Neutral Points of Oscillation Modes along Equilibrium Sequences of Rapidly Rotating Polytropes in General Relativity --- Application of The Cowling Approximation ---

摘要

Relativistic Cowling approximation in which all metric perturbations areomitted is applied to non-axisymmetric infinitesimal oscillations of uniformlyrotating general relativistic polytropes. Frequencies of lower order f-modes which are important in analysis of secularinstability driven by gravitational radiation are investigated and neutralpoints of the mode along equilibrium sequences of rotating polytropes aredetermined. Since this approximation becomes more accurate as stars are morerelativistic and/or as they rotates more rapidly, we will be able to analyzehow a rotation period of a neutron star may be limited by this instability. Possible errors in determining neutral points caused by omitting metricperturbations are also estimated.