Identifying Synchrotron-dominated Supernova Remnants

Nonthermal supernova remnants (SNRs) are important objects for the study ofcosmic ray physics, however, due to the current limited sample, their overallproperties are not clearly understood. We propose XMM observations tocharacterize the spectra of four candidate synchrotrondominated shells. Anyconfirmation of nonthermal emission will allow the inference of maximumelectron energies, while detecting thermal emission will provide information onthe remnant age, ambient density, composition, and supernova type. Either case,or both, will further our understanding of SNR evolution and particleacceleration. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]