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Cosmic-ray energy s...
Cosmic-ray energy spectrum and composition up to the ankle : the case for a second Galactic component
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- Thoudam, Satyendra (författare)
- Linnéuniversitetet,Institutionen för fysik och elektroteknik (IFE),Radboud Univ Nijmegen, Netherlands
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- Rachen, J. P. (författare)
- Radboud Univ Nijmegen, Netherlands
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- van Vliet, A. (författare)
- Radboud Univ Nijmegen, Netherlands
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- Achterberg, A. (författare)
- Radboud Univ Nijmegen, Netherlands
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- Buitink, S. (författare)
- Vrije Univ Brussel, Belgium
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- Falcke, H. (författare)
- Radboud Univ Nijmegen, Netherlands ; NIKHEF, Netherlands ; ASTRON, Netherlands
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- Horandel, J. R. (författare)
- Radboud Univ Nijmegen, Netherlands ; NIKHEF, Netherlands
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(creator_code:org_t)
- 2016-10-25
- 2016
- Engelska.
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 595
- Relaterad länk:
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https://www.aanda.or...
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https://urn.kb.se/re...
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- Motivated by the recent high-precision measurements of cosmic rays by several new-generation experiments, we have carried out a detailed study to understand the observed energy spectrum and composition of cosmic rays with energies up to about 10(18) eV. Our study shows that a single Galactic component with subsequent energy cut-offs in the individual spectra of different elements, optimised to explain the observed elemental spectra below similar to 10(14) eV and the "knee" in the all-particle spectrum, cannot explain the observed all-particle spectrum above similar to 2 x 10(16) eV. We discuss two approaches for a second component of Galactic cosmic rays re-acceleration at a Galactic wind termination shock, and supernova explosions of Wolf-Rayet stars, and show that the latter scenario can explain almost all observed features in the all-particle spectrum and the composition up to similar to 10(18) eV, when combined with a canonical extra-galactic spectrum expected from strong radio galaxies or a source population with similar cosmological evolution. In this two-component Galactic model, the knee at similar to 3 x 10(15) eV and the "second knee" at similar to 10(17) eV in the all-particle spectrum are due to the cut-offs in the first and second components, respectively. We also discuss several variations of the extra-galactic component, from a minimal contribution to scenarios with a significant component below the "ankle" (at similar to 4 x 10(18) eV), and find that extragalactic contributions in excess of regular source evolution are neither indicated nor in conflict with the existing data. We also provide arguments that an extra-galactic contribution is unlikely to dominate at or below the second knee. Our main result is that the second Galactic component predicts a composition of Galactic cosmic rays at and above the second knee that largely consists of helium or a mixture of helium and CNO nuclei, with a weak or essentially vanishing iron fraction, in contrast to most common assumptions. This prediction is in agreement with new measurements from LOFAR and the Pierre Auger Observatory which indicate a strong light component and a rather low iron fraction between similar to 10(17) and 10(18) eV.
Ämnesord
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
Nyckelord
- diffusion
- stars: winds
- outflows
- ISM: supernova remnants
- galaxies: ISM
- cosmic rays
- Astroparticle Physics
- Astropartikelfysik
Publikations- och innehållstyp
- ref (ämneskategori)
- art (ämneskategori)
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