The Ultraviolet Spectrum of an Oxygen-rich Supernova Remnant in the Small Magellanic Cloud

Abstract

We present ultraviolet and optical spectral data for the oxygen-rich supernova remnant 1E 0102-7219 in the Small Magellanic Cloud. The ultraviolet data were obtained with the IUE satellite and are the first data to seriously constrain the ultraviolet emission from an oxygen-rich remnant. Emission lines of O I, [O II], O III], O IV], C III], C IV, [Ne IV], and Mg II have been unambiguously detected in the UV. The presence of O I recombination lines in the UV and optical permits a scaling of relative line intensities for comparison with models. We have calculated shock models for material with abundances appropriate to massive stellar ejecta and find a number of differences between these models and the observations. The UV lines are observed to be weaker relative to optical lines than expected from the models, and values of certain ratios, such as C IV λ1550/C III λ1909, are difficult to explain. We have also calculated models of photoionization by the remnant's X-ray emission, and these provide a better qualitative match to the observed spectra, although a combination of shock heating and photoionization may be necessary to explain all of the relative line intensities. We derive approximate abundances in the ejecta and discuss the implications these have for the precursor star.