Quark Matter In Massive Compact Stars

TL;DR

This paper investigates the conditions under which quark matter can exist in massive compact stars, considering recent observational constraints, and explores the implications for different types of quark and hybrid stars.

Contribution

It provides a parameterized analysis of quark star equations of state, highlighting the effects of strong coupling, color-superconductivity, and nuclear matter stiffness on star mass limits.

Findings

Strange stars can reach 2 M_sun if strong coupling and superconductivity are included.

Hybrid stars' maximum mass depends on the nuclear matter EoS stiffness.

Quark matter appearance is sensitive to the phase transition and EoS properties.

Abstract

The recent observation of the pulsar PSR J1614-2230 with a mass of 1.97 +/- 0.04 M_sun gives a strong constraint on the quark and nuclear matter equations of state (EoS). We explore the parameter ranges for a parameterized EoS for quark stars. We find that strange stars, made of absolutely stable strange quark matter, comply with the new constraint only if effects from the strong coupling constant and color-superconductivity are taken into account. Hybrid stars, compact stars with a quark matter core and an hadronic outer layer, can be as massive as 2 M_sun, but only for a significantly limited range of parameters. We demonstrate that the appearance of quark matter in massive stars depends crucially on the stiffness of the nuclear matter EoS. We show that the masses of hybrid stars stay below the ones of hadronic and pure quark stars, due to the softening of the EoS at the quark-hadron phase transition.