r-过程核合成的场所和重元素丰度的离散

首先考虑到随前身星质量增加Ⅱ型超新星爆发α元素的产量并不单调增加,从而导致Ⅱ型超新星所污染的星际气体的α元素丰度出现反转的因素,将贫金属星Ba的观测丰度分为2支,其中i支元素丰度产生于较低质量超新星,y支元素丰度产生于较高质量超新星,采用FM2004的Ⅱ型超新星爆发Mg元素的产量,利用Tsujimoto提出的方法,根据观测到的极贫金属星Ba和Mg丰度数值计算各种质量超新星r-过程的产量,得出星系中r-过程元素核合成的主要质量区间.然后,根据得到的不同质量Ⅱ型超新星r-过程的产量关系,改进Fields等所提出的方法,解释观测到的贫金属星中子俘获元素的弥散性;另外,还根据3成份(晕、厚、薄盘)多相模型(气体、分子云、大小质量恒星以及剩余物质),利用所得到的产量计算了r-过程元素的均匀化学演化.     

Ⅱ型超新星r-过程元素核合成产量及主要产量区间

根据观测到的极贫金属星中元素Sr,Y,Ba与元素Si丰度的相关性,利用WW1995与FM2004给出的Ⅱ型超新星Si的理论产量计算了极贫金属环境下各种质量超新星r-过程元素的核合成产量,将所得结果与前人的结果作了对比;进一步讨论了星系化学演化中r-过程元素核合成的主要产量区间.     

极贫金属环境下超新星爆发的中子俘获元素核合成产量

极贫金属环境下超新星爆发([Fe/H]＜-2.5)形成于星系演化的早期,研究极贫金属环境下超新星爆发的重元素丰度分布及核合成,对于探索星系形成及化学演化和核天体物理学中的基本问题都起着关键作用.分析了大量极贫金属环境下超新星爆发的元素丰度的观测数据,得出中子俘获元素Sr,Y和Ba与元素Si的相关性规律,计算了极贫金属环...     

星系晕较重r-过程元素产量和丰度的离散

采用Fields等所提出的模型,将超新星爆发产生r过程元素的事件分为2类:A类(r-rich)事件和B类(r-poor)事件,结合所得到的Ⅱ型超新星r-过程元素的产量和产区,计算了贫金属星较重r-过程元素的弥散,并与观测进行对比分析,解释早期星系化学演化.得到的主要结论:从星系化学演化角度看,星系r-过程元素主要来源于大质量星,r过程核合成主要产生场所是较高质量的Ⅱ型超新星,质量范围在28M⊙≤M≤35M⊙.利用计算得到的产量及初始质量函数φ(m),确定产生较重r过程元素的Ⅱ型超新星占Ⅱ型超新星总数的比例(大约为4%),计算得到星系晕中Eu,Ba,Ce,La,Nd,Pr,Sm等元素的丰度离散情况;并对计算结果进行分析.     

贫金属星HD 122956的中子俘获元素丰度

根据贫金属星ＨＤ１２２９５６的中子俘获元素的观测丰度,利用贫金属星中子俘获元素丰度的计算模型,采用最小二乘法精确地确定了三种不同的中子俘获过程对该贫金属星中子俘获元素丰度的贡献,从理论上预言了贫金属星ＨＤ１２２９５６的中子俘获元素的丰度,并给出了计算结果与预测结果的比较。     

考虑时间延迟后较重r-过程元素的化学演化

考虑有效产生r-过程(快中子俘获过程)元素的Ⅱ型超新星延迟爆发的因素,大体上经过10次大质量Ⅱ型超新星(M>35 M⊙)先爆发后,产生r-过程元素的Ⅱ型超新星(M=(28～35) M⊙)才开始爆发. 从星系化学演化角度看,r-过程元素的主要来源为较大质量Ⅱ型超新星(M=(28～35) M⊙). Ⅱ型超新星占Ⅱ型超新星总数的4%.核合成区域内种子核和中子源主要来自恒星自身的核反应.经计算得到星系晕中较重的r-过程元素Eu,Ba,Ce,La,Nd,Pr,Sm等元素丰度的离散情况及其化学演化.     

重金属星的形成

重金属星是重金属丰度超丰的星,重金属是通过中子俘获形成的,中子俘获有两种过程,快中子俘获过程（r-过程）,慢中子俘获过程（s-过程）,AGB星是产生重金属的重要产地,贫金属的AGB星容易形成铅星,这已获得观测的支持。     

s-过程和r-过程核素双超丰恒星的形成

慢中子俘获和快中子俘获过程核素双超丰的恒星,是先经历AGB星污染,再经历超新星爆发形成的,分析双超丰贫金属星HE 1305-0007可证实这一点.     

恒星典型中子俘获元素丰度观测误差对分量系数的影响

根据贫金属星中子俘获元素丰度的计算模型，研究了典型中子俘获元素丰度的观测误差对代表各核合成过程相对贡献的分量系数的影响，给出了分量系数的变化范围。     

r-过程的天体物理环境

r-过程即快中子俘获过程,发生r-过程的天体物理环境有多个,理论分析和观测事实表明,r-过程主要发生在Ⅱ型超新星爆发的天体物理环境,宇宙中大多数的r-过程元素产生于这个过程。     

A neutron-star-driven X-ray flash associated with supernova SN 2006aj

Supernovae connected with long-duration gamma-ray bursts (GRBs) are hyper-energetic explosions resulting from the collapse of very massive stars ( approximately 40 M\circ, where M\circ is the mass of the Sun) stripped of their outer hydrogen and helium envelopes. A very massive progenitor, collapsing to a black hole, was thought to be a requirement for the launch of a GRB. Here we report the results of modelling the spectra and light curve of SN 2006aj (ref. 9), which demonstrate that the supernova had a much smaller explosion energy and ejected much less mass than the other GRB-supernovae, suggesting that it was produced by a star whose initial mass was only approximately 20 M\circ. A star of this mass is expected to form a neutron star rather than a black hole when its core collapses. The smaller explosion energy of SN 2006aj is matched by the weakness and softness of GRB 060218 (an X-ray flash), and the weakness of the radio flux of the supernova. Our results indicate that the supernova-GRB connection extends to a much broader range of stellar masses than previously thought, possibly involving different physical mechanisms: a 'collapsar' (ref. 8) for the more massive stars collapsing to a black hole, and magnetic activity of the nascent neutron star for the less massive stars.     

The massive binary companion star to the progenitor of supernova 1993J

The massive star that underwent a collapse of its core to produce supernova (SN)1993J was subsequently identified as a non-variable red supergiant star in images of the galaxy M81 taken before explosion. It showed an excess in ultraviolet and B-band colours, suggesting either the presence of a hot, massive companion star or that it was embedded in an unresolved young stellar association. The spectra of SN1993J underwent a remarkable transformation from the signature of a hydrogen-rich type II supernova to one of a helium-rich (hydrogen-deficient) type Ib. The spectral and photometric peculiarities were best explained by models in which the 13-20 solar mass supergiant had lost almost its entire hydrogen envelope to a close binary companion, producing a 'type IIb' supernova, but the hypothetical massive companion stars for this class of supernovae have so far eluded discovery. Here we report photometric and spectroscopic observations of SN1993J ten years after the explosion. At the position of the fading supernova we detect the unambiguous signature of a massive star: the binary companion to the progenitor.     

A runaway collision in a young star cluster as the origin of the brightest supernova

Supernova SN 2006gy in the galaxy NGC 1260 is the most luminous recorded. Its progenitor might have been a very massive (>100 Mo, where is the mass of the Sun) star, but that interpretation is incompatible with hydrogen in the spectrum of the supernova; stars >40 Moare believed to have shed their hydrogen envelopes several hundred thousand years before the explosion. Alternatively, the progenitor might have arisen from the merger of two massive stars. Here we show that the collision frequency of massive stars in a dense and young cluster (of the kind to be expected near the centre of a galaxy) is sufficient to provide a reasonable chance that SN 2006gy resulted from such a bombardment. If this is the correct explanation, then we predict that when the supernova fades (in a year or so) a dense cluster of massive stars will become visible at the site of the explosion.     

不透明度对Ⅱ型超新星光变曲线的影响

本文考虑了各种过程对不透明度的贡献,并把不透明度写成参量形式,利用热力学定律和扩散方程得到了Ⅱ型超新星光极大后光变曲线解析解的普遍表达式。进而讨论了各种不透明度对超新星光变曲线的影响,采用我们的方法比较好地解释了超新星的一些观测特性,并拟合了两颗SNⅡ—L观测光变曲线     

Imprints of fast-rotating massive stars in the Galactic Bulge

The first stars that formed after the Big Bang were probably massive, and they provided the Universe with the first elements heavier than helium ('metals'), which were incorporated into low-mass stars that have survived to the present. Eight stars in the oldest globular cluster in the Galaxy, NGC?6522, were found to have surface abundances consistent with the gas from which they formed being enriched by massive stars (that is, with higher α-element/Fe and Eu/Fe ratios than those of the Sun). However, the same stars have anomalously high abundances of Ba and La with respect to Fe, which usually arises through nucleosynthesis in low-mass stars (via the slow-neutron-capture process, or s-process). Recent theory suggests that metal-poor fast-rotating massive stars are able to boost the s-process yields by up to four orders of magnitude, which might provide a solution to this contradiction. Here we report a reanalysis of the earlier spectra, which reveals that Y and Sr are also overabundant with respect to Fe, showing a large scatter similar to that observed in extremely metal-poor stars, whereas C abundances are not enhanced. This pattern is best explained as originating in metal-poor fast-rotating massive stars, which might point to a common property of the first stellar generations and even of the 'first stars'.     

关于（Sz（q），1）——弧正则图的构造

本文讨论了5度的容许Suzuki单群Sz（q）的正则图Г,利用其点稳定化子Г=S（q）α,α∈V（Г）,并利用SZ（q）的2－元给出了该正则图Г的构造。     

X-ray illumination of the ejecta of supernova 1987A

When a massive star explodes as a supernova, substantial amounts of radioactive elements--primarily (56)Ni, (57)Ni and (44)Ti--are produced. After the initial flash of light from shock heating, the fading light emitted by the supernova is due to the decay of these elements. However, after decades, the energy powering a supernova remnant comes from the shock interaction between the ejecta and the surrounding medium. The transition to this phase has hitherto not been observed: supernovae occur too infrequently in the Milky Way to provide a young example, and extragalactic supernovae are generally too faint and too small. Here we report observations that show this transition in the supernova SN 1987A in the Large Magellanic Cloud. From 1994 to 2001, the ejecta faded owing to radioactive decay of (44)Ti as predicted. Then the flux started to increase, more than doubling by the end of 2009. We show that this increase is the result of heat deposited by X-rays produced as the ejecta interacts with the surrounding material. In time, the X-rays will penetrate farther into the ejecta, enabling us to analyse the structure and chemistry of the vanished star.     

Pulsational pair instability as an explanation for the most luminous supernovae

The extremely luminous supernova SN 2006gy (ref. 1) challenges the traditional view that the collapse of a stellar core is the only mechanism by which a massive star makes a supernova, because it seems too luminous by more than a factor of ten. Here we report that the brightest supernovae in the modern Universe arise from collisions between shells of matter ejected by massive stars that undergo an interior instability arising from the production of electron-positron pairs. This 'pair instability' leads to explosive burning that is insufficient to unbind the star, but ejects many solar masses of the envelope. After the first explosion, the remaining core contracts and searches for a stable burning state. When the next explosion occurs, several solar masses of material are again ejected, which collide with the earlier ejecta. This collision can radiate 10(50) erg of light, about a factor of ten more than an ordinary supernova. Our model is in good agreement with the observed light curve for SN 2006gy and also shows that some massive stars can produce more than one supernova-like outburst.     

A giant outburst two years before the core-collapse of a massive star

The death of massive stars produces a variety of supernovae, which are linked to the structure of the exploding stars. The detection of several precursor stars of type II supernovae has been reported (see, for example, ref. 3), but we do not yet have direct information on the progenitors of the hydrogen-deficient type Ib and Ic supernovae. Here we report that the peculiar type Ib supernova SN 2006jc is spatially coincident with a bright optical transient that occurred in 2004. Spectroscopic and photometric monitoring of the supernova leads us to suggest that the progenitor was a carbon-oxygen Wolf-Rayet star embedded within a helium-rich circumstellar medium. There are different possible explanations for this pre-explosion transient. It appears similar to the giant outbursts of luminous blue variable stars (LBVs) of 60-100 solar masses, but the progenitor of SN 2006jc was helium- and hydrogen-deficient (unlike LBVs). An LBV-like outburst of a Wolf-Rayet star could be invoked, but this would be the first observational evidence of such a phenomenon. Alternatively, a massive binary system composed of an LBV that erupted in 2004, and a Wolf-Rayet star exploding as SN 2006jc, could explain the observations.     

An infrared ring around the magnetar SGR 1900+14

Magnetars are a special class of slowly rotating (period approximately 5-12 s) neutron stars with extremely strong magnetic fields (>10(14 )G)--at least an order of magnitude larger than those of the 'normal' radio pulsars. The potential evolutionary links and differences between these two types of object are still unknown; recent studies, however, have provided circumstantial evidence connecting magnetars with very massive progenitor stars. Here we report the discovery of an infrared elliptical ring or shell surrounding the magnetar SGR 1900+14. The appearance and energetics of the ring are difficult to interpret within the framework of the progenitor's stellar mass loss or the subsequent evolution of the supernova remnant. We suggest instead that a dust-free cavity was produced in the magnetar environment by the giant flare emitted by the source in August 1998. Considering the total energy released in the flare, the theoretical dust-destruction radius matches well with the observed dimensions of the ring. We conclude that SGR 1900+14 is unambiguously associated with a cluster of massive stars, thereby solidifying the link between magnetars and massive stars.