Linear Stability Analysis of Differentially Rotating Polytropes: New Results for them = 2f‐Mode Dynamical Instability
Author(s) -
Shigeyuki Karino,
Yoshiharu Eriguchi
Publication year - 2003
Publication title -
the astrophysical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.376
H-Index - 489
eISSN - 1538-4357
pISSN - 0004-637X
DOI - 10.1086/375768
Subject(s) - instability , physics , mode (computer interface) , stability (learning theory) , rotation (mathematics) , differential rotation , linear stability , classical mechanics , mechanics , mathematics , quantum mechanics , geometry , machine learning , computer science , operating system , magnetic field
We have studied the $f$-mode oscillations of differentially rotatingpolytropes by making use of the linear stability analysis. We found that thecritical values of $T/|W|$ where the dynamical instability against the $m = 2$$f$-mode oscillations sets in decrease down to $T/|W| \sim 0.20$ as the degreeof differential rotation becomes higher. Here $m$ is an azimuthal mode numberand $T$ and $W$ are the rotational energy and the gravitational potentialenergy, respectively. This tendency is almost independent of thecompressibility of the polytropes. These are the {\it first exact results} ofthe linear stability analysis for the occurrence of the dynamical instabilityagainst the $m = 2$ $f$-modes.Comment: 8 pages, 8 figures, accepted to Ap
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