The Mid-Infrared Evolution of the FU Orionis Disk

Abstract

We present new SOFIA-FORCAST observations obtained in Feburary 2016 of the archetypal outbursting low mass young stellar object FU Orionis, and compare the continuum, solid state, and gas properties with mid-IR data obtained at the same wavelengths in 2004 with Spitzer-IRS. In this study, we conduct the first mid-IR spectroscopic comparison of an FUor over a long time period. Over a 12 year period, UBVR monitoring indicates that FU Orionis has continued its steady decrease in overall brightness by ~ 14%. We find that this decrease in luminosity occurs only at wavelengths < 20 microns. In particular, the continuum short ward of the silicate emission complex at 10 microns exhibits a ~ 12% (~ 3 sigma) drop in flux density, but no apparent change in slope; both the Spitzer and SOFIA spectra are consistent with a 7200 K blackbody. Additionally, the detection of water absorption is consistent with the Spitzer spectrum. The silicate emission feature at 10 microns continues to be consistent with unprocessed grains, unchanged over 12 years. We conclude that either the accretion rate in FU Orionis has decreased by ~ 12-14% over this time baseline, or that the inner disk has cooled, but the accretion disk remains in a superheated state outside of the innermost region.

arXiv comment12 pages, 7 figures

References in corpus (37)

• The Spitzer Space Telescope Mission
• The Infrared Spectrograph on the Spitzer Space Telescope
• Using FU Orionis Outbursts to Constrain Self-Regulated Protostellar Disk Models
• Circumstellar Dust Disks in Taurus-Auriga: The Submillimeter Perspective
• Accretion Disks Around Young Objects. II. Tests of Well-Mixed Models with Ism Dust
• The SMART Data Analysis Package for the Infrared Spectrograph on the Spitzer Space Telescope
• Early Science with SOFIA, the Stratospheric Observatory for Infrared Astronomy
• CASSIS: The Cornell Atlas of Spitzer/IRS Sources
• Non-steady Accretion in Protostars
• Imaging the water-snow line during a protostellar outburst
• Variable protostellar accretion with episodic bursts
• 2-D simulations of FU Orionis disk outbursts
• Episodic formation of cometary material in the outburst of a solar-like young star
• The Hot Inner Disk of FU Ori
• Crystalline silicates and dust processing in the protoplanetary disks of the Taurus young cluster
• Long-term Evolution of Protostellar and Protoplanetary Disks. I. Outbursts
• CO rovibrational emission as a probe of inner disk structure
• Continuum Variability of Deeply Embedded Protostars as a Probe of Envelope Structure
• C2D Spitzer-IRS spectra of disks around T Tauri stars. IV. Crystalline silicates
• First Science Observations with SOFIA/FORCAST: The FORCAST Mid-infrared Camera
• CASSIS: The Cornell Atlas of Spitzer/Infrared Spectrograph Sources. II. High-resolution observations
• Spitzer-IRS Observations of FU Orionis Objects
• Evolution of dust and ice features around FU Orionis objects
• High-precision C17O, C18O and C16O measurements in young stellar objects: analogues for CO self-shielding in the early solar system
• FU Orionis: A Binary Star?
• Flickering in FU Orionis
• CO2 Ice toward Low-luminosity, Embedded Protostars: Evidence for Episodic Mass Accretion via Chemical History
• Dead Zones around Young Stellar Objects: FU Orionis Outbursts and Transition Discs
• Keck Interferometer Observations of FU Orionis Objects
• An Analysis of the Environments of FU Orionis Objects with Herschel
• The Early ALMA View of the FU Ori Outburst System
• Depletion of molecular gas by an accretion outburst in a protoplanetary disk
• Anomalous CO2 Ice Toward HOPS-68: A Tracer of Protostellar Feedback
• Protoplanetary dust porosity and FU Orionis Outbursts: Solving the mystery of Earth's missing volatiles
• Constraining mass ratio and extinction in the FU Orionis binary system with infrared integral field spectroscopy
• On Rapid Disk Accretion and Initial Conditions in Protostellar Evolution
• Disk-Magnetosphere Interaction and Outflows: Conical Winds and Axial Jets

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• FU Orionis outbursts, preferential recondensation of water ice, and the formation of giant planets
• HD 145263: Spectral Observations of Silica Debris Disk Formation via Extreme Space Weathering?
• The disk of FU Orionis viewed with MATISSE/VLTI: first interferometric observations in $L$ and $M$ bands
• Making Terrestrial Planets: High Temperatures, FU Orionis Outbursts, Earth, and Planetary System Architectures
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