اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدMetastability of hadronic compact stars
43
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Pure hadronic compact stars, above a threshold value of their gravitational mass (central pressure), are metastable to the conversion to quark stars (hybrid or strange stars). In this paper, we present a systematic study of the metastability of pure hadronic compact stars using different relativistic models for the equation of state (EoS). In particular, we compare results for the quark-meson coupling (QMC) model with those for the Glendenning--Moszkowski parametrization of the non-linear Walecka model (NLWM). For QMC model, we find large values ($M_{cr} = 1.6$ -- $1.9 M_odot$) for the critical mass of the hadronic star sequence and we find that the formation of a quark star is only possible with a soft quark matter EoS. For the Glendenning--Moszkowski parametrization of the NLWM, we explore the effect of different hyperon couplings on the critical mass and on the stellar conversion energy. We find that increasing the value of the hyperon coupling constants shifts the bulk transition point for quark deconfinement to higher densities, increases the stellar metastability threshold mass and the value of the critical mass, and thus makes the formation of quark stars less likely. For the largest values of the hyperon couplings we find a critical mass which may be as high as 1.9 - 2.1 $M_odot$. These stellar configurations, which contain a large central hyperon fraction ($f_{Y,cr} sim 30 %$), would be able to describe highly-massive compact stars, such as the one associated to the millisecond pulsars PSR B1516+02B with a mass $M = 1.94^{+ 0.17}_{- 0.19} M_{odot}$.
قيم البحث
اقرأ أيضاً
We study the axion cooling of neutron stars within the Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) model, which allows for tree level coupling of electrons to the axion {and locks the Peccei-Quinn charges of fermions via an angle parameter}. This exten
ds our previous study [Phys. Rev. D 93, 065044 (2016)] limited to hadronic models of axions. We explore the two-dimensional space of axion parameters within the DFSZ model by comparing the theoretical cooling models with the surface temperatures of a few stars with measured surface temperatures. It is found that axions masses $m_age 0.06$ to 0.12 eV can be excluded by x-ray observations of thermal emission of neutron stars (in particular by those of Cas A), the precise limiting value depending on the angle parameter of the DFSZ model. It is also found that axion emission by electron bremsstrahlung in neutron star crusts is negligible except for the special case where neutron Peccei-Quinn charge is small enough, so that the coupling of neutrons to axions can be neglected.
Strong interaction physics under extreme conditions of high temperature and/or density is of central interest in modern nuclear physics for experimentalists and theorists alike. In order to investigate such systems, model approaches that include hadr
ons and quarks in a unified approach, will be discussed. Special attention will be given to high-density matter as it occurs in neutron stars. Given the current observational limits for neutron star masses, the properties of hyperonic and hybrid stars will be determined. In this context especially the question of the extent, to which exotic particles like hyperons and quarks affect star masses, will be discussed.
We investigate systematically the quark-hadron mixed phase in dense stellar matter, and its influence on compact star structures. The properties of quark matter and hadronic matter are fixed based on various model predictions. Beside adopting constan
t values, the surface tension $Sigma$ for the quark-hadron interface is estimated with the multiple reflection expansion method and equivparticle model. To fix the structures of quark-hadron pasta phases, a continuous dimensionality of the structure is adopted as proposed by Ravenhall, Pethick, and Wilson. The corresponding properties of hybrid stars are then obtained and confronted with pulsar observations. It is found that the correlation between radius and tidal deformability in traditional neutron stars preserves in hybrid stars. For those permitted by pulsar observations, in almost all cases the quark phase persists inside the most massive compact stars. The quark-hadron interface plays an important role on hybrid star structures once quark matter emerges. The surface tension $Sigma$ estimated with various methods increases with density, which predicts stiffer EOSs for the quark-hadron mixed phase and increases the maximum mass of hybrid stars. The EOSs of hybrid star matter are well constrained at densities $nlesssim 0.8$ fm${}^{-3}$, while larger uncertainty is expected at higher densities.
The properties of neutron stars constituted of a crust of hadrons and an internal part of hadrons and kaon condensate are calculated within the quark-meson-coupling model. We have considered stars with nucleons only in the hadron phase and also stars
with hyperons as well. The results are compared with the ones obtained from the non-linear Walecka model for the hadronic phase.
We conjecture and verify a set of universal relations between global parameters of hot and fast-rotating compact stars, including a relation connecting the masses of the mass-shedding (Kepler) and static configurations. We apply these relations to th
e GW170817 event by adopting the scenario in which a hypermassive compact star remnant formed in a merger evolves into a supramassive compact star that collapses into a black hole once the stability line for such stars is crossed. We deduce an upper limit on the maximum mass of static, cold neutron stars $ 2.15^{+0.10}_{-0.07}le M^star_{mathrm{TOV}} le 2.24^{+0.12}_{-0.10} $ for the typical range of entropy per baryon $2 le S/A le 3$ and electron fraction $Y_e = 0.1$ characterizing the hot hypermassive star. Our result implies that accounting for the finite temperature of the merger remnant relaxes previously derived constraints on the value of the maximum mass of a cold, static compact star.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
