THE 6.0 AND 6.8 MU-M ABSORPTION FEATURES IN THE SPECTRUM OF NGC-7538-IRS9

Short Wavelength Spectrometer observations of the 6.0 and 6.8 mu m abs orption features towards the obscured young stellar object NGC 7538: I RS9 are presented and compared to the features of a number of species measured in the solid phase. It is found that while solid H2O provides the bulk of the 6 mu m band, additional absorption is required near 5 .83 mu m and 6.25 mu m. It is proposed that formic acid (HCOOH) is a p lausible candidate for the blue excess, while the red excess could be related to the C-C stretching mode in aromatic structures. Subsequentl y, a number of candidates for the 6.8 mu m band are reviewed. Unfortun ately, none of these appears to satisfy the observational constraints and no plausible identification can at this point be presented.