Ultraviolet and Visible Spectropolarimetry of the Red Rectangle and HD 44179

Abstract

We present the first ultraviolet and visible spectropolarimetry of the biconical nebula the Red Rectangle and its associated binary HD 44179. These observations were made between 1992 November and 1995 November using the Faint Object Spectrograph on board the Hubble Space Telescope and two separate ground-based observations. These new data gives more clues to the geometrical picture of the region. Previous results have typically reported linear polarizations in the visible and infrared of 1%--2%. We present results that clearly show an increase in the continuum polarization shortward of 2000 A into the 10%--15% range. In addition, the position angle is seen to rotate by 65 deg in the same wavelength region, probably a result of the bipolar geometry and the existence of an optically thick equatorial disk. It is also seen that lines due to Mg II absorption, H alpha emission, and several lines due to CO are polarized differently than the continuum. There also appear to be features attributable to OH, which would be extremely unusual considering the assumed carbon-rich atmosphere that is present.