The possibility of twin star solutions in a model based on lattice QCD thermodynamics

Abstract

The properties of compact stars and in particular the existence of twin star solutions are investigated within an effective model that is constrained by lattice QCD thermodynamics. The model is modified at large baryon densities to incorporate a large variety of scenarios of first order phase transitions to a phase of deconfined quarks. This is achieved by matching two different variants of the bag model equation of state, in order to estimate the role of the Bag model parameters on the appearance of a second family of neutron stars. The produced sequences of neutron stars are compared with modern constrains on stellar masses, radii, and tidal deformability from astrophysical observations and gravitational wave analyses. It is found that those scenarios in our analysis, in which a third family of stars appeared due to the deconfinement transition, are disfavored from astrophysical constraints.

Electrically charged supermassive twin stars

“…If such a phase transition is sharp, a third family of compact stars can be present in the mass-radius diagram, with smaller radii but similar masses to those predicted for the disconnected second family branch [2][3][4][5][6][7][8][9]. The description of these twin star configurations has been a theme of debate in recent years [10][11][12][13][14][15][16][17][18][19][20][21], mainly motivated by the perspective that future X-ray astronomy will be able to measure the masses and radii of compact stars with a high precision. The studies performed, e.g., in Refs.…”

The slope, the hill, the drop, and the swoosh: Learning about the nuclear matter equation of state from the binary Love relations

“…NSs with nearly the same mass but different radii. For cross-overs, large "bumps" in the speed of sound (c 2 s ≡ d p/d where p is the pressure and the energy density) can appear [8,17,[19][20][21][22][23][24][25]. A fast increase in c 2 s points to a rapid change in the characteristics of strongly interacting matter, due to (i) appearance of strangeness or more massive degrees of freedom, (ii) change in effective degrees of freedom, (iii) restoration or breaking of symmetries, and (iv) strengthening or weakening of different strong interactions.…”

“…Fig. 2 in [9] and [8,17,19,34,35,39,40,[45][46][47][48][49][50][51][52][61][62][63][64][65][66][67][68][69][70][71][72][73]. Reason (ii) could be related to first-order phase transitions [38,44,52,[74][75][76][77][78] or an "unphase transition", as predicted by the quarkionic model [35,40,42,48,79,80] or crossover transitions/Gibbs constructions to/with (stiff) quark matter [36,37,45,51,[81][82][83]…”

Low Density Neutron Star Matter with Quantum Molecular Dynamics: The Role of Vector Interactions

“…Matter in neutron stars presents the largest densities achieved in the Universe, making their equation of state (EOS) hard to determine. Seeking the EOS of neutron-star matter (NSM) is a flourishing field of interest due to the presence of neutron rich matter with magnetic fields that can be larger than 10 12 G with the possibility of exotic particles, and a phase transition to deconfined quark matter [1]. The crust of a neutron star contains highly compressed nuclei embedded in a sea of electrons.…”