A new view on the maximum mass of differentially rotating neutron stars

TL;DR

This paper investigates how differential rotation affects the maximum mass of neutron stars, revealing that certain configurations can significantly exceed the mass of non-rotating stars, with implications for gravitational wave signals.

Contribution

It provides a comprehensive analysis of the maximum mass of differentially rotating neutron stars across various solution types using a highly accurate relativistic code.

Findings

Maximum mass can be up to 4 times higher than non-rotating stars.

Maximum mass depends on differential rotation degree and solution type.

New solution types allow for higher mass configurations.

Abstract

We study the main astrophysical properties of differentially rotating neutron stars described as stationary and axisymmetric configurations of a moderately stiff $\Gamma=2$ polytropic fluid. The high level of accuracy and of stability of our relativistic multidomain pseudo-spectral code enables us to explore the whole solution space for broad ranges of the degree of differential rotation, but also of the stellar density and oblateness. Staying within an astrophysicaly motivated range of rotation profiles, we investigate the characteristics of neutron stars with maximal mass for all types of families of differentially rotating relativistic objects identified in a previous article Ansorg, Gondek-Rosinsla, Villain (2009). We find that the maximum mass depends on both the degree of differential rotation and on the type of solution. It turns out that the maximum allowed mass can be up to 4 times higher than what it is for non-rotating stars with the same equation of state. Such values are obtained for a modest degree of differential rotation but for one of the newly discovered type of solutions. Since such configurations of stars are not that extreme, this result may have important consequences for the gravitational wave signal to expect from coalescing neutron star binaries or from some supernovae events.