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Session 57 - Astrophysical Diagnostics from Polarimetry.
Display session, Wednesday, June 12
Prior to the flight of the Wisconsin Ultraviolet Photo Polarimeter Experiment (WUPPE) on Astro-2, studies of ultraviolet (UV) interstellar linear polarization have generally catagorized the wavelength dependence in two ways: that which agrees with an extrapolation of the Serkowski Law into the UV and that which has a polarization greater than the extrapolation (see Clayton et al. 1995 and references within). Only one object (HD 197770) had been reported to deviate from either of these behaviors. It is important to note that earlier work has been limited in scope primarily by the amount of data available (14 published sightlines). However, with the flight of Astro-2, WUPPE has tripled the number of UV interstellar polarization observations (Anderson et al. 1995, 1996). These new data will provide a significant improvement to our ability to test interstellar dust grain models and study the effects of sightline environments.
We present the modeling results for several WUPPE (Astro-2) sightlines, including two which clearly depart from the previously mentioned catagorizations: HD 147933 and HD 197770. In addition to "classial" grain modeling technques (series solution, Effective Medium Theory), we also employ the Maximum Entropy Method and the Discrete Dipole Approximate.
WUPPE is supported by NASA contract NAS 5-26777.
Anderson, C.M., Weitenbach, A.J., amp; Code, A.D. 1995, Proceedings of the Conference on Polarimetry in the Interstellar Medium, eds. Roberge amp; Whittet, Troy, NY, June 1995.
Anderson, C.M. et al. 1996, ApJ, submitted.
Clayton, G. C. et al. 1995, ApJ, 445, 947
Program listing for Wednesday