Chandra High-Energy Transmission Grating ( HETG ) X-ray spectra are extracted from 17 bright , narrow regions of Cas A and provide unique measurements of their kinematic and plasma states .
From the dominant emission lines , e.g .
He-like Si , we derive accurate Doppler shifts in the range - 2500 to + 4000 km s ^ { -1 } ; these agree well with transverse-velocity measurements and allow the features to be located in 3D .
Plasma diagnostics of these regions indicate temperatures largely around 1 keV with some above 3 keV .
Using as well the non-dispersed zeroth-order data , we determine NEI model parameters for the regions which lead to density estimates .
Values of n _ { e } \approx 100 \mathrm { cm } ^ { -3 } are likely the maximum of a range of densities in this X-ray emitting material .
The common “ oxygen-rich ” assumption is coarsely tested by comparing the integrated \ion O8 line flux and continuum levels .
It appears that most of the continuum is due to another source , e.g. , from He .