Evolutionary transition between rapidly rotating compact stars after supernova explosion

We propose a formation scenario of strange stars from rapidly rotating neutron stars after supernova explosions due to the spin-down of the compact stars. By considering a process where the total baryon mass is conserved but the angular momentum is lost due to the emission of gravitational waves and/or magnetic dipole radiation, we find that the transition from a rapidly rotating neutron star to a slowly rotating strange star is possible. The large amount of energy of 5 x 10(53) ergs can be released, which is large by some factors compared to the transition between spherical stars. The liberated energy might become a new energy source for a delayed explosion of supernova. Thus our scenario suggests that the supernova associated with gamma-ray bursts becomes promising targets of future observation of gravitational waves.