The Influence of Viscosity on the Truncation of Accretion Disks Around Black Holes

The influence of viscosity on the truncation radius of the accretion disks around the black holes for black hole X-ray binaries and low luminosity AGNs, as well as the changes between the high and low state in black hole X-ray binaries are studied in this paper using the accretion disk-corona model. From the previous studies it is indicated that the coronal structure is very sensitive to the viscosity. So we calculated in detail the coronal structures for a series of viscosity coefficients. In order to compare with the observational results, analytical fitting of the numerical results was made for the relations between the maximum evaporation rate and the viscosity coefficient α, M ˙ / M ˙ EDD ≈ 1.08α3.35 and between the truncation radius and the viscosity coefficient, R/Rs ≈ 36.11α−1.94. These results can be used to explain the transitions between the high and low spectral states and the changes in the truncation radius. In particular, these results are applied to two black hole X-ray binaries, XTE J1118+480 and GX 339-4, and to one AGN, NGC 4636.