Gravitational waves from small spin-up and spin-down events of neutron stars

It was recently reported that there exists a population of 'glitch candidates' and 'antiglitch candidates' which are effectively small spin-ups and spin-downs of a neutron star with magnitudes smaller than those seen in typical glitches. The physical origin of these small events is not yet understood. In this paper, we outline a model that can account for the changes in spin, and crucially, is independently testable with gravitational wave observations. In brief, the model posits that small spin-up/spin-down events are caused by the excitation and decay of non-axisymmetric f-modes which radiate angular momentum away in a burst-like way as gravitational waves. The model takes the change in spin frequency as an input and outputs the initial mode amplitude and the signal-to-noise ratio achievable from gravitational wave detectors. We find that the model presented here will become falsifiable once third generation gravitational wave detectors, like the Einstein Telescope and Cosmic Explorer, begin taking data.

Automated summary

It has been reported recently that there is a group of 'glitch candidates' and 'antiglitch candidates' which are small spin-ups and spin-downs of a neutron star, with magnitudes smaller than typical glitches. The physical origin of these small events is not yet understood. This paper proposes a model that can explain the changes in spin and can be independently tested using gravitational wave observations. The model suggests that small spin-up/spin-down events are caused by the excitation and decay of non-axisymmetric f-modes that radiate angular momentum away as gravitational waves. The model takes the change in spin frequency as input and outputs the initial mode amplitude and signal-to-noise ratio achievable from gravitational wave detectors. It is found that this model will become falsifiable once third generation gravitational wave detectors, like the Einstein Telescope and Cosmic Explorer, begin collecting data.