Structure and Cooling of Neutron and Hybrid Stars

Abstract

The study of neutron stars is a topic of central interest in the investigation of the properties of strongly compressed hadronic matter. Whereas in heavy-ion collisions the fireball, created in the collision zone, contains very hot matter, with varying density depending on the beam energy, neutron stars largely sample the region of cold and dense matter with the exception of the very short time period of the existence of the proto-neutron star. Therefore, neutron star physics, in addition to its general importance in astrophysics, is a crucial complement to heavy-ion physics in the study of strongly interacting matter. In the following, model approaches will be introduced to calculate properties of neutron stars that incorporate baryons and quarks. These approaches are also able to describe the state of matter over a wide range of temperatures and densities, which is essential if one wants to connect and correlate star observables and results from heavy-ion collisions. The effect of exotic particles and quark cores on neutron star properties will be considered. In addition to the gross properties of the stars like their masses and radii their expected inner composition is quite sensitive to the models used. The effect of the composition can be studied through the analysis of the cooling curve of the star. In addition, we consider the effect of rotation, as in this case the particle composition of the star can be modified quite drastically.

Hypernuclear matter in strong magnetic field

“…Masses of the order of ≤ 1.8M ⊙ were obtained in non-relativistic phenomenological models [13,14], while microscopic models based on hyperon-nucleon potentials, which include the repulsive three-body forces, predict low maximal masses for hypernuclear stars [15,16]. The avenues for reconciliation of the large pulsar mass and the hyperonization (and more generally strangeness) of dense matter have been explored recently in Refs [17][18][19][20][21][22][23][24][25][26][27][28].…”

Hadron-Quark Crossover and Massive Hybrid Stars

“…From the observational point of view, a massive NS, PSR J1614-2230, with M obs = (1.97 ± 0.04)M was recently discovered [14]. Conflict between the 2M -NS which requires stiff EOS and the Y -mixing which gives soft EOS leads to a challenging problem whether massive neutron stars are in contradiction to the existence of the exotic components such as the hyperons and deconfined quarks [15][16][17][18][19][20][21][22][23]. † These authors contributed equally to this work.…”

Melting of antikaon condensate in protoneutron stars

“…For example, the equations of state involving hyperons lead to maximum neutron star mass below 2M ⊙ when the hyperon-scalar meson coupling is determined from existing hypernuclei data and hyperon-vector meson couplings are estimated from SU(6) quark model [2,3]. Recently, it has been demonstrated that the neutron star mass of 2M ⊙ could be achieved by making hyperon-vector meson coupling stronger [4][5][6]. On the other hand, it was shown that the EoS including antikaon condensates might result in 2M ⊙ neutron stars if the magnitude of the attractive antikaon optical potential depth is 140 MeV or less [7].…”