Magnetic fields and particle acceleration in Cas A

Abstract:
I will present the results of a recent study of soft and hard X-ray
emission from the bright young supernova remnant Cas A.
An upper limit on non-thermal bremsstrahlung above 100 keV allows
us to infer a lower limit on the average magnetic field in this remnant,
which turns out to be close to the equipartition value based on radio
synchrotron observations.
For those high magnetic fields the maximum electron cosmic ray energy is
loss limited, so it is unlikely that the hard X-ray emission from
the inside of Cas A is synchrotron radiation. 
However, the narrow rim of X-ray emission at the forward shock of Cas A
is likely to be synchrotron radiation, and in fact allows us to
measure the magnetic field close to the shock front.
The magnetic fields in Cas A have important consequences for the
cosmic ray population in Cas A, which is likely to be applicable to other
supernova remnants as well.