We examine the effects of the different viscosity prescriptions and the magnitude of the viscosity parameter , \alpha , on the structure of the slim disk , and discuss the observational implications on accretion-flow structure into a stellar-mass black hole .
In contrast with a standard disk , in which the “ \alpha ” value does not affect significantly the local flux , radiation from the slim disk is influenced by the \alpha value .
For the range of \alpha = 10 ^ { -2 } \sim 10 ^ { 0 } we calculate the disk spectra and from spectral fitting we derive T _ { in } ^ { obs } , maximum temperature of the disk , R _ { in } ^ { obs } , the size of the region emitting blackbody radiation with T _ { in } ^ { obs } , and p \equiv - { dln } T _ { eff } / { dln } ~ { } r , the slope of the effective temperature distribution .
It was founded that the estimated T _ { in } ^ { obs } slightly increases as \alpha increases .
This is because the larger the magnitude of viscosity is , the larger becomes the accretion velocity and , hence , the more enhanced becomes advective energy transport , which means less efficient radiative cooling and thus higher temperatures .

Furthermore we check different viscosity prescriptions with the form of the viscous stress tensor of t _ { r \varphi } = - \alpha \beta ^ { \mu } p _ { total } , where \beta is the ratio of gas pressure ( p _ { gas } ) to total pressure , p _ { total } ( = p _ { gas } + p _ { rad } ) , and \mu is a parameter ( 0 \leq \mu \leq 1 ) .
For \mu = 0 we have previously found that as luminosity approaches the Eddington , L _ { E } , R _ { in } ^ { obs } decreases below 3 r _ { g } ( 3 r _ { g } corresponds to the radius of the marginally stable circular orbit , r _ { ms } , with r _ { g } being Schwarzschild radius ) and the effective temperature profile becomes flatter , T _ { eff } \propto r ^ { -1 / 2 } .
Such a slim-disk nature does not appear when \mu is large , \mu \sim 0.5 , even at the Eddington luminosity .
Hence , the temperature of the innermost region of the disk sensitively depends on the \mu value .
We can rule out the case with large \mu~ { } ( \sim 0.5 ) , since it will not be able to produce a drop in R _ { in } ^ { obs } with an increase in luminosity as was observed in an ultraluminous X-ray source , IC 342 , source 1 .