Hybrid stars with color superconducting cores in an extended FCM model

Abstract

We investigate the influence of repulsive vector interactions and color superconductivity on the structure of neutron stars using an extended version of the field correlator method (FCM) for the description of quark matter. The hybrid equation of state is constructed using the Maxwell description, which assumes a sharp hadron-quark phase transition. The equation of state of hadronic matter is computed for a density-dependent relativistic lagrangian treated in the mean-field approximation, with parameters given by the SW4L nuclear model. This model described the interactions among baryons in terms of $\sigma ,\omega ,\rho ,{\sigma }^{\ast }$, and $\varphi$ mesons. Quark matter is assumed to be in either the CFL or the 2SC+s color superconducting phase. The possibility of sequential (hadron-quark, quark-quark) transitions in ultra-dense matter is investigated. Observed data related to massive pulsars, gravitational-wave events, and NICER are used to constrain the parameters of the extended FCM model. The successful equations of state are used to explore the mass-radius relationship, radii, and tidal deformabilities of hybrid stars. A special focus lies on investigating consequences that slow or fast conversions of quark-hadron matter have on the stability and the mass-radius relationship of hybrid stars. We find that if slow conversion should occur, a new branch of stable massive stars would exist whose members have radii that are up to 1.5~km smaller than those of conventional neutron stars of the same mass. Such objects could be possible candidates for the stellar high-mass object of the GW190425 binary system.

This article has the same content as the one published in Universe 2021, 7(10), 370

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Cited by in corpus (10)

• Two first-order phase transitions in hybrid compact stars: higher-order multiplet stars, reaction modes and intermediate conversion speeds
• Could a slow stable hybrid star explain the central compact object in HESS~J1731-347?
• Oscillating magnetised hybrid stars under the magnifying glass of multi-messenger observations
• Asteroseismology using quadrupolar f-modes revisited: breaking of universal relationships in the slow hadron-quark conversion scenario
• Breaking of universal relationships of axial wI-modes in hybrid stars: rapid and slow hadron-quark conversion scenarios
• Non-equilibrium effects on stability of hybrid stars with first-order phase transitions
• Rotating Hybrid Stars with Color-Flavor-Locked Quark Matter
• Impact of Multiple Phase Transitions in Dense QCD on Compact Stars
• Oscillating Magnetized Color Superconducting Quark Stars
• Classification of $g$-modes for neutron stars with a strong transition: Novel universal relation including slow stable hybrid stars