Post-glitch relaxation following the ninth glitch of the Vela pulsar

Abstract

The relaxation observed by McCulloch, Hamilton, & Deshpande (1993) following the ninth observed glitch of the Vela pulsar provides a stringent test of the phenomenological vortex creep theory developed by Alpar et al. (1993) to explain post-glitch behavior following its previous eight glitches. Their theory predicts that the relaxation following the ninth glitch would be characterized by linear response with short time scale relaxation times, 10 hr, 3.2 days, and 33 days, respectively, a long-term torque linear in time, and a permanent offset in the frequency derivative. We present the results of an analysis of the post-glitch behavior following the ninth glitch and find excellent agreement with these predictions. We use their theory to deduce a minimum crustal moment of inertia for the solid crust of the neutron star of some 2.6% of the total moment of inertia of the star, and discuss the implication of our findings for the mass of the Vela pulsar.