We study the dynamical instability against bar-mode deformation of
differentially rotating stars. We performed numerical simulation and linear
perturbation analysis adopting polytropic equations of state with the
polytropic index n=1. It is found that rotating stars of a high degree of
differential rotation are dynamically unstable even for the ratio of the
kinetic energy to the gravitational potential energy of O(0.01).
Gravitational waves from the final nonaxisymmetric quasistationary states are
calculated in the quadrupole formula. For rotating stars of mass 1.4M⊙​
and radius several 10 km, gravitational waves have frequency several 100 Hz and
effective amplitude ∼5×10−22 at a distance of ∼100 Mpc.Comment: 5 pages, 7 figures, accepted for publication in MNRA