A Neutron Star Is Born

Abstract

A neutron star was first detected as a pulsar in 1967. It is one of the most mysterious compact objects in the universe, with a radius of the order of 10 km and masses that can reach two solar masses. In fact, neutron stars are star remnants, a kind of stellar zombie (they die, but do not disappear). In the last decades, astronomical observations yielded various contraints for neutron star masses, and finally, in 2017, a gravitational wave was detected (GW170817). Its source was identified as the merger of two neutron stars coming from NGC 4993, a galaxy 140 million light years away from us. The very same event was detected in γ-ray, x-ray, UV, IR, radio frequency and even in the optical region of the electromagnetic spectrum, starting the new era of multi-messenger astronomy. To understand and describe neutron stars, an appropriate equation of state that satisfies bulk nuclear matter properties is necessary. GW170817 detection contributed with extra constraints to determine it. On the other hand, magnetars are the same sort of compact object, but bearing much stronger magnetic fields that can reach up to 1015 G on the surface as compared with the usual 1012 G present in ordinary pulsars. While the description of ordinary pulsars is not completely established, describing magnetars poses extra challenges. In this paper, I give an overview on the history of neutron stars and on the development of nuclear models and show how the description of the tiny world of the nuclear physics can help the understanding of the cosmos, especially of the neutron stars.

Rapidly rotating neutron stars in $f(R,T)$ gravity

“…For a didactic and more extensive explanation on EoS, we refer the reader to ref. [56] and references therein.…”

“…And, to adjust other properties such as symmetry energy and the fact that protons and neutrons have slightly different masses, other mesons and interactions were included, leading to extensive generalizations and parameterization of this model [61]. Therefore, the more general Lagrangian density of the NLWM model is given by [56,61,62]:…”

“…Finally, after some analytical calculations it is possible to obtain the energy density and pressure in the NLWM model. These quantities are given as follows [56,61]:…”

Hypermassive quark cores

“…The detailed calculations of the EoS for symmetric nuclear matter, as well as for β stable matter in the QHD formalism are well documented and can be easily found in the literature [2,17,26].…”

“…Since the quantum chromodynamics (QCD) phase diagram became widely accepted, the possibility that neutron stars could, in fact, contain both a hadronic and a quark phase, started to be considered [1,2]. In the same way that asymptotic freedom allows matter to become deconfined when the density increases at low temperatures, a similar behavior can take place in the interior of neutron stars.…”