The dual dust chemistries of planetary nebulae with [WCL] central stars

Abstract

The rather rare class of central stars of planetary nebulae that show very low-excitation Wolf–Rayet spectra has been a subject of great interest, particularly in the infrared, since its discovery in the late 1960s. Further peculiarities have been found with the advent of infrared spectroscopy from <it>ISO</it>. Notably, these objects simultaneously betray the presence of regions of carbon-rich and oxygen-rich dust chemistry. We compare and contrast complete <it>ISO</it> spectra between 2 and 200 μm of a sample of six [WC8] to [WC11] central stars, finding many similarities. Among this sample, one star provides strong evidence of quasi-periodic light variations, suggestive of a dust cloud orbiting in a plane from which we view the system.