The unusual second derivative of the millisecond pulsar 1620-26: The consequence of a giant glitch?

We suggest that the unusually large second derivative of angular velocity of PSR 1620-26 may result from a recent giant glitch which occurred more than 30 yr ago, instead of being caused by a second companion orbiting around the binary system of the pulsar. Our model parameters predict that either the core magnetic field of this pulsar is much stronger than its surface magnetic field if the internal torque is produced by the core superfluid, or the third derivative of Omega is actually larger than the present upper limit by a factor of several if the internal torque is produced by the crustal superfluid. The former case will indicate that the internal magnetic fields of both the canonical pulsars and millisecond pulsars are the same. We further suggest that PSR 1620-26 should be a soft X-ray source with Lx approximately equals 5 x 1032/ergs and characteristic energy Egamma approximately equals 200 eV.published_or_final_versio