Gravitational wave transient signal emission via Ekman pumping in neutron stars during post-glitch relaxation phase

TL;DR

This paper investigates gravitational wave signals emitted during neutron star post-glitch relaxation, focusing on hydrodynamic processes like Ekman pumping with more realistic assumptions about internal properties.

Contribution

It introduces a more comprehensive model of fluid flow in neutron stars during post-glitch relaxation, analyzing gravitational wave emission with relaxed physical assumptions.

Findings

Possible gravitational wave signals within aLIGO sensitivity.

Wave decay time-scales vary widely based on internal properties.

Detection prospects depend on specific physical parameters.

Abstract

Glitches in the rotational frequency of a spinning neutron star could be promising sources of gravitational wave signals lasting between a few microseconds to a few weeks. The emitted signals and their properties depend upon the internal properties of the neutron star. In neutron stars, the most important physical properties of the fluid core are the viscosity of the fluid, the stratification of flow in the equilibrium state and the adiabatic sound speed. Such models were previously studied by van Eysden and Melatos [73] and Bennett et al. [26] 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 [76, 17]. We explore the hydrodynamic properties of the flow of fluid during this phase following more relaxed assumptions on the stratification of flow and the pressure-density gradients within the neutron star than previously studied. We calculate the time-scales of duration as well as the amplitudes of the resulting gravitational wave signals, and we detail their dependence on the physical properties of the 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.