Water Ice, Silicate and PAH Emission Features in the ISO Spectrum of the Carbon-rich Planetary Nebula CPD-56 8032
Cohen, Martin · Barlow, M. J. · Sylvester, R. J. · Liu, X. -W. · Cox, P. · Lim, T. · Schmitt, B. · Speck, A. K.
Original · EN
Combined ISO SWS and LWS spectroscopy is presented of the late WC-type planetary nebula nucleus CPD-56 8032 and its carbon-rich nebula. The extremely broad coverage (2.4-197 microns) 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 (hereafter PAHs) in the 3-14 micron region, bands from crystalline silicates longwards of 18 microns, and the 43- and 62-micron 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.
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