Rotating hybrid compact stars

TL;DR

This paper models hybrid stars with multiple phases of matter, exploring their static and rotating properties, phase transitions, and potential collapse to black holes, providing new insights into their internal structure and evolution.

Contribution

It introduces a detailed equation of state for hybrid stars with phase transitions and analyzes their static and rotating configurations, including collapse scenarios.

Findings

Massive hybrid stars (~2 solar masses) with radii 13-16 km.

Discovery of new transitional sequences during spin-down.

Internal structure snapshots showing phase growth/shrinkage with spin.

Abstract

Starting from equations of state of nucleonic and color-superconducting quark matter and assuming a first-order phase transition between these, we construct an equation of state of stellar matter, which contains three phases: a nucleonic phase, as well as two-flavor and three-flavor color-superconducting phases of quarks. Static sequences of the corresponding hybrid stars include massive members with masses of $\sim 2 M_{\odot}$ and radii in the range of $13< R < 16$ km. We investigate the integral parameters of rapidly rotating stars and obtain evolutionary sequences that correspond to constant rest-mass stars spinning down by electromagnetic and gravitational radiation. Physically new transitional sequences are revealed that are distinguished by a phase transition from nucleonic to color-superconducting matter for some configurations that are located between the static and Keplerian limits. The snapshots of internal structure of the star, displaying the growth or shrinkage of superconducting volume as the star's spin changes, are displayed for constant rest mass stars. We further obtain evolutionary sequences of rotating supramassive compact stars and construct pre-collapse models that can be used as initial data to simulate a collapse of color-superconducting hybrid stars to a black hole.