ABSTRACT

The general relativistic expression for the Kepler frequency of a star can be found only through the application of the expression as a self-consistency condition on the solution of the relativistic equations for rotating stars. Besides the absolute upper limit on rotation set by the Kepler frequency, there is instability that sets in at a somewhat lower rotational frequency, and which therefore appears to set a more stringent limit on stable rotation than mass shedding. The gravitational-radiation reaction driven instability originates from counter-rotating surface vibrational modes on rotating neutron stars, which at sufficiently high rotational star frequencies are dragged forward along in the star’s rotational direction. In order to determine which rotating neutron stars are actually stable, a detailed analysis of their perturbations must be carried out which includes the influence of gravitational radiation and viscosity.