Thermal evolution of hybrid stars within the framework of a nonlocal Nambu–Jona-Lasinio model

Abstract

We study the thermal evolution of neutron stars containing deconfined quark matter in their core. Such objects are generally referred to as quark-hybrid stars. The confined hadronic matter in their core is described in the framework of non-linear relativistic nuclear field theory. For the quark phase we use a non-local extension of the SU(3) Nambu Jona-Lasinio model with vector interactions. The Gibbs condition is used to model phase equilibrium between confined hadronic matter and deconfined quark matter. Our study indicates that high-mass neutron stars may contain between 35 and 40% deconfined quark-hybrid matter in their cores. Neutron stars with canonical masses of around 1.4 M⊙ would not contain deconfined quark matter. The central proton fractions of the stars are found to be high, enabling them to cool rapidly. Very good agreement with the temperature evolution established for the neutron star in Cassiopeia A (Cas A) is obtained for one of our models (based on the popular NL3 nuclear parametrization), if the protons in the core of our stellar models are strongly paired, the repulsion among the quarks is mildly repulsive, and the mass of Cas A has a canonical value of 1.4 M⊙.

Constraining Strangeness in Dense Matter with GW170817

“…It has been shown that vector interaction contributions in the description of quark matter plays a crucial role in the description of massive hybrid stars in agreement with observational data [25,59,76,92,[133][134][135][136][137][138]. These contributions have been investigated for different quark models [135,137,138]), and applied to neutron stars studies [59,76,[134][135][136].…”

Axion cooling of neutron stars

“…The first aspect of our strategy is to use a conservative model of cooling which is not contaminated by the uncertainties in the rates of rapid neutrino emission processes, which in turn strongly depend on the composition of dense matter at densities above the saturation of nuclear matter. Modern simulations of cooling of neutron stars (see, for example, the work by different groups on hadronic models [38][39][40][41][42][43] and hybrid star models [44][45][46][47]) demonstrate that fast neutrino processes do not operate in low-mass neutron stars with M ≤ 1.5M ⊙ because each such process is associated with a certain density threshold (which need not be sharp, see in particular Refs. [40,41] for this type of modeling).…”

Many Aspects of Magnetic Fields in Neutron Stars

“…For that purpose we consider the thermal evolution of these objects, by making use of state of the art cooling calculations [62][63][64]. We employ the most recent thermal emission and cooling mechanisms available, that have also been used to explain the thermal properties of the cooling neutron star in Cassiopeia A [62,[65][66][67].…”