Rotating compact strange stars

TL;DR

This paper models rotating strange stars using a QCD-based equation of state, revealing their unique properties, high rotation frequencies, and differences from neutron stars, with implications for their stability and maximum mass limits.

Contribution

It provides the first detailed numerical models of rotating strange stars based on a QCD-inspired EOS, highlighting their distinct physical characteristics and rotational behaviors.

Findings

Strange stars have higher surface redshift than MIT bag model stars.

Maximum rotation frequencies of strange stars exceed those of neutron stars.

Supramassive strange stars spin up as they lose angular momentum before collapse.

Abstract

We compute numerical models of uniformly rotating strange stars (SS) in general relativity for the recently proposed QCD-based equation of state (EOS) of strange quark matter (Dey et al. 1998). Static models based on this EOS are characterised by a larger surface redshift than strange stars within the MIT bag model. The frequencies of the fastest rotating configurations described by Dey model are much higher than these for neutron stars (NS) and for the simplest SS MIT bag model. We determine a number of physical parameters for such stars and compare them with those obtained for NS. We construct constant baryon mass equilibrium sequences both normal and supramassive. Similarly to the NS a supramassive SS, prior to collapse to a black hole, spins up as it loses angular momentum. We find the upper limits on maximal masses and maximal frequencies of the rotating configurations. We show that the maximal rotating frequency for each of considered evolutionary sequences is never the Keplerian one. A normal and low mass supramassive strange stars gaining angular momentum always slows down just before reaching the Keplerian limit. For a high mass supramassive SS sequence the Keplerian configuration is the one with the lowest rotational frequency in the sequence. The value of $T/W$ for rapidly rotating SS of any mass is significantly higher than those for ordinary NS. For Keplerian configurations it increases as mass decreases. The results are robust for all linear self-bound equations of state.