Quakes of Compact Stars

TL;DR

This paper develops a theoretical model incorporating elastic deformation theories to explain pulsar glitches via starquakes, comparing neutron and strangeon star models, and finds that strangeon starquakes can account for observed glitch amplitudes.

Contribution

It introduces a quantitative elastic deformation model for starquakes in pulsars, analyzing stress loading and quake types in neutron and strangeon star models, which is rarely addressed.

Findings

Strangeon starquakes can explain observed glitch amplitudes.

The required starquake magnitude is larger than Earthquakes.

Differences between neutron and strangeon star models are significant.

Abstract

Glitches are commonly observed for pulsars, which are explained by various mechanisms. One hypothesis attributes the glitch effect to the instantaneous moment of inertia change of the whole star caused by a starquake, which is similar to earthquakes caused by fast dislocation occurring on planar faults for the static stress, though the quake-induced dynamics responsible for glitch (superfluid vortex vs. pure starquake) remains still unknown. However, a theoretical model to quantitatively explain the stress loading, types of starquakes, and co-seismic change of moment of inertia is rarely discussed. In this study, we incorporate elastic deformation theories of earthquakes into the starquake problems. We compute the field of stress loading associated with rotation deceleration and determine the optimal type of starquakes at various locations. Two types of pulsar structure models, i.e. neutron and strangeon star models, are included in the computation and their differences are notable. Our calculation shows that the observed glitch amplitude can be explained by the starquakes in the strangeon star model, though the required scaled starquake magnitude is much larger than that occurred on the Earth. We further discuss the possibility to compute the energy budget and other glitch phenomena using the starquake model in the elastic medium framework.