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G. Sonneborn (NASA/GSFC), R.C. Iping (NASA/GSFC and CUA), W.P. Blair (JHU), J.M. Shull (U. Colorado), FUSE Science Team
O VI 1032, 1038 A emission from the circumstellar interaction around SN 1987A has been detected in spectra obtained by the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. O VI is the highest ionization state yet detected from the shocked circumstellar gas. The O VI emission line profile is badly chopped up by foreground O VI interstellar absorption, making intrinsic O VI flux estimates very uncertain. The observation of SN 1987A used the narrowest FUSE aperture (1.25 x 20 arcsec) to eliminate any potential contamination by stray FUV light from the two companion stars (Stars 2 and 3). The analysis used data from only the LiF1 channel to ensure precise slit positioning throughout the observation. The two companion stars, both spectral type B1, were also observed by FUSE with the 4 x 20 arcsec slit to improve throughput. These spectra provide the line profiles of interstellar absorption on the sight lines within 3 arcsec of SN 1987A. The interstellar line profiles were used as an aide in analyzing the O VI emission from SNR 1987A. The source of the O VI emission is probably Spot 1, the first region of shock interaction with the inner circumstellar ring discovered in SN 1987A. The aperture width and orientation make it very unlikely that any of the other known interaction regions contribute to the observed O VI flux.
This work was supported in part by NASA grant NAG5-8631 to Catholic University of America and NASA contract NAS5-32985 to the Johns Hopkins University.