631 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
On some problems of gamma-astronomy
Gamma ray emissions from young supernova remnants are discussed and calculated. The positron annihilation line is also calculated. Decay of charged pions in remnants cause generation of high energy neutrinos. This emission of neutrinos is reviewed. The CR origin and gamma emission from Magellanic clouds help to establish the intensity gradient in the galaxy. This gamma astronomical data is briefly discussed
Neutrino-antineutrino annihilation around collapsing star
Stellar collapse is accompanied by emission of E sub neutrino approximately 10 MeV neutrinos and antineutrinos with the energy output W sub neutrino approximately 10 to the 53rd power to 10 to the 54th power erg. Annihilation of these particles in the vicinity of collapsar is considered. The physical consequences are discussed
Disappointing model for ultrahigh-energy cosmic rays
Data of Pierre Auger Observatory show a proton-dominated chemical composition
of ultrahigh-energy cosmic rays spectrum at (1 - 3) EeV and a steadily heavier
composition with energy increasing. In order to explain this feature we assume
that (1 - 3) EeV protons are extragalactic and derive their maximum
acceleration energy, E_p^{max} \simeq 4 EeV, compatible with both the spectrum
and the composition. We also assume the rigidity-dependent acceleration
mechanism of heavier nuclei, E_A^{max} = Z x E_p^{max}. The proposed model has
rather disappointing consequences: i) no pion photo-production on CMB photons
in extragalactic space and hence ii) no high-energy cosmogenic neutrino fluxes;
iii) no GZK-cutoff in the spectrum; iv) no correlation with nearby sources due
to nuclei deflection in the galactic magnetic fields up to highest energies.Comment: 4 pages, 7 figures, the talk presented by A. Gazizov at NPA5
Conference, April 3-8, 2011, Eilat, Israe
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