Do triaxial supramassive compact stars exist?

TL;DR

This paper investigates the existence of supramassive triaxial rotating compact stars under relativistic gravity, revealing potential insights into the nuclear matter equation of state through gravitational wave observations.

Contribution

It demonstrates the existence of supramassive triaxial solutions for rotating compact stars with relativistic gravity and specific equations of state, expanding understanding of stellar configurations.

Findings

Supramassive triaxial solutions exist for certain EOSs.

Maximum mass differences depend on the EOS.

Potential to probe phase transitions via gravitational waves.

Abstract

We study quasiequilibrium solutions of triaxially deformed rotating compact stars -- a generalization of Jacobi ellipsoids under relativistic gravity and compressible equations of state (EOS). For relatively stiff (piecewise) polytropic EOSs, we find supramassive triaxial solutions whose masses exceed the maximum mass of the spherical solution, but are always lower than those of axisymmetric equilibriums. The difference in the maximum masses of triaxial and axisymmetric solutions depends sensitively on the EOS. If the difference turns out to be only about 10%, it will be strong evidence that the EOS of high density matter becomes substantially softer in the core of neutron stars. This finding opens a novel way to probe phase transitions of high density nuclear matter using detections of gravitational waves from new born neutron stars or magnetars under fallback accretion.