We present the first results on the hard X-ray continuum image ( up to 15 keV ) of the supernova remnant Cas A measured with the EPIC cameras onboard XMM-Newton .
The data indicate that the hard X-ray tail , observed previously , that extends to energies above 100 keV does not originate in localised regions , like the bright X-ray knots and filaments or the primary blast wave , but is spread over the whole remnant with a rather flat hardness ratio of the 8 - 10 and 10 - 15 keV energy bands .
This result does not support an interpretation of the hard X-radiation as synchrotron emission produced in the primary shock , in which case a limb brightened shell of hard X-ray emission close to the primary shock front is expected .
In fact a weak rim of emission near the primary shock front is discernable in the hardest X-ray image but it contains only a few percent of the hard X-ray emissivity .
The equivalent width of the Fe-K line blend varies by more than an order of magnitude over the remnant , it is hard to explain this as Fe-emission from the reverse shock heated ejecta given the ejecta temperature and the age of the remnant .
The uniquely high wavelength-dispersive RGS-spectrometer has allowed , for the first time , to extract monochromatic images in several highly ionised element species with high spectral resolution .
We present here a preliminary result on the measurement of the O viii Ly- \alpha and Ly- \beta brightness distribution and brightness ratios .
The large observed decrease of the Ly- \alpha /Ly- \beta ratio going from the N to the SE can be explained by small-scale ( 10 ″ ) variations in the N _ { H } column over the remnant and the potential presence of resonance scattering of the O viii Ly- \alpha photons in the limb brightened shell .