1999ApJ...516L..99V

We present Infrared Space Observatory SWS06 mode observations of the 21 µm feature in eight sources, including a first detection of the feature in IRAS Z02229+6208. The observed feature peak-to-continuum ratios range from 0.13 in IRAS Z02229+6208 to 1.30 in IRAS 07134+1005. The normalized spectra, obtained by the removal of the underlying continua and by scaling the features to the same peak flux value, show that all features have the same intrinsic profile and peak wavelength. There is no evidence for any discrete substructure due to molecular bands in the observed spectra, suggesting that the 21 µm feature is due to either a solid substance or a mixture of many similarly structured large molecules.