一种改进的恒星辐射流体动力学方程

本文将本文作者发展的辐流体动力学方程精细化了，在新的理论公式中，描述物质与辐射场的热力学变量被彻底分开了，这不仅使得理论自身内部更为一致，也给变星脉动理论计算带来方便，本文亦证明了新老理论是相容的。     

预报第23周平滑月平均太阳黑子数的一种方法

利用已知的22个完整太阳活动周平滑月平均黑子数的记录，对正在进行的太阳周发展趋势给出了预测方法，并应用于第23周，同时与其他预报方法的结果进行了比较。     

Geminga 多波段研究的新进展

简要介绍了特殊天体Ｇｅｍｉｎｇａ的发现、证认、定位和距离测量等工作,详细综 了近年来有关Ｇｅｍｉｎｇａ低频射电辐射和高能辐射的观测进展以及人们对这些结果的理论解释。Ｇｅｍｉｎｇａ是否代表一类没有射电辐射的射电脉冲星（辐射能由转动能量而来的非吸积型脉冲星）,理论上具有重要意义,以前人们在高于１０３ＭＨｚ的射电波段对Ｇｅｍｉｎｇａ做过多次高灵敏度观测,都没有测到有意义。以前人们在高于１０３ＭＨｚ的射电     

γ射线脉冲星的辐射光度

本文以极冠模型为基础,计算了脉冲星γ射线辐射光度,指出对不同的脉冲星必须考虑辐射立体角和可见辐射区对观测光度的影响．考虑了这些观测效应后,计算的光度和观测值基本符合．预言了一些可能的γ射线脉冲星,并对其性质进行了研究．     

脉冲星辐射区结构研究

为了研究脉冲星本质与磁层动力学过程,如何从观测限定脉冲星辐射区域的部位和几何结构是其中一个基本且关键的问题.介绍了目前各种脉冲星辐射区几何限定方法的主要思想和结果,并对其异同和各自的优势作了比较和评述;根据已有的限定结果总结了其对辐射束结构、加速区模型和射电辐射机制等理论问题研究的帮助和启示;从各种方法的发展过程来看,完善能够限定脉冲星多波段辐射区域三维结构的方法,并与辐射区和加速区等理论问题的研究更紧密地结合是该领域的重要发展方向.     

叠加在微波Ⅳμ型大爆发上的尖峰辐射

本概述了１９８８年１２月１６日特大微波Ⅳμ型爆发的观测特征，以及由ＭＨＤ调制磁流管的磁场强度产生准周期振荡，一部分高能电子被磁场俘获，作同步加速回旋辐射，产生微微汉Ⅳμ型爆发，另一部分高能电子以一定入射角喷注在磁拱上，形成螺距角各向异性的空心束分布，从而激发出电子回旋脉泽辐射（ＥＣＭ），它们的垂直分量的能量便产生了尖峰辐射，叠加在Ⅳμ型爆发之上，结合怀柔的太阳磁场图，采用双极磁场模型，作出了定理     

河外星际尘埃辐射对微波背景辐射的影响

本文借助于观测到的大、小麦哲伦云的星际尘埃辐射，估计总星系内的“冷”星际尘埃热再辐射对宇宙微波背景辐射的影响．结果表明：总星系内的星际“冷”尘埃的热辐射所形成的背景辐射对微波背景辐射的扰动强烈地依赖于宇宙减速因子和“冷”尘埃量，在宇宙背景探测者（ＣＯＢＥ）的观测结果的限制下，无论宇宙减速因子取何种值，“冷”尘埃所占的比例都是非常少的，如果Ｏｓｔｒｉｋｅｒ所作的平均每个星系内由尘埃产生的蓝光光深τＢ＝０．５的假定是合理的，那么星际尘埃量随温度的分布是非常不均匀的。     

Gravitational microlensing of gamma-ray bursts at medium optical depth

Gravitational lensing of a gamma-ray burst (GRB) by a single point mass will produce a second, delayed signal. Several authors have discussed using microlensed GRBs to probe a possible cosmological population of compact objects. We analyse a closely related phenomenon: the effect of microlensing by low to medium optical depth in compact objects on the averaged observed light curve of a sample of GRBs. We discuss the cumulative measured flux as a function of time resulting from delays caused by microlensing by cosmological compact objects. The time-scale and curvature of this function describe unique values for the compact object mass and optical depth. For GRBs with durations larger than the detector resolution, limits could be placed on the mass and optical depth of cosmological compact objects. The method does not rely on the separation of lensed bursts from those that are spatially coincident.     

Cosmic Gamma-Ray Bursts

Since their discovery in 1973, Gamma-Ray Bursts (GRBs) have remained for many years one of the most elusive mysteries in High Energy-Astrophysics. Despite the fact that ∼800 GRBs are detected every year in the full sky, only a few of them can be localized accurately to less than half a degree. Thus the main problem regarding the nature of GRBs has usually been the lack of knowledge of their distance scale. For many years, follow-up observations by other satellites and ground-based telescopes were conducted, but no counterparts at other wavelengths were found. The breakthrough took place in 1997, thanks to the observation by BSAX and RXTE of the fading X-ray emission that follows the more energetic gamma-ray photons once the GRB event has ended. This emission (the afterglow) extends at longer wavelengths, and the good accuracy in the position determination has led to the discovery of the first counterparts at other wavelengths, greatly improving our understanding of these puzzling sources. Now it is widely accepted that GRBs originate at cosmological distances but the central engines that power these extraordinary events remain still unknown. This revised version was published online in July 2006 with corrections to the Cover Date.     

Are there cosmological evolution trends on gamma-ray burst features?

The variability of a gamma-ray burst (GRB) is thought to be correlated with its absolute peak luminosity, and this relation had been used to derive an estimate of the redshifts of GRBs. Recently, Amati et al. presented the results of spectral and energetic properties of several GRBs with known redshifts. Here, we analyse the properties of two groups of GRBs: one group with known redshift from afterglow observation and another group with redshift derived from the luminosity–variability relation. We study the redshift dependence of various GRBs features in their cosmological rest frames, including the burst duration, the isotropic luminosity and radiated energy, and the peak energy E_p of ν F _ν spectra. We find that, for these two groups of GRBs, their properties are all redshift-dependent, i.e. their intrinsic duration, luminosity, radiated energy and peak energy E_p are all correlated with the redshift, which means that there are cosmological evolution effects on gamma-ray burst features, and this can provide an interesting clue to the nature of GRBs. If this is true, then the results also imply that the redshift derived from the luminosity–variability relation may be reliable.     

The Synchrotron-self-Compton Radiation Accompanying Shallow Decaying X-Ray Afterglow： the Case of GRB 940217

High energy emission (> tens MeV) of Gamma-Ray Bursts (GRBs) provides an important clue on the physical processes occurring in GRBs that may be correlated with the GRB early afterglow. A shallow decline phase has been well identified in about half of Swift Gamma-ray Burst X-ray afterglows. The widely considered interpretation involves a significant energy injection and possibly time-evolving shock parameter(s). We calculate the synchrotron-self-Compton (SSC) radiation of such an external forward shock and show that it could explain the well-known long term high energy (i.e., tens MeV to GeV) afterglow of GRB 940217. We propose that cooperation of Swift and GLAST will help to reveal the nature of GRBs.     

Gamma-ray bursts from stellar remnants: probing the Universe at high redshift

A gamma-ray burst (GRB) releases an amount of energy similar to that of a supernova explosion, which combined with its rapid variability suggests an origin related to neutron stars or black holes. Since these compact stellar remnants form from the most massive stars not long after their birth, GRBs should trace the star formation rate in the Universe; we show that the GRB flux distribution is consistent with this. Because of the strong evolution of the star formation rate with redshift, it follows that the dimmest known bursts have z  ∼ 6, much above the value usually quoted and beyond the most distant quasars. This explains the absence of bright galaxies in well-studied GRB error boxes. The increased distances imply a peak luminosity of 8.3 × 10⁵¹ erg s⁻¹ and a rate density of 0.025 per million years per galaxy. These values are 20 times higher and 150 times lower, respectively, than are implied by fits with non-evolving GRB rates. This means either that GRBs are caused by a much rarer phenomenon than mergers of binary neutron stars, or that their gamma-ray emission is often invisible to us due to beaming. Precise burst locations from optical transients will discriminate between the various models for GRBs from stellar deaths, because the distance between progenitor birth place and burst varies greatly among them. The dimmest GRBs are then the most distant known objects, and may probe the Universe at an age when the first stars were forming.     

Gamma-ray bursts, ultra-high-energy cosmic rays, and cosmic gamma-ray background

We argue that gamma-ray bursts (GRBs) may be the origin of the cosmic gamma-ray background radiation observed in the GeV range. It has theoretically been discussed that protons may carry a much larger amount of energy than electrons in GRBs, and this large energy can be radiated in the TeV range by synchrotron radiation of ultra-high-energy protons ( 10²⁰ eV). The possible detection of GRBs above 10 TeV suggested by the Tibet and HEGRA groups also supports this idea. If this is the case, most of TeV gamma-rays from GRBs are absorbed in intergalactic fields and eventually form GeV gamma-ray background, whose flux is in good agreement with the recent observation.     

Gamma-Ray Bursts: Should cosmologists care?

Gamma-Ray Burst (GRB) locations are distributed isotropically on the sky, but the intensity distribution of the bursts seems clearly incompatible with spatial homogeneity. Of the scenarios that attempt to provide an explanation, there are two that enjoy current popularity: (1) GRBs are produced by high-velocity neutron stars that have formed an extended (100 kpc) spherical halo or corona around our galaxy. (2) The bursters are at cosmological distances, with redshifts near unity for the weaker events. The major evidence used to argue for or against each of these scenarios remains inconclusive. Assuming, not unreasonably, that the cosmological scenario is correct, one can discuss the advantages and disadvantages of studying GRBs as opposed to other objects at moderate redshift. We find that the advantages of GRBs-high intensity, penetrating radiation, rapid variability, and no expected source evolution-are offset by observational difficulties pertaining to the extraction of cosmological information from GRB data. If the cosmological scenario proves to be correct and if the observational difficulties are overcome, then cosmologists certainly should care.     

The Prompt Ultraviolet/Soft X-ray Emission of GRBs

We discuss the prompt emission of gamma-ray bursts (GRBs), allowing for γγ pair production and synchrotron self-absorption. The observed hard spectra suggest heavy pair-loading in GRBs. The re-emission of the generated pairs results in the energy transmission from high-energy gamma-rays to long-wavelength radiation. Due to strong self-absorption, the synchrotron radiation by pairs is in optically thick regime. Thus, the re-emission would appear as a thermal-like spectral bump in the extreme-ultraviolet/soft X-ray band, other than the peak from the main burst. The confirmation of the thermal-like feature and the double-peak structure by future satellites, such as Swift, would indicate that the dominant radiation mechanism in GRBs is synchrotron rather than inverse-Compton radiation.     

GRBs search results with the ARGO-YBJ experiment operated in scaler mode

The ARGO-YBJ experiment is almost completely installed at the YangBaJing Cosmic Ray Laboratory (4300 m a.s.l., Tibet, P.R. China). The lower energy limit of the detector (E∼1 GeV) is reached with the scaler mode, i.e., recording the single particle rate at fixed time intervals. In this technique, due to its high altitude location and large area (∼6700 m²), this experiment is the most sensitive among all present and past ground-based detectors. In the energy range under investigation, signals due to local (e.g. solar GLEs) and cosmological (e.g. GRBs) phenomena are expected as significant enhancements of the counting rate over the background. Results on the search for GRBs in coincidence with satellite detections are presented. For the ARGO-YBJ Collaboration.     

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.