Rotating neutron stars with quark cores

TL;DR

This paper investigates the effects of quark matter phase transitions on the properties of rotating neutron stars using advanced models, providing insights into the equation of state at high densities and aligning with recent gravitational wave observations.

Contribution

It introduces a combined modeling approach using DD-RMF and vBag models to study rotating neutron stars with quark cores, analyzing their properties and constraints from recent observations.

Findings

Maximum neutron star mass decreases with quark phase transition.

Moment of inertia and other quantities vary with the bag constant.

Results align with recent GW constraints on neutron star masses.

Abstract

The rotating neutron star properties are studied with a phase transition to quark matter. The density-dependent relativistic mean-field model (DD-RMF) is employed to study the hadron matter, while the Vector-Enhanced Bag model (vBag) model is used to study the quark matter. The star matter properties like mass, radius,the moment of inertia, rotational frequency, Kerr parameter, and other important quantities are studied to see the effect on quark matter. The maximum mass of rotating neutron star with DD-LZ1 and DD-MEX parameter sets is found to be around 3$M_{\odot}$ for pure hadronic phase and decreases to a value around 2.6$M_{\odot}$ with phase transition to quark matter, which satisfies the recent GW190814 constraints. For DDV, DDVT, and DDVTD parameter sets, the maximum mass decreases to satisfy the 2$M_{\odot}$. The moment of inertia calculated for various DD-RMF parameter sets decreases with the increasing mass satisfying constraints from various measurements. Other important quantities calculated also vary with the bag constant and hence show that the presence of quarks inside neutron stars can also allow us to constraint these quantities to determine a proper EoS. Also, the theoretical study along with the accurate measurement of uniformly rotating neutron star properties may offer some valuable information concerning the high-density part of the equation of state.