Oblateness effects on the spindown of fast pulsars

The recent discovery^1,2 of the very rapidly rotating pulsar PSR1937+214 has triggered off many theoretical speculations^3-5. Assuming that the pulsar is a fast-rotating superdense fluid, we show here that the increase in the moment of inertia and in the gravitational self-energy of the spheroid due to its oblateness lead to substantial differences in the time evolution of the pulsar from that predicted by the standard models. Careful observations of its Ṗ, P̈ and its spectrum can put constraints on the properties of neutron star matter. Even with the existing observation of P = 1.56 ms, considerations of dynamical stability of the rapidly rotating neutron star yield a lower limit ρ̄>1.7×10¹⁴ g cm ^-3 for the mean stellar density.