Existence of nonaxisymmetric polytropes sustained by internal motions
Abstract
We have succeeded in developing a numerical code to obtain structures of nonaxisymmetric polytropes the shapes of which are sustained by internal flows. In order to compute stationary nonaxisymmetric polytropes, two important points must be properly treated: (i) how to specify the boundary condition for the flow velocity, and (ii) how to handle the boundary condition on the stellar surface which is not known beforehand. As for the boundary condition for the flow velocity, we specify the form of the distribution of the difference between the theta component of the flow velocity and its mean value at one meridional crosssection. Concerning the surface condition, we introduce a `surfacefitted' coordinate system in numerical computations. By applying our new numerical code we have obtained many stationary nonaxisymmetric equilibrium models the shapes of which are nonrotating in the inertial frame. Two main results of our computations are as follows: (i) the theta component of the flow velocity must depend on the height from the equator for polytropes to be deformed to some extent and (ii) the flow is compressible. Unless we include this zdependence for the flow, it seems that stationary states can exist only for nearly incompressible polytropes and only for very slightly deformed nonaxisymmetric configurations as far as `bar'type nonaxisymmetric configurations are concerned.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 September 1996
 DOI:
 10.1093/mnras/282.2.653
 Bibcode:
 1996MNRAS.282..653U
 Keywords:

 METHODS: NUMERICAL;
 STARS: GENERAL;
 STARS: INTERIORS;
 STARS: ROTATION