1997A&A...323..442W

Infrared photometry and spectroscopy of the unassociated (infrared-only) IRAS source, IRAS 18530+0817, indicate that it is a highly unusual evolved star surrounded by a dense envelope of cool gas and dust. The IRAS data reveal a large infrared excess and significant flux variability in the 12-25µm region, as well as a prominent, silicate emission feature at 8.5-11.5µm. The shape of the feature also appears to vary; in 1993 it was apparently attenuated by an absorption with a sharp edge at 9.5µm, which may be circumstellar or photospheric in origin. At other times the silicate feature appears to be self-absorbed by varying amounts. Near-infrared spectra of IRAS 18530+0817 are dominated by steam absorptions, with the K-band spectrum showing only a narrow band of relatively unabsorbed continuum at 2.15-2.29µm. The object appears to possess the strongest stellar photospheric H₂O absorptions yet observed. We tentatively conclude that the central star of IRAS 18530+0817 is a late-type, O-rich, AGB star (a Mira variable) surrounded by an envelope of O-rich dust.