Color-flavor locked quark stars in light of the compact object in the HESS J1731-347 and the GW190814 event

Abstract

The central compact object within HESS J1731-347 possesses unique mass and radius properties that renders it a compelling candidate for a self-bound star. In this research, we examine the capability of quark stars composed of color superconducting quark matter to explain the latter object by using its marginalized posterior distribution and imposing it as a constraint on the relevant parameter space. Namely, we investigate quark matter for ${N}_{f}=2,3$ in the color superconducting phase, incorporating perturbative QCD corrections, and we derive their properties accordingly. The utilized thermodynamic potential of this work possesses an MIT bag model formalism with the parameters being established as flavor-independent. In this instance, we conclude the favor of the 3-flavor over the 2-flavor color superconducting quark matter and we isolate our interest on the former, without neglecting the possible favor of the latter in a different framework. The parameter space is further confined due to the additional requirement for a high maximum mass (${M}_{\mathrm{TOV}}\ensuremath{\ge}2.6{M}_{\ensuremath{\bigodot}}$), accounting for GW190814's secondary companion. Our study places significant emphasis on the speed of sound and the trace anomaly which was proposed as a measure of conformality [Y. Fujimoto et al., Phys. Rev. Lett. 129, 252702 (2022).]. We conclude that it is possible for color-flavor locked quark stars to reach high masses without violating the conformal bound or the $⟨\mathrm{\ensuremath{\Theta}}{⟩}_{{\ensuremath{\mu}}_{B}}\ensuremath{\ge}0$, provided that the quartic coefficient ${\ensuremath{\alpha}}_{4}$ does not exceed an upper limit which depends on the established ${M}_{\mathrm{TOV}}$. For ${M}_{\mathrm{TOV}}=2.6{M}_{\ensuremath{\bigodot}}$, we find that the limit reads ${\ensuremath{\alpha}}_{4}\ensuremath{\le}0.594$. Lastly, a further study takes place on the agreement of color-flavor locked quark stars with additional astrophysical objects including the GW170817 and GW190425 events, followed by a relevant discussion.

Topics & Concepts