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During the March 1995 Astro-2 mission, we obtained observations of four Wolf-Rayet (W-R) stars of WN subtype. The data are comprised of simultaneous far-UV spectroscopy with the Hopkins Ultraviolet Telescope (HUT), and UV spectroscopy and spectropolarimetry with the Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE).
Present generation atmosphere codes for W-R stars neglect Fe-line opacities, and assume spherical geometry, homogeneity, and time independence. We chose W-R stars for Astro-2 observation in which the assumptions of the Standard Model are violated, in an effort to quantify by how much current models are in error at worst.
The four W-R stars observed during the Astro-2 mission are WR 6 (WN5), WR 134 (WN 6), WR 24 (WN 7+a) and WR 40 (WN8). The HUT observations provide a first overview of the far-UV spectra of stars of the WN sequence below 1200 \AA. The program stars are also known from our ground-based work to be W-R stars which have shown the line effect, i.e., changes of polarization across emission lines in their optical spectra. The WUPPE data allow for a study of line effects in the UV portion of their spectra. Some of the program stars were observed repeatedly during the Astro-2 mission, to investigate their variability on timescales of hours or days.
In this paper, we shall display HUT and WUPPE data of the program stars, discuss preliminary results within the framework of the available calibrations, and provide a first assessment of the deviation of these observations from the Standard Model of W-R atmospheres.
We acknowledge support by NASA (George C. Marshall Space Flight Center) grant number NAG8-1073.
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