Exploring ultraviolet astronomical polarimetry: results from the Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE)

In December 1990, the Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) on the Astro-1 shuttle Spacelab mission obtained approximately eight hours of pioneering ultraviolet spectropolarimetric observations on more than 20 galactic and extragalactic objects. WUPPE is a 0.5 m Cassegrain telescope coupled to a Monk-Gilleson spectrometer with a magnesium fluoride polarizing beamsplitter preceded by magnesium fluoride halfwave retarders. Two spectra from 135 to 330 nm with orthogonal polarization are detected simultaneously by a pair of intensified photodiode arrays. The first flight measured for the first time the ultraviolet polarization induced by interstellar dust, the UV intrinsic polarization of the rapidly rotating `Be' stars, and the large polarization in a `hidden' active galactic nucleus. A second flight of Astro is currently scheduled for 1994.