SIMBAD references

We present a detailed study of the parameter space of circumstellar dust disk models for young stellar objects. Fitting the observed spectral energy distributions of FU Ori and DN Tau the problem of finding the best χ²-fit in a topologically complicated multidimensional parameter space is solved using a special Metropolis algorithm. The proposed automated fitting method is of simple structure, stable, and of general use for all kinds of fitting problems. Comparing the resulting disk parameters with earlier estimates we discuss methods used in recent papers to deduce constraints directly from the fit. In all cases we find a global ambiguity in acceptable fits. The only constraints we find for FU Ori are a temperature index limit of q<0.7, β>1 for the opacity index, and a total disk mass of 1/10 M_☉ with an order of magnitude variation. For the spectrum of DN Tauri we find acceptable fits with inner radii r_i<1.6 AU, q<0.65, and density indices p<1.6. This qualifies some of the previously found constraints, since the used methods did not sufficiently cover the entire parameter space.