GRAVITATIONAL RADIATION DRIVEN SECULAR INSTABILITY OF ROTATING POLYTROPES

摘要

We investigate secular instability of rapidly rotating polytropes by taking account of the gravitational radiation reaction and the viscosity of the neutron star matter. We use a new method to solve the linearized equations describing the oscillation of rotating stars. The maximum angular velocity of neutron stars is obtained when two dissipative forces mentioned above exist. The instability due to the dissipative forces is sensitive to the temperature of a star because the viscosity depends on the temperature. In the low- and high-temperature regions the maximum angular velocity is restricted by the mass shedding state. At intermediate temperatures around 10~9 K, however, the secular instability limits the maximum rotation rate, which will affect newly born neutron stars. From the analysis in this paper the shortest rotation period of N = 1 poly-trope is estimated to be about 1 ms which corresponds to the angular velocity of 95% of the critical one. This paper corrects an error in the damping times reported by Ipser & Lindblom (1991).