Yashaswi Gangwar | Searcharxiv

arXiv2026

Magnus mountains on spinning neutron stars

We investigate the formation of a "Magnus mountain'' on a neutron star, arising from the non-axisymmetric Magnus force acting on the elastic crust by pinned superfluid vortices. Such a deformed star would act as a source of continuous gravitational waves. We consider a compressible two-component stellar model and solve the coupled equations of motion for the fluid and elastic components self-consistently, allowing the stellar deformation and the resulting mass quadrupole to be determined. For simplicity, we model the star as an infinitely long cylinder, consisting of a fluid region with a thin ocean and crust. We find that the current quadrupole is zero, while the Magnus forces are strong enough to produce (dimensionless) mass quadrupoles as large as $\sim 10^{-5}$, and so would be limited only by the finite strength of the vortex pinning and the breaking strain of the star's elastic crust. Such large deformations are promising from the point of view of the detection of continuous gravitational waves by current and future detectors, and motivate further work on more realistic stellar models.

astro-ph.HE↗

arXiv2024

Applying the starquake model to study the formation of elastic mountains on spinning neutron stars

When a neutron star is spun-up or spun-down, the changing strains in its solid elastic crust can give rise to sudden fractures known as starquakes. Early interest in starquakes focused on their possible connection to pulsar glitches. While modern glitch models rely on pinned superfluid vorticity rather than crustal fracture, starquakes may nevertheless play a role in the glitch mechanism. Recently, there has been interest in the issue of starquakes resulting in non-axisymmetric shape changes, potentially linking the quake phenomenon to the building of neutron star mountains, which would then produce continuous gravitational waves. Motivated by this issue, we present a simple model that extends the energy minimisation-based calculations, originally developed to model axisymmetric glitches, to also include non-axisymmetric shape changes. We show that the creation of a mountain in a quake necessarily requires a change in the axisymmetric shape too. We apply our model to the specific problem of the spin-up of an initially non-rotating star, and estimate the maximum mountain that can be built in such a process, subject only to the constraints of energy and angular momentum conservation.

astro-ph.HE↗