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

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. 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 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 the equilibrium sequences of a NS following a stable transition from differential rotation to uniform rotation. During this transition, the decrease in frequency relative to angular momentum loss is significantly smaller for EoS containing hyperons, compared to nucleonic EoS.