Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992phdt........11g&link_type=abstract
Ph.D. Thesis Maryland Univ., College Park.
Astronomy and Astrophysics
Astronomy
1
Active Galactic Nuclei, Astronomical Models, Emission, Galactic Radiation, Neutrons, Relativistic Particles, Accretion Disks, Active Galaxies, Compton Effect, Luminosity, Synchrotron Radiation, Variability
Scientific paper
Active galactic nuclei produce large amounts of radiation from relatively small regions. How this energy is generated is one of the main topics of research on active galaxies. This work emphasizes the effects of relativistic neutrons on the observed spectrum and on the variability properties of active galactic nuclei. The energy emitted as radiation is initially injected into the system as relativistic protons from a static shock front. The shape of the energy distribution function of the protons is assumed to be a power law form. Through inelastic hadronic collisions the energy in the protons is put into neutrinos, positrons, electrons, and neutrons. The emitted radiation from roughly the near infrared to gamma rays of a few MeV energy is due to emission in the core near the shock front. The neutrons that are sufficiently energetic escape the core and, when they decay, they transfer their energy to charged particles in outer regions that are orders of magnitude larger in size than the core. In this thesis the effects of this energy transport on steady-state and time-dependent active nuclei are studied. When matter falls into the core at roughly the Eddington mass accretion rate the neutron energy transport gives rise to radio-loud and gamma ray loud objects. Both the radio and the gamma ray photons in these objects come from the regions farthest from the central core. A small increase in the infalling medium's density prevents the neutrons from reaching these distances and such models yield radio and gamma ray quiet objects; that is, one sees only the radiation from the core. When the luminosity varies with time, one may expect the radiation from the core to vary on a shorter timescale than radiation from the outer regions. The main parameters in the model are varied in order to determine the relative importance of synchrotron, inverse Compton, and photon-photon interactions. In the time-dependent model, the response of the system to three types of pulses in the proton injection rate were studied. The three forms were a delta function, a step function, and a top-hat function. Two timescales control the observable changes in the radiation, the proton collision timescale and the light travel time to the radiating region for each frequency. The response was mostly as expected from the steady-state model.
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