朱雀卫星伽玛暴持续时间的分布

伽玛暴持续时间的分布是对伽玛暴进行分类的一个依据。本文利用高斯混合模型和最大期望算法对朱雀卫星2005年至2014年在轨运行期间所探测到的741个伽玛暴持续时间的分布进行了分析,同时利用贝叶斯信息准则比较了具有不同高斯成分个数的模型。分析结果支持双高斯成分的模型比其他模型更好的描述了朱雀卫星所探测到的伽玛暴持续时间的分布,同时这一结论与其他卫星数据的分析结果一致,均支持存在两种类型的伽玛暴。     

伽玛射线暴内光度和峰值能量关系的统计分析

以前的研究表明:在伽玛射线暴(简称伽玛暴)间各向同性等值光度Liso和静止系中vFv谱的峰值能量E′p之间存在关系式LisooE′p2.Liang等人用Preece等人给出的91个BATSE伽玛暴的2408个时间分辨谱样本对这一关系式进行了验证,得出这一关系式不但在伽玛暴内成立,而且在伽玛暴之间也是成立的.为了进一步验证这一关系式,我们收集了Kaneko等人2006年发表的350个BATSE伽玛暴能谱的数据,并对其中185个伽玛暴能谱的5218个时间分辨谱样本进行统计分析,我们得出的结果与Liang等人的结果是一致的.     

雨燕捕捉伽玛射线暴

就像夜空中明灭的焰火，伽玛射线暴瞬间“点亮”了星空。它是宇宙中最猛烈的爆发!但它稍纵即逝的天性使得科学家难以捕捉和研究。而这并不说明我们对它一无所知。美国宇航局派遣雨燕探测器将为我们揭开谜团。     

SWIFT伽玛暴的谱延迟距离指示器

早期研究发现,BASTE长暴的相对谱延迟RSL是一个有用的宇宙距离指示器。本文从SWIFT卫星数据中,挑选10个单脉冲长伽玛暴(T90>2.6)作为样本,对样本进行降噪和去除背景,用交叉相关函数分析1,3能道的谱延迟,通过拟合研究各脉冲参数Asymmetry,Fm,Fp,tm,FWHM,τ31和相对谱延迟的关系,发现相对谱延迟和红移具有很好的相关性,这充分表明SWIFT长暴的相对谱延迟仍然是一个很好的红移指示器。     

各向同性火球中考虑同步自吸收的伽玛暴余辉

基于Huang,Y．F．等人的统一动力学模型,研究了星际介质环境下各向同性火球所抛壳层的动力学量随时间的演化,考虑了同步自吸收效应,用数值计算方法得到不同频率下随时间演化的伽玛暴余辉,同柱状喷流下伽玛暴余辉比较,得出相应结论．     

Swift/BAT伽玛暴的经验谱能关系

我们选取76个红移已知Swift伽玛暴(含有61个长暴和15个短暴),分析了各向同性能量,光度和峰值能量之间的相关性,研究发现Swift长暴存在Amati关系,而短暴存在Ghirlanda关系和Amati关系。我们还发现了Swift/BAT长暴和短暴的Ep.i-Lp关系都分别存在且是一致的,并且符合Zhang,DaiHuang之前利用多个卫星数据得到的结果。     

伽玛暴微光变特征时标研究

伽玛暴光变曲线一般由若干个脉冲组成的“大轮廓”叠加着一些微光变组成的,大部分伽玛暴光变曲线没有呈现周期性,而这些微光变成分可能携带重要的辐射区性质.采用平滑滤波器把伽玛暴光变曲线中的“大轮廓”成分和微光变成分分离,然后采用“最大熵”功率谱密度估算法计算微光变信号的功率谱密度,并分析其周期特征时标.文中分析了Swift/...     

一种对伽玛暴瞬时谱的新解释

研究了幂律分布电子的同步曲率辐射在伽玛暴（gamma-ray burst,GRB）的物理条件下的表现,并用同步曲率辐射机制代替同步辐射来解释伽玛暴的瞬时谱,尤其是那些出现拐点和高能过剩的谱,还拟合了几个实际的有拐点和高能过剩的伽玛射线暴的瞬时谱.从中可以看出,同步曲率辐射机制对整个瞬时谱能够做出统一和合理的解释.在对高能过剩部分的解释中,同步曲率辐射机制不需再人为引入任何其他机制,因此可调参数少.此外,该机制还能对发射区磁场给出更加详细的描述,尤其是对磁场的曲率半径有了严格的约束,因此对磁场的形成机制给出严格的限制,支持了磁场产生于激波的理论模型.将来对更高能部分的更精细的观测将能够对我们的模型进行进一步检验.最后用同步曲率辐射对GRB 941017的谱的瞬时谱部分的演化进行了拟合和讨论.     

研究GBM和BAT同时触发的暴

结合Swift和Fermi两个卫星的各自优点,选择Fermi/GBM和Swift/BAT同时触发的伽玛暴观测数据,发现GBM暴持续时间的平均值比BAT暴要小,但是它们的持续时间分布、伽玛暴本身的流量分布以及光子峰值能量分布(log N-log P分布)之间不存在系统性差异.所以,不同仪器的观测差异可能是由于仪器本身的灵敏度引起的,与暴的性质无关.     

500m口径球面射电天文望远镜(FAST)对高红移伽玛暴余辉的探测

伽玛射线暴(简称伽玛暴)可以发生在很远的宇宙深处,其余辉(尤其射电余辉)的长时标发射使得长期观测成为可能,从而可测量其红移并证认宇宙学起源和研究寄主星系性质。随着红移的增大,伽玛暴射电余辉的流量密度也会随之减少,这对高红移伽玛暴的探测造成一定的困难。然而,500 m口径球面射电天文望远镜(FAST)具有很高的探测灵敏度,利于对暗弱的高红移暴的观测。我们利用余辉动力学模型分析了射电余辉流量密度随红移(距离)的变化关系,以此评估FAST对高红移射电余辉的观测能力,同时预测其对不同类型伽玛暴射电余辉的探测率。     

An origin in the local Universe for some short gamma-ray bursts

Gamma-ray bursts (GRBs) divide into two classes: 'long', which typically have initial durations of T90 > 2 s, and 'short', with durations of T90 < 2 s (where T90 is the time to detect 90% of the observed fluence). Long bursts, which on average have softer gamma-ray spectra, are known to be associated with stellar core-collapse events-in some cases simultaneously producing powerful type Ic supernovae. In contrast, the origin of short bursts has remained mysterious until recently. A subsecond intense 'spike' of gamma-rays during a giant flare from the Galactic soft gamma-ray repeater, SGR 1806-20, reopened an old debate over whether some short GRBs could be similar events seen in galaxies out to approximately 70 Mpc (refs 6-10; redshift z approximately 0.016). Shortly after that, localizations of a few short GRBs (with optical afterglows detected in two cases) have shown an apparent association with a variety of host galaxies at moderate redshifts. Here we report a correlation between the locations of previously observed short bursts and the positions of galaxies in the local Universe, indicating that between 10 and 25 per cent of short GRBs originate at low redshifts (z < 0.025).     

The afterglow of GRB 050709 and the nature of the short-hard gamma-ray bursts

The final chapter in the long-standing mystery of the gamma-ray bursts (GRBs) centres on the origin of the short-hard class of bursts, which are suspected on theoretical grounds to result from the coalescence of neutron-star or black-hole binary systems. Numerous searches for the afterglows of short-hard bursts have been made, galvanized by the revolution in our understanding of long-duration GRBs that followed the discovery in 1997 of their broadband (X-ray, optical and radio) afterglow emission. Here we present the discovery of the X-ray afterglow of a short-hard burst, GRB 050709, whose accurate position allows us to associate it unambiguously with a star-forming galaxy at redshift z = 0.160, and whose optical lightcurve definitively excludes a supernova association. Together with results from three other recent short-hard bursts, this suggests that short-hard bursts release much less energy than the long-duration GRBs. Models requiring young stellar populations, such as magnetars and collapsars, are ruled out, while coalescing degenerate binaries remain the most promising progenitor candidates.     

曲率效应导致的伽马暴高能尾

根据"曲率效应",预言伽马暴随动谱中高能端的一根发射线可以形成观测谱中的一个翘起的高能尾.这解释了为什么从来没有在伽马暴中观测到窄发射线.翘尾的峰是洛仑兹因子的线性函数.这表明,当该发射线被证认时,翘尾峰可成为火球膨胀速度的指示器.     

An unexpectedly rapid decline in the X-ray afterglow emission of long gamma-ray bursts

'Long' gamma-ray bursts (GRBs) are commonly accepted to originate in the explosion of particularly massive stars, which give rise to highly relativistic jets. Inhomogeneities in the expanding flow result in internal shock waves that are believed to produce the gamma-rays we see. As the jet travels further outward into the surrounding circumstellar medium, 'external' shocks create the afterglow emission seen in the X-ray, optical and radio bands. Here we report observations of the early phases of the X-ray emission of five GRBs. Their X-ray light curves are characterised by a surprisingly rapid fall-off for the first few hundred seconds, followed by a less rapid decline lasting several hours. This steep decline, together with detailed spectral properties of two particular bursts, shows that violent shock interactions take place in the early jet outflows.     

An exceptionally bright flare from SGR 1806-20 and the origins of short-duration gamma-ray bursts

Soft-gamma-ray repeaters (SGRs) are galactic X-ray stars that emit numerous short-duration (about 0.1 s) bursts of hard X-rays during sporadic active periods. They are thought to be magnetars: strongly magnetized neutron stars with emissions powered by the dissipation of magnetic energy. Here we report the detection of a long (380 s) giant flare from SGR 1806-20, which was much more luminous than any previous transient event observed in our Galaxy. (In the first 0.2 s, the flare released as much energy as the Sun radiates in a quarter of a million years.) Its power can be explained by a catastrophic instability involving global crust failure and magnetic reconnection on a magnetar, with possible large-scale untwisting of magnetic field lines outside the star. From a great distance this event would appear to be a short-duration, hard-spectrum cosmic gamma-ray burst. At least a significant fraction of the mysterious short-duration gamma-ray bursts may therefore come from extragalactic magnetars.     

Can the lumpy distribution of galaxies be detected by X-ray observations?

Published data from X-ray telescopes are not adequate to reveal the fluctuations in the surface brightness of the background radiation caused by clustering or superclustering of the sources giving rise to the background.     

ICBP90介导PI3K/AKT通路阻断剂LY294002抑制Jurkat T细胞增殖

目的:探讨磷脂酰肌醇3激酶/丝氨酸苏氨酸蛋白激酶B(PI3K/AKT)信号通路特异性抑制剂LY294002在JurkatT细胞增殖中的作用.方法:以急性T细胞白血病胞(Jurkat T 细胞)为模型,PD98059和阿霉素为阳性对照,在倒置显微镜下观察LY294002对Jurkat T细胞的集落形成的影响,四甲基偶氮唑蓝(MTT)检测LY294002处理后Jurkat T细胞的增殖,流式细胞术检测LY294002处理后Jurkat T细胞周期的变化,Western blotting方法检测Jurkat T细胞中ICBP90蛋白的表达以确定其与LY294002抑制Jurkat T细胞增殖的关系.结果:LY294002能够显著抑制Jurkat T细胞的集落形成和增殖,使Jurkat T细胞停滞于G2/M 期,导致Jurkat T细胞ICBP90蛋白的表达显著降低,LY294002与阿霉素联合用药可产生一定的协同效应. 结论:LY294002通过下调Jur-katT细胞ICBP90蛋白的表达,抑制Jurkat T细胞增殖.