Glitches, torque evolution and the dynamics of young pulsars

Abstract

The Crab pulsar has suffered in 1975 and 1989 two glitches in which the frequency did not relaxed to the extrapolated pre-glitch value but rather spun up showing long-term changes in the frequency derivative dot Omega. This particular behaviour has been interpreted as evidence for an evolution of the torque acting upon the star. A variable torque may be related to non-canonical braking indexes, for which some determinations have been possible. We briefly analyse in this work the consistency of postulating a growth in the angle between the magnetic moment and the rotation axis as the cause of such events. We show that this hypothesis leads to the determination of the initial period, initial and present angles, according to the assumed angle growth, for young pulsars whose respective braking indices n_{obs} and jerk parameters m_{obs} are known, and some insights on the equation of state.