The influence of rotation in radiation driven wind from hot stars: New solutions and disk formation in Be stars

The theory of radiation driven wind including stellar rotation is re-examined. After a suitable change of variables, a new equation for the mass loss rate is derived analytically. The solution of this equation remains within 1% confidence when compared with numerical solutions. Also, a non-linear equation for the position of the critical (singular) point is obtained. This equation shows the existence of an additional critical point, besides the standard m–CAK critical point. For a stellar rotation velocity larger than ∼ 0.7 – 0.8 Vbreakup, there exists only one critical point, located away from the star’s surface. Numerical solutions crossing through this new critical point, are attained. In these cases, the wind has a very low terminal velocity and therefore a higher density wind. Disk formation in Be stars is discussed in the frame of this new line driven stellar wind solution. Subject headings: hydrodynamics — methods: analytical— stars: early-type — stars: mass-loss — stars: rotation — stars: winds, outflows