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Paper: Ultraviolet and visible spectropolarimetric variability in P Cygni
Volume: 233, P Cygni 2000: 400 Years of Progress
Page: 261
Authors: Nordsieck, K. H.; Wisniewski, J.; Babler, B. L.; Meade, M. R.; Anderson, C. M.; Bjorkman, K. S.; Code, A. D.; Fox, G. K.; Johnson, J. J.; Weitenbeck, A. J.; Zellner, N. E. B.
Abstract: We report on new data, including four vacuum-ultraviolet spectropolarimetric observations by the Wisconsin Ultraviolet Photo-Po-larimeter Experiment (WUPPE) on the Astro-1 and Astro-2 shuttle missions, and 15 new visible-wavelength observations obtained by the HPOL CCD spectropolarimeter at the Pine Bluff Observatory of the University of Wisconsin. This includes three HPOL observations made within 12 hours of each of the three Astro-2 WUPPE observations, giving essentially simultaneous observations extending from 1500 to 10500 A. An analysis of these data yields estimates on the properties of wind "clumps" when they are detectable by the polarization of their scattered light. We find that the clumps must be detected near the base of the wind, r/R* = 1.3 - 2.5. At this time the clump density is at least 1013/cm-3, 20 times that of the mean wind, and the temperature is roughly 10,000 K, about 20% cooler than the mean wind. The clumps leading to the largest observed polarization must have electron optical depths of 0.1 - 1 and an angular extent of 0.1 - 1 ster, and account for at most 2% of the wind mass loss. The H and HeI emission lines from the wind are unpolarized, but their P Cygni absorption is enhanced by a factor of four in the scattered light. We speculate on the possible relationship of the clumps detected polarimetrically to those seen as Discrete Absorption Components (DACs) and in interferometry.
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