Neutron star sequences and the starquake glitch model for the Crab and the Vela pulsars

Abstract

We construct for the first time, the sequences of stable neutron star (NS) models capable of explaining simultaneously, the glitch healing parameters, Q, of both the pulsars, the Crab (Q≥0.7) and the Vela (Q≤0.2), on the basis of starquake mechanism of glitch generation, whereas the conventional NS models cannot give such consistent explanation. Furthermore, our models also yield an upper bound on NS masses similar to those obtained in the literature for a variety of modern equations of state (EOSs) compatible with causality and dynamical stability. If the lower limit of the observational constraint of (i) Q≥0.7 for the Crab pulsar and (ii) the recent value of the moment of inertia for the Crab pulsar (evaluated on the basis of time-dependent acceleration model of the Crab Nebula), I Crab,45≥1.93 (where I 45=I/1045 g cm2), both are imposed together on our models, the models yield the value of matching density, E b =9.584×1014 g cm−3 at the core-envelope boundary. This value of matching density yields a model-independent upper bound on neutron star masses, M max≤2.22M ⊙, and the strong lower bounds on surface redshift z R ≃0.6232 and mass M≃2.11M ⊙ for the Crab (Q≃0.7) and the strong upper bound on surface redshift z R ≃0.2016, mass M≃0.982M ⊙ and the moment of inertia I Vela,45≃0.587 for the Vela (Q≃0.2) pulsar. However, for the observational constraint of the ‘central’ weighted mean value Q≈0.72, and I Crab,45>1.93, for the Crab pulsar, the minimum surface redshift and mass of the Crab pulsar are slightly increased to the values z R ≃0.655 and M≃2.149M ⊙ respectively, whereas corresponding to the ‘central’ weighted mean value Q≈0.12 for the Vela pulsar, the maximum surface redshift, mass and the moment of inertia for the Vela pulsar are slightly decreased to the values z R ≃0.1645, M≃0.828M ⊙ and I Vela,45≃0.459 respectively. These results set an upper and lower bound on the energy of a gravitationally redshifted electron-positron annihilation line in the range of about 0.309–0.315 MeV from the Crab and in the range of about 0.425–0.439 MeV from the Vela pulsar.