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Mikhailov A.A.,Yu G Shafer Institute Of Cosmophysical Research And Aeronomy
AIP Conference Proceedings | Year: 2013

A new method search of sources and anisotropy of arrival directions of 10 EeV particles is suggested. It was found that particles flux comes from the galactic plane and that arrival directions correlate with pulsar directions at more than 4-5σ expected in a case of isotropy. Also it is found some correlation of arrival directions with pulsars from only one side of galactic center. © 2013 American Institute of Physics. Source


Volk H.J.,Max Planck Institute for Nuclear Physics | Berezhko E.G.,Yu G Shafer Institute Of Cosmophysical Research And Aeronomy
Astrophysical Journal | Year: 2013

Recent observations of diffuse Galactic γ-ray emission (DGE) by the Fermi Large Area Telescope (Fermi-LAT) have shown significant deviations, above a few GeV to about 100 GeV, from DGE models that use the GALPROP code for the propagation of cosmic ray (CR) particles outside their sources in the Galaxy and their interaction with the target distributions of the interstellar gas and radiation fields. The surplus of radiation observed is most pronounced in the inner Galaxy, where the concentration of CR sources is strongest. The present study investigates this "Fermi-LAT Galactic Plane Surplus" by estimating the γ-ray emission from the sources themselves, which is disregarded in the above DGE models. It is shown that the expected hard spectrum of CRs, still confined in their sources (source cosmic rays, SCRs), can indeed explain this surplus. The method is based on earlier studies regarding the so-called EGRET GeV excess, which by now is generally interpreted as an instrumental effect. The contribution from SCRs is also predicted to increasingly exceed the DGE models above 100 GeV, up to γ-ray energies of about 10 TeV, where the corresponding surplus exceeds the hadronic part of the DGE by about one order of magnitude. Above such energies, the emission surplus should decrease again with energy due to the finite lifetime of the assumed supernova remnant sources. Observations of the DGE in the inner Galaxy at 15 TeV with the ground-based Milagro γ-ray detector and, at TeV energies, with the ARGO-YBJ detector are interpreted to provide confirmation of a significant SCR contribution to the DGE. © 2013. The American Astronomical Society. All rights reserved. Source


Berezhko E.G.,Yu G Shafer Institute Of Cosmophysical Research And Aeronomy | Ksenofontov L.T.,Yu G Shafer Institute Of Cosmophysical Research And Aeronomy | Volk H.J.,Max Planck Institute for Nuclear Physics
Astrophysical Journal | Year: 2015

A nonlinear kinetic theory, combining cosmic-ray (CR) acceleration in supernova remnants (SNRs) with their gas dynamics, is used to re-examine the nonthermal properties of the remnant of SN 1987A for an extended evolutionary period of 5-50 year. This spherically symmetric model is approximately applied to the different features of the SNR, consisting of (i) a blue supergiant wind and bubble, and (ii) of the swept-up red supergiant (RSG) wind structures in the form of an H ii region, an equatorial ring (ER), and an hourglass region. The RSG wind involves a mass loss rate that decreases significantly with elevation above and below the equatorial plane. The model adapts recent three-dimensional hydrodynamical simulations by Potter et al. in 2014 that use a significantlysmaller ionized mass of the ER than assumed in the earlier studies by the present authors. The SNR shock recently swept up the ER, which is the densest region in the immediate circumstellar environment. Therefore, the expected gamma-ray energy flux density at TeV energies in the current epoch has already reached its maximal value of ∼10-13 erg cm-2 s-1. This flux should decrease by a factor of about two over the next 10 years. © 2015. The American Astronomical Society. All rights reserved. Source


Berezhko E.G.,Yu G Shafer Institute Of Cosmophysical Research And Aeronomy | Ksenofontov L.T.,Yu G Shafer Institute Of Cosmophysical Research And Aeronomy | Volk H.J.,Max Planck Institute for Nuclear Physics
Astrophysical Journal | Year: 2012

The properties of the Galactic supernova remnant (SNR) SN 1006 are theoretically re-analyzed in light of the recent H.E.S.S. results. Nonlinear kinetic theory is used to determine the momentum spectrum of cosmic rays (CRs) in space and time in the supernova remnant SN 1006. The physical parameters of the model-proton injection rate, electron-to-proton ratio, and downstream magnetic field strength-are determined through a fit of the result to the observed spatially integrated synchrotron emission properties. The only remaining unknown astronomical parameter, the circumstellar gas number density, is determined by a normalization of the amplitude of the γ-ray flux to the observed amplitude. The bipolar morphology of both nonthermal X-ray and γ-ray emissions is explained by the preferential injection of suprathermal nuclei and subsequent magnetic field amplification in the quasi-parallel regions of the outer supernova shock. The above parameters provide an improved fit to all existing nonthermal emission data, including the TeV emission spectrum recently detected by H.E.S.S., with the circumstellar hydrogen gas number density N H ≈0.06 cm-3 close to values derived from observations of thermal X-rays. The hadronic and leptonic γ-ray emissions are of comparable strength. The overall energy of accelerated CRs at the present epoch is of the order of 5% of the total hydrodynamic explosion energy, and is predicted to rise with time by a factor of ≈2. The relevance of CR escape from the SNR for the spectrum of the γ-ray emission is demonstrated. The sum of the results suggests that SN 1006 is a CR source with a high efficiency of nuclear CR production, as required for the Galactic CR sources, both in flux as well as in cutoff energy. © 2012. The American Astronomical Society. All rights reserved. Source


Ksenofontov L.T.,Yu G Shafer Institute Of Cosmophysical Research And Aeronomy | Volk H.J.,Max Planck Institute for Nuclear Physics | Berezhko E.G.,Yu G Shafer Institute Of Cosmophysical Research And Aeronomy
Astrophysical Journal | Year: 2010

The properties of the - presumably - youngest Galactic supernova remnant (SNR) G1.9+0.3 are investigated within the framework of nonlinear kinetic theory of cosmic ray acceleration in SNRs. The observed angular size and expansion speed as well as the radio and X-ray emission measurements are used to determine relevant physical parameters of this SNR. Under the assumption that SNR G1.9+0.3 is the result of a Type Ia supernova near the Galactic center (at the distance d = 8.5kpc), the nonthermal properties are calculated. In particular, the expected TeV gamma-ray spectral energy density is predicted to be as low as εγ F γ ≈ 5 × 10 -15ergcm-2s-1, strongly dependent (F γ ∝ d -11) upon the source distance d. © 2010 The American Astronomical Society. All rights reserved. Source

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