Raymond J. Protheroe

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I give a brief critical review of the predicted intensity of diffuse high energy neutrinos of astrophysical origin over the energy range from ∼ 10 eV to ∼ 10 eV. Neutrinos from interactions of galactic cosmic rays with interstellar matter are guaranteed, and the intensity can be reliably predicted to within a factor of 2 up to 10 eV. Somewhat less certain(More)
We consider the implications of the recent determination of the universal infrared background for the propagation of photons up to 20 TeV from the active galaxy Markarian 501 as observed by HEGRA. At 20 TeV the mean free path for photon-photon collisions on the infrared background would be much shorter than the distance to Markarian 501, implying absorption(More)
The amplitude of the magnetic field near the Galactic Centre has been uncertain by two orders of magnitude for several decades. On a scale of approximately 100 parsecs (pc), fields of approximately 1,000 microgauss (microG; refs 1-3) have been reported, implying a magnetic energy density more than 10,000 times stronger than typical for the Galaxy.(More)
I discuss the shape of the high energy end of the spectrum of particles arising from diffusive shock acceleration in the presence of (i) additional diffusive escape from the accelerator, (ii) continuous energy losses, (iii) energy changes arising from interactions. The form of the spectrum near cut-off is sensitive to these processes as well as to the(More)
High energy gamma-ray emission has been observed above 100 MeV from at least 40 active galactic nuclei (AGN) by the EGRET instrument on the Compton Gamma Ray Observatory (CGRO), and above 300 GeV gamma rays have been detected by the Whipple observatory from two AGN. The sources detected so far are \blazars" indicating a jet origin for the gamma rays. They(More)
We describe the results of a hybrid matrix{Monte Carlo calculation of cascading of UHE cosmic rays and-rays through the cosmic background radiation elds over cosmological distances. We calculate the-ray and neutrino emission that results from the cascade, as well as the eeect of cascading on the primary spectrum. We discuss the results for various cosmic(More)
The unresolved nuclear region of M87 emits strong non-thermal emission from radio to X-rays. Assuming this emission to originate in the pc scale jet aligned at θ ∼ 30 to the line of sight, we interpret this emission in the context of the Synchrotron Proton Blazar (SPB) model. We find the observed nuclear jet emission to be consistent with M87 being a(More)