2008A&A...491..267S

We address the task of modeling soft X-ray and optical light curves of X-ray novae in the high/soft state. The analytic model of viscous evolution of an externally truncated accretion α-disk is used. Relativistic effects near a Kerr black hole and self-irradiation of an accretion disk are taken into account. The model is applied to the outbursts of X-ray nova Monocerotis 1975 (A0620-00) and X-ray nova Muscae 1991 (GRS1124-68). Comparison of observational data with the model yields constraints on the angular momentum (the Kerr parameter) of the black holes in A0620-00 and GRS1124-68: 0.3-0.6 and ≤0.4, and on the viscosity parameter α of the disks: 0.7-0.95 and 0.55-0.75. We also conclude that the accretion disks should have an effective geometrical thickness 1.5-2 times greater than the theoretical value of the distance between the photometric layers.