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Session 45 - Supernovae.
Display session, Tuesday, January 14
Metropolitan Ballroom,

[45.15] Approaching the "Knee" of the Cosmic Ray Spectrum: X-ray Synchrotron Radiation from Young Shell-type Supernova Remnants

J. W. Keohane (NASA/GSFC and U. Minnesota), G. E. Allen, E. V. Gotthelf, R. Petre, A. F. Ptak (NASA/GSFC), S. P. Reynolds (N.C. State), J. Rho (SACLAY/SAP)

The problem of the acceleration of cosmic rays is still one of the great unsolved mysteries of astrophysics. By observing radio-bright shell-type SNRs in the x-ray above about 7 keV, we are now given the opportunity to begin to understand whether or not these objects accelerate electrons to energies approaching the ``knee'' of the cosmic ray spectrum.

We will discuss on-going research discussing the likelyhood that the hard x-ray emission, from the four shell-type galactic supernova remnants with the highest radio-synchrotron surface-brightness (Cas A, W49B, Kepler and 3C 397), may be of synchrotron origin -- implying electron energies up to 100 TeV or so. The soundness of the evidence depends on the particular supernova remnant in question.

For the two composite supernova remnants (W49B and 3C 397), we can take advantage of their differing radio and soft x-ray morphologies, by using ASCA's imaging capabilities. We will show evidence suggesting that the 7-12 keV continuum emission (as observed by the ASCA GIS) is more spatially correlated with VLA radio-synchrotron maps than with the thermal soft x-ray emission. Though there may be other explanations for this, involving dual temperature thermal models, the existence of a synchrotron component is an elegant explanation for these observations.

For the two supernova remnants with similar thermal x-ray and radio-synchrotron morphologies (Cas A and Kepler) imaging is less useful. We will refer to current work (Allen et al., this meeting) and future work utilizing the hard response of XTE to search for harder x-ray emission where thermal and non-thermal models differ.

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