Upper Limit on the Frequency of Pulsars

Neutron stars for which the ratio $\frac{T}{\mathrm{}\left|W\right|\mathrm{}}$ of kinetic to gravitational potential energy exceeds ∼ 0.08 are likely to be unstable and to spin down by gravitational-wave—driven oscillations. A class of pulsars with nearly identical frequencies may thus result from the collapse of accreting, rapidly rotating white dwarfs. It is likely that the fast pulsar, PSR 1937 + 214, rotates more slowly than this, but the question remains open partly because of uncertainty in the equation of state.