Two-Dimensional Hydrodynamic and Evolution Sequences of Rotating Stars
International Astronomical Union Colloquium
Two-dimensional hydrodynamic simulations were calculated for ZAMS models with Z=0.02, and masses of 3, 5, 8, 12, and 20 M⊙. For each mass five models were calculated - one nonrotating and four with progressively higher rotation rates. The rotating models were categorized by the ratio of the polar to the equatorial radius, with values of 0.985, 0.92, 0.84, and 0.72. The simulations were performed with the fully two-dimensional implicit code ROTORC (actually what is known as 2.5 dimensions, with
... 5 dimensions, with azimuthal symmetry, but with a conservation law for the rotational velocity in the azimuthal direction).All models showed considerable core overshooting. To first order, the value is about 0.5 Hp, but with a fairly large variation of about 0.2 Hp. It is not clear why the variation is so large, but comparison with other turbulence models shows that overshooting/is one of the more sensitive features of the model (Deupree, 1998). However, there are some trends that may be significant. For the two highest masses there was apparently no dependence on the rotation rate, but the three smaller masses showed a linear decrease in the extent of overshooting with increasing rotation. There is a hint that the 20 M⊙model has slightly larger overshooting than models of the other masses. With the random variations, it is difficult to assign a level of significance to these trends.