Global O VI line emission from the Cygnus Loop supernova remnant and direct kinematic measurement of the associated shock

A far-ultraviolet spectrophotometric emission-line mapping of the Cygnus Loop supernova remnant is presented. These are results from the first flight of the rocket-borne, High Resolution Emission Line Spectrometer. The spatial distribution of the emission is that of a limb-brightened shell, and similar to soft X-ray maps. The emission-line profiles, which are broader than the instrument resolution, were consistent with uniformly expanding shell models. Best-fit values give a radial expansion velocity to the emissive region of 185(+/-19) km/s and a reddening-corrected average surface brightness of 8.8(+/-3.6) x 10 exp -6 ergs/sq cm s sr in the doublet. Comparison of the observed brightness with predictions of both radiative and nonradiative shock models provides constraints for the global blast wave ram pressure as well as a "covering factor" of the intermediate velocity shock.