Confronting recent light compact star observations with color-flavor locked quark matter

TL;DR

This paper investigates whether color-flavor locked quark matter models can explain recent observations of compact stars with low masses and varying radii, considering different hypotheses about their internal composition.

Contribution

It evaluates the compatibility of the CFL MIT bag model with recent compact star measurements under various stability hypotheses.

Findings

Strange quark matter stability can explain both measurements within constraints.

Hybrid star models with early phase transitions are inconsistent with massive star existence.

A slow stable hybrid star scenario can reconcile observations with theoretical models.

Abstract

Recent analyses on the properties of the central compact object in the HESS J1731-347 remnant and the PSR J1231-1411 pulsar indicated that these two compact objects are characterized by similar (low) masses and possibly different radii. This paper aims at reconciling the aforementioned measurements by utilizing the widely employed color-flavor locked (CFL) MIT bag model. The main objective is related to the examination of the acceptable values for the color superconducting gap $\Delta$ and the bag parameter $B$. Furthermore, our analysis involves two distinct hypotheses for the nature of compact stars. Firstly, we considered the case of absolute stability for strange quark matter and we found that it is possible to explain both measurements, while also respecting the latest astronomical constraints on the masses and radii of compact stars. Secondly, we studied the case of hybrid stellar matter (transition from hadrons to quarks), and concluded that, when early phase transitions are considered, the simultaneous reconciliation of both measurements leads to results that are inconsistent to the existence of massive compact stars. However, we showed that all current constraints may be satisfied under the consideration that the HESS J1731-347 remnant contains a slow stable hybrid star.