Equation of state of hot dense hyperonic matter in the Quark–Meson-Coupling (QMC-A) model

Abstract

We report a new equation of state (EoS) of cold and hot hyperonic matter constructed in the framework of the quark-meson-coupling (QMC-A) model. The QMC-A EoS yields results compatible with available nuclear physics constraints and astrophysical observations. It covers the range of temperatures from T=0 to 100 MeV, entropies per particle S/A between 0 and 6, lepton fractions from YL=0.0 to 0.6, and baryon number densities nB=0.05-1.2 fm-3. Applications of the QMC-A EoS are made to cold neutron stars (NS) and to hot proto-neutron stars (PNS) in two scenarios, (i) lepton rich matter with trapped neutrinos (PNS-I) and (ii) deleptonized chemically equilibrated matter (PNS-II). We find that the QMC-A model predicts hyperons in amounts growing with increasing temperature and density, thus suggesting not only their presence in PNS but also, most likely, in NS merger remnants. The nucleon-hyperon phase transition is studied through the adiabatic index and the speed of sound cs. We observe that the lowering of (cs/c)2 to and below the conformal limit of 1/3, is strongly correlated with the onset of hyperons. Rigid rotation of cold and hot stars, their moments of inertia and Kepler frequencies are also explored. The QMC-A model results are compared with two relativistic models, the chiral mean field model (CMF), and the generalized relativistic density functional (GRDF) with DD2 (nucleon-only) and DD2Y-T (full baryon octet) interactions. Similarities and differences are discussed.

Progress in Constraining Nuclear Symmetry Energy Using Neutron Star Observables Since GW170817

“…On the other hand, the possibility for GW190814's secondary as a neutron star can be accomplished by: (1) choosing/constructing stiff EOSs having a maximum mass larger than 2.5 M [76,[141][142][143][144][145][146][147][148][149][150]; (2) considering the effects of fast rotations, which can increase the maximum mass by about 20% when a star rotates at the Kepler frequency (the maximum frequency at which the gravitational attraction is still sufficient to keep matter bound to the pulsar surface) [42,43,139,140,145,[151][152][153][154][155][156][157] ; (3) considering other effects/models that can modify the maximum mass of a neutron star, such as the magnetic field [147], twin star [158], two families of compact stars [142], finite temperature [153], antikaon condensation [159], net electric charge [144], etc.…”

Equation of State and Composition of Proto-Neutron Stars and Merger Remnants with Hyperons

“…After the first observation of a massive compact star in 2010 [17] which was followed by further observations of such objects [18,19] the interest in the covariant density functional (CDF) theories of superdense matter resurged because its parameters became subject to astrophysical constraints in addition to the (low-density) constraints coming from laboratory nuclear physics (for reviews see [20][21][22]). CDF based models tuned to the astrophysical constraints that account for the finite temperature, neutrino component, and strangeness in the form of hyperons appeared in recent years [23][24][25][26][27][28][29][30][31][32][33][34].…”

Strangeness in astrophysics: Theoretical developments

“…This can be constructed by tuning the strength of the attractive and repulsive interactions, and also exploring the nature of different couplings [5,6]. In addition, it was shown that including not Figure 1: Speed of sound squared for the following models as a function of baryon number density in nuclear saturation units: SLy [20], QHC19 [10], CMF [6,[14][15][16], QMC-A EoS [11,12], and Triplets [13]. Figure modified from Ref.…”

“…[9]. Note that equations of state constructed from state of-the-art models for neutron stars generically lead to characteristic non-trivial, non-monotonic structure in the speed of sound [6,[10][11][12][13][14][15][16]. In the particular case of Ref.…”