We investigate the viscous evolution of the accretion disk in 4U 1543 - 47 , a black hole binary system , during the first 30 days 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 RXTE/PCA data .
Different scenarios of disk decay evolution are possible depending on a degree of self-irradiation of the disk by the emission from its centre .
If the self-irradiation , which is parametrized by factor C _ { \mathrm { irr } } , had been as high as \sim 5 \times 10 ^ { -3 } , then the disk would have been completely ionized up to the tidal radius and the short time of the decay would have required the turbulent parameter \alpha \sim 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 _ { \mathrm { irr } } \approx ( 2 - 3 ) \times 10 ^ { -4 } , the resulting \alpha lie in the interval 0.5 - 1.5 for the black hole masses in the range 6 - 10 ~ { } \mathrm { M } _ { \odot } , while the radius of the ionized disk is variable and controlled by irradiation .
For very weak irradiation , C _ { \mathrm { irr } } < 1.5 \times 10 ^ { -4 } , the burst decline develops as in normal outbursts of dwarf novae with \alpha \sim 0.08 - 0.32 .
The optical data indicate that C _ { \mathrm { irr } } in 4U 1543 - 47 ( 2002 ) was not greater than approximately ( 3 - 6 ) \times 10 ^ { -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 1-D code freddi to model the viscous evolution of an accretion disk .
Analytic approximations are derived to estimate \alpha in X-ray novae using \dot { M } ( t ) .