tokens: by disk emission, even in the optical/near-IR, and changes at optical/near-IR wavelengths would reflect changes in the superheated disk rather than the central protostar. FU Ori ( D = 450–500 pc; Hartmann Kenyon 1996 ) is a wide (05) binary system consisting of a outbursting young stellar object modeled as a 0.3 M ⊙ with a 0.04 M ⊙ circumstellar disk (Zhu et al. 2007 ) at an A V of ∼1.8 (Zhu et al. 2010 ) and a more massive young companion ( M > 0.5 M ⊙ ; Reipurth Aspin 2004 ; Wang et al. 2004 ; Hales et al. 2015 ). The companion (FU Ori S) is at 227 au projected separation (Pueyo et al. 2012 ) at an A V of 10 ± 2 (Pueyo et al. 2012 ). In this work, we present new mid-IR photometry and spectroscopy of FU Ori obtained with the Stratospheric Observatory for Infrared Astronomy (SOFIA) in 2016, and we compare with previous observations with the Spitzer Space Telescope in 2004. We find that the continuum flux density at wavelengths shorter than 8 μ m (arising from the hot inner disk) has decreased by 12%–14%, dominating the change in bolometric luminosity. The continuum at wavelengths greater than 10 μ m has decreased only 7% within uncertainties. Additionally, we find that the H 2 O vapor absorption resulting from the superheated disk photosphere remains present. Finally, we note no significant changes in the 10 μ m silicate emission feature, which shows no evidence of crystallinity. Taken together, these observations suggest that the decrease in viscous dissipation energy over this period has occurred predominantly in the innermost section of the disk, which is changing rapidly. 2. OBSERVATIONS 2.1. SOFIA-FORCAST Spectroscopy We observed FU Ori with the Faint Object infraRed CAmera for the SOFIA Telescope (FORCAST; Herter et al. 2012 ) on board the SOFIA (Young et al. 2012 ) on two separate flights (on 2016 February 4 and 18, flights 272 and 279, respectively); see Table 1 for the Observing Log. The observations were performed in C2N (two-position chop with nod) mode, using the slit, and the NMC (nod-match-chop) pattern in which the chops and nod are in the same direction and have the same amplitude. In each case, an off-source calibrator was selected from an ensemble of observations from cycles 2–4, using the observation closest in zenith angle and altitude to the science target (A. Helton 2016, private communication). We did not use dithering. The FORCAST grism was used in three spectral bands, G063 (∼5–8 μ m), G111 (∼9–13 μ m), and G227 (∼18–25 μ m), from 5 to 25 μ m to achieve a spectral resolving power of R ∼ 200. The achieved signal-to-noise ratios (S/Ns) for the individual grism segments were 30 (G063, measured from 5.7 to 6.3 μ m), 46 (G111, measured from 11 to 12 μ m), and 22 (G227, measured from 21 to 26 μ m). The total observation time was 12,904 s (3.58 hr), including imaging, which totaled approximately 0.33 hr (see below). Table 1 Observing Log Notes. Observations were performed over two different flights, 272 (2016 February 04) and
ner_tags: O O O O O O B-Wavelength O O O B-Wavelength O O O O O O O O O O O O O B-CelestialObject I-CelestialObject O B-Formula I-Formula I-Formula I-Formula B-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O B-Wavelength O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O B-Formula I-Formula I-Formula I-Formula I-Formula O B-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O B-CelestialObject I-CelestialObject I-CelestialObject O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O B-Wavelength O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O B-Wavelength O O O O B-CelestialObject I-CelestialObject O O O B-Telescope I-Telescope I-Telescope I-Telescope I-Telescope B-Telescope O O O O O O O O O O B-Telescope I-Telescope I-Telescope O O O O O O O O O O O O O B-Wavelength I-Wavelength I-Wavelength O O O O B-CelestialObjectRegion I-CelestialObjectRegion O O O O O O O O O O O O O O O O B-Wavelength I-Wavelength I-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength I-Wavelength I-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObjectRegion I-CelestialObjectRegion I-CelestialObjectRegion I-CelestialObjectRegion I-CelestialObjectRegion O O O O O O O B-Telescope O O O B-CelestialObject I-CelestialObject O O B-Instrument I-Instrument I-Instrument I-Instrument O O B-Telescope I-Telescope B-Instrument B-Citation I-Citation I-Citation I-Citation O O O O B-Telescope B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O B-Instrument O O O O O O O B-Wavelength B-Wavelength I-Wavelength I-Wavelength B-Wavelength B-Wavelength I-Wavelength I-Wavelength O B-Wavelength B-Wavelength I-Wavelength I-Wavelength O B-Wavelength I-Wavelength I-Wavelength I-Wavelength I-Wavelength O O O O O O O B-Formula I-Formula I-Formula O O O O O O O O O O O O O O O B-Wavelength I-Wavelength I-Wavelength I-Wavelength I-Wavelength O O O O B-Wavelength I-Wavelength I-Wavelength I-Wavelength I-Wavelength O O O O O B-Wavelength I-Wavelength I-Wavelength I-Wavelength I-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O