共查询到20条相似文献,搜索用时 62 毫秒
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天文学家们认为我们银河系内隐藏着年龄大于100亿岁的老年星。按照恒星演化理论,恒星越老,所含金属越少(在天文学中,“金属”一词泛指重于氦的元素),故目前识别老年恒星的惟一途径是审视它们的光谱;光谱中某种金属的特征谱线越暗淡说明该恒星所含此种金属的量越稀少,无此谱线说明该恒星不含此金属。但知易行难,欲从银河系2000亿颗恒星中挑选出老寿“星”不啻是大海捞针。迄今为止,较易做到的是观察数百万颗孤立单星的光谱,并从中筛选出金属特征谱线既少且暗淡的星。 相似文献
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锆钛酸铅镧(Pb0.94La0.06Zr0.96Ti0.04O3,PLZT)具有良好的介电和储能性质,是高效、高能量密度电容元件和存储器件的基体材料.为研究该材料的中子辐照损伤,首先基于Geant4程序包模拟了能量为1—14 MeV中子辐照浩钛酸铅镧(PLZT)材料产生的反冲原子能谱,然后根据产生的反冲原子种类和最大能量,利用二元碰撞方法模拟了不同能量的离子在PLZT中产生的位移损伤(包括空位和间隙原子),最后根据反冲原子能谱和对应能量离子在材料中产生的缺陷数目计算了不同能量的中子在PLZT材料中产生缺陷浓度以及分布.结果发现,对于1—14 MeV能区的快中子而言,其在厚度为3 cm的PLZT材料中产生的缺陷数目近似与中子能量无关,约为460±120空位/中子.辐照损伤在3cm厚度内随深度的增加而略有减小,总体变化小于50%,该减小主要是由于中子的反散射导致.本工作为计算中子在材料中的位移损伤提供了一种方法,同时模拟结果可为研究PLZT基电子器件的中子辐照效应提供指导. 相似文献
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对快中子引起的核反应作预平衡修正,即考虑直接–半直接俘获作为统计平衡前1激子态和3激子态的γ发射过程,5个及5个以上激子态的粒子(中子、质子及α粒子等)及γ发射过程用达到统计平衡的复合核过程描述,在中子入射能量3MeV至20MeV能区对40Ca和208Pb的辐射俘获截面进行了理论计算并与实验结果作了比较,得到了较好符合的结果.同时,对统计平衡前后γ发射对(n,γ)截面的贡献及直接俘获、半直接俘获和两者的相干项的特性进行了讨论 相似文献
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We present a model of a remnant of supernova, and we analyze the correlation with the observational data to short periods oscillations between a neutron star and a strange matter star. The results confirm previous conclusions. 相似文献
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WEN De-Hua CHEN Wei LIU Liang-Gang 《理论物理通讯》2007,47(4):653-657
Properties and deformations of the rotating neutron stars in uniform strong magnetic field are calculated. The magnetic field will soften the equation of state of the neutron star matters and make an obvious effect on the structure of the rotating neutron star. If the magnetic field is superstrong (B=10^17 T), the mass, radius, and the deformation will become smaller effectively. 相似文献
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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
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中子星的制动机制是中子星研究中的基本问题。磁偶极辐射模型给出中子星的制动指数为3,而所有观测到的中子星的制动指数都小于3,这表明中子星除磁偶极辐射之外还存在其他的转动能量损失方式。考虑中子星的转动动能损失来自:磁偶极辐射、由于单极感应引起的粒子流逃逸以及中子星和量子真空摩引起的能量损失。基于这3 种辐射机制,给出了改进后的中子星能量损失功率的计算公式和周期对时间一阶导数与周期的依赖关系。考察了6 颗中子星( J1119–6127, B1509–58, J1846–0258,B0531+21, B0540–69 和B0833–45 ) 的周期-周期一阶导数关系,制动指数、表面磁场强度以及磁倾角之间的关系。研究表明,星风效应中,真空间隙电势差为常数时磁倾角只能在有限范围内取值,而其他情况下磁倾角在0s 90°之间连续取值。The neutron stars’ braking mechanism is a fundamental problem in the study of neutron stars. The braking index exactly equal to 3 in pure magnetodipole radiation model, however, all the observed braking index of rotationpowered pulsars is less than 3. This indicates that the additional energy loss ways must exist besides the magnetodipole radiation. The magnetodipole radiation, the ejection of particle outflow and quantum vacuum friction are considered as the source of the loss of rotational kinetic energy of rotation-powered pulsars. Based on the three mechanism of loss of the energy, the relation between the period of pulsars and the first derivative of the period to time and the pulsars’ energy losing power are given. The relationship of the periods and the first derivative of the periods of six pulsars(J1119−6127,B1509−58, J1846−0258, B0531+21, B0540−69 and B0833−45) is studied. The relation between the surface magnetic field intensity and the magnetic inclination is discussed. Research shows that when the electric potential difference of vacuum gap is a constant the inclination angle is limited in a smaller range and in the other cases the inclination is the continuous value between 0∼90 degrees. 相似文献
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在过去的十余年中,对非对称核物质的对称能的研究无论从实验还是理论上都取得了较大的突破,这对中子结构及其物态方程的理解具有十分重要的意义。本研究将采用一个相对保守的对称能斜率范围(25 Me VL105Me V)来研究其对快速转动中子星性质的约束,这些性质包括:质量-半径关系、转动惯量、引力红移以及转动形变等。通过该对称能斜率的约束,发现典型中子星(M=1.4M⊙)的半径约束在10.28~13.43 km范围内,这与最近的相关观测相一致。如果观察发现了质量较小的毫秒脉冲星,则将为核物质的对称能较软提供有效的证据。另外还发现,对角动量的一致性可为快转中子星转动惯量的上限提供约束。最后,根据具有低质量伴星的双星EXO0748-676的红移观测,给出了该脉冲星的质量下限(1.5M⊙)。 相似文献
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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
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In the framework of the relativistic mean field theory including the hyperon-hyperon(YY) interactions,protoneutron stars with a weakly interacting light U boson are studied. The U-boson leads to the increase of the star maximum mass. The modification to the maximum mass by the U-boson with the strong YY interaction is larger than that with the weak YY interaction. The maximum mass of the protoneutron star is less sensitive to the U-boson than that of the neutron star. The inclusion of the U-boson narrows down the mass window for the hyperonized protoneutron stars. As g~2/μ~2 increases, the species of hyperons, which can appear in a stable protoneutron star decrease. The rotation frequency, the red shift, the momentum of inertia and the total neutrino fraction of PSR J1903-0327 are sensitive to the U-boson and change with g~2/μ~2 in an approximate linear trend. The possible way to constrain the coupling constants of the U-boson is discussed. 相似文献
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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
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采用相对论平均场方法研究了致密物质的性质, 构造了包括较宽温度、 同位旋不对称度和密度范围的适用于超新星模拟研究的状态方程, 均匀物质由相对论平均场理论描述, 非均匀物质由托马斯 费米近似给出。讨论了包含超子自由度的中子星物质的状态方程。 计算结果表明, 包含超子可以有效地软化高密度区的状态方程, Λ超子的超流态有可能存在于大质量中子星内部。The properties of dense matter are studied within the relativistic mean field theory. The equation of state (EOS) of dense matter are constructed covering a wide range of temperature, proton fraction, and density for the use of supernova simulations. The relativistic mean field theory is employed to describe the uniform matter, while the Thomas Fermi approximation is adopted to describe the non uniform matter. The EOS of neutron star matter is discussed with the inclusion of hyperons. It is found that the EOS at high density can be significantly softened by the inclusion of hyperons. The 1S0 superfluidity of Λ hyperons may exist in massive neutron stars. 相似文献