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A.W. Fullerton (U. Victoria & JHU), N.R. Walborn (STScI), P.A. Crowther (UCL), L. Bianchi (JHU), J.B. Hutchings (HIA/CNRC), D.L. Massa (Emergent IT/GSFC), A. Pellerin (U. Laval), G. Sonneborn (NASA/GSFC), A.J. Willis (UCL)
We present an atlas of far-ultraviolet (FUV; 905--1187~{Å}) spectra of early-type stars in the Large and Small Magellanic Clouds obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE). In contrast to the ultraviolet wavelengths accessible to IUE\/ and HST\/, the FUV region includes resonance lines from a greater variety of species, which include elements that are cosmically abundant (e.g., {\ion{C}{3} \lambda977}, {\ion{N}{3} \lambda991}, {\ion{O}{6} \lambda\lambda1031, 1038} ) and those that are comparatively rare (e.g., {\ion{S}{4} \lambda\lambda1063, 1073}, {\ion{S}{6} \lambda\lambda933, 944}, {\ion{P}{5} \lambda\lambda1118, 1128} ). The FUV transitions also sample a wider range of ionization conditions than the lines found at longer ultraviolet wavelengths. Consequently, they serve as powerful diagnostics of the physical conditions in the photospheres and winds of hot stars.
The complete atlas contains FUV spectra for more than 50 Magellanic stars. It covers all temperature classes from O2 to B1, but is biased toward more luminous objects. Since early-type stars in the Magellanic Clouds are usually much less reddened than their Galactic counterparts, it provides an unprecedented view of the line spectra of early-type stars down to the Lyman limit. The FUV spectra are presented as a series of montages arranged according to optical spectral types, some of which have been revised recently on the basis of high-quality ground-based data. The montages illustrate the systematic behavior of prominent stellar wind features as a function of temperature and luminosity class. In particular, the {\ion{S}{4} \lambda\lambda1063, 1073} resonance lines and {\ion{C}{3} \lambda1176} feature exhibit a strong luminosity effect. Metallicity effects lead to pronounced differences in the appearance of spectra with similar classifications in the two galaxies. Since high-quality optical and HST\/ spectra are available for many of the FUSE\/ targets, comprehensive atmospheric analyses designed to investigate the origin of these morphological trends are now possible.
This work is based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985.