Nonaxisymmetric dynamic instabilities of rotating polytropes. II. Torques, bars, and mode saturation with applications to protostars and fizzlers

被引:35
作者
Imamura, JN [1 ]
Durisen, RH
Pickett, BK
机构
[1] Univ Oregon, Inst Theoret Sci, Eugene, OR 97403 USA
[2] Univ Oregon, Dept Phys, Eugene, OR 97403 USA
[3] Indiana Univ, Dept Astron, Bloomington, IN 47405 USA
[4] NASA, Ames Res Ctr, Moffett Field, CA 94035 USA
关键词
black hole physics; binaries : general; hydrodynamics; instabilities; stars : formation; stars : rotation;
D O I
10.1086/308199
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Dynamic nonaxisymmetric instabilities in rapidly rotating stars and protostars have a range of potential applications in astrophysics, including implications for binary formation during protostellar cloud collapse and for the possibility of aborted collapse to neutron star densities at late stages of stellar evolution ("fizzlers"). We have recently presented detailed linear analyses for polytropes of the most dynamically unstable global modes, the barlike modes. These produce bar distortions in the regions near the rotation axis but have trailing spiral arms toward the equator. In this paper, we use our linear eigenfunctions to predict the early nonlinear behavior of the dynamic instability and compare these "quasi-linear" predictions with several fully nonlinear hydrodynamics simulations. The comparisons demonstrate that the nonlinear saturation of the barlike instability is due to the self-interaction gravitational torques between the growing central bar and the spiral arms, where angular momentum is transferred outward from bar to arms. We also find a previously unsuspected resonance condition that accurately predicts the mass of the bar regions in our own simulations and in those published by other researchers. The quasi-linear theory makes other accurate predictions about consequences of instability, including properties of possible end-state bars and increases in central density, which can be large under some conditions. We discuss in some detail the application of our results to binary formation during protostellar collapse and to the formation of massive rotating black holes.
引用
收藏
页码:946 / 964
页数:19
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