2017MNRAS.468.4735L

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 {dot}M(t). The observed {dot}M(t) 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 ∼5 x 10^–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 α ∼ 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) x 10^–4, the resulting α lie in the interval 0.5-1.5 for the black hole masses in the range 6-10 M_☉, while the radius of the ionized disc is variable and controlled by irradiation. For very weak irradiation, C_irr < 1.5 x 10^–4, the burst decline develops as in normal outbursts of dwarf novae with α ∼ 0.08-0.32. The optical data indicate that C_irr in 4U 1543-47 (2002) was not greater than approximately (3-6) x 10^–4. Generally, modelling of an X-ray nova burst allows one to estimate α 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 α in X-ray novae using {dot}M(t).