伽马射线暴

正伽马射线暴(简称伽马暴)是起源于大质量恒星坍缩(长伽马暴)或者致密双星并合(短伽马暴)等短时标极端剧烈的高能灾变天体,是宇宙大爆炸之后最猛烈的爆发现象,也是宇宙宏观速度最快的天体。伽马暴本身辐射及其余辉辐射来自新生黑洞或者磁星所驱动的极端相对论喷流,并且理论上预期其还伴随强引力波、高能中微子和高能宇宙线辐射。因此,伽马暴是研究黑洞     

宇宙中的双黑洞

在星系形成的等级结构模型中,亚星系的结构先形成,之后再不断地通过并合形成越来越大的星系.伴随着星系的并合,星系中心的大质量黑洞也不断经历并合.在富气体星系的并合过程中,气体落入星系的中心,可能触发恒星的形成和黑洞的吸积.黑洞不断通过并合和气体吸积,从小到大形成现在观测到的在不同红移处的超大质量黑洞,因此,在星系的演化过程中,不同红移处必然存在很多大质量黑洞双体系统,甚至三体系统.本文将主要对宇宙中大质量双黑洞的观测和理论做一个简要的评述.美国升级后的激光干涉引力波天文台宣称首次直接探测到了引力波,该引力波源为几十倍太阳质量黑洞双星的并合.这么大质量的致密双黑洞是如何形成的?它们的并合率为什么这么高?本文也会简单提及恒星级双黑洞的形成和演化模型.     

两类Seyfert星系的黑洞质量与吸积率

收集了89个Seyfert星系样本,利用反响映射法和恒星弥散速度法计算了Seyfert星系的黑洞质量,分别研究了Seyfert 1和Seyfert 2星系的黑洞质量与吸积率、热光度和红移之间的相关性,结果发现Seyfert 1星系的黑洞质量与吸积率、热光度和红移之间具有强相关性,Seyfert 2星系的黑洞质量与吸积率之间具有弱的负相关性,与热光度和红移之间具有弱相关性.两类Seyfert星系的区别除了源于吸积盘倾角不同外,还可能与星系的环境、演化和星系核的活动有关.     

活动星系核的演化与吸积率

红移,中心黑洞质量和吸积率是类星体演化的重要参数,通过三种方法计算了405个类星体和Seyfert星系样本的中心黑洞质量,并分析了中心黑洞质量和吸积率的分布,进而验证了：1.类星体-Seyfert星系的演化序列;2.平谱射电类星体（FSRQ）-BL Lac天体-射电星系（RG）的演化序列。     

星系紫外深场巡天观测进展

紫外波段是星系能谱分布中的重要部分.其包含大量原子、离子和分子的共振线以及研究重要物理过程的连续辐射,提供了理论研究重要的观测限制.在星系研究中,紫外辐射追踪大质量恒星,是测量和理解宇宙中恒星形成历史的重要工具.紫外辐射也可追踪大质量黑洞吸积盘,是理解吸积物理过程的重要手段.其涉及的关键科学问题包括宇宙正午时期的恒星形成历史与星系演化、宇宙重子物质缺失、宇宙再电离能量来源以及星系吸积和外流反馈等.本文重点阐述了紫外深场巡天观测的发展现状及其在星系科学研究中发挥的作用.主要介绍了深场仪器的基本参数、深场观测的目的和任务,以及数据及科学产出,并对国内外正在计划中的未来紫外观测进行了总结和展望.     

星系中心大黑洞的宇宙学演化

在冷暗物质晕等级成团宇宙学模型中,伴随着暗物质晕并合,星系中心黑洞也断地并合和增长.于展Press-Schechter公式（EPS）我们编写了一自适应时间长Monte Carlo程序,重构了表征暗物质晕等级成团并合树.在成功地建立了黑洞和暗物质晕宇宙学演化模型后,我们通过引入直接吸积（包标准薄盘吸积和磁流体力学吸积）和随吸积两类黑洞吸积模式,论了黑洞自旋和质量宇宙学演化.通过与观测到AGN光度函数比较,我们发现黑洞通过磁流体力学吸积模式增长,与观测符合最好.于以上理论框架,我们还研究了双大质量黑洞演化,发现双黑洞通过共转气体吸积盘吸积对双黑洞质量比分存在显著影响.     

科学家谈天文学重要方向 星系的演化

正星系的形成和演化是天体物理的前沿领域。该领域以现代宇宙学提供的大尺度结构形成和演化的成熟理论作为基本框架,通过观测和统计研究宇宙各时期星系的形态结构、星族构成、气体吸积、恒星演化、黑洞成长、化学元素、恒星和气体动力学等物理性质及其演变过程,试图阐明宇宙中各类星系的物理起源、演化关系以及它们与宇宙大尺度结构的物理联系,从而总结出支配星系演化的普适物理规律。目前被普遍接受的星系形成理论认为,星系在暗物质晕中形成和演化,其基本图     

黑洞的吸积过程

正黑洞在宇宙中是普遍存在的。观测表明,宇宙中大部分星系中心都存在一个质量在几十万到几十亿倍的太阳质量的超大质量黑洞,而每个星系中都存在几千万个恒星级质量的黑洞。黑洞吸积是指黑洞周围的气体在黑洞引力的作用下向黑洞下落的物理过程。这一过程会释放出很强的辐射,并伴随着物质外流。现代天体物理的许多重要分支都是以黑洞吸积作为其理论基础的,包括活动星系核、伽玛射线暴、黑洞X     

活动星系核中黑洞质量与宇宙学红移的研究

收集了209个活动星系核（46个平谱射电类星体,78个BLLac天体,85个射电星系）样本,估算出爱丁顿吸积率,讨论了黑洞质量、热光度、红移量和爱丁顿吸积率之间的关系,得出了以下结论：（1）活动星系核的一个演化序列为：平谱射电类星体（FsRQ）——BL Lac天体——射电星系（RG）的演化;（2）三类星体的中心黑洞质量、红移量和热光度有较大差异：皆为FSRQ〉BLLac〉RG;（3）吸积率与热光度之间的相关性很强,吸积率的变化将导致热光度的变化。     

Q＆A

<正>Q:"正常黑洞"的质量范围是多少?10倍太阳质量以下的天体能形成黑洞吗?(读者:Eugaron)A:现在的观测和理论认为,自然界中的黑洞按其质量可以分为几类:位于星系中心的10~6~10~(10)倍太阳质量的超大质量黑洞,由对低亮度的活动星系核的观测推测得到的具有数十倍到百万倍太阳质量的中等质量黑洞;由恒星演化到晚期形成的3.8~20倍左右太阳质量的恒星质量黑洞;在宇宙早期的高密度环境下产生的质量下限为普朗克质量的迷你黑洞,这类黑洞还可能是暗物质的     

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 unusual gamma-ray burst GRB 101225A explained as a minor body falling onto a neutron star

The tidal disruption of a solar-mass star around a supermassive black hole has been extensively studied analytically and numerically. In these events, the star develops into an elongated banana-shaped structure. After completing an eccentric orbit, the bound debris falls into the black hole, forming an accretion disk and emitting radiation. The same process may occur on planetary scales if a minor body passes too close to its star. In the Solar System, comets fall directly into our Sun or onto planets. If the star is a compact object, the minor body can become tidally disrupted. Indeed, one of the first mechanisms invoked to produce strong gamma-ray emission involved accretion of comets onto neutron stars in our Galaxy. Here we report that the peculiarities of the 'Christmas' gamma-ray burst (GRB 101225A) can be explained by a tidal disruption event of a minor body around an isolated Galactic neutron star. This would indicate either that minor bodies can be captured by compact stellar remnants more frequently than occurs in the Solar System or that minor-body formation is relatively easy around millisecond radio pulsars. A peculiar supernova associated with a gamma-ray burst provides an alternative explanation.     

An ultra-relativistic outflow from a neutron star accreting gas from a companion

Collimated relativistic outflows-also known as jets-are amongst the most energetic phenomena in the Universe. They are associated with supermassive black holes in distant active galactic nuclei, accreting stellar-mass black holes and neutron stars in binary systems and are believed to be responsible for gamma-ray bursts. The physics of these jets, however, remains something of a mystery in that their bulk velocities, compositions and energetics remain poorly determined. Here we report the discovery of an ultra-relativistic outflow from a neutron star accreting gas within a binary stellar system. The velocity of the outflow is comparable to the fastest-moving flows observed from active galactic nuclei, and its strength is modulated by the rate of accretion of material onto the neutron star. Shocks are energized further downstream in the flow, which are themselves moving at mildly relativistic bulk velocities and are the sites of the observed synchrotron emission from the jet. We conclude that the generation of highly relativistic outflows does not require properties that are unique to black holes, such as an event horizon.     

原初典型恒星及其星核黑洞的形成、演化和结构的基本规律

本文在文献[1]、[2]的基础上,应用相对论性牛顿万有引力定律,对原初典型恒星及其星核M。黑洞的形成、演化和结构,作了更深入的探索研究．得到了一系列很有意义的结果：1、导出了原初典型恒星Mo及其星核Ms黑洞质量的上界和下界．进而导出了原初典型恒星在其简并中子黑涧（Mos=Mo）态下一分为二的死亡大爆炸中释放能量的上下界（即超新星爆发所释放能量的上下界）;2、导出了星核Ms黑洞独有的一系列鼎级极限物理特性．导出了黑洞无内阻理想流体的超流效应及黑洞吸集粒子的经纬分流的筛选效应．证明了星核Ms黑洞是具有不再爆炸、不再坍缩、不再发射的“三不”特性的稳定天体;3、在相对论性引力理论框架内,证明了光速最大原理;4、导出了原初典型恒星在一分为二的死亡大爆炸中静质量Mo、场（暗）质量△MG的结构和分布规律．揭示了星核Ms黑洞结构的奥秘;5、导出了恒星、星系、总星系等典型层次天体的真空中场（暗）质量的分布规律．     

M87的TeV辐射光变

2005年第一次在M87中观测到TeV辐射爆发,分析表明TeV爆发的光变时标非常短且相对孤立.M87的喷流的视向倾角较大(～30?),是银河系外观测到的第一个非blazar类TeV源,这暗示着新的产生TeV辐射过程.考虑到TeV源有可能是产生于黑洞吸积盘上的等离子体云团,刚诞生的时候可能围绕中心黑洞作开普勒运动,本文在完全广义相对论框架下计算了这种情况下TeV辐射的光变.模型中不仅考虑了TeV源作开普勒运动的效应,还计算了轨道上不同点发出的TeV光子在到达无穷远处观测者的过程中被来自吸积盘上的软光子吸收的光深差异.计算表明TeV源的光变主要由不同轨道上的TeV光子的光深变化主导,TeV源作开普勒运动的效应基本可以忽略.在TeV源距离黑洞比较近的时候,随着黑洞自旋的增大光深显著减小,在黑洞自旋为零时,光深变化曲线明显不对称,TeV源越靠近黑洞这些效应越显著.     

Long gamma-ray bursts and core-collapse supernovae have different environments

When massive stars exhaust their fuel, they collapse and often produce the extraordinarily bright explosions known as core-collapse supernovae. On occasion, this stellar collapse also powers an even more brilliant relativistic explosion known as a long-duration gamma-ray burst. One would then expect that these long gamma-ray bursts and core-collapse supernovae should be found in similar galactic environments. Here we show that this expectation is wrong. We find that the gamma-ray bursts are far more concentrated in the very brightest regions of their host galaxies than are the core-collapse supernovae. Furthermore, the host galaxies of the long gamma-ray bursts are significantly fainter and more irregular than the hosts of the core-collapse supernovae. Together these results suggest that long-duration gamma-ray bursts are associated with the most extremely massive stars and may be restricted to galaxies of limited chemical evolution. Our results directly imply that long gamma-ray bursts are relatively rare in galaxies such as our own Milky Way.     

A debris disk around an isolated young neutron star

Pulsars are rotating, magnetized neutron stars that are born in supernova explosions following the collapse of the cores of massive stars. If some of the explosion ejecta fails to escape, it may fall back onto the neutron star or it may possess sufficient angular momentum to form a disk. Such 'fallback' is both a general prediction of current supernova models and, if the material pushes the neutron star over its stability limit, a possible mode of black hole formation. Fallback disks could dramatically affect the early evolution of pulsars, yet there are few observational constraints on whether significant fallback occurs or even the actual existence of such disks. Here we report the discovery of mid-infrared emission from a cool disk around an isolated young X-ray pulsar. The disk does not power the pulsar's X-ray emission but is passively illuminated by these X-rays. The estimated mass of the disk is of the order of 10 Earth masses, and its lifetime (> or = 10(6) years) significantly exceeds the spin-down age of the pulsar, supporting a supernova fallback origin. The disk resembles protoplanetary disks seen around ordinary young stars, suggesting the possibility of planet formation around young neutron stars.     

Very fast optical flaring from a possible new Galactic magnetar

Highly luminous rapid flares are characteristic of processes around compact objects like white dwarfs, neutron stars and black holes. In the high-energy regime of X-rays and gamma-rays, outbursts with variabilities on timescales of seconds or less are routinely observed, for example in gamma-ray bursts or soft gamma-ray repeaters. At optical wavelengths, flaring activity on such timescales has not been observed, other than from the prompt phase of one exceptional gamma-ray burst. This is mostly due to the fact that outbursts with strong, fast flaring are usually discovered in the high-energy regime; most optical follow-up observations of such transients use instruments with integration times exceeding tens of seconds, which are therefore unable to resolve fast variability. Here we show the observation of extremely bright and rapid optical flaring in the Galactic transient SWIFT J195509.6+261406. Our optical light curves are phenomenologically similar to high-energy light curves of soft gamma-ray repeaters and anomalous X-ray pulsars, which are thought to be neutron stars with extremely high magnetic fields (magnetars). This suggests that similar processes are in operation, but with strong emission in the optical, unlike in the case of other known magnetars.