Probing me Reverse Shock in an Oxygen-Rich Supernova Remnant

The aim of this project is to examine the O VI emission at three positions around the X- ray bright ring of the remnant in order to investigate the relation between the O VI emission, the X-ray O VII and O VIII emission, and the optical [OIII} emission, and how these vary around the rim of the remnant. All three pointings and the background pointing have now been observed; the archive notification for the most recent dataset was Oct 30, 2003. After reprocessing and screening, the net exposure time for the SE exposure is only 54 percent of the approved time (15 kilosec). for the SE exposure, the available statistics are not good enough for analysis. A request for reobservation to make up for the lost time in the SE pointing has been approved. Broad O VI 1032 and O VI 1038 emission is detected with velocity width of at least 800 km/s, and possibly exceeding 1000 km/s. The Flanagan et al. analysis of the Chandra grating data show bulk velocities in the X-ray gas of order +/- 1000 km/s. In the region of the FUSE E0lO2-SE pointing, the Chandra data indicate both blue-shifted and red-shifted emission. Analysis of the velocity structure of the O VI emission will provide additional constraints on the kinematics of the gas: is it emission from a tilted expanding barrel, or a more symmetric expansion? The O VI fluxes are also needed to assess whether the O VI is radiation from recombining O VII or instead fiom cooler gas ionizing toward O VII. The emission is faint, however, which complicates the analysis. Because the lines are so broad, absorption by intervening H2, CII, and foreground OVI must be considered. A number of stars in the SMC have been observed which provide information on foreground OVI absorption. The initial analyses have concentrated on the Li1F channel since the guidance is based on that channel. The Li2F channel is being examined exposure by exposure to see if any of the data can be used to improve the signal to noise in the Li1F data.