Models of the spectral energy distributions of FU Orionis stars

Observed spectral energy distributions (SEDs) of FU Orionis, V1057 Cygni, and V1515 Cygni are fitted by theoretical spectra, which are calculated from models consisting of outbursting accretion disks together with flattened envelopes. Temperature in the envelopes is determined by approximate radiative equilibrium with a central source. The disk models are two-dimensional and include reprocessing of disk radiation by the disk. The theoretical spectra are calculated using a radiative transfer code and frequency-dependent opacities, at a spectral resolution of lambda/Delta lambda = 14. Excellent matches to the data are obtained for all three objects with reasonable model parameters. Radiative transfer is also used to calculate a time series of images showing the progress of an outburst as imaged through a B-band filter.