1,355,029 research outputs found
Small-angle scattering and diffusion: Application to relativistic shock acceleration
No full textCopyright © 2003. Space Science Reviews. All rights reserved. Printed in U.S.A. Submitted to Cornell University’s online archive www.arXiv.org in 2003 by Ray Protheroe. Post-print sourced from www.arxiv.org.We investigate ways of accurately simulating the propagation of energetic charged particles over small times where the standard Monte Carlo approximation to diffusive transport breaks down. We find that a small-angle scattering procedure with appropriately chosen step-lengths and scattering angles gives accurate results, and we apply this to the simulation of propagation upstream in relativistic shock acceleration.R.J. Protheroe, A. Meli and A.-C. Done
Estimating jet power in proton blazar models
No full text© Copyright © 2002. Astronomical Society of the Pacific. All rights reserved. Printed in U.S.A. Submitted to Cornell University’s online archive www.arXiv.org in 2002 by Ray Protheroe. Post-print sourced from www.arxiv.org.We discuss the various contributions to the jet luminosity in proton blazar models of active galactic nuclei and describe a method of estimating the jet luminosity from the observed spectral energy distribution (SED) and the fitted model parameters. We apply this to a synchrotron proton blazar (SPB) model for Markarian 501.R.J. Protheroe, A. Mück
R.j. Protheroe
No full textIn this lecture I give an overview of shock acceleration, interactions of high energy cosmic rays with, and propagation through, the background radiation, and the resulting electron-photon cascade. I argue that while the origin of the highest energy cosmic rays is still uncertain, it is not necessary to invoke exotic models such as emission by topological defects to explain the existing data. It seems likely that shock acceleration at Fanaroff-Riley Class II radio galaxies can account for the existing data. However, new cosmic ray data, as well as better estimates of the extragalactic radiation fields and magnetic fields will be necessary before we will be certain of the origin of the highest energy particles occurring in nature. 1 Introduction Cosmic rays with energies up to 100 TeV are thought to arise predominantly through shock acceleration by supernova remnants (SNR) in our Galaxy [1]. A fraction of the cosmic rays accelerated should interact within the supernova remnant and prod..
Cosmic Rays from the Nucleus of M87
No full text© 2003 by Universal Academy PressThe unresolved nuclear region of M87 emits strong non-thermal emission from radio to X-rays, and this has been interpreted as jet emission from a misaligned BL Lac Object in the context of the Synchrotron Proton Blazar (SPB) model (Protheroe et al 2003). In this model extragalactic cosmic rays are generated as neutrons produced in pion photoproduction interactions decaying into protons after escaping from the host galaxy. Because energetic protons are deflected by the intergalactic magnetic field, the protons from the decay of neutrons emitted in all directions, including along the jet axis where the Doppler factor and hence emitted neutron energies are higher, can contribute to the observed ultra-high energy cosmic rays. We consider the propagation of these cosmic ray protons to Earth and conclude that M87 could account for the observed flux if the extragalactic magnetic field topology were favourable.Alina-C. Donea, Raymond J. Protheroe and Anita Reime
A hadronic model for gamma-ray loud quasars
No full text©2003 by Universal Academy PressWe discuss the spectral energy distribution (SED) of quasars in a hadronic model having both internal and external target photon fields. The high energy part of the SED results from a cascade initiated by electrons from charged pion decay and Bethe-Heitler pair production and gamma-rays from neutral pion decay, and involves synchrotron radiation, inverse-Compton scattering and photonphoton pair production. We apply this model to 3C 273.R.J. Protheroe, A.-C. Done
Application of the synchrotron proton blazar model to BL Lac objects.
No full textWe apply the synchrotron proton blazar (SPB) model to the April 1997 flare of Markarian 501 and find we are able to fit the observed spectral energy distribution. We explore the effect of target photon density on the high energy part of the spectral energy distribution (SED) for fixed assumed magnetic field, emission region size and Doppler factor and find that the luminosity and peak frequency of the high energy part of the SED may depend on the luminosity of the low energy part of the SED in high-frequency peaked BL Lac objects (HBL).Raymond J. Protheroe and Anita Muck
Hedda Gabler
No full textCast: Darlene Johnson, Brian Protheroe, Rhys McConnochie, Sam Kelly, Sarah Stephenson. Directed by Philip Hedley ; produced by Harold Mantell. Narrator, Irene Worth. Director of photography, Michael Delaney ; editor, Carlo Arcamone.Presents an abridged version of Ibsen's play, Hedda Gabler, the story of a woman's tormented search for self-fulfillment in a world dominated by men
Ultra high energy cosmic rays
No full text© CSIRO 2004Cosmic rays with energies above 1018 eV are currently of considerable interest in astrophysics and are to be further studied in a number of projects which are either currently under construction or the subject of well-developed proposals. This paper aims to discuss some of the physics of such particles in terms of current knowledge and information from particle astrophysics at other energiesR. J. Protheroe and R. W. Cla
Supplementary_photos – Supplemental material for Celebrating the health literacy skills of parents: A photovoice study
No full textSupplemental material, Supplementary_photos for Celebrating the health literacy skills of parents: A photovoice study by Emee Vida Estacio, Lavinia Nathan and Joanne Protheroe in Journal of Health Psychology</p
Tori and TeV gamma-ray emission in AGN
No full textThe absorption of TeV gamma-rays in active galactic nuclei by photon-photon pair production on infrared radiation from a parsec scale torus at temperature ˜ 1000 K surrounding the accretion disk/base of jet was discussed by Protheroe and Biermann (Astropart. Phys., 6, 293, 1997). Here we briefly review the evidence for the existence of dusty infrared tori in blazars, and construct torus models consistent with infrared and optical polarimetry data. This leads us to propose a symbiosis between large and small-scale dust features and broad line regions in AGN. We discuss the radiation fields of the accretion disk, broad line region and dusty torus as target photons for pion photoproduction by protons and photon-photon pair production by γ-rays. We use our results to constrain the sites of emission of TeV gamma rays.A.-C. Donea and R. J. Prothero
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