21,032 research outputs found
Very High Energy Gamma Rays from Supernova Remnants and Constraints on the Galactic Interstellar Radiation Field
The large-scale Galactic interstellar radiation field (ISRF) is the result of
stellar emission and dust re-processing of starlight. Where the energy density
of the ISRF is high (e.g., the Galactic Centre), the dominant gamma-ray
emission in individual supernova remnants (SNRs), such as G0.9+0.1, may come
from inverse Compton (IC) scattering of the ISRF. Several models of the ISRF
exist. The most recent one, which has been calculated by us, predicts a
significantly higher ISRF than the well-used model of Mathis, Mezger, and
Panagia. However,comparison with data is limited to local observations. Based
on our current estimate of the ISRF we predict the gamma-ray emission in the
SNRs G0.9+0.1 and RXJ1713, and pair-production absorption features above 20 TeV
in the spectra of G0.9+0.1, J1713-381, and J1634-472. We discuss how GLAST,
along with current and future very high energy instruments, may be able to
provide upper bounds on the large-scale ISRF.Comment: To appear in the proceedings of the 1st GLAST Symposiu
FURTHER RESEARCHES ON THE CLOSURE OF THE CORONARY ARTERIES
Includes bibliographical references.Mode of access: Internet
Cosmic-ray electron injection from the ionization of nuclei
We show that the secondary electrons ejected from the ionization of heavy
ions can be injected into the acceleration process that occurs at supernova
remnant shocks. This electron injection mechanism works since ions are ionized
during the acceleration when they move already with relativistic speed, just
like ejected electrons do. Using the abundances of heavy nuclei measured in
cosmic rays at Earth, we estimate the electron/proton ratio at the source to be
~10^-4, big enough to account for the nonthermal synchrotron emission observed
in young SNRs. We also show that the ionization process can limit the maximum
energy that heavy ions can reach.Comment: 4 pages, 1 figure, accepted for publication in Physical Review
Letter
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