Supernova Explosion in the Process of Stellar Evolution

Supernova explosion is a peculiar astronomical phenomenon,which has aroused great interest and extensive research by astronomers.At present,however,it is erroneously believed that the supernova explosion is a splendid funeral of a dying star.In fact,new astronomical observations and the author’s theoretical studies have shown that in the process of a star’s never-ending evolution,numerous supernova explosions may occur,and supernova explosion will run through many stages of stellar evolution.Whenever the atmosphere of the star becomes very dense and its surface is covered with a thick layer of material again,a thermonuclear reaction can be ignited again,causing a supernova explosion.Especially,when the star has undergone a number of supernovae explosions and its surface is covered with multiple layers of supernova explosion remnants,the core of the massive star may undergo sudden gravitational collapse,causing a violent supernova;when a star is impacted by a falling celestial body,it also produces violent supernova explosions.

Influence of Supernova SN Ia Rate and the Early Star Formation Rate on the Galactic Chemical Evolution

Based on the recently developed numerical approach to understand the formation and the chemical evolution of the milky-way galaxy in the solar neighborhood we study the influence of the supernova type SN Ia rates on the galactic chemical evolution. Supernova SN Ia plays an important role in producing the iron inventory of the galaxy. We also study the dependence of the chemical evolution on the star formation rate prevailing during the initial one billion years of the evolution of the galaxy. This era marks the formation of the galactic halo and the thick disk. A comparison of the elemental abundance distributions of the dwarf stars in the solar neighborhood is made among the various models simulated in the present work. In order to explain the majority of the observed elemental evolutionary trends, specifically those related with the galactic evolution of iron and oxygen, it would be essential to incorporate a major component of prompt SN Ia to the galactic evolution. The prompt SN Ia would produce significant fraction of SN Ia within the initial ~100 million years from the time of star formation. The essential requirement of prompt SN Ia would result in a significant enhancement of SN Ia rates during the earliest epoch of the galaxy. The elemental evolutionary trends also favor an enhancement in the star formation rate during the initial one billion years of the galaxy at least by a factor of three compared to the trend prevailing during the latter evolutionary time of the galaxy.

Determination of the stellar reaction rate for ^(12)C(α, γ)^(16)O: using a new expression with the reaction mechanism

The astrophysical reaction rate of 12C（α,γ）16O plays a key role in massive star evolution. However, this reaction rate and its uncertainties have not been well determined yet, especially at T9=0.2. The existing results even disagree with each other to a certain extent. In this paper, the El, E2 and total （E1＋E2） 12C（α,γ）16O reaction rates are calculated in the temperature range from T9=0.3 to 2 according to all the available cross section data. A new analytic expression of the 12C（α,γ）16O reaction rate is brought forward based on the reaction mechanism. In this expression, each part embodies the underlying physics of the reaction. Unlike previous works, some physical parameters are chosen from experimental results directly, instead of all the parameters obtained from fitting. These parameters in the new expression, with their 3σ fit errors, are obtained from fit to our calculated reaction rate from T9=0.3 to 2. Using the fit results, the analytic expression of 12C（α,γ）16Oreaction rate is extrapolated down to T9=0.05 based on the underlying physics. The 12C（α,γ）16O reaction rate at T9=0.2 is （8.78 ± 1.52） × 10^15 cm3s^-1mol^-1. Some comparisons and discussions about our new 12C（α,γ）16Oreaction rate are presented, and the contributions of the reaction rate correspond to the different part of reaction mechanism are given. The agreements of the reaction rate below T9=2 between our results and previous works indicate that our results are reliable, and they could be included in the astrophysical reaction rate network. Furthermore, we believe our method to investigate the 12C（α,γ）16O reaction rate is reasonable, and this method can also be employed to study the reaction rate of other astrophysical reactions. Finally, a new constraint of the supernovae production factor of some isotopes are illustrated according to our 12C（α,γ）16O reaction rates.

The dusty and extremely red progenitor of the typeⅡsupernova 2023ixf in Messier 101

Stars with initial masses in the range of 8-25 solar masses are thought to end their lives as hydrogen-rich supernovae(SNeⅡ).Based on the pre-explosion images of Hubble space telescope(HST)and Spitzer space telescope,we place tight constraints on the progenitor candidate of type IIP SN 2023ixf in Messier 101.Fitting of the spectral energy distribution(SED)of its progenitor with dusty stellar spectral models results in an estimation of the effective temperature as 3091+422-258K.The luminosity is estimated as lg(L/L⊙)~4.83,consistent with a red supergiant(RSG)star with an initial mass of 12-1+2M⊙.The derived mass loss rate(6×10^(-6)-9×10^(-6)M⊙yr^(-1))is much lower than that inferred from the flash spectroscopy of the SN,suggesting that the progenitor experienced a sudden increase in mass loss when approaching the final explosion.In the infrared bands,significant deviation from the range of regular RSGs in the color-magnitude diagram and period-luminosity space of the progenitor star indicates enhanced mass loss and dust formation.Combined with new evidence of polarization at the early phases of SN 2023ixf,such a violent mass loss is likely a result of binary interaction.

简并双星的形成途径及其Monte-Carlo分析

本文系统地研究了简并双星的形成，提出了简并双星形成的三种形成途径：稳定的洛希瓣物质交流公共包层途径、公共包层公共包层途径、核暴露公共包层途径，并对简并双星的形成进行了ＭｏｎｔｅＣａｒｌｏ模拟，探讨了模型参量（潮汐星风增强系数、稳定的洛希瓣物质交流过程中物质转移效率、双星初始质量比分布、公共包层抛射效率）对结果的影响．本模型成功地解释了简并双星的形成，解释了简并双星的质量分布、质量比分布和周期分布，解释了简并双星的诞生率和Ｉａ型超新星的诞生率．本文主要结论如下：（１）稳定的洛希瓣物质交流－公共包层途径与公共包层－公共包层途径是简并双星形成的主要途径．（２）银河系中简并双星的诞生率为０．０３ｙｒ－１，以氦白矮星为主星（亮子星）的简并双星其诞生率为０．０１７ｙｒ－１．（３）银河系中可探测简并双星（冷却时间小于１０８年）数量为三百万，其中以氦白矮星为主星的简并双星占５６％．（４）对可探测简并双星而言，其周期分布的峰值为６小时．（５）简并双星０９５７６６６，１１０１＋３６４和Ｆｅｉｇｅ３６产生于稳定的洛希瓣物质交流公共包层途径，而简并双星０１３５０５２可能由两颗碳氧白矮星组成．（６）稳定的洛希瓣物质交流?

大质量恒星的死亡和超新星爆发

超新星是某些类型的恒星演化到末期发生的一种源自星体核心的整体灾难性爆发现象。一颗单独的恒星的命运归根结底是由它诞生时的质量和化学成分决定的。大质量单星走向死亡的历程,以其初始质量的不同,有若干不同的路径。随着更多的超新星前身星得到确切证认,对大质量恒星演化理论的改进和完善将会获得有力的推动。

CNO燃烧核反应的研究

本文利用势垒穿透模型计算重离子融合反应截面,我们发现理论计算结果同现有的实验数据符合得相当好。在此基础上,对^(12)C+^(12)C,^(12)C+^(14)N,^(12)C+^(16)O,^(14)N+^(14)N,^(14)N+^(16)O和^(16)O+^(16)O六种融合反应,在T_9=-0.1—5.0温度范内数值计算了这些热核反应率,并给出了它们随温度变化的近似解析表达式.对^(12)C+^(12)C,^(12)C+^(16)O和^(16)O+^(16)O这三种热核反应率,我们的新结果明显地低于Caughlan等人在1985年的列表值,特别是^(16)O+^(16)O的热核反应率比文[21中值低7—20倍,这将对整个大质量恒星的演化、超新星爆发以及核合成带来较大的影响,本文简略地讨论了这些影响.

超新星(续)

超新星爆炸是发生在宇宙空间中极为壮观、丰富多彩和引人入胜的重要现象,涉及许多有趣的、尚待探索的物理学研究领域和天体物理学及宇宙学若干相关分支的重要应用.本文试图描述超新星现象研究在各方面的重要意义,提供基本观测事实和理论框架信息以及介绍我们正在从事的部分相关研究工作.

超新星

超新星爆炸是发生在宇宙空间中极为壮观、丰富多彩和引人入胜的重要现象,涉及许多有趣的、尚待探索的物理学研究领域和天体物理学及宇宙学若干相关分支的重要应用.本文试图描述超新星现象研究在各方面的重要意义,提供基本观测事实和理论框架信息以及介绍我们正在从事的部分相关研究工作.

核心坍缩型超新星前身星简述

大质量恒星(>8 M■,M■表示太阳质量)的死亡伴随着超新星爆发和伽玛射线暴等剧烈现象.研究和限制不同类型超新星的前身星属性一直是天体物理领域的热点.本文总结了核心坍缩型超新星前身星的观测和理论研究现状,介绍了质量损失和自转等因素的影响.

Towards an understanding of Type Ia supernovae from a synthesis of theory and observations

Motivated by the fact that calibrated light curves of Type Ia supernovae （SNe Ia） have become a major tool to determine the expansion history of the Universe, considerable attention has been given to, both, observations and models of these events over the past 15 years. Here, we summarize new observational constraints, address recent progress in modeling Type Ia supernovae by means of three-dimensional hydrodynamic simulations, and discuss several of the still open questions. It will be be shown that the new models have considerable predictive power which allows us to study observable properties such as light curves and spectra without adjustable non-physical parameters. This is a necessary requisite to improve our understanding of the explosion mechanism and to settle the question of the applicability of SNe Ia as distance indicators for cosmology. We explore the capabilities of the models by comparing them be applied to study the origin of the diversity with observations and we show how such models can of SNe Ia.

Supernova survey system in Beijing Astronomical Observatory (Ⅰ)——Facilities of survey

The robotic supernova survey system of Beijing Astronomical Observatory (BAO) is based on the 60-cm telescope of BAO, which includes a CCD camera attached to the prime focus and a software system for facility control and image reduction.

The Beijing Astronomical Observatory supernova survey (Ⅱ)——Results in 1996

Six supernovae (SNe) discovered in 1996 by the Beijing Astronomical Observatory Supernova (SN) Survey (BAOSS) are reported. SN 1996W, the first supernova discovered by the survey, has been monitored photometrically and spectroscopically for a long time. The spectra and photometry showed that it was a typical type Ⅱ-P supernova. SN 1996cb, the sixth SN discovered in 1996 and a peculiar one like SN 1993J, has also been observed intensively for a long time.

Nucleosynthesis in thermonuclear supernovae

We review our understanding of the nucleosynthesis that occurs in thermonuclear supernovae and their contribution to Galactic Chemical evolution. We discuss the prospects to improve the modeling of the nucleosynthesis within simulations of these events.

“Chi-Fang-Qi”: Is it the aureole of an ancient supernova?

An annotation for the statement about Jing- Xing (Great Star) in the most famous Chinese ancient his- torical book Shi Ji (Historical Records) authored by Sima Qian reads as follows: “There was a red aureole (“Chi-Fang-Qi”) which connected with a deep-color aureole (“Qing-Fang-Qi”). Two yellow stars were in the red aureole, one yellow star was in the deep-color aureole”. The author of the annotation was Meng Kang, an officer as well as a scholar of the Wei State in the Three Kingdoms period. The same records are to be found in two other Chinese historical books compiled by the authors of later ages in Tang Dy- nasty ――Jin History and Sui History. The scene illustrated by the record of “Chi-Fang-Qi” is very similar to the pictures of SN1987A taken by the Hubble Space Telescope. Let it be noted that although the ancient authors were often with se- rious wrong understandings of some astronomical phenom- ena such as supernovae, their depictions about natural phe- nomena they witnessed were mostly objective, and it was unlikely that they fictionally made the record of “Chi-Fang-Qi”. We infer that the ancient observers might have ever watched a very bright supernova with an aureole structure in its remnant and then left such a record. Meng Kang perhaps was the first to give the record about “Chi-Fang-Qi”, and he might have lived in the period from about AD 180 to AD250, very near to AD 185, so, here the supernova the ancient people watched was most likely the one in the year of AD 185. This supposition is consistent with the distance parameter of the most possible remnant of SN185 derived by some modern measurements. If the corre- lation between the record of “Chi-Fang-Qi” and the super- nova remnant can be further proven true, it would be an important verification of the modern theory about stellar evolution.

恒星物理研究与发展

文章介绍了恒星物理的研究现状和发展趋势,包括恒星形成、恒星结构与演化、双星演化与应用、恒星振动、恒星化学丰度、系外行星系统、Ia型超新星与伽马射线暴、星族合成等等,并对国内恒星学科的发展进行了展望。

超新星——恒星死亡前演出的壮丽一幕

超新星是恒星演化的最终阶段，是最激烈的天体物理现象．文章介绍了超新星发现的历史，它的观测特征，以及它在天文学和物理学研究中的意义．还介绍了中国科学院北京天文台在发现超新星和对超新星观测研究方面的最新结果．

核天体物理学的某些重大疑难问题

本文简介与评述了当今核天体物理学的几个最为突出的重大疑难问题，如（１）恒星晚期演化研究中最为关键的几个核反应截面的不确定性；（２）Ⅰａ型超新星爆发理论基本环节中的争论及其一些严重矛盾的问题；（３）Ⅱ型超新星爆发现有理论和它迄今尚未能自洽地获得（观测到的）爆发这一重大矛盾的关键原因及为突破这个困难人们最近所作的较为成功的探讨［２５，２６］；（４）星际２６Ａｌ问题和它所面临的困难及提出合成２６Ａｌ核的可能新途径［２８］．

2012年,参宿四会爆炸吗?

恒星是宇宙的基本组成单元,中小质量的恒星(如太阳)占绝大部分.中小质量的恒星演化到最后,外壳被损失掉,成为漂亮的行星状星云,而恒星的核则成为白矮星.大质量恒星演化到最后会发生超新星爆炸,产生巨大的能量,留下一个中子星或黑洞.参宿四是一颗大质量恒星,种种迹象表明,它将发生超新星爆炸,但在2012年爆炸的可能性微乎其微,天上不会出现两个"太阳",也不会对地球上人们的生活产生实质性的影响.