Bayesian constraints on quark stars from multi-messenger observations

TL;DR

This paper uses Bayesian analysis to explore quark star models under current observational constraints, highlighting their ability to explain ultra-low mass objects and the impact of priors on high-mass interpretations.

Contribution

It introduces a comprehensive Bayesian framework for quark star equations of state, incorporating color-superconducting phases and perturbative QCD corrections, and assesses observational constraints.

Findings

Quark star models can naturally explain ultra-low mass objects like HESS J1731-347.

High-mass object interpretations are highly prior-dependent, affecting the inferred stiffness of the equation of state.

Current data tightly constrain the effective bag constant and stiffness but cannot distinguish between different color-superconducting phases.

Abstract

We perform a systematic Bayesian analysis of quark star equations of state under current multimessenger constraints, investigating the impact of prior assumptions and extreme-mass observations. Quark matter is modeled within an interacting MIT bag framework that consistently accommodates color-superconducting phases (2SC, 2SC+s, and CFL) and perturbative QCD corrections. We find that quark star models exhibit a distinct advantage in naturally accommodating the ultra-low mass object HESS J1731-347, a configuration that is challenging for standard neutron star models. In the high-mass regime, the interpretation of the secondary component of GW190814 is shown to be strongly prior-dependent: only broad priors allow for the substantial stiffness required to support such a massive object ($\sim$2.6 M$_\odot$), while more restrictive priors favor a softer equation of state consistent with standard pulsar populations. Microscopically, we demonstrate that current data tightly constrain the effective bag constant and the overall stiffness, but cannot distinguish between different color-superconducting phases. Furthermore, we validate a reduction of the model to two effective parameters without loss of information. Our results indicate that if quark stars exist, their sound speeds consistently exceeds the conformal limit ($c_s^2>1/3$) at stellar densities.