空间硬X射线望远镜HAPI-1及其对蟹状星云脉冲星的观测

HAPI-1是我国第一个用于空间高能天文观测的硬X射线望远镜系统,由面积145cm~2厚0.5cm的CsI(T1)主探测晶体及其下部厚5cm的NaI(T1)反符合晶体构成复合晶体探测器,采用脉冲形状甄别技术区分两种晶体的输出信号,多种物质构成的夹层式屏蔽筒和准直器使望远镜具有约4°视场角(HWHM),电子学、姿态控制和数据获取系统使望远镜具有对20—200keV能区高能光子到达时刻和能量进行空间定向观测的能力。本文介绍HAPI-1的构成和主要性能,以及1984年5月利用该望远镜在我国高空科学气球上对蟹状星云脉冲星的观测结果。     

脉冲星观测及研究

本文评述了脉冲星的观测研究状况以及列出了北京天文台在232MHz上获得的脉冲星观测结果。     

脉冲星的γ辐射

本文根据Ｒ－Ｓ模型讨论脉冲星的γ辐射，在讨论光子被电磁场吸收时，我们把中子星磁层分成两部分，一部分以电场吸收为主，另一部分以磁场吸收为主。本文以电子在电磁场中的级联过程为基础，计算了Ｃｒａｂ、Ｖｅｌａ等六个已知γ射线脉冲星的一些物理量，发现与观测基本相符。另外我们还预言了一些很可能是γ射线脉冲星的候选者。     

γ射线脉冲星脉冲位相关系的研究

本文分析γ射线脉冲星最近的观测数据，研究各波段辐射位相的一些关联，它们对于揭示γ射线脉冲星的辐射机制可能有重要的意义，     

GLAST——新一代γ射线大面积空间望远镜

据媒体报道,2008年5月,科学家将开启一扇神奇的新窗口来观察宇宙,此即“γ射线大面积空间望远镜”将在美国卡纳维拉尔角肯尼迪航天中心发射升空。它是一颗多国合作完成的科学探测卫星,其英文全称为：Gamma-ray Large Area Space Telescope,缩写为GLAST。GLAST卫星将通过一个从未被人探测过的电磁波频段观察深空高能天体,有望揭开暗物质和其他神秘现象背后的真相。     

γ射线脉冲星的代参数和能谱分析

为了对脉冲星的高能辐射进行研究,根据脉冲星观测的实际情况,重新推导了脉冲星代参数的计算公式.发现脉冲星的代参数与其γ射线能谱有很好的线性相关性,并拟合了代参数和能谱之间的线性关系.     

“费米”眼中的最高能宇宙

题图：由“费米”第一年的数据制作而成的迄今最深、最锐利的γ射线全天图。它显示的是“费米”上的大面积望远镜（LAT）所探测到的毹量大于300兆电子伏或能量高于可见光约1．5亿倍以上的γ射线的分布,颜色越明亮说明γ射线辐射越强。版权：NASA/DOE/Fermi LAT Collaboration。     

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．     

乌鲁木齐天文站脉冲星观测研究新进展

乌鲁木齐天文站自 1 999年研制完成 1 .5GHz频段室温双偏振消色散接收系统。 2 0 0 2年又完成 1 .5GHz频段致冷式双偏振消色散接收系统。我们成功地完成了第一个国际合作协议的任务。为在我国建立高灵敏度的观测脉冲星设备和取得优秀的脉冲星观测结果作出了贡献。为了进一步发展乌站脉冲星观测 ,第二个合作协议包括利用致冷式系统进行脉冲星大样本的监测和建立低频段的基带技术的消色散系统。     

Detectivity of Unidentified Egret Sources as Gamma-Ray Pulsars with the Magic Telescope

Most of the unidentified gamma ray sources detected near the Galactic plane by EGRET aboard CGRO are expected to be gamma ray pulsars. We present a study about the detectability and identification of some unidentified EGRET sources with the MAGIC telescope. We list some unidentified gamma ray sources from the third EGRET catalogue to be detected with MAGIC taking into account some important conditions such as the variability parameter of the source, spectral index, inclusion in the GeV catalogue (ApJ 488, 1997, p. 872) and possible associations with known X-ray/radio sources located within the error box of the unidentified gamma ray source. We show the required observation time of these gamma ray pulsar candidates to be detected by MAGIC telescope considering reasonable values of cut-off energy. To be more realistic, we have chosen the zenith angle corresponding to the source culmination in the simulation of the effective area A since the observation time is function of the effective area. In addition to this study, it is very important to consider the extrapolated EGRET flux at MAGIC energies above 30 GeV of the gamma ray pulsar candidates taking the MAGIC sensitivity.     

类Crab脉冲星的三维磁层外隙模型

利用三维脉冲星磁层模型研究了磁层外隙的几何结构,首先用自治模型确定“外隙”的垂直尺度,在该模型中外隙尺度受回流的外隙流（带有隙加速的带电粒子发射的曲率光子）加热极帽而产生的热光子的碰撞而成对生成所限,外隙的横向尺度也受本地对生成所限,在脉冲星的磁层中,原则上有两个拓扑分离的外隙,允许同时进入和流出粒子,不过,流入粒子流产生的辐射形态受隙了本地对生成和恒星附近的磁对生成的严格制约,根据外隙及其本地结构的三维模型计算了类Crab脉冲星的辐射和相位分解谱。     

In-flight measurement of the absolute energy scale of the Fermi Large Area Telescope

The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to survey the gamma-ray sky from 20 MeV to several hundreds of GeV. In this energy band there are no astronomical sources with sufficiently well known and sharp spectral features to allow an absolute calibration of the LAT energy scale. However, the geomagnetic cutoff in the cosmic ray electron-plus-positron (CRE) spectrum in low Earth orbit does provide such a spectral feature. The energy and spectral shape of this cutoff can be calculated with the aid of a numerical code tracing charged particles in the Earth’s magnetic field. By comparing the cutoff value with that measured by the LAT in different geomagnetic positions, we have obtained several calibration points between ∼6 and ∼13 GeV with an estimated uncertainty of ∼2%. An energy calibration with such high accuracy reduces the systematic uncertainty in LAT measurements of, for example, the spectral cutoff in the emission from gamma ray pulsars.     

Pulsar Radio and Gamma-Ray Emission

A total of eight gamma-ray sources are identified with pulsars and these include some of the strongest gamma-ray sources in the sky. About 20 of the unidentified gamma-ray sources are very likely to be associated with currently known pulsars and there is little doubt that many of the others, at least those at low Galactic latitudes, will ultimately be identified with pulsars. How many of these and future gamma-ray detections will be detectable at radio wavelengths depends on the details of the radio and gamma-ray beaming. There is good evidence that the radio beams in young and millisecond pulsars are very wide, implying that most gamma-ray pulsars will be detectable in the radio band.     

A tool to estimate the Fermi Large Area Telescope background for short-duration observations

The proper estimation of the background is a crucial component of data analyses in astrophysics, such as source detection, temporal studies, spectroscopy, and localization. For the case of the Large Area Telescope (LAT) on board the Fermi spacecraft, approaches to estimate the background for short (≲1000 s duration) observations fail if they ignore the strong dependence of the LAT background on the continuously changing observational conditions. We present a (to be) publicly available background-estimation tool created and used by the LAT Collaboration in several analyses of Gamma Ray Bursts. This tool can accurately estimate the expected LAT background for any observational conditions, including, for example, observations with rapid variations of the Fermi spacecraft’s orientation occurring during automatic repointings.     

On the Characteristic and Dynamic Ages of Pulsars

A method that is independent of the model for the distribution of free electrons in the galaxy is proposed for revealing possible oscillations of pulsars in the direction perpendicular to the galactic plane. Oscillations of pulsars in this direction with a half period of approximately 10⁸ years on the scale of characteristic ages are found by this method, which is independent of the distance scale.     

脉冲星Geminga MeV 脉冲辐射证据

利用直接解调方法分析COMPTELVPI数据,得到了脉冲星Geminga10-30MeV脉冲辐射存在的证据：全位相及分位相成像均得到了Geminga．分位相成像结果显示,光变曲线的峰值位于pulse1附近,而其它位相区域只能给出上限．由于成像分析不存在选择效应,该成像结果表明,Geminga在MeV能区仍存在脉冲辐射．虽然Geminga的弱MeV辐射使得很难就VP1数据作时间分析,但仍得到了一些周期信号的迹象,并且与成像结果不相矛盾．进一步考察EGRET观测Geminga在30MeV以上的强度比Pulse2／Pulse1,发现在VP1观测的较低能区,Pulse1有渐强于Pulse2的趋势,这和我们在MeV能区的成像及时间分析结果相一致．成像得到的流强表明,Geminga的能谱至少在10MeV以上不应出现偏折．     

Spatial Distribution of Pulsars

The spatial distributions of pulsars with ages of less than 10⁶ years and more than 10⁶ years are shown to be quite different. The spatial distributions of pulsars with ages of less than 106 years and of the remnants of supernova outbursts are essentially the same. They lie near the galactic plane in a thin zone of width 400 pc. The overwhelming majority of pulsars with ages exceeding 106 years lie outside this zone. These facts suggest a genetic relationship between pulsars and supernova remnants. The spatial distribution of pulsars with different emission periods also supports this point.