Low T/|W| dynamical instability in differentially rotating stars: diagnosis with canonical angular momentum |
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| Authors: | Motoyuki Saijo † Shin'ichirou Yoshida ‡ |
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| Institution: | Laboratoire de l'Univers et de ses Théories, Observatoire de Paris, F-92195 Meudon Cedex, France;Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA |
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| Abstract: | We study the nature of non-axisymmetric dynamical instabilities in differentially rotating stars with both linear eigenmode analysis and hydrodynamic simulations in Newtonian gravity. We especially investigate the following three types of instability; the one-armed spiral instability, the low T /| W | bar instability, and the high T /| W | bar instability, where T is the rotational kinetic energy and W is the gravitational potential energy. The nature of the dynamical instabilities is clarified by using a canonical angular momentum as a diagnostic. We find that the one-armed spiral and the low T /| W | bar instabilities occur around the corotation radius, and they grow through the inflow of canonical angular momentum around the corotation radius. The result is a clear contrast to that of a classical dynamical bar instability in high T /| W | . We also discuss the feature of gravitational waves generated from these three types of instability. |
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| Keywords: | gravitational waves hydrodynamics instabilities stars: evolution stars: oscillations stars: rotation |
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