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1.
DIPANKAR BHATTACHARYA 《Pramana》2011,77(1):29-37
The concept of limiting mass, introduced by Chandrasekhar in case of white dwarfs, plays an important role in the formation
and stability of compact objects such as neutron stars and black holes. Like white dwarfs, neutron stars have their own mass
limit, and a compact configuration would progress from one family to the next, more dense one once a mass limit is crossed.
The mass limit of neutron stars depends on the nature of nuclear forces at very high density, which has so far not been determined
conclusively. This article reviews how observational determinations of the properties of neutron stars are starting to impose
significant constraints on the state of matter at high density. 相似文献
2.
Based on covariant density functional theory, we study the effects of rotation on the nucleon direct URCA(N-DURCA) process for traditional and hyperonic neutron stars. The calculated results indicate that, for a fixed mass sequence of rotational traditional neutron stars, the neutrino emissivity of the star is nearly invariant with increasing frequency, while it always increases for rotational hyperonic neutron stars. Thus, rotation has different effects on the N-DURCA process for these two kinds of neutron stars. 相似文献
3.
The equation of state of neutron stars is studied in the newly developed density dependent relativistic Hartree-Fock (DDRHF) theory with the effective interaction PKO1 and applied to describe the properties of neutron stars. The results are compared with the recent observational data of compact stars and those calculated with the relativistic mean field (RMF) effective interactions. The maximum mass of neutron stars calculated with PKO1 is about 2.45 M☉, which consists with high pulsar mass from PSR B1516+02B recently reported. The influence of Fock terms on the cooling of neutron stars is discussed as well. 相似文献
4.
The role of hypernuclear physics for the physics of neutron stars is delineated. Hypernuclear potentials in dense matter control the hyperon composition of dense neutron star matter. The three-body interactions of nucleons and hyperons determine the stiffness of the neutron star equation of state and thereby the maximum neutron star mass. Two-body hyperon–nucleon and hyperon–hyperon interactions give rise to hyperon pairing which exponentially suppresses cooling of neutron stars via the direct hyperon URCA processes. Nonmesonic weak reactions with hyperons in dense neutron star matter govern the gravitational wave emissions due to the r-mode instability of rotating neutron stars. 相似文献
5.
F. W. Giacobbe 《Pramana》2003,60(3):415-422
An analytical method of estimating the mass of a stellar iron core, just prior to core collapse, is described in this paper.
The method employed depends, in part, upon an estimate of the true relativistic mass increase experienced by electrons within
a highly compressed iron core, just prior to core collapse, and is significantly different from a more typical Chandrasekhar
mass limit approach. This technique produced a maximum stellar iron core mass value of 269 × 1030 kg (1.35 solar masses). This mass value is very near to the typical mass values found for neutron stars in a recent survey
of actual neutron star masses. Although slightly lower and higher neutron star masses may also be found, lower mass neutron
stars are believed to be formed as a result of enhanced iron core compression due to the weight of non-ferrous matter overlying
the iron cores within large stars. And, higher mass neutron stars are likely to be formed as a result of fallback or accretion
of additional matter after an initial collapse event involving an iron core having a mass no greater than 2.69 × 1030 kg 相似文献
6.
《中国物理C(英文版)》2017,(11)
We study the properties of two-flavor quark matter in the Dyson-Schwinger model and investigate the possible consequences for hybrid neutron stars,with particular regard to the two-solar-mass limit.We find that with some extreme values of the model parameters,the mass fraction of two-flavor quark matter in heavy neutron stars can be as high as 30 percent and the possible energy release during the conversion from nucleonic neutron stars to hybrid stars can reach 10~(52) erg. 相似文献
7.
The equations of state of the neutron star matter are calculated in the relativistic mean-field approximation with different hyperon coupling constants. The properties of neutron stars are studied by solving
the Oppenheimer-Volkoff equation. It manifests the properties of neutron stars — change explicitly as different hyperon coupling constants are
concerned. 相似文献
8.
By using the Einstein-Tolman expression of the energy-momentum pseudo-tensor, the energy density ofthe gravitational field of the static spherically symmetric neutron stars is calculated in the Cartesian coordinate system.It is exciting that the energy density of gravitational field is positive and rational. The numerical results ot the energydensity of gravitational field of neutron stars are calculated. For neutron stars with M = 2M , the ratio of the energydensity of gravitational field to the energy density of pure matters would be up to 0.54 at the surface. 相似文献
9.
The equations ofstate of the neutron star matter are calculated in the relativistic mean-field approximation witl different hyperon coupling constants. The properties of neutron stars are studied by solving the OppenheimerVolkoff equation. It manifests the properties of neutron stars - change explicitly as different hyperon coupling constants are concerned.`` 相似文献
10.
In this paper, the abnormal neutron stars containing abnormal protons are compared with the normal neutron stars in order to determine which of them are metastable and the phase transition between netastable and stable stars is discussed. 相似文献
11.
The equations describing the moment of inertia and the dragging of inertial frames of slowly rotating neutron stars are derived according to Rosen's bimetric theory of gravitation. Numerical calculations of the properties of neutron stars according to the bimetric theory and general relativity were made using several equations of state. The general trend found is that in the bimetric theory neutron stars with a given mass induce a smaller dragging of inertial frames than in general relativity. The moment of inertia of low-mass stars also is smaller in the bimetric theory. For high-mass stars, however, the moment of inertia is found to be larger in the bimetric theory.In partial fulfillment of the requirements for the D.Sc. degree. 相似文献
12.
We demonstrate that the largest measured mass of a neutron star establishes an upper bound to the energy density of observable cold baryonic matter. An equation of state-independent expression satisfied by both normal neutron stars and self-bound quark matter stars is derived for the largest energy density of matter inside stars as a function of their masses. The largest observed mass sets the lowest upper limit to the density. Implications from existing and future neutron star mass measurements are discussed. 相似文献
13.
A. Pérez Martínez H. Pérez Rojas H. J. Mosquera Cuesta 《The European Physical Journal C - Particles and Fields》2003,29(1):111-123
A relativistic degenerate neutron gas in equilibrium with a background of electrons and protons in a magnetic field exerts
its pressure anisotropically, having a smaller value perpendicular to than along the magnetic field. For critical fields the
magnetic pressure may produce the vanishing of the equatorial pressure of the neutron gas. Taking this as a model for neutron
stars, the outcome could be a transverse collapse of the star. This fixes a limit to the fields to be observable in stable
neutron star pulsars as a function of their density. The final structure left over after the implosion might be a mixed phase
of nucleons and a meson condensate, a strange star, or a highly distorted black hole or black ”cigar”, but not a magnetar,
if viewed as a superstrongly magnetized neutron star. However, we do not exclude the possibility of superstrong magnetic fields
arising in supernova explosions which lead directly to strange stars. In other words, if any magnetars exist, they cannot
be neutron stars.
Received: 25 November 2002 / Revised version: 25 February 2003 / Published online: 5 May 2003 相似文献
14.
15.
GU Jian-Fa GUO Hua LI Xi-Guo LIU Yu-Xin XU Fu-Rong 《理论物理通讯》2007,47(1):111-118
Antikaon condensation and kaon and antikaon production in protoneutron stars are investigated in a chiral hadronic model (also referred to as the FST model in this paper). The effects of neutrino trapping on protoneutron stars are analyzed systematically. It is shown that neutrino trapping makes the critical density of K^- condensation delay to higher density and fifo condensation not occur. The equation of state (EOS) of (proto)neutron star matter with neutrino trapping is stiffer than that without neutrino trapping. As a result, the maximum masses of (proto)neutron stars with neutrino trapping are larger than those without neutrino trapping. If hyperons are taken into account, antikaon does not form a condensate in (proto)neutron stars. Meanwhile, the corresponding EOS becomes much softer, and the maximum masses of (proto)neutron stars are smaller than those without hyprons. Finally, our results illustrate that the Q values for K^+ and K^- production in (proto)neutron stars are not sensitive to neutrino trapping and inclusion of hyperons. 相似文献
16.
WENDe-Hua CHENWei WANGXian-Ju AIBao-Quan LIUGuo-Tao LIULiang-Gang 《理论物理通讯》2003,40(5):637-640
By using the Einstein-Tolman expression of the energy-momentum pseudo-tensor, the energy density of the gravitational field of the static spherically symmetric neutron stars is calculated in the Cartesian coordinate system.It is exciting that the energy density of gravitational field is positive and rational The xmmerical results of the energy density of gravitational field of neutron stars are calculated. For neutron stars with M=2M, the ratio of the energy density of gravitational field to the energy density of pure matters would be up to 0.54 at the surface. 相似文献
17.
18.
In this paper,we include the density dependence behavior of the symmetry energy in the improved quark mass density dependent (IQMDD) model.Under the mean field approximation,this model is applied to investigate neutron star matter and neutron stars successfully.Effects of the density dependence of the symmetry energy on neutron stars are described. 相似文献
19.
Schatz H Aprahamian A Barnard V Bildsten L Cumming A Ouellette M Rauscher T Thielemann FK Wiescher M 《Physical review letters》2001,86(16):3471-3474
We calculate the rapid proton ( rp) capture process of hydrogen burning on the surface of an accreting neutron star with an updated reaction network that extends up to Xe, far beyond previous work. In both steady-state nuclear burning appropriate for rapidly accreting neutron stars (such as the magnetic polar caps of accreting x-ray pulsars) and unstable burning of type I x-ray bursts, we find that the rp process ends in a closed SnSbTe cycle. This prevents the synthesis of elements heavier than Te and has important consequences for x-ray burst profiles, the composition of accreting neutron stars, and potentially galactic nucleosynthesis of light p nuclei. 相似文献
20.
We investigate the role of Bose-Einstein condensation (BEC) of anti-kaons on the equation of state (EoS) and other properties
of compact stars. In the framework of relativistic mean field model we determine the EoS for β-stable hyperon matter and compare it to the situation when anti-kaons condense in the system. We observe that anti-kaon condensates
soften the EoS, thereby lowering the maximum mass of the stars. We also demonstrate that the presence of antikaon condensates
in the high density core of compact stars may lead to a new mass sequence beyond white dwarf and neutron stars. The limiting
mass of the new sequence stars is nearly equal to that of neutron star branch though they have distinctly different radii
and compositions. They are called neutron star twins. 相似文献