Quasi-stationary sequences of hyper massive neutron stars with exotic equations of state

TL;DR

This paper investigates how differential rotation, temperature, and strangeness influence the quasi-stationary sequences of hyper massive neutron stars, revealing effects on spin-up phenomena and stability related to exotic matter and thermal conditions.

Contribution

It introduces detailed models of hyper massive neutron stars with exotic equations of state, including hyperons and temperature effects, and analyzes their rotational and stability properties.

Findings

Hyperons significantly enhance the spin-up phenomenon.

Higher temperatures make the spin-up more robust.

Strangeness and thermal effects influence T/W instability and rotational transition behavior.

Abstract

In this work, we study the effect of differential rotation, finite temperature and strangeness on the quasi stationary sequences of hyper massive neutron stars (HMNS). We generate constant rest mass sequences of differentially rotating and uniformly rotating stars. The nucleonic matter relevant to the star interior is described within the framework of the relativistic mean field model with the DD2 parameter set. We also consider the strange $\Lambda$ hyperons using the BHB$\Lambda\phi$ equation of state (EoS). Additionally, we probe the behaviour of neutron stars (NS) with these compositions at different temperatures. We report that the addition of hyperons to the EoS produces a significant boost to the spin-up phenomenon. Moreover, increasing the temperature can make the spin-up more robust. We also study the impact of strangeness and thermal effects on the T/W instability. Finally, we analyse equilibrium sequences of a NS following a stable transition from differential rotation to uniform rotation. The decrease in frequency relative to angular momentum loss during this transition is significantly smaller for EoS containing hyperons, compared to nucleonic EoS.