贫金属星的表面丰度与慢中子俘获过程

在不依赖于特定恒星模型的前提下,采用参数化热脉冲模型,对三颗铅星的表面丰度进行了拟合计算.结果表明,无论是否考虑分叉道的影响,结果均能很好地重现观测数据.另外,铅星与非铅星的模型参量对比显示,铅星的平均中子辐照量远大于非铅星,而其挖掘程度明显小于非铅星.这说明尽管参数化热脉冲模型过于简单,但对约束恒星模型仍具有重要意义.     

AGB星演化过程中的元素核合成

简述AGB星元素核合成理论的发展历程 .特别是 ,对慢中子俘获过程 (s 过程 )的机制及相关的AGB星演化图像作了简单介绍. The development of nucleosynthesis theory in Asymptotic Giant Branch (AGB) stars is reviewed. Particularly, the slow neutron capture processes (s processes) and the evolution of AGB stars are briefly described.     

贫金属星的中子俘获元素

利用分量系数公式并结合太阳系元素丰度的最新数据,计算了6?4颗贫金属星的中子俘获元素丰度.结果显示,快中子俘获过程(r过程)是贫金属星中子俘获元素的主要来源,且金属丰度小于–2.5的贫金属星的重中子俘获元素产量可能来自于纯r过程;重中子俘获元素与轻中子俘获元素来自于不同的天体物理场所     

3M⊙ AGB星中26Al核合成的网络计算和反应率灵敏度分析

研究了3$M_{\odot}$AGB星中26Al核合成的网络计算和核反应率的灵敏度分析。结合最新的核反应率数据,建立了一个从碳到硅完整的核反应网络,计算了26Al的丰度。结果表明,26Al首先在AGB星中有效合成,随着核反应的进行,然后被一系列的核反应消耗。MgAl循环出现在26Al的网络中。我们将核反应网络中的主要核反应分为三类:(n, ${\rm{\gamma }}$),(p,${\rm{\gamma }}$)和($\alpha$, ${\rm{\gamma }}$),并对核反应率的灵敏度进行了详细的分析。已经确定了每一类中最有影响的核反应,它们是25Mg(n, ${\rm{\gamma }}$)26Mg,25Mg(p, ${\rm{\gamma }}$)26Al,26Mg(p, ${\rm{\gamma }}$)27Al,21Ne(p, ${\rm{\gamma }}$)22Na,18O($\alpha$, ${\rm{\gamma }}$)22Ne和22Ne($\alpha$,${\rm{\gamma }}$)26Mg。在目前网络所涉及的所有核反应中,25Mg(p, ${\rm{\gamma }}$)26Al是对26Al的产量有最大的影响,它值得核实验物理学家的关注。     

基于LASSO算法的恒星α元素丰度估计方法研究

主要研究了一种新的基于LASSO算法的恒星α元素丰度估计方法。海量恒星的α元素(O, Mg, Si, Ca 和Ti)丰度信息将有助于我们了解银河系的演化进程。但目前从中低分辨率光谱中确定α元素丰度的方法主要是模板匹配法,但该方法算法复杂,优化参数较为困难且对噪声敏感,因此有必要研究新的方法。实验结果显示,LASSO算法对ELODIE光谱的α丰度的估计精度为0.003(0.078)dex。为验证光谱分辨率变化对LASSO算法结果的影响,我们首先用ELODIE光谱通过高斯卷积得到了分辨率为42 000, 21 000, 10 500, 4 200和2 100的光谱,然后使用LASSO算法估计α元素丰度,精度分别为0.003 3(0.078)dex,-0.05(0.059)dex,-0.007(0.060)dex,0.008 0(0.069)dex和-0.004 5(0.067)dex。上述结果证明LASSO算法对分辨率变化不敏感。为验证LASSO算法对信噪比变化的鲁棒性,使用ELODIE光谱分别构造了信噪比为30, 25, 20, 15和5的光谱。LASSO算法在上述数据集上的精度分别为-0.002(0.076)dex, -0.09(0.073)dex, 0.003 6(0.075)dex, 0.007 6(0.078)dex 和-0.009(0.08)dex,因而LASSO算法对信噪比变化不敏感。因此,LASSO算法适用于低分辨率低信噪比的LAMOST和SDSS光谱。LASSO算法在SDSS光谱上的估计精度为0.003 7(0.097)dex,而在球状星团和疏散星团成员星上的结果显示LASSO算法给出的丰度与文献给出α丰度值误差在1σ以内。因此,LASSO算法能够用于估计恒星的α元素丰度。     

中低分辨率光谱的恒星Mg元素丰度估计方法研究

主要研究了一种新的基于ELM算法的中低分辨光谱的恒星Mg元素丰度估计方法。大科学工程郭守敬望远镜（LAMOST）为我们提供了海量的中低分辨率的光谱,确定这些光谱的Mg元素丰度将有助于我们深入了解银河系的形成历史和演化过程。目前从中低分辨率光谱中确定Mg元素丰度的方法主要是模板匹配法,但该方法算法复杂,优化参数较为困难且对噪声敏感,因此有必要研究新的方法。实验结果显示,ELM算法对MILES光谱的Mg丰度的估计的精度为0.009 9（0.15）dex,而对信噪比大于50的LAMOST光谱的精度为0.002 7（0.11）dex。通过与其他算法进行对比,证实ELM算法是一种能精确估计中低分辨率光谱的Mg元素丰度的算法,能够应用于LAMOST后期的光谱数据中。     

Debye屏蔽对碳等离子体电荷态丰度分布的影响

基于组态相互作用方法,使用Debye模型研究了等离子体屏蔽效应对碳离子结构和不同电荷态离子丰度分布的影响.以类氦碳离子(C V)的1s_(1/2)~2→(1s_(1/2)ns_(1/2))_1(n=2,3,4,5)磁偶极(M1)跃迁为例,详细研究了Debye屏蔽因子对跃迁几率的影响.研究了离子丰度分布随屏蔽因子的变化,结果表明在相同的等离体温度和密度条件下,考虑了屏蔽效应的离子丰度分布整体向低电离度的离子偏移,平均电离度降低.     

强激光辐照凹槽靶引起的高阶电离离子的丰度增强

高功率激光辐照固体靶时,靶面上的激光辐射场基本上可以与原子内壳层的电子束缚场相比拟。激光迅速地将元素大部分电子剥离从而产生高温高密度的等离子体并发射丰富的软X射线谱。当激光功率进一步提高时,等离子体的离子将进一步地被剥离、处激发态上的电子可能进一步被激发到更高的能级上并发射更为丰富、更强的X射线。     

热辐射对热团簇衰变率和丰度的影响

本文量化了辐射冷却对单分子衰变速率、热簇以及非特定激发能量的分子的影响.检测出两种不同的区域,可以通过发射光子的能量大小进行定义,并根据光子发射速率常数和颗粒的热性质确定它们之间的边界.此外,通过丰度光谱计算了相当于小光子能量的连续冷却情况.两种不同区域分别是连续性冷却和单分子衰变的单光子猝灭.辐射效应通过重新定义每个单独的团簇用于进行蒸发的时间进行参数化,可用有效辐射时间常数来表示.     

天体元素生成与原子核的性质

介绍了元素合成的总体框架,特别是其中通过原子核聚变释放能量的核燃烧方式和中子俘获过程,并重点说明了原子核的性质作为输入参数对各种天体过程物理图象的影响． Synthesis of stellar elements is outlined, including the nuclear burning processes by which lighter nuclei are combined to form heavier nuclei through fusion with energy releasing and the neutron capture processes. The scenarios of the stellar evolution as functions of improving nuclear properties are illustrated.     

Mass Fraction of 13C-Pocket in Metal-Poor AGB Stars and the Primary Nature of Neutron Source

Chemical abundances of very metal-poor s-rich stars contain excellent information to set new constraints on models of neutron-capture processes at low metallicity. Using the parametric approach based on the radiative s-process nucleosynthesis model, we obtain the mass fraction q of 13 C-pocket, the overlap factor r, the neutron exposure per interpulse △τ, and the component coefficients of the s-process and the r-process for 25 s-rich stars, respectively. We find that q deduced for the lead stars is comparable to the overlap factor r, which is larger than the standard case （hereafter ST case） of the AGB model （q - 0.05） about 10 times, and AT are about 10 times smaller than the ST case （AT = 7.0 mbarn^-1）. Although the two parameters obtained for the lead stars are very different from the ST case of the AGB stellar model, it is worth noting that the total amounts of 13 C in metal-poor condition are close to the ST case. The above relation is a significant evidence for the primary nature of the neutron source and the lead stars could be polluted by low-mass AGB stars. Because interpulse period declines with increasing stellar mass, for high-mass AGB star, the neutron irradiation may be terminated due to their shorter interpulse period. Thus the neutron exposure per interpulse of the larger AGB stars should be about 10 times smaller than the ST case. In this ease, the primary nature of the neutron source also exists.     

Analysis of some Elements in Fuel Oil by using Neutron Capture Gamma Ray Spectroscopy

The analysis of some elements in fuel oil was done by using neutron capture gamma ray spectroscopy. The gamma rays emitted after the reaction of (n, γ) from the fuel oil atoms bombarded with the thermal neutrons emitted from a ²⁵²Cf source were investigated in the energy interval 0 … 10 MeV. The impurity elements in the sample were determined.     

Oscillations of Short Periods in Neutron and Strange Stars

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.     

Comparison of Properties of the Simplest Neutron Stars in Three RMF Models

We study some properties of the simplest neutron stars （NSs） in the Glendenning Moszkowski （GM） model, the hybrid derivative coupling （HD） model and the Zimanyi Moszkowski （ZM） model in the framework of relativistic mean field （RMF） theory with and without the interaction by exchanging the ~-meson. We show that the maximal mass of the NSs becomes smaller, but the redshift becomes larger from the GM model to the HD model, then to the ZM model. The interaction with the 6-meson exchange enlarges the maximal mass of neutron stars, increases the relative population of charged particles （proton, electron and muon） and descends the relative population of neutron.     

密封容器中钚材料同位素丰度和年龄的测量

根据相对效率法的原理，利用PC/FRAM分析软件，开展了用高分辨γ谱仪测量密封容器中钚材料的同位素丰度和年龄的实验研究.研究结果表明，同位素丰度和年龄的分析精度随能谱测量精度的提高而提高，如果能谱的测量精度不够，通过PC/FRAM分析得出的钚材料的同位素丰度和年龄有偏低的可能.因此，在能谱测量过程中，建议通过监测某个特征峰的峰面积计数来判定239Pu丰度和年龄的测量精度是否已满足测量要求.Based on the concept of relative detection efficiency, some experiments have been conducted to measure the isotopic abundance and the age of the plutonium material in a sealed container by a high-resolution γ-ray spectrometer. The PC/FRAM software analyzes the spectra. The study shows that the analysis precision of the isotopic abundance and the age will rise as the spectral measurement precision increases, and that If the spectral measurement precision is not enough, the analyzed results by the PC/FRAM software might be lower. Hence, the study suggests that a spectral peak is monitored to show lights on the spectral measurement precision during the process of spectrum acquirement.     

利用密度相关的相对论平均场理论对核物质与中子星的研究(英文)

研究和详细地比较了RMF理论中不同的有效相互作用强度的密度依赖性, 并且讨论了这种密度依赖性对于核物质和中子星性质的影响. 对于核物质, 不同的参数组给出的对称核物质的饱和点非常接近, 基本都在经验值的范围内. 对于中子星, 考虑超子后不同参数组给出的质量极限的范围为1.52—2.06 M☉, 半径为10.24—11.38 km.The density dependencies of various effective interaction strengths in the relativistic mean field and their influences on the properties of nuclear matter and neutron stars are studied and carefully compared. The differences of saturation properties given by various effective interactions are subtle in symmetric nuclear matter. The Oppenheimer Volkoff mass limits of neutron stars calculated from different equations of state are 1.52—2.06 M☉, and the radii are 10.24—11.38 km with hyperons included.     

中子星内壳层的物态方程和质子丰度

求解了恒定均匀的强磁场中核子的能谱和波函数，在手征表象中给出含核子反常磁矩(AMM)项的Dirac方程的解；并且计算了中子星内壳层物质的物态方程(EOS)和粒子丰度，发现在强磁场中磁能将使中子星内壳层的压强增加但物质仍然是丰中子，AMM项对质子的极化度有明显效应.     

Gravitational Effects on the Vortex Distribution in Relativistic Superfluid Stars

Neutron stars are supposed to be mainly formed by a neutron superfluid. The angular momentum is given by the vortex array within the fluid, and a good account of the observable effects is determined by its coupling with the crust. In this article we show that the gravitational field introduces important modifications in the vortex distribution and shape. The inertial frame dragging on the quantum fluid produces a decrease in the vortex density, which for realistic models is in the order of 15%. This effect is relevant for neutron star rotation models and can provide a good framework for checking the quantum effect of the frame dragging.     

中子辐射俘获反应机制的质量能量相关性研究

对A?<10?0核质量区内的核素,研究中子辐射俘获反应中不同反应机制对辐射俘获截面的贡献随靶核质量数和中子入射能量变化的规律.所考虑的反应机制有复合核统计过程和复合核弹性散射道中的辐射俘获及形状弹性散射道中的直接–半直接辐射俘获两种非统计过程.在中子入射能量0.1—20MeV区间,给出了²⁷Al,⁴⁰Ca,⁶³Cu和⁹³Nb的理论计算结果及与实验数据的比较,并对呈现的变化规律进行了分析讨论