实验室模拟研究超新星遗迹演化动力学过程

文章详细分析讨论了超新星遗迹演化过程中冲击波动力学过程以及激光等离子体喷流的动力学的特点,阐述了利用激光等离子体实验产生与超新星遗迹演化动力学类似的冲击波结构来模拟研究超新星遗迹动力学与演化过程.这些分析与讨论对于实验室利用高能激光模拟研究超新星遗迹演化动力学过程具有重要的意义.     

电荷屏蔽对Ⅱ型超新星瞬时爆发能量的影响

讨论了电荷屏蔽效应对WS15M_⊙前身星模型瞬时爆发能量的影响,对电子俘获率的计算基于平均重核模型,数值模拟表明电荷屏蔽降低了电子俘获率,延长了爆发时间,使中微子泄漏的总能量增加,从而导致激波的能量略微降低.给出的方法可以适用于其他考虑电荷屏蔽效应的超新星数值模拟. 关键词： 超新星 瞬时爆发 数值模拟 电荷屏蔽     

Spectral hardening of cosmic ray protons and helium nuclei in supernova remnant shocks

The observed hardening of the spectra of cosmic ray protons and helium nuclei is studied within the model of nonlinear diffusive shock acceleration of supernova remnants(SNRs). In this model, the injected particles with energies below the spectral "knee" are assumed to be described by two populations with different spectral indexes around 200 GeV. The high-energy population is dominated by the particles with energies above 200 GeV released upstream of the shock of SNR, and the low-energy population is attributed to the particles with energies below 200 GeV released downstream of the shock of SNR. In this scenario, the spectral hardening of cosmic ray protons and helium nuclei observed by PAMELA, AMS-02, and CREAM experiments can be reproduced.     

Possible CP-violation effects in core-collapse supernovae

We study CP-violation effects when neutrinos are present in dense matter, such as outside the proto-neutron star formed in a core-collapse supernova. Using general arguments based on the Standard Model, we confirm that there are no CP-violating effects at the tree level on the electron neutrino and anti-neutrino fluxes in a core-collapse supernova. On the other hand significant effects can be obtained for muon and tau neutrinos even at the tree level. We show that CP-violating effects can be present in the supernova electron (anti-)neutrino fluxes as well, if muon and tau neutrinos have different fluxes at the neutrinosphere. Such differences could arise due to physics beyond the Standard Model, such as the presence of flavor-changing interactions.     

Neutrino-nucleon scattering rate in proto-neutron star matter

We present a calculation of the neutrino-nucleon scattering cross-section which takes into account the nuclear correlations in the relativistic random phase approximation (RPA). Our approach is based on a quantum-hadrodynamics model with exchange of σ, ω, π, ρ and δ mesons. In view of applications to neutrino transport in the final stages of supernova explosion and proto-neutron star cooling, we study the evolution of the neutrino mean free path as a function of density, proton-neutron asymmetry and temperature. Special attention was paid to the issues of renormalization of the Dirac sea, residual interactions in the tensor channel, coupling to the delta-meson and meson mixing. In contrast with the results of other authors, we find that the neutral-current process is not sensitive to the strength g' of the residual contact interaction. As a consequence, it is found that RPA corrections with respect to the mean-field approximation amount to only 10% to 15% at high density. Received: 27 June 2001 / Accepted: 14 January 2002     

Spin flip of neutrinos with magnetic moment in core-collapse supernova

Neutrinos with magnetic moment experience chirality flips while scattering off charged particles. It is known that if neutrino is a Dirac fermion, then such chirality flips lead to the production of sterile right-handed neutrinos inside the core of a star during the stellar collapse, which may facilitate the supernova explosion and modify the supernova neutrino signal. In the present paper we reexamine the production of right-handed neutrinos during the collapse using a dynamical model of the collapse. We refine the estimates of the values of the Dirac magnetic moment which are necessary to substantially alter the supernova dynamics and neutrno signal. It is argued in particular that Super-Kamiokande will be sensitive at least to μ _{ν Dirac} = 10⁻¹³μ_B in case of a galactic supernova explosion. Also we briefly discuss the case of Majorana neutrino magnetic moment. It is pointed out that in the inner supernova core spin flips may quickly equilibrate electron neutrinos with nonelectron antineutrinos if μ _{ν Majorana} ≳ 10⁻¹²μ_B. This may lead to various consequences for supernova physics.     

Effect of pressure grads on convection in inner core of type II supernova

By adjusting the pressure grads in the stage of formation of the shock wave, a successful prompt explosion process has been numerically simulated through a progenitor model of 15Msolar, in which the effects of pressure grads on various convections, including the Rayleigh-Taloy （R-T） convection, the lepton driven convection and the negative entropy grads driven convection, in an inner core are analysed. The simulation results showthat the increase of the pressure grads in the inner core region may cause a powerful convection, which causes energy transfer from the inner core to the shock wave rapidly and efficiently.     

Constraints on the kinetic energy of type-Ic supernova explosion from young PSR J1906+0746 in a double neutron star candidate

So far among the nineteen pairs of detected double neutron star (DNS) systems, it is a usual fact that the first-born recycled pulsar is detected, however the youngest DNS system PSR J1906+0746, with the characteristic age of 113 kyr, is one of the three detected DNS as a non-recycled and second-born NS, which is believed to be formed by an electron capture or a low energy ultra-stripped iron core-collapse supernova (SN) explosion. The SN remnant around PSR J1906+0746 is too dim to be observed by optical telescopes, then its x-ray flux limit has been given by Chandra. A reference pulsar PSR J1509-5850 with the young characteristic age of 154 kyr was chosen as an object of comparison, which has an SN remnant observed by Chandra and is believed to be formed by iron core SN explosion. We impose a restriction on the maximum kinetic energy of electron-capture (EC) SN explosion that induces the formation of PSR J1906+0746. The estimated result is (4-8)×10⁵⁰ erg (1 erg=10^-7 J), which is consistent with that of the published simulations of the EC process, i.e., a lower value than that of the conventional iron core SN explosion of (1-2)×10⁵¹ erg. As suggested, EC process for NS formation is pertained to the subluminous type Ic SN by the helium star with ONeMg core, thus for the first time we derived the kinetic energy of EC SN explosion of DNS, which may be reconciled with the recent observation of type Ic SN 2014ft with kinetic energy of 2×10⁵⁰ erg.     

超新星爆发环境核素56,57,59,60Co的电子俘获

基于壳模型与Random Phase Approximation理论, 利用Shell-Model Monte Carlo方法, 研究了超新星爆发环境核素^56,57,59,60Co的电子俘获与电子丰度变化率. 我们的结果与利用Aufderheide方法计算的结果进行了误差对比. 结果表明: 电子俘获率受温度和密度的影响大大增加, 甚至增加达6个数量级以上(如在ρ₇=0.43, Y_e=0.48核素^57,59,60Co). 另一方面, 随着温度和密度的增大, 电子丰度变化率大大降低, 甚至减小达5个数量级以上(如在ρ₇=5.86, Y_e=0.47核素⁵⁹Co). 通过对误差因子的分析表明, 在低温低密度环境二种结果误差较大; 而在高温高密度环境, 二种结果误差相对较小. 关键词： 电子俘获 超新星     

Flavor evolution of the neutronization neutrino burst from an O-Ne-Mg core-collapse supernova

We present results of 3-neutrino flavor evolution simulations for the neutronization burst from an O-Ne-Mg core-collapse supernova. We find that nonlinear neutrino self-coupling engineers a single spectral feature of stepwise conversion in the inverted neutrino mass hierarchy case and in the normal mass hierarchy case, a superposition of two such features corresponding to the vacuum neutrino mass-squared differences associated with solar and atmospheric neutrino oscillations. These neutrino spectral features offer a unique potential probe of the conditions in the supernova environment and may allow us to distinguish between O-Ne-Mg and Fe core-collapse supernovae.     

Matter Effects on Neutrino Oscillations in Different Supernova Models

In recent years,with the development of simulations about supernova explosion,we have a better understanding about the density profiles and the shock waves in supernovae than before.There might be a reverse shock wave,another sudden change of density except the forward shock wave,or even no shock wave,emerging in the supernova.Instead of using the expression of the crossing probability at the high resonance,PH,we have studied the matter effects on neutrino oscillations in different supernova models.In detail,we have calculated the survival probability of νe(P_s)and the conversion probability of ν_x(P_c) in the Schrodinger equation within a simplified two-flavor framework for a certain case,in which the neutrino transfers through the supernova matter from an initial flavor eigenstate located at the core of the supernova.Our calculations was based on the data of density in three different supernova models obtained from simulations.In our work,we do not steepen the density gradient around the border of the shock wave,which differs to what was done in most of the other simulations.It is found that the mass and the density distribution of the supernova do make a difference on the behavior of P_s and P_c.With the results of P_s and P_c,we can estimate the number of νe(and ν_x) remained in the beam after they go through the matter in the supernova.     

超新星核中的夸克相变及夸克质量效应

分别基于组夸克质量模型和流夸克质量模型, 讨论了超新星核心区两味夸克物质到更稳定的三味夸克物质的相变过程. 结果表明, 两种质量模型下相变的特征时标都短于10^-8s, 且质量越小的流夸克质量模型的相变速率越快;组分夸克质量模型下所得到的超新星核区的s夸克丰度, 中微子丰度及中微子总能量(除温度)相比前人的结果有轻微的增加, 而流夸克质量模型下所得到的这些参量的增加更为明显, 采用流夸克质量模型更有利于超新星的中微子延迟爆发机理的成功. 关键词： 夸克相变 组分夸克质量 流夸克质量 超新星     

The mass effect of the quark phase transition in supernova core

Constituent quark mass model is adopted as a tentative one to study the phase transition between two-flavour quark matter and more stable three-flavour quark matter in the core of supernovae. The result shows that the transition has a significant influence on the increasing of the core temperature, the neutrino abundance and the neutrino energies, which contributes to the enhancement of the successful probability of supernova explosion. However, the equilibrium values of these parameters （except the temperature） from the constituent quark mass model in this work are slightly bigger than those obtained from the other model. And we find that the constituent quark mass model is also applicable to describing the transition in the supernova core.     

基于Log-Polar变换的星图识别方法

基于Log-Polar变换提取特征模式,并将特征模式进行字符串编码,在KMP算法的基础上给出一种适合于星图识别的字符串匹配算法用以实现观测星和导航星的匹配识别。与栅格算法在相同实验条件下的比较表明:该方法对星点位置噪声和星等噪声具有更强的抗干扰能力,且具有更小的存储容量,但其识别速度还有待于进一步提高。     

不同水底介质对有限域中装药沉底爆炸特性的影响

通过开展装药沉底爆炸原理性实验研究,得到了不同水底条件对装药沉底爆炸气泡运动和冲击波压力的影响规律:沉底装药水下爆炸气泡通常呈半球形,依附在水底并同时急剧膨胀达到最大半径,随后气泡做收缩运动并连带水底介质颗粒迅速上浮,同时形状发生显著变化,如在石底和泥底时气泡在水底射流的作用下呈蘑菇状上浮,砂底时气泡则呈现出柱状上浮、未出现明显脉动运动即已坍塌破裂;沉底爆炸与水底介质发生强烈耦合作用而形成不同程度的反射波,通常水下石底的反射冲击波较泥底和砂底更强烈,且一般迭加后的冲击波峰值压力高于入射波阵面压力;不同水底介质条件下,装药与水底发生的强烈耦合作用均对水底造成强冲击破坏。     

药柱冲击波在有机玻璃中的衰减特性研究

用作图法得到了药柱与有机玻璃隔板界面处的冲击波压力,利用AUTODYN 6.1软件模拟了药柱冲击波在有机玻璃隔板中的衰减过程,并用锰铜压力计法测量了药柱冲击波在不同厚度有机玻璃隔板中的压力,并根据理论公式计算了有机玻璃中相应的冲击波速度、波后质点速度和密度。结果表明,理论计算结果、数值模拟结果与试验测量结果一致,并根据试验结果得到了冲击波压力在有机玻璃中的衰减规律;AUTODYN 6.1软件能够准确地预测冲击波在有机玻璃隔板中的衰减特性。     

像差对星敏感器星点定位精度的影响

光学系统星点定位精度是表征星敏感器性能的一个重要指标,像差对该精度有一定影响。分析光学系统像差对星点定位精度的影响,在计算典型中等精度星敏感器光学系统星点定位误差的基础上,提出用实际测得的星点光斑能量质心位置计算理想位置的误差补偿新方法。计算结果表明:像差对高精度(如角秒级)星敏感器姿态测量精度的影响不可忽略;采用星点定位误差补偿后,星敏感器三轴姿态测量误差RMS值分别为0.38″,0.38″,5.77″,仅为原来的1/17。     

基于背景自适应预测的星点提取算法

在分析星图中的星点目标和背景特性的基础上,提出了一种基于背景自适应预测的星点提取算法。为准确预测背景并兼顾算法的速度,只在背景边缘处使用区域最大值背景预测法,其余部分直接使用固定权值进行预测。分割残差星图,提取各星点的目标区域,阈值采用自适应的取值方式。利用质心算法求取各星点目标的精确位置。实验结果表明,基于背景自适应预测的星点提取算法性能优于现有的星点提取算法,是一种有效的星点提取算法,可以降低大量由于强边缘而引起的虚警,能够更准确地预测背景。     

星敏感器技术研究现状及发展趋势

本文综述了星敏感器技术的研究现状和未来发展趋势。首先,总结了国内外星载星敏感器的发展历程。接着,根据星敏感器工作原理,分析讨论了星点质心定位算法、星图识别算法和姿态解算算法等星敏感器关键技术的发展现状。通过讨论星点质心定位精度对星敏感器测量精度影响,分析了星点质心定位算法以及对应误差补偿的研究现状;基于星座特征、字符模式和智能行为,介绍了星图识别算法并进行了对比分析;根据确定姿态解算算法和动态姿态解算算法分析了姿态解算算法的研究现状。最后,对星敏感器的未来发展进行了展望,讨论了航空机载星敏感器、微小型星敏感器和甚高精度星敏感器的发展趋势以及未来重点研究内容。