centauro events are bubbles of a metastable superdense state of nuclear matter, created in high energy (E is approximately 10 to the 15th power eV) cosmic ray collisions at the top of the atmosphere. If these bubbles are created with a Lorentz factor gamma approximately = 10 at their CM frame, the objections against the origin of these events in cosmic ray interactions are overcome. Assuming further, that the Centauro events are to the explosive decay of these metastable bubbles, a relationship between their lifetime, tau, and the threshold energy for bubble formation, E sub th, is derived. The minimum lifetime consistent with such an interpretation in tau is approximately 10 to the -8th power sec, while the E sub th appears to be insensitive to the value of tau and always close to E sub th is approximately 10 to the 15th power eV. Finally it is speculated that if the available CM energy is thermalized in such collisions, these bubbles might be manifestations of excitations of the SU(2) x U(1) false vacuum. The absence of neutral pions in the Centauro events is then explained by the decay of these excitations

[en] A model for a class of quasars and active galactic nuclei is proposed in which a shock around a massive black hole randomizes the infall kinetic energy of spherically accreting matter producing a nonthermal spectrum of high energy protons. It is suggested that these protons are responsible for the secondary production (via proton decay) of the radio emitting high energy electrons and also of high energy gamma-rays (via proton decay and inverse Compton interactions of the electrons). The correlation between radio and gamma-ray emission implied by the model is in good agreement with observations of 3C273. Observation of the flux of high energy neutrinos from quasars may provide a test for the model

[en] A model for the origin of relativistic particles and gamma rays in active galactic nuclei and quasars, together with recent HEAO-1 observations of the spectra of active galaxies from 2 to 165 keV, provide the basis for a reexamination of the nature of the extragalactic gamma ray background. Active galaxies account for the observed background if their X-ray spectra steepen to E.021 above 100 keV, as observed in Cen-A, together with a further steepening to E.021 as a result of absorption of gamma rays by photon-photon pair production interactions with X-ray photons. The compactness of active galaxies required to give this steepening is consistent with estimates of their typical luminosity and radius

[en] The authors examine the possibility of neutron viscosity as the mechanism responsible for the dissipation of kinetic energy into luminosity in the innermost parts (r < 100 R sub s) of accretion disks surrounding compact objects. They present simplified models of such self-consistent, steady state accretion flows in which the viscosity is provided by neutron collisions with the accreting ions. Their results indicate that neutrons can indeed provide the necessary dissipation to sustain the steady state accretion of matter, and thus present a promising way of modeling the bright galactic X-ray sources such as Cyg X-1

[en] Active galactic nuclei (AGNs) and quasars (QSOs) appear to emit roughly equal energy per decade from radio to gamma-ray energies (e.g. Ramaty and Ligenfelter 1982). This argues strongly for a nonthermal radiation mechanism (see Rees 1984). In addition, statistical studies have indicated that the spectra of these objects in the IR-UV and 2 to 50 keV x-ray band, can be fitted very well with power laws of specific indices. These spectral indices do not seem to depend on the luminosity or morphology of the objects (Rothschild et al. 1983; Malkan 1984), and any theory should account for them in a basic and model independent way. If shocks accelerate relativistic protons via the first-order Fermi mechanism (e.g. Axfor 1981), the radiating electrons can be produced as secondaries throughout the source by proton-proton (p-p) collisions and pion decay, thus eliminating Compton losses (Protheroe and Kazanas 1983). As shown by Kazanas (1984), if relativistic electrons are injected at high energies, e+-e- pair production results in a steady state electron distribution that is very similar to that observed in AGNs, independent of the details of injection and the dynamics of the source. The conditions required by this mechanism are met in the shock model of Eichler (1984) and Ellison and Eichler (1984) which allows the self-consistent calculation of the shock acceleration efficiency