Presupernova evolution of rotating massive stars. I. Numerical method and evolution of the internal stellar structure

被引:831
作者
Heger, A [1 ]
Langer, N
Woosley, SE
机构
[1] Univ Calif Santa Cruz, Dept Astron & Astrophys, Santa Cruz, CA 95064 USA
[2] Max Planck Inst Astrophys, D-85740 Garching, Germany
[3] Inst Phys, D-14469 Potsdam, Germany
关键词
hydrodynamics; methods : numerical; stars early-type; stars : evolution; stars : interiors; stars rotation;
D O I
10.1086/308158
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The evolution of rotating stars with zero-age main-sequence (ZAMS) masses in the range 8-25 M. is followed through all stages of stable evolution. The initial angular momentum is chosen such that the star's equatorial rotational velocity on the ZAMS ranges from zero to similar to 70% of breakup. The stars rotate rigidly on the ZAMS as a consequence of angular momentum redistribution during the pre-mainsequence evolution. Redistribution of angular momentum and chemical species are then followed as a consequence of Eddington-Sweet circulation, Solberg-Hoiland instability, the Goldreich-Schubert-Fricke instability, and secular and dynamic shear instability. The effects of the centrifugal force on the stellar structure are included. Convectively unstable zones are assumed to tend toward rigid rotation, and uncertain mixing efficiencies are gauged by observations. We find, as noted in previous work, that rotation increases the helium core masses and enriches the stellar envelopes with products of hydrogen burning. We determine, for the first time, the angular momentum distribution in typical presupernova stars along with their detailed chemical structure. Angular momentum loss due to (nonmagnetic) stellar winds and the redistribution of angular momentum during core hydrogen burning are of crucial importance for the specific angular momentum of the core. Neglecting magnetic fields, we find angular momentum transport from the core to the envelope to be unimportant after core helium burning. We obtain specific angular momenta for the iron core and overlying material of 10(16)-10(17) cm(2) s(-1). These values are insensitive to the initial angular momentum and to uncertainties in the efficiencies of rotational mixing. They are small enough to avoid triaxial deformations of the iron core before it collapses, but could lead to neutron stars which rotate close to breakup. They are also in the range required for the collapsar model of gamma-ray bursts. The apparent discrepancy with the measured rotation rates of young pulsars is discussed.
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页码:368 / 396
页数:29
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