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Description
We investigate the viscous evolution of the accretion disc in 4U 1543-47, a black hole binary system, during the first 30 d after the peak of the 2002 burst by comparing the observed and theoretical accretion rate evolution dM(t)/dt. The observed dM(t)/dt is obtained from spectral modelling of the archival Proportional Counter Array aboard the RXTE observatory (RXTE/PCA) data. Different scenarios of disc decay evolution are possible depending on a degree of self-irradiation of the disc by the emission from its centre. If the self-irradiation, which is parametrized by factor C_irr_, had been as high as ~5x10^-3^, then the disc would have been completely ionized up to the tidal radius and the short time of the decay would have required the turbulent parameter {alpha}~3. We find that the shape of the \dot M(t) curve is much better explained in a model with a shrinking high-viscosity zone. If C_irr_~(2-3)x10^-4^, the resulting {alpha} lie in the interval 0.5-1.5 for the black hole masses in the range 6-10M_{sun}_, while the radius of the ionized disc is variable and controlled by irradiation. For very weak irradiation, C_irr_<1.5x10^-4^, the burst decline develops as in normal outbursts of dwarf novae with {alpha}~0.08-0.32. The optical data indicate that C_irr_ in 4U 1543-47 (2002) was not greater than approximately (3-6)x10^-4^. Generally, modelling of an X-ray nova burst allows one to estimate {alpha} that depends on the black hole parameters. We present the public 1D code FREDDI to model the viscous evolution of an accretion disc. Analytic approximations are derived to estimate {alpha} in X-ray novae using dM(t)/dt.
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