共查询到18条相似文献，搜索用时 421 毫秒
1.
Swift时代伽马暴的观测及研究进展 总被引：1，自引：0，他引：1
Swift卫星从2004年11月20日升空开始运转到现在已有2年多时间.到目前为止,它-共观测到了200多个伽马暴及其余辉现象.由于Swift观测到了早期X射线余辉、短暴余辉和高红移伽马暴等新的重要现象,伽马暴研究进入了新的时代.该文首先对伽马暴的研究历史做简短回顾,然后简要介绍伽马暴的物理图像和Swift卫星的构成及特点,最后全面评述Swift的观测成就及由此引起的理论挑战. 相似文献
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BATSE(Compton Gamma-Ray Observatory/Bursts and Transient SourceExperiment)、Swift(Swift Gamma-ray Burst Explorer)和Fermi卫星(Fermi GammaraySpace Telescope)提供了大量的GRB样本.研究比较3种仪器观测的暴的特征,发现虽然有红移暴的数目、所有暴中长暴的比例以及光子流量分布(lgN-lgP分布)等有显著差异,但是暴的持续时间、伽玛辐射总流量、谱硬度比等均没有显著差异.考虑Swift和Fermi暴的观测能段不同,进行修正以后,发现lgN-lgP分布的差异也基本消除.有红移暴的数目、长暴占总暴数的比例是由仪器本身的灵敏度决定的,即不同仪器决定不同GRB的观测特征,但是它们的本质是一致的. 相似文献
3.
伽玛射线暴是一种来自宇宙空间随机方向的短时间内伽玛射线突然增亮的现象。伽玛射线暴虽然早在1967年就由Vela卫星观测到,但直到1997年人们才通过余辉观测确定其寄主星系,并通过寄主星系的红移最终确定了伽玛射线暴的宇宙学起源。对伽玛射线暴研究概况进行了评述:详细介绍了伽玛射线暴及其余辉的观测进展,特别是近期Swift卫星和Fermi卫星带来的新发现;系统描述了伽玛射线暴标准火球模型、伽玛射线暴余辉物理(相对论性外流与暴周环境介质的相互作用过程、辐射产生机制等)及伽玛射线暴的前身星等。也对伽玛射线暴的未来研究进行了展望。 相似文献
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《天文研究与技术》2016,(3)
伽玛暴是宇宙中最剧烈的爆发现象之一,观测伽玛暴预警和暂现源实验卫星(Compton Gamma-Ray Observatory/Bursts and Transient Source Experiment,BATSE)、高能暂现源探测卫星(High Energy Transient Explorer,HETE)和Fermi提供了大量的伽玛暴样本,对这些数据进行分析,用统计的方法寻找其中蕴含的伽玛暴辐射物理信息是必要的。伽玛暴能谱νFν的峰值能量Ep是伽玛暴一个很重要的物理量,并且每个暴的峰值能量不同。研究比较不同仪器观测的伽玛暴νFν谱的峰值能量Ep分布,发现伽玛暴的峰值能量Ep分布很宽,不同仪器的Ep分布相似,BATSE样本Ep分布的峰值比HETE-2和Fermi样本的Ep峰值要大一些,这可能是由于选取的BATSE样本都是亮暴造成的。3种仪器观测的Log N-Log Ep分布也没有显著差异。即从统计学的角度上讲,3种暴的Ep分布没有本质不同,不同仪器观测到的伽玛暴的辐射物理信息应该是一致的。 相似文献
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某些伽玛射线暴(简称伽玛暴)的中心致密天体可能是一颗具有强磁场的毫秒脉冲星,它通过磁偶极辐射可对伽玛暴外激波注入能量,从而导致早期余辉光变曲线的变平.近年来,从Swift卫星观测到的大量伽玛暴X射线余辉中发现,很多X射线余辉光变曲线在暴后10~2～10~4s期间的确存在明显的变平现象.利用周期为毫秒量级的磁星能量注入模型对11个加玛暴的X射线余辉光变曲线进行了拟合,显示该模型在解释余辉变平现象上的有效性和广泛性,通过对余辉光变曲线的拟合,同时也给出了相关中心磁星的磁场强度和旋转周期. 相似文献
7.
Swift卫星的X射线望远镜观测揭示部分伽玛暴的早期余辉光变曲线有一个缓慢衰减的成分,而相当一部分却没有这样的成分.研究比较这两种暴的观测性质发现两类暴的持续时间、伽玛辐射总流量、谱指数、谱硬度比峰值能量等物理量均没有显著差异.然而有该成分的那些伽玛暴谱比较软、早期X射线余辉比较弱、伽玛射线辐射效率显著高于没有这个成分的那些暴.结果表明两类暴的前身星和中心机制一致,是否呈现这个缓慢衰减成分可能取决于外部介质. 相似文献
8.
在高能电磁波段,天文探测器的角分辨率较低,面对大量的伽玛射线观测数据时,研究人员需要利用数据分析软件迅速找出一些未知天体的位置。利用2008年发射运行的国际费米伽玛射线空间望远镜(Fermi)的高能伽玛射线数据(100 Me V),对伽玛射线暴(Gamma-ray Burst,GRB)进行了详细的快速精准定位,主要研究了不同时间和能量选择时对天体源的探测置信度的影响。研究结果表明,选择伽玛射线暴触发时间零点(T0)到T0+1 000 s以内的时间范围可以很好地定位伽玛射线暴的高能对应体位置。实验得到的高能伽玛射线TS位置图最佳位置与低能电磁波段的后随观测位置很好地符合,表明实验算法可以有效地计算该类天体伽玛射线暂现源的真实位置。 相似文献
9.
太阳爆发探测小卫星高能暴谱仪 总被引：1，自引：0，他引：1
太阳爆发探测小卫星(Small Explorer for Solar Eruptions,简称SMESE)是中国法国合作小卫星.SMESE计划在下一个太阳活动峰年(-2011年)发射上天,同时观测太阳上两类最剧烈爆发现象:耀斑和日冕物质抛射(CME),瞄准当代科学的前沿课题,同时兼顾空间天气学的应用需要.高能暴谱仪(High Energy Burst Spectrometer,简称HEBS)是太阳爆发探测小卫星上3大主要载荷之一,采用世界最新高能量分辨LaBr3闪烁探测器,观测太阳10 keV-600 MeV的高能辐射.其能量分辨优于3.0%@662 keV,高于目前通用闪烁探测器的2倍以上,可望在耀斑和CMEs的能量释放,粒子加速,以及耀斑和CMEs之间的关系研究方面取得突破. 相似文献
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We study time-resolved spectra of the prompt emission of Swift γ-ray bursts (GRB). Our goal is to see if previous BATSE claims of the existence of a large amount of spectra with the low-energy photon indices harder than 2/3 are consistent with Swift data. We perform a systematic search of the episodes of the spectral hardening down to the photon indices ≤2/3 in the prompt emission spectra of Swift GRBs. We show that the data of the Burst Alert Telescope (BAT) instrument on board of Swift are consistent with BATSE data, if one takes into account differences between the two instruments. Much lower statistics of the very hard spectra in Swift GRBs are explained by the smaller field of view and narrower energy band of the BAT telescope. 相似文献
12.
A. Panaitescu 《Monthly notices of the Royal Astronomical Society》2008,385(3):1628-1634
We calculate the GeV afterglow emission expected from a few mechanisms related to gamma-ray bursts (GRBs) and their afterglows. Given the brightness of the early X-ray afterglow emission measured by Swift /X-Ray Telescope, Gamma-ray Large Area Space Telescope (GLAST)/Large Area Telescope (LAT) should detect the self-Compton emission from the forward shock driven by the GRB ejecta into the circumburst medium. Novel features discovered by Swift in X-ray afterglows (plateaus and chromatic light-curve breaks) indicate the existence of a pair-enriched, relativistic outflow located behind the forward shock. Bulk and inverse-Compton upscattering of the prompt GRB emission by such outflows provide another source of GeV afterglow emission detectable by LAT. The large-angle burst emission and synchrotron forward-shock emission are, most likely, too dim at high photon energy to be observed by LAT. The spectral slope of the high-energy afterglow emission and its decay rate (if it can be measured) allow the identification of the mechanism producing the GeV transient emission following GRBs. 相似文献
13.
The BATSE (Compton Gamma-ray Observatory/Bursts and Transient Source Experiment), Swift (Swift Gamma-ray Burst Explorer) and Fermi (Fermi Gamma-ray Space Telescope) satellites have provided us with a large amount of GRB sample. After a systematical study and comparison of the properties of the GRBs detected by these 3 kinds of instruments, it is found that although significant differences exist in the number of red-shifted bursts, the proportion of long bursts in total bursts and the photon flux distribution (lgN − lg P), but no significant difference exists in the duration time, the total flux of Gamma-ray radiation and the spectral hardness ratio. Considering that the observational energy bands of the Swift- and Fermi-detected bursts are different, after making corrections the difference in the lgN − lg P distribution can be basically eliminated. The differences in the number of red-shifted bursts and the proportion of long bursts in total bursts are caused by the different sensitivities of instruments. Namely, various instruments give different observed characteristics of GRBs, but they are consistent in nature. 相似文献
14.
R. Wijnands E. Rol E. Cackett R. L. C. Starling R. A. Remillard 《Monthly notices of the Royal Astronomical Society》2009,393(1):126-132
We present an analysis of the Swift Burst Alert Telescope (BAT) and X-ray telescope (XRT) data of GRB060602B, which is most likely an accreting neutron star in a binary system and not a gamma-ray burst. Our analysis shows that the BAT burst spectrum is consistent with a thermonuclear flash (type I X-ray burst) from the surface of an accreting neutron star in a binary system. The X-ray binary nature is further confirmed by the report of a detection of a faint point source at the position of the XRT counterpart of the burst in archival XMM–Newton data approximately six year before the burst and in more recent XMM–Newton data obtained at the end of 2006 September (nearly four months after the burst). Since the source is very likely not a gamma-ray burst, we rename the source Swift J1749.4−2807, based on the Swift /BAT discovery coordinates. Using the BAT data of the type I X-ray burst, we determined that the source is at most at a distance of 6.7 ± 1.3 kpc . For a transiently accreting X-ray binary, its soft X-ray behaviour is atypical: its 2–10 keV X-ray luminosity (as measured using the Swift /XRT data) decreased by nearly three orders of magnitude in about 1 day, much faster than what is usually seen for X-ray transients. If the earlier phases of the outburst also evolved this rapidly, then many similar systems might remain undiscovered because the X-rays are difficult to detect and the type I X-ray bursts might be missed by all the sky surveying instruments. This source might be part of a class of very fast transient low-mass X-ray binary systems of which there may be a significant population in our Galaxy. 相似文献
15.
Polarization evolution accompanying the very early sharp decline of gamma-ray burst X-ray afterglows
Yi-Zhong Fan Dong Xu Da-Ming Wei 《Monthly notices of the Royal Astronomical Society》2008,387(1):92-96
In the synchrotron radiation model, the polarization property depends on both the configuration of the magnetic field and the geometry of the visible emitting region. Some peculiar behaviours in the X-ray afterglows of gamma-ray bursts (GRBs) observed with Swift , such as energetic flares and a plateau followed by a sharp drop, might be highly linearly polarized because the outflows powering these behaviours may be dominated by Poynting flux. The breakdown of the symmetry of the visible emitting region may also be well hidden in the peculiar X-ray data and may give rise to interesting polarization signatures. In this paper, we focus on the polarization accompanying the very early sharp decline of GRB X-ray afterglows. We show that strong polarization evolution is possible in both the high latitude emission model and the dying central engine model, which are used to interpret this sharp X-ray decline. It is thus not easy to efficiently probe the physical origin of the very early X-ray sharp decline with future polarimetry. Strong polarization evolution is also possible in the decline phase of X-ray flares and in the shallow decline phase of X-ray light curves characterized by chromatic X-ray versus optical breaks. A detector such as the X-ray Telescope (XRT), but with polarization capability, on board a satellite like Swift would be suitable for testing our predictions. 相似文献
16.
Yi-Qing Lin 《中国天文和天体物理学报》2009,9(6)
The gamma-ray burst (GRB) mission Swift has made a much deeper GRBsurvey than any previous one. I present a systematical comparison between GRB samples detected with pre-Swift missions and those from Swift, in order to investigate whether they show any statistical difference. Our Swift GRB sample includes the bursts detected by Swift/BAT before 2007 September. With both flux-limited surveys and redshift-known GRB samples, I show that, apparently, the observed distributions of the redshifts, T90, and log N-log P are significantly different, but not for the spectral hardness ratio, fluence and Eiso. The redshifts of the Swift GRB sample are statistically larger than those of pre-Swift GRBs, with a mean of 1.95±0.17 compared to ～ 1 for pre-Swift GRBs. The cosmological effect on the observables is thus considerable. This effect on the spectral hardness ratio, fluence and Eiso is cancelled out, and the distributions of these quantities indeed do not show significant differences between the Swift and pre-Swift GRBs. Taking this effect into account, I found that the corrected distributions of T90 for long GRBs and log N - log P observed with Swift/BAT are also consistent with those observed with CGRO/BATSE. These results indicate that the Swift and pre-Swift GRBs are from the same population. 相似文献
17.
J. I. Cabrera C. Firmani V. Avila-Reese G. Ghirlanda G. Ghisellini L. Nava 《Monthly notices of the Royal Astronomical Society》2007,382(1):342-355
We study the spectral and energetics properties of 47 long-duration gamma-ray bursts (GRBs) with known redshift, all of them detected by the Swift satellite. Due to the narrow energy range (15–150 keV) of the Swift -BAT detector, the spectral fitting is reliable only for fitting models with two or three parameters. As high uncertainty and correlation among the errors is expected, a careful analysis of the errors is necessary. We fit both the power law (PL, two parameters) and cut-off power law (CPL, three parameters) models to the time-integrated spectra of the 47 bursts, and we present the corresponding parameters, their uncertainties and the correlations among the uncertainties. The CPL model is reliable only for 29 bursts for which we estimate the ν f ν peak energy E pk . For these GRBs, we calculate the energy fluence and the rest-frame isotropic-equivalent radiated energy, E γ,iso , as well as the propagated uncertainties and correlations among them. We explore the distribution of our homogeneous sample of GRBs on the rest-frame diagram E 'pk versus E γ,iso . We confirm a significant correlation between these two quantities (the 'Amati' relation) and we verify that, within the uncertainty limits, no outliers are present. We also fit the spectra to a Band model with the high-energy PL index frozen to −2.3, obtaining a rather good agreement with the 'Amati' relation of non- Swift GRBs. 相似文献
18.
P. A. Curran A. J. van der Horst R. A. M. J. Wijers 《Monthly notices of the Royal Astronomical Society》2008,386(2):859-863
Gamma-ray burst (GRB) afterglow observations in the Swift era have a perceived lack of achromatic jet breaks compared to the BeppoSAX or pre- Swift era. Specifically, relatively few breaks, consistent with jet breaks, are observed in the X-ray light curves of these bursts. If these breaks are truly missing, it has serious consequences on the interpretation of GRB jet collimation and energy requirements, and the use of GRBs as cosmological tools. Here, we address the issue of X-ray breaks that are possibly 'hidden' and hence the light curves are misinterpreted as being single power laws. We do so by synthesizing X-ray telescope (XRT) light curves and fitting both single and broken power laws, and comparing the relative goodness of each fit via Monte Carlo analysis. Even with the well-sampled light curves of the Swift era, these breaks may be left misidentified, hence caution is required when making definite statements on the absence of achromatic breaks. 相似文献