909 research outputs found
Hadronic blazar models and correlated X-ray/TeV flares
The hypothesis that AGN jets might be the sources of the ultra-high energy
cosmic rays has originally motivated the venture of TeV gamma ray astronomy.
Surprisingly, after the discovery of TeV emission from blazars the attention
has shifted to more traditional explanations which do not involve energetic
hadrons, and there is even common believe that a hadronic interpretation is
disfavored by observations. It is shown here that this is not the case, and
that the currently observed spectra and variability features of blazars can be
perfectly understood within hadronic blazar models. I also discuss how hadronic
models might be observationally distinguished from common leptonic models, and
point out some interesting aspects which could be relevant for the
understanding of the differences between blazar classes.Comment: 12 pages LaTeX (aipproc), 3 eps figures included. Invited review
presented at the workshop "GeV-TeV Gamma-Ray Astrophysics", Snowbird, Utah,
199
Conspiratorial cosmology - the case against the Universe
Based on the cosmological results of the Planck Mission, we show that all
parameters describing our Universe within the \Lambda CDM model can be
constructed from a small set of numbers known from conspiracy theory. Our
finding is confirmed by recent data from high energy particle physics. This
clearly demonstrates that our Universe is a plot initiated by an unknown
interest group or lodge. We analyse possible scenarios for this conspiracy, and
conclude that the belief in the existence of our Universe is an illusion, as
previously assumed by ancient philosophers, 20th century science fiction
authors and contemporary film makers.Comment: 4 page
Ultrahigh-Energy Photons as a Probe of Nearby Transient Ultrahigh-Energy Cosmic-Ray Sources and Possible Lorentz-Invariance Violation
Detecting neutrinos and photons is crucial to identifying the sources of
ultrahigh-energy cosmic rays (UHECRs), especially for transient sources. We
focus on ultrahigh-energy gamma-ray emission from transient sources such as
gamma-ray bursts, since >EeV gamma rays can be more direct evidence of UHECRs
than PeV neutrinos and GeV-TeV gamma rays. We demonstrate that coincident
detections of about 1-100 events can be expected by current and future UHECR
detectors such as Auger and JEM-EUSO, and the detection probability can be
higher than that of neutrinos for nearby transient sources at <50-100 Mpc. They
may be useful for constraining the uncertain cosmic radio background as well as
knowing the source properties and maximum energy of UHECRs. They can also give
us more than 10^4 times stronger limits on the Lorentz-invariance violation
than current constraints.Comment: 4 pages, 3 figures, replaced to match the published version (PRL,
103, 081102
On photohadronic processes in astrophysical environments
We discuss the first applications of our newly developed Monte Carlo event
generator SOPHIA to multiparticle photoproduction of relativistic protons with
thermal and power law radiation fields. The measured total cross section is
reproduced in terms of excitation and decay of baryon resonances, direct pion
production, diffractive scattering, and non-diffractive multiparticle
production. Non--diffractive multiparticle production is described using a
string fragmentation model. We demonstrate that the widely used
`--approximation' for the photoproduction cross section is reasonable
only for a restricted set of astrophysical applications. The relevance of this
result for cosmic ray propagation through the microwave background and hadronic
models of active galactic nuclei and gamma-ray bursts is briefly discussed.Comment: 9 pages including 4 embedded figures, submitted to PAS
Prompt high-energy neutrinos from gamma-ray bursts in photospheric and synchrotron self-Compton scenarios
We investigate neutrino emission from gamma-ray bursts (GRBs) under
alternative scenarios for prompt emission (the photospheric and synchrotron
self-Compton scenarios) rather than the classical optically thin synchrotron
scenario. In the former scenario, we find that neutrinos from the pp reaction
can be very important at energies around 10-100 TeV. They may be detected by
IceCube/KM3Net and useful as a probe of baryon acceleration around/below the
photosphere. In the latter scenario, we may expect about EeV pgamma neutrinos
produced by soft photons. Predicted spectra are different from that in the
classical scenario, and neutrinos would be useful as one of the clues to the
nature of GRBs (the jet composition, emission radius, magnetic field and so
on).Comment: 5 pages, 3 figures, replaced to match the final version published as
PRD Rapid Communication, 78, 101302. Minor typos fixe
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