Ultraviolet spectropolarimetry of the Be star PP carinae with the Wisconsin ultraviolet photo-polarimeter experiment
We present the first ultraviolet spectropolarimetric observations of the Be star PP Car, obtained with the Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) aboard the Astro 1 mission. Usable polarization data were obtained from 1400 to 2330 Å, along with a good spectrum from 1400 to 3200 Å. These data show a lower polarization shortward of the Balmer jump than had been predicted by standard models, and a broad UV polarization dip around 1900 Å is seen. These results are in agreement with those found from the WUPPE observations of two other Be stars, ζ Tau and π Aqr, which were published earlier. All these observations are an important probe of the Be circumstellar envelopes and demonstrate the need for the inclusion of metal-line effects in circumstellar disk models of Be star UV polarization.