Evidence for cosmic-ray acceleration in supernova remnants from X-ray observations

Spatially-resolved X-ray spectroscopic observations over the past several years have led to the discovery of non-thermal X-ray emission arising in the shells of most young Galactic supernova remnants, most notably SN 1006 and Cas A. In addition, the X-ray emission from the shells of a few newly-discovered supernova remnants is dominated by a non-thermal component. This emission is thought to be synchrotron emission from electrons shock accelerated to hundreds of TeV, and thus represents strong evidence that cosmic rays are accelerated in SNR shocks. The inferences made using the X-ray observations are corroborated by the detection of TeV γ-rays from two of these remnants. We review the status of the X-ray observations and describe how they can be used to provide insight into the shock-acceleration process.