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Spectra obtained in the far UV wavelength range 1200-2000 A with the International Ultraviolet Explorer (IUE) of the peculiar emission object LMC Anonymous, or Sanduleak's Star in the Large Magellanic Cloud, indicate the presence of circumstellar-high-excitation gas, which is rich in CNO processed material. Although LMC Anonymous is a field star whose nebular line-forming region can not be resolved, and whose mass may be considerably smaller than the massive-luminous galactic object η Carinae, the far-UV spectrum of LMC Anonymous closely resembles that of the S Condensation of η Carinae. The similarity between LMC Anonymous and the S Condensation is apparent from the absolute intensity of the N v, N IV], and N m] emission hnes compared with the reduced strength of C IV or C III] emission. The narrow-low velocity emission lines observed in SN 1987 A indicate strong evidence for circumstellar emission that is rich in CNO-processed material, which was formed when the progenitor was in the high mass-loss phase as a red supergiant. IUE spectra of the S-Condensation and SN 1987 A may provide important clues concerning the nature of LMC Anonymous, which indicates departures from normal cosmic abundances of nitrogen relative to carbon that are extreme. This could suggest that carbon envelope burning and dredge-up have occurred simultaneously during the helium shell burning stage. These points are discussed in detail.


This article was originally published in Astrophysical Journal, volume 341, in 1989. DOI: 10.1086/167500

Peer Reviewed



IOP Publishing



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