Shell Shock and Cloud Shock: Results from Spatially-Resolved X-ray   Spectroscopy with Chandra in the Cygnus Loop
  We use the Chandra X-ray Observatory to analyze interactions of the blast wave and the inhomogeneous interstellar medium on the western limb of the Cygnus Loop supernova remnant. This field of view includes an initial interaction between the blast wave and a large cloud, as well as the encounter of the shock front and the shell that surrounds the cavity of the supernova progenitor. Uniquely, the X-rays directly trace the shock front in the dense cloud, where we measure temperature kT = 0.03 keV. We find kT~0.2 keV in regions where reflected shocks further heat previously-shocked material. Applying one-dimensional models to these interactions, we determine the original blast wave velocity v_bw~330 km/s in the ambient medium. We do not detect strong evidence for instabilities or non-equilibrium conditions on the arcsecond scales we resolve. These sensitive, high-resolution data indicate no exceptional abundance variations in this region of the Cygnus Loop. 
N. A. Levenson (Univ. Kentucky), J. R. Graham, and J. L. Walters (UC   Berkeley)