Probing shock properties with nonthermal x-ray filaments in Cas A

Thin nonthermal X-ray filaments are often seen in young supernova remnants. We used data from the 1 Ms Chandra observation of Cassiopeia A to study spectral properties of some of the filaments in this remnant. For all the cases that we examined, the X-ray spectrum across the filaments hardens, at about 10% level, going outward, while observed filament widths depend only weakly on the photon energy. Using a model that includes radiative cooling, advection, and diffusion of accelerated particles behind the shock, we estimated the magnetic field, turbulence level, and shock obliquity