Water ice, silicate, and polycyclic aromatic hydrocarbon emission features in the Infrared Space Observatory spectrum of the carbon-rich planetary nebula CPD -56°8032

Combined Infrared Space Observatory Short-Wavelength Spectrometer and Long-Wavelength Spectrometer spectroscopy is presented of the late WC-type planetary nebula nucleus CPD -56 degrees 8032 and its carbon-rich nebula. The extremely broad coverage (2.4-197 mu m) enables us to recognize the clear and simultaneous presence of emission features from both oxygen- and carbon-rich circumstellar materials. Removing a smooth continuum highlights bright emission bands characteristic of polycyclic aromatic hydrocarbons in the 3-14 eta m region, bands from crystalline silicates longward of 18 mu m, and the 43 and 62 mu m bands of crystalline water ice. We discuss the probable evolutionary state and history of this unusual object in terms of (a) a recent transition from an O-rich to a C-rich outflow following a helium shell flash or (b) a carbon-rich nebular outflow encountering an O-rich comet cloud.