Gravitational radiation instability in rotating stars

We have shown elsewhere that gravitational radiation leads to an instability to nonaxisymmetric perturbations in stars that are rotating rapidly enough to be secularly unstable in Newtonian theory, and we explore here some astrophysical consequences. Neutron stars are unstable when exceeds 10$sup 3$-10$sup 4$ s$sup -1$ and lose their excess angular momentum in seconds. Unstable white dwarfs spin down to stability or to collapse in times that vary from weeks to 10$sup 3$ years. All stars with ergoregions are unstable; this fact imposes stringent upper limits on the rotation of relativistic configurations.