γ射线暴的研究进展（Ⅱ）：γ暴的辐射机制及能谱形成

在中子星作为γ暴源的基础上讨论了各种辐射机制及能谱形成。由于中子星表面磁场很强，我们首先讨论了强磁场中的辐射过程，包括同步辐射和吸收，单光子和双光子的产生和湮灭，康普顿散射，轫致辐射等。     

BATSEγ射线暴和太阳硬X射线暴的强度和时间特征

本文研究了CGRO卫星上BATSE探测器对硬X天空监测过程中触发和记录到的1 0 0 0多个γ暴和 40 0 0多个太阳硬X射线暴的强度和时间性质 ,发现它们的强度分布相似 ,这也许意味着硬X射线天空中两种主要的爆发现象机制相似 ,同时对将γ暴的强度分布作为其宇宙学起源的证据提出了疑问 .对太阳暴的持续时间分析表明 ,其强度和持续时间呈正相关 ,而γ暴是弱负相关 .太阳暴的强度和持续时间在BATSE运行过程中有长时标变化 ,最近对γ暴的研究也发现了这种现象     

BATSEγ射线暴和太阳硬X射线暴的强度和时间特征

本研究了ＣＧＲＯ卫星上ＢＡＴＳＥ探测器对硬Ｘ天空监测过程中触发和记录到的１０００多个γ暴和４０００多个太阳硬Ｘ射线暴的强度和时间性质，发现它们的强度分布相似，这也许意味着硬Ｘ射线天空中两种主要的爆发现象机制相似，同时对将γ暴的强度分布作为其宇宙学起源的证据提出了疑问。     

γ射线暴研究概况

γ射线暴(简称γ暴)的研究自1997年以来由于余辉的发现而有了很大的突破。在此，对γ暴的观测作了简要的概述，而对γ暴的理论进展和存在问题进行了较为全面的评述，内容包括γ暴本身、余辉、能源机制、寄主星系、暴周环境、高能粒子和引力波辐射、宇宙学意义等。     

等时面与γ射线暴余辉

在γ射线暴（ 简称γ暴） 的火球模型下,γ暴余辉存在等时面,面上发射的光子会同时被观测到．通过对等时面积分来计算辐射流量Ｆν（ｔ） ,结果表明等时面的引入对峰值以及峰值前后流量随观测者时间的变化关系有明显的影响     

Ⅰ型X射线暴多峰结构的研究进展

Ⅰ型X射线暴(热核暴)是发生在小质量X射线中子星双星系统中X射线波段流量突然大幅度增加的一种高能现象.在热核闪模型下,此现象被认为主要由中子星表面热核不稳定燃烧主要引起的.典型X射线暴的光变曲线呈现快速上升(1～5 s)、e指数下降(10～100 s)的单峰结构.随着X射线暴样本的增加,在观测上出现了一类多峰结构的热核...     

γ射线暴的研究进展（Ⅰ）：γ暴的观测特征及能源机制

文中评述了过去２０年中对γ暴的观测结果，包括它的时间特性，能谱特征和空间分布。γ暴的时间结构非常复杂，持续时间相关很大，从小于１ｓ到１０００ｓ，平均大约为１５ｓ。     

软伽玛射线再暴体（SGRs）研究进展

对SGRs的主要观测特征－－在软伽玛射线波段的重复爆发及持久性的周期的X射线辐射－－进行了回顾，介绍了SGRs的一些理论模型，其中磁星（具有甚强磁场的中子星）模型较合理地解释了现有的观测事实。     

γ射线暴的研究进展（Ⅳ：特强γ射线暴和软γ重复暴

最近CGRO上的仪器观测到了两个迄今为止发现的最强的λ暴GB930131和GB940217,其光子最高能量均达GeV量级;GB930131的峰值计数率达2×10~6个光子s~(-1);而GB940217的持续时间竟长达90min。另外沉寂了多年的软重复暴源SGR1900 14和SGR1806-20的再次爆发也由BATSE发现。一系列的观测还发现这些软重复暴均与X射线源对应且与超新星遗迹成协。文中对特强暴和软重暴(SGR)的性质及研究进展作了较为详细的评述。     

尘埃消光对伽玛射线暴余辉的影响

为了研究尘埃消光对伽玛射线暴余辉的影响,基于严格的Mie理论和最新的星际尘埃光学性质,进行了高精度的数值计算,并分析具有不同物理参数的尘埃所产生的消光曲线.结果表明,介质密度和金属丰度是决定消光总量的主要物理参数,而尘埃颗粒大小的分布则是产生不同消光曲线轮廓的重要物理参数.如果尘埃颗粒相互聚集形成导致尺度增大,将产生较平或者较灰的消光曲线,同时绝对总量将减少;相反,如果尘埃颗粒由于某种原因发生离解导致尺度变小,将产生较陡的消光曲线,同时消光总量将增加.这些结果将对理解光学暗暴的形成机制提供重要的启示.     

Gamma-ray Burst Afterglows from Cylindrical Jets in a Dense Environment

It is widely accepted that many gamma-ray bursts (GRBs) are produced by relativistic jets. Previous studies on the beaming effects in GRBs are mainly based on the conical geometry. However, some observations of the relativistic jets in radio galaxies, active galactic nuclei, and “micro-quasars” have shown that many of these outflows are cylindrical, but not conical. In this study, we assume that the jets that produce GRBs are cylindrical, and that the circum-burst environment is dense and optically thick. In the prompt burst phase, the strong X-ray emission can sublimate the circum-burst medium to form an optically thin channel, from which the optical photons are allowed to escape. As a result, the optical afterglows can be observed only for the observers who are positioned on the axes of jets. It is shown that the observed optical afterglows usually decay very rapidly (in the form of S_v oc t^^v^^l₁ where p is the index of electron power-law distribution), due to the joint effect of the lateral expansion of the cylindrical jet and the absorption of optical photons by the dust outside the channel. Our model provides a possible explanation for the dark gamma-ray bursts.     

Flare activity and an optical superflare of the X-ray object 1RXS J220111+281849

A UBVR monitoring of the X-ray source 1RXS J220111+281849 was performed during August 2–21, 1999. Seven moderately intense ultraviolet flares with 1–3^m amplitudes were detected. The object exhibits both rapid and slow flares. An unusual superintense flare with an $11\mathop .\limits^m 0$ amplitude in U was detected on August 18, 1999. Light curves of the flares are presented, and their physical parameters are briefly analyzed.     

Gamma射线爆光曲线的一个简单激波模型

采用一个简单的激波模型来讨论了珈玛射线爆光变曲线的轮廓。根据激波理论,爆炸产生压力脉冲并以压力波的形式传播,既有压缩波也有膨胀波。压缩波的合并产生激波,它的强度被随后并入的压缩波或膨胀波分别增强或减弱。该模型能自然地描述珈玛爆光变曲线和光变曲线具有的"快速上升指数下降"的轮廓特征。我们认为这一特征是压缩波和膨胀波的传播特性导致的。     

Polarization in Gamma-Ray Bursts Produced by Pinch Discharge

Large-voltage, high-temperature plasma columns produced by pinch discharge can generate γ-ray flashes with energy spectra and spectral evolution consistent with what are observed in γ-ray bursts (GRBs), and the inverse Compton scattering (ICS) during the discharge process can produce high linear polarization. Our calculation indicates that the observed polarization depends on the angle between the line-of-sight todischarge, but only weakly depends onthe GRB and the direction of the pinch discharge, but only weakly depends on observed γray energy.     

具平缓电子能谱的伽玛射线暴的解析光变曲线

在标准的伽玛暴余辉模型中,电子通过费米一级加速后形成单幂律能谱分布dn/dγe∝γe-p(p≈2.3),但在某些伽玛暴事件中观测到了平缓的电子能谱分布(即p＜2).在单幂律谱和分段幂律谱两种情况下,分别给出了具有平缓电子能谱的伽玛暴余辉的解析光变曲线,并以GRB 060908为例进行了讨论.同时提出了伽玛暴低能谱危机的...     

Fitting X-ray Afterglow Light curves of Gamma-ray Bursts by Using the Magnetar Energy Injection Model

The central compact object for some gamma-ray bursts (GRBs) may be a strongly magnetized millisecond pulsar. It can inject energy to the outer shock of the GRB by through the magnetic dipole radiation, and therefore causes the shallow decay of the early afterglow. Recently, from a large number of GRB X-ray afterglows observed by Swift/XRT(X-ray telescope), it is revealed that many of them exhibit the shallow decay about 10²∼10⁴ s after the burst prompt emission. We have fitted the X-ray afterglow light curves of 11 GRBs by using the energy injection model of a magnetar with the rotation period in the millisecond order of magnitude. The obtained result shows the validity and universality of the magnetar energy injection model in explaining the shallow decay of afterglows, and simultaneously provides some constraints on the magnetic field strength and rotation period of the central magnetar.     

X-ray Lines in Gamma-ray Bursts and Cerenkov Line Mechanism

X-ray emission and absorption features are of great importance in our understanding the nature and environment of gamma-ray bursts (GRBs). So far, iron emission lines have been detected in at least four GRB afterglows. In this paper, the observational properties and physical constraints on materials surrounding GRB sources are reviewed, and several classes of theoretical models are also discussed. We will specially concentrate on the Cerenkov line mechanism, in which the broad iron lines are expected, and a small mass of Fe is required to produce the large line luminosity. In addition, our interpretation can favor the recent jet unified model for different classes of gamma-ray bursts with a standard energy reservoir.     

磁星能量注入模型拟合伽玛射线暴X射线余辉光变曲线

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.