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Session 99 - Supernovae & Supernova Remnants.
Oral session, Friday, January 09
I will present evidence for turbulent magnetic field amplification in Cassiopeia A, particle acceleration in IC 443 and limits on X-ray synchrotron radiation from a number of other shell-type supernova remnants. I will also discuss the implications of these results to the current picture of supernova remnant evolution and the origin of the cosmic rays.
When a deep ROSAT HRI image of Cas A is deabsorbed using H I and OH radio absorption data, it becomes well-correlated with radio continuum maps. This strong point-by-point correlation is consistent with equipartition between the magnetic field and hot gas -- implying that Cas A's plasma is fully turbulent and continuously amplifying the magnetic field.
X-ray imaging spectroscopy of IC 443, with the ASCA satellite, reveals two regions of particularly hard emission: an unresolved source embedded in an extended emission region, and a ridge of emission coincident with the southeastern rim. Both features are located on part of the radio shell where the shock wave is interacting with molecular gas, and together they account for a majority of the emission at 7 keV. I will argue that the features are most likely tracing enhanced particle acceleration by shocks that are formed as the supernova blast wave impacts the ring of molecular clouds.
In addition to IC 443, I will discuss the likelihood that the hard X-ray emission from a number of other shell-type galactic supernova remnants may be of synchrotron origin. On one hand, these results imply that X-ray synchrotron radiation exists, and must be considered when conducting a program in X-ray spectroscopy. On the other hand, upper limits on radio to X-ray break frequencies also suggest that, while supernova shocks can explain the origin of cosmic rays up to the ``knee,'' it is still unclear whether they account for the highest energy Galactic cosmic rays.
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Program listing for Friday