538 research outputs found
On gamma and neutrino radiation from Cyg X-3
The production of high energy gamma and neutrino radiation is studied for Cyg X-3. A heating model is proposed to explain the presence of only one gamma-pulse during 4.8 h period of the source. The acceleration mechanisms are discussed. High energy neutrino flux from Cyg X-3 is calculated
Diffusive propagation of UHECR and the propagation theorem
We present a detailed analytical study of the propagation of ultra high
energy (UHE) particles in extragalactic magnetic fields. The crucial parameter
which affects the diffuse spectrum is the separation between sources. In the
case of a uniform distribution of sources with a separation between them much
smaller than all characteristic propagation lengths, the diffuse spectrum of
UHE particles has a {\em universal} form, independent of the mode of
propagation. This statement has a status of theorem. The proof is obtained
using the particle number conservation during propagation, and also using the
kinetic equation for the propagation of UHE particles. This theorem can be also
proved with the help of the diffusion equation. In particular, it is shown
numerically, how the diffuse fluxes converge to this universal spectrum, when
the separation between sources diminishes. We study also the analytic solution
of the diffusion equation in weak and strong magnetic fields with energy losses
taken into account. In the case of strong magnetic fields and for a separation
between sources large enough, the GZK cutoff can practically disappear, as it
has been found early in numerical simulations. In practice, however, the source
luminosities required are too large for this possibility.Comment: 16 pages, 13 eps figures, discussion of the absence of the GZK
cut-off in strong magnetic field added, a misprint in figure 6 corrected,
version accepted for publication in Ap
High Energy Neutrinos: Sources and Fluxes
We discuss briefly the potential sources of high energy astrophysical
neutrinos and show estimates of the neutrino fluxes that they can produce. A
special attention is paid to the connection between the highest energy cosmic
rays and astrophysical neutrinos.Comment: 7 pages, 2 figures, submitted to the Proceedings of TAUP 2005
workshop, corrected left panel of figure
Anti-GZK effect in UHECR spectrum
In this paper we discuss the anti-GZK effect that arises in the framework of
the diffusive propagation of Ultra High Energy (UHE) protons. This effect
consists in a jump-like increase of the maximum distance from which UHE protons
can reach the observer. The position of the jump is independent of the
Intergalactic Magnetic Field (IMF) strength and depends only on the energy
losses of protons, namely on the transition energy from adiabatic and
pair-production energy losses. The Ultra High Energy Cosmic Rays (UHECR)
spectrum presents a low-energy steepening approximately at this energy, which
is very close to the position of the observed second knee. The dip, seen in the
universal spectrum as a signature of the proton interaction with the Cosmic
Microwave Background (CMB) radiation, is also present in the case of diffusive
propagation in magnetic fields.Comment: 4 pages, 4 eps figures, talk given at IFAE 2005: Incotri Fisica Alte
Energie, Catania, Italy, 30 March - 2 April 200
Neutrinos: the Key to UHE Cosmic Rays
Observations of ultrahigh energy cosmic rays (UHECR) do not uniquely
determine both the injection spectrum and the evolution model for UHECR sources
- primarily because interactions during propagation obscure the early Universe
from direct observation. Detection of neutrinos produced in those same
interactions, coupled with UHECR results, would provide a full description of
UHECR source properties.Comment: three pages, three figures. corrected typo
Bounds on hep neutrinos
The excess of highest energy solar-neutrino events recently observed by
Superkamiokande can be in principle explained by anomalously high
-neutrino flux . Without using SSM calculations, from the
solar luminosity constraint we derive that cannot exceed
the SSM estimate by more than a factor three. If one makes the additional
hypothesis that neutrino production occurs where the He concentration
is at equilibrium, helioseismology gives an upper bound which is (less then)
two times the SSM prediction. We argue that the anomalous -neutrino flux
of order of that observed by Superkamiokande cannot be explained by
astrophysics, but rather by a large production cross-section.Comment: 7 pages, RevTeX fil
A standard source for high energy neutrino astronomy
A standard source of high energy neutrinos composed of a source of accelerated particles imbedded in a cloud of low density gas is described. The main mechanism of neutrino production in the source is pp-collision, and the main process of detection is through muons produced underground by the neutrions. The flux of neutrino-produced muons is computed for sources with different spectral index
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