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W.P. Blair, R. Sankrit, R. Shelton, K.R. Sembach, H.W. Moos (JHU/CAS), J.C. Raymond (SAO), FUSE Science Team
In 1999 September, during its commissioning phase, the Far Ultraviolet Spectroscopic Explorer satellite was pointed at a bright optical/X-ray supernova remnant (SNR) known as N49 in the Large Magellanic Cloud. The observation was for 34 ksec, about 14 ksec of which was in orbital night. A 30\arcsec\ square aperture was used, resulting in a velocity resolution of ~100 \rm km ~ s-1. The purpose of the observation was to observe several bright emission lines expected from earlier work at longer wavelengths and to demostrate FUSE's diffuse source sensitivity by searching for faint lines never seen previously in SNR UV spectra. Both of these goals were accomplished.
Since the object is roughly 1\arcmin\ in extent, the spectrograph aperture was filled with emission. Strong emission lines of O~VI \lambda\lambda1031.9, 1037.6 and C~III \lambda977 were seen, doppler broadened to \rm ± 225 ~ km ~ s-1 and with centroids red-shifted to 275 \rm km ~ s-1, consistent with the LMC. Superimposed on the emission lines are absorptions from intervening gas. Absorptions in C~III and O~VI \lambda1031.9 at +260 \rm km ~ s-1 are attributed to warm and hot gas (respectively) in the LMC. The O~VI \lambda1037.6 line is more severely affected by overlying interstellar and \rm H2 absorption from both the LMC and our galaxy. Conspicuous by its absence is N~III \lambda991, which is normally strong in SNR shocks, indicating a low N abundance in the shocked material.
A number of faint lines from hot gas have been detected in these data. These include He~II \lambda1085, [Ne~V] \lambda\lambda1137,1146, and C~III \lambda1176, S~VI \lambda\lambda933,944, Ne~VI \lambda\lambda999,1006, and possibly S~IV \lambda1073. Many of these lines have either never been seen or only marginally detected by previous SNR observations.
The work is supported by NASA Contract NAS5-32985 to the Johns Hopkins University.
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The author(s) of this abstract have provided an email address for comments about the abstract: wpb@pha.jhu.edu