FUSE Observations of an X-Ray Bright Region in the Vela Supernova Remnant

We present the results of a FUSE observation of an X-ray selected knot in the Vela supernova remnant. Spectra were obtained through the 30"x30" low resolution aperture and the 4"x20" medium resolution aperture. O VI 1032,1038 and C III 977 are detected strongly in both spectra, and S VI 933,944 is detected weakly only in the larger aperture spectrum. We also report the first detection of C II 1037 emission in a supernova remnant. The spectra show the presence of two kinematic components along the line of sight - one with both low and high excitation emission centered at a velocity of -50 km/s and another with only low excitation emission centered at a velocity of +100 km/s. We associate the -50 km/s component with the observed X-ray knot, and find a dynamical pressure of 3.7x10^{-10} dyne cm^{-2} driving the shock. We compare our results with data obtained using the Hopkins Ultraviolet Telescope at nearby locations and find that differences in the spectra imply the existence of two emitting components in the X-ray knot. Based on the X-ray morphology seen in a ROSAT HRI image, we identify two distinct regions which can be associated with these two components whose ultraviolet emission differs dramatically. These observations demonstrate the importance of high spectral resolution in understanding the proper physical relationships between the various emitting components in supernova remnants.