2006ApJ...648.1099G

We present 5-35 µm spectra, taken with the Infrared Spectrograph (IRS) on the Spitzer Space Telescope, of five FU Orionis objects: FU Ori, V1515 Cyg, V1057 Cyg, BBW 76, and V346 Nor. All but V346 Nor reveal amorphous silicate grains in emission at 10 and 20 µm, and show water-vapor absorption bands at 5.8 and 6.8 µm and SiO or possibly methane absorption at 8 µm. These absorption features closely match these bands in model stellar photospheres–signs of the gaseous photospheres of the inner regions of these objects' accretion disks. The continuum emission at 5-8 µm is also consistent with such disks, and, for FU Orionis and BBW 76, longer wavelength emission may be fit by a model that includes moderate disk flaring. V1057 Cyg and V1515 Cyg have much more emission at longer wavelengths than the others, perhaps evidence of a substantial remnant of their natal, infalling envelopes.