Gravitational Wave transient signal emission via Ekman Pumping in Neutron Stars during post-glitch relaxation phase

Abstract

Glitches in the rotational frequency of a spinning neutron star could be promising sources of gravitational wave signals lasting between a few {\mu}s to a few weeks. The emitted signals and their properties depend upon the internal properties of the neutron star. In stellar models that assume a super-fluid core for the neutron star, the most important physical properties are the viscosity of the super-fluid, the stratification of flow in the equilibrium state and the adiabatic sound speed. Such models were previously studied by van Eysden and Melatos (2008) and Bennett et al. (2010) following simple assumptions on all contributing factors, in which the post-glitch relaxation phase could be driven by the well-known process of 'Ekman pumping'. We explore the hydrodynamic properties of the flow of super-fluid during this phase following more relaxed assumptions on the stratification of flow and/or the pressure-density gradients within the neutron star than previously studied. We calculate the time-scales of duration as well as the characteristic strengths of the resulting gravitational wave signals, and we detail their dependence on the physical properties of the super-fluid core. We find that it is possible for the neutron star to emit gravitational wave signals in a wide range of decay time-scales and within the detection sensitivity of aLIGO for selected domains of physical parameters.