Quasi-Keplerian Be-Star Disks with Mimicking Viscosity

Classical Be stars are fast-rotating B-type stars with gaseous quasi-Keplerian disks formed by equatorial ejection of material. While the viscous decretion disk (VDD) model reproduces many observed properties, the role of radiative line driving in shaping these disks remains unclear. We investigated the combined influence of viscosity and radiative acceleration on the hydrodynamic structure of Be star disks by coupling the m-CAK theory of line-driven winds with a mimicking viscous prescription governed by the parameter gamma vis. We solved the steady-state hydrodynamic equation of motion using Hydwind for typical B-type stellar parameters in transonic-slow outflows. We analyzed the velocity and density structures and derived the mass-loss rates and radial velocities at the adopted outer integration radius, r=50,R. The combined action of line driving and viscosity yields regular m-CAK-slow solutions for equatorial outflow with a VDD-inspired rotational prescription. For quasi-Keplerian exponents (gamma vis 0.5) and near-critical rotation (about 0.96 -- 0.99), the models produce an outflowing disk with an m-CAK-type critical point at r c 20 -- 30,R. At 50,R, these quasi-Keplerian solutions reach radial velocities of 76.9 -- 139.2, km,s-1. Within the present 1D parameterized framework, the m-CAK line force yields stationary solutions without imposing an outer boundary condition. Our results provide a controlled 1D test of how a VDD-inspired rotational prescription modifies the topology of stationary m-CAK-slow solutions. The model is an exploratory bridge toward future non-Sobolev multidimensional radiation-hydrodynamic treatments that recover quasi-Keplerian rotation and modest outflow velocities of Be disks.