Non-thermal X-ray Emission from Supernova Remnants

Recent studies of narrow, X-ray synchrotron radiating filaments surrounding young supernova remnants indicate that magnetic fields strengths are relatively high, B ∼ 0.1 mG, or even higher, and that diffusion is close to the Bohm limit. I illustrate this using Cas A as an example. Also older remnants such as RCW 86 appear to emit X-ray synchrotron radiation, but the emission is more diffuse, and not always confined to a region close to the shock front. I argue that for RCW 86 the magnetic field is likely to be low (B ≈ 17 μG), and at the location where the shell emits Xray synchrotron radiation the shock velocity is much higher than the average shock velocity of ∼ 600 km s−1.