Discovery of an edge-on dust disk around the [WC10] central star CPD-56°8032

We present Hubble Space Telescope ultraviolet and optical Space Telescope Imaging Spectrograph spectroscopy of the [WCL] planetary nebula central star CPD -56degrees8032, obtained during its latest light-curve minimum. The UV spectrum shows the central star's continuum light distribution to be split into two bright peaks separated by 0.10. We interpret this finding as due to an edge-on disk or torus structure that obscures direct light from the star, which is seen primarily via its light scattered from the disk's rims or lobes. CPD -56degrees8032 is an archetype of dual dust chemistry [WCL] planetary nebulae, which exhibit strong infrared emission features from both carbon-rich and oxygen-rich materials, and for which the presence of a disk harboring the O-rich grains had been suggested. Our direct observation of an edge-on occulting dust structure around CPD -56degrees8032 provides strong support for such a model and for binary interactions being responsible for the correlation between the dual dust chemistry phenomenon in planetary nebulae and the presence of a hydrogen-deficient [WCL] Wolf-Rayet central star.