Glitch Behavior of Pulsars and Contribution from Neutron Star Crust

Abstract

Pulsars are highly magnetized rotating neutron stars (NSs) with a very stable rotation speed. Irrespective of their stable rotation rate, many pulsars have been observed to feature a sudden jump in the spin frequency, known as a pulsar glitch. The glitch phenomena are considered to be an exhibit of superfluidity of neutron matter inside the NS’s crustal region. The magnitude of such a rapid change in rotation rate relative to the stable rotation frequency can quantify the ratio of the moment of inertia (MoI) of the crustal region to the total MoI of the star, also called the fractional moment of inertia (FMI). In this paper, we have calculated the FMI for different masses of a star using six different representative unified equations of state constructed under a relativistic mean field framework. We have performed an event-wise comparison of the FMI obtained from data with that from theoretically calculated values with and without considering the entrainment effect. It is found that larger glitches cannot be explained by the crustal FMI alone, even without entrainment.