NGC 4321中超新星1979_c的照相研究

1979年4月23日—12月27日,我们用北京天文台40/200cm双筒天体照相仪对旋涡星系M100(NGC 4321)中的亮超新星SN1979c进行了照相观测.本文简述了观测情况,并结合前人的观测,分析讨论了我们的结果. 它的光变曲线可以`划分为四个阶段.5月8日—6月5日间光变曲线有驼峰状突起.其光度变化既不同于Ⅰ型超新星,也与典型的Ⅱ型超新星不完全吻合. 计算得到超新星亮度极大时的绝对照相星等为M_(pg)(max)=-19~(m)78;极大光度L_SN(max)=1.076×10~(10)L⊙. 我们利用Balinskaya和Carney等人1980年发表的三色测光资料计算了这颗超新星在不同时刻的色温度变化,推算出它极大时刻的色温度约为T_c(max)≈9.0×10~3K. 爆发期间超新星辐射的总能量E_t=4.2×10~(16)L⊙. 根据这颗超新星的光变曲线、在星系中的位置及爆发期间辐射的总能量等主要特征,我们认为SN1979c是某些性质比较特殊的II型超新星.     

Ⅰ型超新星起源于白矮星——一种超新星起源理论

超新星爆发是宇宙间一种巨大的高能现象,历来都是天体物理学的重要课题。最近J.Isern,J.Labay和R.Canal提出了一种新的超新星起源理论。他们认为;Ⅰ型超新星和小质量的双X射线源(亦称Ⅱ型X射线源)都是由密近双星系统中的吸积白矮星的崩散形成的。 Ⅰ型超新星具有高度的测光及分光相似性,放射衰变模型成功地说明了它们的光变曲线。每次爆发将合成0.2—1.0M的~(56)Ni,确切值由哈勃常数的取值决定,当H_0～100 km·Mpc~(-1)·s~(-1)时,合成质量最小,并且爆发后留下残骸。     

高速Ia型超新星的蓝色超出: 星周介质的尘埃散射

Ia型超新星起源于碳氧白矮星在质量接近钱德拉塞卡极限时的热核爆炸,并被广泛地用作宇宙学距离的标准烛光.然而, Ia型超新星的前身星系统和爆炸机制还存在很多不明确的地方.近几十年来, Ia型超新星的星周环境得到了越来越多的关注.星周介质的空间分布性质为探究Ia型超新星的物理起源提供了重要线索.同时星周尘埃的散射会在Ia型超新星晚期的光变曲线、光谱和偏振等方面产生可观测效应.光谱上正常的Ia型超新星可以分成两类:喷射物速度正常和高速Ia型超新星.对比两者的光变曲线可以发现高速Ia型超新星在光极大后几个月内有明显颜色偏蓝的超出.该蓝色超出可以通过星周介质中的尘埃散射拟合得到.同时, Ia型超新星晚期光谱的拟合可以限制星周尘埃的颗粒大小等性质,晚期的偏振信号可以有效地限制星周尘埃的空间分布.拟合结果表明针对Ia型超新星晚期的多次图像偏振观测是揭示其星周尘埃环境特征的重要手段.     

超新星和中子星

现在我们对超新星的认识是跳跃式地发展的,近来突破性的进展是:Ⅰ型超新星的光变曲线的观测与1M的Ni~(50)的衰变模型符合得较好:Ⅱ型超新星的观测可描述为在超巨星壳层底部有10~(50)尔格能量沉积而产性爆发,形成中子星。本文探讨了超新星和中子星的关系,以及在超新星研究中的某些观点,介绍了超新星的观测特性、前身星的特点以及超新星模型。Ⅱ型超新星释放能量很可能与内部收缩成中子星和产生脉冲星联系在一起,而Ⅰ型超新星爆发将整个恒星毁掉不留下致密天体。某些脉冲星(中子星)可能是失去外层的大质量星爆发而产生的,这些事件并不伴随着明亮的超新星出现。超新星等于中子星形成的观念似乎应当解除.     

Distribution of 56Ni Yields of Type Ia Supernovae and its Implication for Progenitors

The amount of 56Ni produced in Type Ia supernova (SN Ia) explosion is probably the most important physical parameter underlying the observed correlation of SN Ia lumi-nosities with their light curves. Based on an empirical relation between the 56Ni mass and the light curve parameter △m15, we obtained rough estimates of the 56Ni mass for a large sample of nearby SNe Ia with the aim of exploring the diversity in SN Ia. We found that the derived 56Ni masses for different SNe Ia could vary by a factor of ten (e.g., MNi = 0.1 - 1.3 M⊙),which cannot be explained in terms of the standard Chandraseldaar-mass model (with a 56Ni mass production of 0.4 - 0.8 M⊙). Different explosion and/or progenitor models are clearly required for various SNe Ia, in particular, for those extremely nickel-poor and nickel-rich producers. The nickel-rich (with MNi 0.8 M⊙) SNe Ia are very luminous and may have massive progenitors exceeding the Chandrasekhar-mass limit since extra progenitor fuel is required to produce more 56Ni to power the light curve. This is also consistent with the find-ing that the intrinsically bright SNe Ia prefer to occur in stellar environments of young and massive stars. For example, 75% SNe Ia in spirals have △m15 < 1.2 while this ratio is only 18% in E/S0 galaxies. The nickel-poor SNe Ia (with MNi < 0.2 M⊙) may invoke the sub-Chandrasekhar model, as most of them were found in early-type E/S0 galaxies dominated by the older and low-mass stellar populations. This indicates that SNe Ia in spiral and E/S0 galaxies have progenitors of different properties.     

Distribution of 56↑Ni Yields of Type Ia Supernovae and its Implication for Progenitors

The amount of 56↑Ni produced in Type Ia supernova （SN Ia） explosion is probably the most important physical parameter underlying the observed correlation of SN Ia luminosities with their light curves. Based on an empirical relation between the 56↑Ni mass and the light curve parameter △m15, we obtained rough estimates of the 56↑Ni mass for a large sample of nearby SNe Ia with the aim of exploring the diversity in SN Ia. We found that the derived 56↑Ni masses for different SNe Ia could vary by a factor of ten （e.g., MNi = 0.1 - 1.3 M⊙）, which cannot be explained in terms of the standard Chandrasekhar-mass model （with a 56↑Ni mass production of 0.4 - 0.8 M⊙）. Different explosion and/or progenitor models are clearly required for various SNe Ia, in particular, for those extremely nickel-poor and nickel-rich producers. The nickel-rich （with MNi 〉 0.8 M⊙） SNe Ia are very luminous and may have massive progenitors exceeding the Chandrasekhar-mass limit since extra progenitor fuel is required to produce more 56↑Ni to power the light curve. This is also consistent with the finding that the intrinsically bright SNe Ia prefer to occur in stellar environments of young and massive stars. For example, 75% SNe Ia in spirals have △ml5 〈 1.2 while this ratio is only 18% in E/S0 galaxies. The nickel-poor SNe Ia （with MNi 〈 0.2 M⊙） may invoke the sub- Chandrasekhar model, as most of them were found in early-type E/S0 galaxies dominated by the older and low-mass stellar populations. This indicates that SNe Ia in spiral and E/S0 galaxies have progenitors of different properties.     

The Study of the Physical Properties and Energy Sources of Five Luminous Type Ibc Supernovae

In this paper,we study five luminous supernovae(LSNe) Ibc(SN 2009ca,ASASSN-15mj,SN 2019omd,SN 2002ued,and SN 2021bmf) whose peak absolute magnitudes M_peak are ≈-19.5 to-21 mag by fitting their multi-band light curves(LCs) with different energy source models.We find that SN 2009ca might be powered by the ⁵⁶Ni model since the required ⁵⁶Ni mass(0.56 M_⊙) is comparable to those of energetic SNe Ic,while the rest four SNe cannot be accounted for the ^56...     

Ia型超新星的爆发机制及其前身星模型

Ia型超新星作为测量遥远星系距离——从而测定宇宙膨胀速率——的“标准烛光”，已经成为宇宙学中具有重要意义的天体。从某些方面来讲，Ia型超新星仍属于神秘天体(或爆发事件)，其前身星及爆发模型还没有得到很好的理解，当前的观测不足以对理论模型作出精确的限制。然而有很好的理由相信大多数Ia型超新星可能是由接近钱德拉塞卡质量极限(≈1.39M⊙)的碳—氧白矮星通过聚变中心的碳和氧所引发的热按爆炸产生的。至于这一爆发通过何种机制完成，例如具体到Ia型超新星爆发时的流体动力学过程，仍存在分歧。最近爆燃阶段的三维数值模拟结果似乎表明，在Ia型超新星爆发晚期引入爆轰机制是没有必要的。另一方面，尽管当前的多数证据表明，C—O白矮星 主序星(或红巨星)的演化模式比C-O白矮星 C-O白矮星的演化模式可能更合理，但双简并白矮星的前身星模型并不能被排除，因为它们能解释一些特殊的Ia型超新星爆发。     

Ⅰa型超新星前身星模型及其相关天体研究

Ia型超新星具有可校准的光度,可当作标准烛光,用来测定宇宙学距离,从而探索宇宙的形状.然而,Ia型超新星的前身星仍不清楚,这将直接影响当前宇宙学结果的可靠性.本文在Ia型超新星前身星模型及其相关天体方面做了系统性的工作,下面是我们取得的一些主要的研究结果:(1)近年来人们观测发现,约有一半的Ia型超新星的延迟时标小于100 Myr(Ia型超新星的延迟时标是指从恒星形成后到发生超新星爆炸的时间间隔).这些超新星是怎么来的?为解决这一难题,我     

超新星SN 1987A的热光度演化──内部中子星的贡献

本文介绍了超新星SN1987A爆发六年多来其热光度演化的研究情况．爆发后的前800天，观测的热光度曲线与由超新星爆发时合成的放射性元素的放射衰变加热模型符合得很好．但900天以后，观测的热光度曲线比考虑了所有放射性元素贡献后的理论曲线下降得还要缓慢．这可能表明有新的能源在起作用．我们认为这个新的能源可能是超新星爆发时产生的中子星的吸积．通过吸积超新星爆发时抛射气壳中小于逃逸速度的部分物质而增大SN1987A的热光度．这一模型能很好地解释900天以后的光度曲线的下降变级以及900至1200天之间光度曲线的凸起，这也为内部中子星的存在提供了间接的证据．     

Ia型超新星前身星模型及其相关天体研究

Ia型超新星具有可校准的光度,可当作标准烛光,用来测定宇宙学距离,从而探索宇宙的形状.然而,Ia型超新星的前身星仍不清楚,这将直接影响当前宇宙学结果的可靠性.本文在Ia型超新星前身星模型及其相关天体方面做了系统性的工作,下面是我们取得的一些主要的研究结果:(1)近年来人们观测发现,约有一半的Ia型超新星的延迟时标小于100 Myr(Ia型超新星的延迟时标是指从恒星形成后到发生超新星爆炸的时间间隔).这些超新星是怎么来的?为解决这一难题,我     

另一类超新星

四十多年前,R.Minkowski就已经辨认出两种基本类型的超新星。两者的光谱、在最亮时的绝对星等以及光变曲线的形状均不同。第一类超新星“Ⅰ型”可以在密近双星中产生,在双星中一颗由碳或氧组成的白矮星吸积其伴星的物质,随着简并星的质量接近于1.4M_⊙的“Chandrasekhar极限”(超过此极限它就不稳定了),失控核反应在突变性爆发中结束,除了膨胀的碎云片之外,没有留下任何遗     

中微子泄漏与超新星爆发

在超新星爆发过程中,中微子的泄漏非常重要.采用一维球对称模型,在不同的中微子泄漏模式下,数值模拟了质量为12 M_⊙、14 M_⊙及15 M_⊙的Ⅱ型超新星爆发过程.结果表明:不同的中微子泄漏模式对超新星塌缩、激波的传播和爆发都具有影响;并给出了最有利于Ⅱ型超新星爆发的相关参数的最佳值.此外还讨论了物态方程与压缩模量对模拟结果的影响.     

Binary population synthesis for the core-degenerate scenario of type Ia supernova progenitors

The core-degenerate(CD) scenario has been suggested to be a possible progenitor model of type Ia supernovae(SNe Ia),in which a carbon-oxygen white dwarf merges with the hot CO core of a massive asymptotic giant branch star during their common-envelope phase.However,the SN Ia birthrates for this scenario are still uncertain.We conducted a detailed investigation into the CD scenario and then gave the birthrates for this scenario using a detailed Monte Carlo binary population synthesis approach.We found that the delay times of SNe Ia from this scenario are ~70 Myr-1400 Myr,which means that the CD scenario contributes to young SN la populations.The Galactic SN la birthrates for this scenario are in the range of~7.4×10~(-5) yr~(-1)- 3.7 × 10~(-4) yr~(-1),which roughly accounts for ~2%-10%of all SNe Ia.This indicates that,under the assumptions made here,the CD scenario only contributes a small portion of all SNe Ia,which is not consistent with the results of Ilkov Soker.     

信息论背景下Ia型超新星宇宙学的贝叶斯统计分析和距离对偶关系检验

<正>本文中,我们系统地表述一种自洽的宇宙学模型分析及其参数估计方法,并将其用于Ia型超新星(SNIa)光度距离作为宇宙学标准烛光的研究.我们利用贝叶斯图论方法及其与随机变量间因果性、信息流和概率独立性的对应关系构建我们的分析,并通过实例展示如何在宇宙学数据分析中恰当地运用联合光变曲线分析(JLA) SNIa数据集合中依赖于参数的协方差矩阵.我们的方法从概念到产出的结果均不同于传统的分析方法.可以证明,通常形如χ~2最小化的传统分析等效于施加在SNIa标准化模型变量先验分布上的隐含失真.通过显性地指明这一失真的形式,我们指出它无论从天体物理还是统计     

6颗Blazar天体的长期光变和色指数变化

文中对6颗Blazar天体15年间的大量准同时性观测数据进行了处理分析,获得了长期的光变曲线和色指数变化曲线。对比分析光变曲线和色指数变化曲线,对色指数和亮度做相关分析,得出Blazar天体的光变包括长期的单色光变和有颜色变化的短期爆发两种成份,由光变的颜色差异我们提出引起Blazar天体光变的物理机制可能是几何效应调制的激波喷流模型。     

The surviving companions in type Ia supernova remnants

The single-degenerate(SD)model is one of the most popular progenitor models of type Ia supernovae(SNe Ia),in which the companion star can survive after an SN Ia explosion and show peculiar properties.Therefore,searching for the surviving companion in type Ia supernova remnants(SNRs)is a potential method to verify the SD model.In the SN 1604 remnant(Kepler’s SNR),although Chandra X-ray observation suggests that the progenitor is most likely a WD+AGB system,the surviving companion has not been found.One possible reason is rapid rotation of the white dwarf(WD),causing explosion of the WD to be delayed for a spin-down timescale,and then the companion evolved into a WD before the supernova explosion,so the companion is too dim to be detected.We aim to verify this possible explanation by carrying out binary evolution calculations.In this paper,we use Eggleton’s stellar evolution code to calculate the evolution of binaries consisting of a WD+red giant(RG).We assume that the rapidly rotating WD can continuously increase its mass when its mass exceeds the Chandrasekhar mass limit(MCh=1.378 M_⊙)until the mass-transfer rate decreases to be lower than a critical value.Eventually,we obtain the final masses of a WD in the range 1.378 M_⊙ to 2.707 M_⊙.We also show that if the spin-down time is less than 10~6 yr,the companion star will be very bright and easily observed;but if the spin-down time is as long as~10~7 yr,the luminosities of the surviving companion would be lower than the detection limit.Our simulation provides guidance in hunting for the surviving companion stars in SNRs,and the fact that no surviving companion has been found in Kepler’s SNR may not be definite evidence disfavoring the SD origin of Kepler’s SN.     

类星体3C 273光学波段的周期分析

搜集了类星体3C 273在光学B波段近100 yr的数据,得出光变曲线,并在此基础上应用Period04软件对它的光变周期进行了分析.发现光变曲线中存在周期为T1=2.06 yr、T2=13.03 yr及T3=21.15 yr的3个光变周期,这与Fan等人的结论(3C 273的光学B波段存在2.0 yr、(13.65±0.20)yr及(22.5±2.0)yr的周期)基本上是一致的.然后用这3个周期再次拟合观测数据做一个周期反演,周期拟合曲线与观测数据的爆发周期规律基本一致,说明这3个周期是比较可靠的.并通过其长周期可以得出其中心黑洞质量为M=1.87×106M⊙,最后讨论了其中心黑洞质量以及3C 273产生这种周期的可能机制.     

当前超新星遗迹研究中的若干热点问题

对银河系内历史性超新星"回光"(light echoes)的观测是研究年轻超新星遗迹的重要手段。通过对"回光"进行观测,可以确认其前身星的物理特性,揭示恒星晚期演化过程和其星周介质的三维空间分布。历史性超新星直接"回光"极其暗弱,对其探测最近几年才因新技术的应用而得以实现。综述了河内超新星遗迹包括仅有的已探测到回光现象的两颗年轻超新星遗迹——第谷(SN1572)和仙后座A(CasA)的最新研究进展。研究结果有利于更好地理解Ⅰ型和Ⅱ型超新星的性质,区别两类超新星的爆发机制,加深对超新星的核合成、重元素合成、星系形成和演化、暗能量等的了解。讨论了利用回光观测可以进一步深入开展的研究课题。     

Hydrogen and helium shell burning during white dwarf accretion

Type Ia supernovae(SNe Ia) are believed to be thermonuclear explosions of carbon oxygen(CO) white dwarfs(WDs) with masses close to the Chandrasekhar mass limit. How a CO WD accretes matter and grows in mass to this limit is not well understood, hindering our understanding of SN Ia explosions and the reliability of using SNe Ia as a cosmological distance indicator. In this work, we employed the stellar evolution code MESA to simulate the accretion process of hydrogen-rich material onto a 1.0 M_⊙CO WD at a high rate(over the Eddington limit) of 4.3 × 10~(-7) M_⊙yr~(-1). The simulation demonstrates the characteristics of the double shell burning on top of the WD, with a hydrogen shell burning on top of a helium burning shell. The results show that helium shell burning is not steady(i.e.it flashes). Flashes from the helium shell are weaker than those in the case of accretion of helium-rich material onto a CO WD. The carbon to oxygen mass ratio resulting from the helium shell burning is higher than what was previously thought. Interestingly, the CO WD growing due to accretion has an outer part containing a small fraction of helium in addition to carbon and oxygen. The flashes become weaker and weaker as the accretion continues.