2000ApJ...531.1028K

We analyze new and published optical photometric data of FU Orionis, an eruptive pre-main-sequence star. The outburst consists of a 5.5 mag rise at B with an e-folding timescale of ∼50 days. The rates of decline at B and V are identical, 0.015±0.001 mag.yr^–1. Random fluctuations superimposed on this decline have an amplitude of 0.035±0.005 mag at V and occur on timescales of 1 day or less. Correlations between V and the color indices U-B, B-V, and V-R indicate that the variable source has the optical colors of a G0 supergiant. We associate this behavior with small-amplitude flickering of the inner accretion disk.