强作用对奇异星观测效应的影响

奇异星是类似于中子星的曲奇异夸克物质组成的致密天体。本文研究了夸克这间的强作用对奇异星观测效应的影响。我们认为：（１）中子星转变为奇异星的行为是一种大的周期突变（ｇｌｉｔｃｈ）现象，这种现象取决于夸克间的强作用；（２）强作用使高温奇异星的振动阻尼也有效，这可能是驱动超新星爆发的新机制；（３）强作用加强了高温情形下奇异星和中子星在转动上的差别，奇异星的最小周期比中子星的小。     

混杂星的r-模不稳定性窗口

考虑到混杂星既具有奇异夸克物质核,又具有中子星固体壳层的特殊结构,运用完全自洽的二级修正方法,研究了在低温极限下(T<109K)混杂星的体粘滞耗散时标,并利用该时标计算了混杂星的临界旋转频率,发现其最小值为704.42 Hz(对应1.42 ms脉冲周期).与中子星和奇异星比较,更好地解释了观测数据.     

裸奇异星研究进展

简要介绍了近几年来裸奇星研究的一些重要进展，包括裸奇异星表面的电学性质和辐射机制，夸克表面存在的一些可能天体物理后果（如射电脉冲星的漂移子脉冲现象和软γ射线重复源的超Eddington辐射现象）等。这些研究结果对从天文观测上区分中子星和奇异星、证认奇异星的存在具有重要意义。     

中子星的相对论平均场描述

从相对论平均场理沦出发,考虑核子、超子和介子的相互作用,研究了中子星的结构和性质以及超子耦合常数对中子星性质的影响.发现当密度较高时,中子星的核心区主要由超子组成,即中子星转变成以超子为主要成分的奇异中子星,并且这种转变受到超子相互作用的影响.当超子耦合常数与核子耦合常数的比值为0.65时,中子星转变为奇异中子星所对应的密度最小,此时计算的中子星的最大质量为1.4 M⊙,与天文观测结果较好符合.     

夸克物质与夸克星

二十世纪六七十年代强子结构研究的进展使人们认识到了亚核子--夸克--的存在,随后,实验和理论上关于夸克之间作用渐近自由性质的发现使学者们明确地提出了"夸克物质"的概念.理论上预言的这种物质是否真的存在将在很大程度上检验目前基本强作用的理论.夸克星就是夸克物质的可能存在形式之一,相关研究也是人们探索超核密度物质状态的重要途径,该文简述脉冲星、中子星及夸克星的研究历史,总结了近年来夸克物质与夸克星研究的重要成果,指出了夸克星与一般中子星的异同以及若干夸克星候选体.     

奇异星周围的中微子主导吸积流

为统一解释伽玛射线暴(简称伽玛暴)与暴后再活动,提出了一个新的伽玛暴中心引擎模型一“奇异星-NDAF”模型(NDAF:Neutrino Dominated Accretion Flow,中微子主导吸积流),并计算了奇异星周围NDAF的结构.与其他中心致密天体不同的是,奇异星会向吸积流反馈以中微子为载体的奇异化相变能量.不考虑NDAF与奇异星的摩擦,结果表明:奇异星周围NDAF的结构对吸积率非常敏感;当吸积率大于0.18 Mo.S-1时,“奇异星-NDAF”模型能统一解释伽玛暴与暴后再活动,这个范围大于无摩擦的“中子星-NDAF”模型能统一解释的范围;在统一解释的情形下, “奇异星-NDAF”模型湮灭总能量的分布非常宽阔,当吸积率大于0.3 M0.S--1时,湮灭总能量大于1051 erg;最后,当吸积率大于0.3 M0.S-1时,“奇异星-NDAF”模型的湮灭光度超过同等吸积率下“黑洞-NDAF”模型一个多量级,有利于解释某些光度极大的伽玛暴.     

LSI 65°010中的中子星周围存在HⅡ区的可能观测证据

对Be／X射线双星LSI＋65°010／2S0114＋65连续四年（1992—1995年）的光学光谱观测发现,在1992年11月它的Ha发射线等值宽度在4天内从－0．43A增至－1．48A,增加了约3．5倍．此剧烈变化支持LSI＋65°10的光学子星是一颗Be星而非超巨星的论点．我们的观测还发现,1994年9月它的Ha发射线轮廓呈明显的双峰结构,但与普通Be星中由于旋转气壳而形成的双峰不同,其红峰处于Ha理论波长附近,紫峰却紫移了7．2A．我们认为此双峰可能产生在LSI＋65°010的不同HⅡ区中,即红峰产生于Be星周围的气壳内,而紫峰很可能产生于在轨道上快速运动的中子星周围的HⅡ区中,此观测可能提供了中子星周围存在HⅡ区的证据．同样,我们认为1992年11月4日观测到的Ha发射线红翼几乎不变,紫翼却大幅增加的现象也是由于中子星周围的HⅡ区造成的．     

夸克星·Q星·灰洞

夸克星·Ｑ星·灰洞对于密度极大的致密星体，除目前公认的中子星和可能存在的黑洞外，是否有其他形式的天体呢？多年来，不少科学家在探讨这一问题。现将已发表的三种可能存在的情形简介于下：夸克星自从核物理学家证实上、下夸克（Ｑｕａｒｋ）是质子和中子的组份后，７...     

中子星内部中微子辐射的相对论修正

通过相对论平均场理论和相关的弱相互作用冷却理论,在有、无超子两种情况下的中子星物质中研究含相对论效应的中子星冷却性质,并且与非相对论情况进行对比分析.考虑到极微小尺度上的引力会偏离牛顿引力,引入引力修正效应.结果表明中微子辐射的相对论效应降低了中微子发射率、发光度以及星体的冷却速度.在考虑引力修正的无超子的中子星物质中,相对论效应所引起的星体冷却速度降幅最大,对于两倍太阳质量的传统物质中子星可达56%,而超子物质中降幅最小,约为38%.     

Be／X射线双星的理论模型

为解释Ｂｅ／Ｘ射线双星波段联合观测结果，已发展了许多理论模型。在本文中简述这些Ｂｅ／Ｘ射线双星理论模型的研究现状，包括枞两个正常的Ｂ型星组成的密近双星演化成为Ｂｅ／Ｘ射线双星的演化模型，描述Ｂｅ星气壳的物理模型，Ｂｅ星和中子星的性质所决定的中子星吸积方式的吸积量及Ｂｅ／Ｘ射线双星Ｘ射线源光变曲线的理论解释。     

The conversion from neutron stars to strange stars and its implications

The conversion from neutron stars with different equation of states (EOSs) for neutron matter into strange stars with different EOSs for strange quark matter has been studied in a general relativistic numerical calculation in this paper. For hot neutron stars, their conversion may lead to great variations in their rotation periods, of which the magnitude would be greatly dependent upon the EOS for neutron matter, and of which the timescale would be greatly determined by the EOS for strange matter. This phenomenon appears as giant glitches, which might provide a probe of EOSs for both neutron matter and strange matter. But for cold neutron stars, their conversion may result in a population of gamma-ray bursts.     

On the Number Density of Sunyaev-Zeldovich Clusters of Galaxies

We study the conversion of a neutron star to a strange star as a possible energy source for gamma-ray bursts. We use different recent models for the equation of state of neutron star matter and strange quark matter. We show that the total amount of energy liberated in the conversion is in the range of &parl0;1-4&parr0;x1053 ergs (1 order of magnitude larger than previous estimates) and is in agreement with the energy required to power gamma-ray burst sources at cosmological distances.     

Neutron Stars with a Quark Core. II. Basic Integral and Structural Parameters

A broad sample of computed realistic equations of state of superdense matter with a quark phase transition is used to construct a series of models of neutron stars with a strange quark core. The integral characteristics of the stellar configurations are obtained: gravitational mass, rest mass, radius, relativistic moment of inertia, and red shift from the star's surface, as well as the mass and radius of the quark core within the allowable range of values for the central pressure. The parameters of some of the characteristic configurations of the calculated series are also given and these are studied in detail. It is found that a new additional region of stability for neutron stars with strange quark cores may exist for some models of the equation of state.     

The effects of strong interaction on the observational discrimination between neutron and strange stars

Strange stars are compact objects similar to neutron stars composed of strange matter. This paper investigates the observational effects of the strong interaction between quarks. We believe: 1) that the conversion of a neutron star to a strange star is a large “period glitch” which is determined by the strong interaction; 2) that the strong interaction results in effective damping of oscillation of hot strange stars, which could be a new mechanism of driving supernova explosions; 3) that the strong interaction increases the difference in rotation between strange and neutron stars under high temperatures, making the minimum period for strange stars lower than that for neutron stars.     

Neutron Stars with a Quark Core. I. Equations of State

An extensive set of realistic equations of state for superdense matter with a quark phase transition is derived on the basis of the three equations of state for neutron matter and the eight variants of strange quark-gluon plasmas in the MIT quark bag model. The characteristics of the phase transitions are described and the calculated equations of state with a density jump are studied in detail.     

An Upper Bound on Neutron Star Masses

We derive an upper bound on neutron star masses by using model equations of state in the nuclear matter density region and the causality limited equation of state in the ultradense region. Supposing that the model equations of state describe neutron star matter at nuclear matter density correctly we find as bound 3.75 M_⊙. For large fiducial densities one gets a maximum mass which is above a previous estimate.     

R-mode instability of strange stars and observations of neutron stars in LMXBs

Using a realistic equation of state(EOS) of strange quark matter, namely,the modified bag model, and considering the constraints on the parameters of EOS by the observational mass limit of neutron stars, we investigate the r-mode instability window of strange stars, and find the same result as in the brief study of Haskell,Degenaar and Ho in 2012 that these instability windows are not consistent with the spin frequency and temperature observations of neutron stars in low mass X-ray binaries.     

Space-Time Geometry of Quark and Strange Quark Matter

We study quarkand strangequarkmatter in the contextof generalrelativity.For this purpose,we solve Einstein's field equations for quark and strange quark matter in spherical symmetric space-times. We analyze strange quark matter for the different equations of state (EOS) in the spherical symmetric space-times,thus we are able to obtain the space-time geometries of quark and strange quark matter. Also,we discuss the features of the obtained solutions. The obtained solutions are consistent with the results of Brookhaven Laboratory,i.e. the quark-gluon plasma has a vanishing shear (i.e. quark-gluon plasma is perfect).     

新状态方程下中子星的性质

利用扩展的Skyrme作用可从Hartree-Fock多体理论中给出一种新的状态方程。本文在这个状态方程的基础上研究了静态中子星的性质。对于SKM和SG2这两个较好的Skyrme相互作用模型计算得到中子星的最大质量分别为Mmax=1.7M。，Max=1.67M。，此外，本文还研究了中子星的其它性质，如引力红移、惯量矩等，计算结果与观测以及Glitch模型符合。最后还发现在这种状态方程下，中子星冷却仅能通过冷却速度相对较慢的修正的Urca过程来实现。为便于比较，文中还计算了AV14＋TBF和Paris TBF这两种三体相互作用模型下的中子星的性质。