绚丽的超新星遗迹

<正>宇宙中的天体,生与死总是相依相伴。比如,中小质量恒星的死,伴随着白矮星和行星状星云的生;大质量恒星的死,伴随着中子星、黑洞和超新星遗迹的生。超新星遗迹,是大质量恒星死亡前发生灾难性的爆炸后,原来恒星包层中的物质被抛射到星际空间而形成的,而爆发后在中心留下来的核心就成了中子星或黑洞。超新星遗迹的诞生超新星遗迹的诞生,伴随着星体的剧烈爆发。这种爆发主要有两大类,一类是核燃烧导致的超新星爆发,另一类是常说的引力坍缩型超新星爆发。     

超新星遗迹与绿色延展天体的相互关系

超新星遗迹是超新星爆发后的残留物,包含爆发喷射物以及周围与其相互作用的物质;绿色延展天体是大质量恒星形成区候选体.这两类天体都与大质量恒星的形成与死亡有密切关系.本文尝试探究超新星遗迹与绿色延展天体的相互关系,以期对超新星是否促进大质量恒星形成这一问题有进一步了解.本研究通过计算得到14组超新星遗迹和绿色延展天体的相对距离,发现最小的也在百秒差距量级.通过分析274个超新星遗迹与298个绿色延展天体的空间分布,发现相对于其他区域,超新星遗迹附近的绿色延展天体明显多一些,但可能是因为超新星遗迹附近分子云密度大造成.斯必泽红外空间望远镜的巡天范围在银纬b=±1°内,在此范围以外的超新星遗迹附近的绿色延展天体是使用美国宇航局广角红外巡天探测器(WISE)巡天数据搜寻的,找到了4个绿色延展天体.得到的初步结论是超新星遗迹并不能直接促使绿色延展天体形成,但它们之间或许有间接联系.     

西欧的巨石文化

在遥远的新石器时代(距今约6000年前),西欧广袤的土地上出现了为数众多的巨石建筑。这些规模宏大的巨石建筑,有的屹立在辽阔的平原上,任凭风吹雨打;有的隐蔽在山坡中,神秘莫测;有的座落在海岛和海湾上,伴随着大海的波涛声渡过了几千年。巨石建筑是引人注目的史前文化遗迹之     

前身星与Ⅱ型超新星爆发的数值模拟

利用考虑物质回落与混合效应的前身星输入数据,在一维球对称瞬时爆发模型下数值模拟了质量为12～15 M⊙Ⅱ型超新星的星核坍缩、激波传播、爆发能量等过程.计算结果表明:前身星的星核质量、密度、温度、物质构成等对Ⅱ型超新星爆发有重要影响,不过,数值模拟仍不能实现超新星的瞬时爆发.     

两种物态方程下铁核塌缩型超新星爆发机制的数值模拟

【目的】物态方程对铁核塌缩型超新星爆发过程中铁核塌缩、激波产生及其传播等都将产生影响。为了探索对超新星爆发机制解释更合理的物态方程,对比分析2种物态方程对铁核塌缩型超新星爆发的影响。【方法】以新前身星模型数据作为输入参量,分别采用Lattimer等(LS物态方程)和王贻仁等(W物态方程)提出的物态方程,对不同初始质量的铁核塌缩型超新星的爆发过程进行数值模拟,并对比分析模拟结果。【结果】在LS物态方程下,铁核塌缩结束时恒星的中心密度最高只达到核密度的1.5倍,且得到的同模区偏小,中微子的能量损失较大,这使激波在向外传播过程中损失了较多能量,不利于解释超新星的成功爆发。【结论】W物态方程更能合理解释超新星的成功爆发。     

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.     

读玉凌家滩

凌家滩遗址位于安徽省含山县铜闸镇五联行政村凌家滩自然村.该遗址1985年发现,1987年至今,在国家文物局和省政府的关心与支持下,安徽省文物考古研究所先后四次对该遗址进行了科学的调查发掘.经钻探该遗址面积达160万平方米,已发掘面积2200平方米,发现新石器时代晚期的氏族墓地一处,祭坛一座,红陶块铺筑的3000平方米神庙或宫殿遗迹一处,红陶块砌筑的水井一口,巨石遗迹三处,出土各种精美玉器与其它珍贵的文物1500余件,取得重大考古成果,被评为1998年度全国考古十大新发现.2001年7月被国务院批准为第五批全国重点文物保护单位.经中国文物研究所碳-14年代测定,凌家滩遗址距今约5300～5500年,是我国新石器时代晚期一处罕见的区域性中心聚落遗址,各类遗存齐全,文化内涵丰富,是中华五千年文明史的实证.……     

快速旋转磁陀星驱动的类超新星现象研究概述

一颗快速旋转的高度磁化中子星(磁陀星)可能诞生于极端的恒星爆发或双致密星并合等过程.这一理论设想在近二十余年的伽马射线暴研究中常被提及且已受到诸多观测尤其是余辉观测的支持.因此,该新生磁陀星与这些爆发或并合产生的抛射物之间的相互作用及其产生的观测特征引起了人们的广泛关注.与此同时,近十余年来,随着宽视场高频次暂现源巡天项目的大量开展,人们陆续发现了为数不少的具有和普通超新星相似特征但又存在明显差异的光学暂现源现象,其典型代表有以高光度为主要特征的超亮超新星和以快速演化为主要特征的快变蓝色暂现源.这些现象为研究新生磁陀星驱动的类超新星爆发和辐射过程提供了现实途径.本文一方面概述了中子星的能量输出、中子星风和抛射物的相互作用及相应的辐射效应,主要包括抛射物热辐射主峰的增亮、主峰前由中子星风驱动的激波突破以及主峰后星风云非热辐射的泄漏等.另一方面,简要介绍了超亮超新星、伽马射线暴及其成协超新星或并合新星、快变蓝色暂现源等现象的主要观测特征,着重讨论了这些观测现象和中子星能源模型之间的相容性,以及模型和观测相结合所给出的参数限制.据此,可以更进一步地了解在相同的物理机制下产生不同观测现象的关键...     

远古踪迹

大理是我国西南最早开发的地区之一。从考古发掘材料来看,早在4000年前,大理就有史前人类活动的踪迹。新石器时代,大理史前人类种植水稻,饲养家畜,进行纺织、捕鱼和狩猎,居住在半穴居或干栏式的建筑之中,过着一种较为稳定的定居生活。大约在距今3000年的时候,大理地区进入了青铜时代。大理地区出土的青铜器带有明显的地域特征,在云南青铜文化中自成体系,形成了学术界一致认同的洱海地区青铜文化。     

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.     

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

An annotation for the statement about JingXing (Great Star) in the most famous Chinese ancient historical book Ski 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 yellaw 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 histurical books compiled by the authors of later ages in Tang Dynasty——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 serious wrong understandings of some astronomical phenomena such as supernovae, their depictions about natural phenomena 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 supernnva 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 correlation between the record of “Chi-Fang-Qi” and the supernova remnant can he further proven true, it would be an important verification of the modern theory about stellar evolution.     

An absence of ex-companion stars in the type Ia supernova remnant SNR 0509-67.5

A type Ia supernova is thought to begin with the explosion of a white dwarf star. The explosion could be triggered by the merger of two white dwarfs (a 'double-degenerate' origin), or by mass transfer from a companion star (the 'single-degenerate' path). The identity of the progenitor is still controversial; for example, a recent argument against the single-degenerate origin has been widely rejected. One way to distinguish between the double- and single-degenerate progenitors is to look at the centre of a known type Ia supernova remnant to see whether any former companion star is present. A likely ex-companion star for the progenitor of the supernova observed by Tycho Brahe has been identified, but that claim is still controversial. Here we report that the central region of the supernova remnant SNR 0509-67.5 (the site of a type Ia supernova 400?±?50 years ago, based on its light echo) in the Large Magellanic Cloud contains no ex-companion star to a visual magnitude limit of 26.9 (an absolute magnitude of M(V) = +8.4) within a region of radius 1.43 arcseconds. (This corresponds to the 3σ maximum distance to which a companion could have been 'kicked' by the explosion.) This lack of any ex-companion star to deep limits rules out all published single-degenerate models for this supernova. The only remaining possibility is that the progenitor of this particular type Ia supernova was a double-degenerate system.     

The record of cultivated rice from archaeobiological evidence in northwestern China 5000 years ago

Pollen, plant seeds and phytoliths from an AMS dated sediment profile at the Xishanping site indicate that the cultivation of rice might start no later than 5070 cal. a BP in the region of Tianshui, Gansu Province. It continued from 5070 to 4300 cal. a BP. This is so far the oldest and the most northwestern record of cultivated rice in Neolithic China, which extends the known region of prehistoric rice cultivation at least 2° longitude to the west. This finding provides important evidence for reconstructing the cultivation region of rice at 5000 a BP （an important time period）, and its spreading history in East Asia, during the Neolithic.     

德斯里是云南濮人的发祥地——从遗迹与史载证明

濮人是分布在我国西南地区的一个古老的民族群体,地处我国西南边陲的云南是古代濮人的重要聚居区,位于滇西澜沧江西岸的德斯里是云南濮人的发祥地之一,早在新石器时代晚期便有濮人在此繁衍生息,我们可以通过当地的原始文化遗迹及相关历史文献资料加以考证。     

能量色散X荧光光谱和人工神经网络在甘肃新石器时代陶片分类研究中的应用

EDXRF spectromerty was applied to provenance studies of Neolitic Age(from 6000 BCto 2000 BC)pottery sherds excavated from Gansu Province in north-west China。Major and trace components analysis of te pottery specimen was carried out,and the artificial neural networks has been used to classift the trace com-ponent of these pottery。The results shown that pottery exchange had been existed during 3000 BC in ancient Gansu Province,China。     

An asymmetric shock wave in the 2006 outburst of the recurrent nova RS Ophiuchi

Nova outbursts take place in binary star systems comprising a white dwarf and either a low-mass Sun-like star or, as in the case of the recurrent nova RS Ophiuchi, a red giant. Although the cause of these outbursts is known to be thermonuclear explosion of matter transferred from the companion onto the surface of the white dwarf, models of the previous (1985) outburst of RS Ophiuchi failed to adequately fit the X-ray evolution and there was controversy over a single-epoch high-resolution radio image, which suggested that the remnant was bipolar rather than spherical as modelled. Here we report the detection of spatially resolved structure in RS Ophiuchi from two weeks after its 12 February 2006 outburst. We track an expanding shock wave as it sweeps through the red giant wind, producing a remnant similar to that of a type II supernova but evolving over months rather than millennia. As in supernova remnants, the radio emission is non-thermal (synchrotron emission), but asymmetries and multiple emission components clearly demonstrate that contrary to the assumptions of spherical symmetry in models of the 1985 explosion, the ejection is jet-like, collimated by the central binary whose orientation on the sky can be determined from these observations.     

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.     

中国西南氐羌民族溯源

通过考古材料及文献分析,认为古氐羌始居于中国西北,源于属新石器时代的马家窑文化和相继发展的齐家文化的"西戎"民族集团,并随历史的发展不断南下、西进、再南下,到达了中国西南地区,成为了中国西南地区汉藏语系藏缅语族各民族的源头。     

An asymptotic-giant-branch star in the progenitor system of a type Ia supernova

Stars that explode as supernovae come in two main classes. A type Ia supernova is recognized by the absence of hydrogen and the presence of elements such as silicon and sulphur in its spectrum; this class of supernova is thought to produce the majority of iron-peak elements in the Universe. They are also used as precise 'standard candles' to measure the distances to galaxies. While there is general agreement that a type Ia supernova is produced by an exploding white dwarf star, no progenitor system has ever been directly observed. Significant effort has gone into searching for circumstellar material to help discriminate between the possible kinds of progenitor systems, but no such material has hitherto been found associated with a type Ia supernova. Here we report the presence of strong hydrogen emission associated with the type Ia supernova SN2002ic, indicating the presence of large amounts of circumstellar material. We infer from this that the progenitor system contained a massive asymptotic-giant-branch star that lost several solar masses of hydrogen-rich gas before the supernova explosion.     

The binary progenitor of Tycho Brahe's 1572 supernova

The brightness of type Ia supernovae, and their homogeneity as a class, makes them powerful tools in cosmology, yet little is known about the progenitor systems of these explosions. They are thought to arise when a white dwarf accretes matter from a companion star, is compressed and undergoes a thermonuclear explosion. Unless the companion star is another white dwarf (in which case it should be destroyed by the mass-transfer process itself), it should survive and show distinguishing properties. Tycho's supernova is one of only two type Ia supernovae observed in our Galaxy, and so provides an opportunity to address observationally the identification of the surviving companion. Here we report a survey of the central region of its remnant, around the position of the explosion, which excludes red giants as the mass donor of the exploding white dwarf. We found a type G0-G2 star, similar to our Sun in surface temperature and luminosity (but lower surface gravity), moving at more than three times the mean velocity of the stars at that distance, which appears to be the surviving companion of the supernova.