Dynamic Fission Instabilities in Rapidly Rotating N = 3/2 Polytropes: A Comparison of Results from FiniteDifference and Smoothed Particle Hydrodynamics Codes
Abstract
The effectiveness of three different hydrodynamics models is evaluated for the analysis of the effects of fission instabilities in rapidly rotating, equilibrium flows. The instabilities arise in nonaxisymmetric Kelvin modes as rotational energy in the flow increases, which may occur in the formation of close binary stars and planets when the fluid protoobject contracts quasiisostatically. Two finitedifference, donorcell methods and a smoothed particle hydrodynamics (SPH) code are examined, using a polytropic index of 3/2 and ratios of total rotational kinetic energy to gravitational energy of 0.33 and 0.38. The models show that dynamic bar instabilities with the 3/2 polytropic index do not yield detached binaries and multiple systems. Ejected mass and angular momentum form two trailing spiral arms that become a disk or ring around the central remnant. The SPH code yields the same data as the finite difference codes but with less computational effort and without acceptable fluid constraints in low density regions. Methods for improving both types of codes are discussed.
 Publication:

The Astrophysical Journal
 Pub Date:
 June 1986
 DOI:
 10.1086/164248
 Bibcode:
 1986ApJ...305..281D
 Keywords:

 Binary Stars;
 Computational Astrophysics;
 Finite Difference Theory;
 Fission;
 Hydrodynamic Equations;
 Stellar Evolution;
 Stellar Rotation;
 Computational Grids;
 Diffusion;
 Perturbation Theory;
 Stellar Mass;
 Stellar Models;
 Stellar Structure;
 Astrophysics;
 HYDRODYNAMICS;
 INSTABILITIES;
 STARS: BINARIES;
 STARS: FORMATION