甚高能和超高能γ射线天文观测现状

甚高能和超高能γ射线天文观测对于天体演化和宇宙线起源有很重要的意义。本文介绍了1972年以来在10~(11)—10~(16)eV能区γ射线天文观测的主要结果和观测站的情况,     

高气压式正比管探测效率的模拟计算

用于硬X射线的天文观测的充氙气高气压式正比计数管,对进入管中不同能量X射线的响应比较复杂,但能量响应(或探测效率)是归算天体观测能谱不可缺少的基本数据。本文对为气球观测用的一个具体正比管结合其实验数据给出了探测效率的模拟计算结果。     

双漏模式中的弥散宇宙γ射线

弥散宇宙γ射线产生于初级宇宙线的传播过程,本文利用宇宙线传播的“双漏模式”得出与实验观测谱接近的银河系弥散宇宙γ射线谱。     

暗物质空间探测器BGO量能器的读出设计

暗物质空间探测器是中国科学院紫金山天文台暗物质空间天文实验室提出的,其目的是为了探测暗物质粒子湮灭可能产生的高能电子和伽玛粒子.整个探测器主要由BGO(Bismuth germanate,锗酸铋)高能图像量能器和闪烁体径迹探测器构成.探测器的能量探测范围将覆盖10 GeV到10 TeV的高能电子和伽玛粒子,其中高能粒子的能量主要沉积在BGO量能器中.为了验证探测器方案,紫金山天文台暗物质空间天文实验室设计了暗物质空间探测器BGO量能器的读出系统原型,并对其进行了初步的测试.     

神舟二号飞船搭载的超软X射线探测器和γ射线探测器初步观测结果

1　科学使命和仪器概况2 0 0 1年 1月 1 0日 ,由中国科学院紫金山天文台研制的超软Ｘ射线探测器和γ射线探测器随神舟二号飞船发射升空并于 1月 1 4日成功投入空间观测 .半年以来 ,两台仪器工作性能稳定 ,遥测参数正常 ,下传的科学数据质量良好 ,完全达到了设计要求 ,并已观测到若干宇宙Ｘ和γ射线爆发事例 ,取得了很有价值的科学数据 .空间天文分系统是载人航天工程空间科学与应用系统的重要组成部分 .它由宽能段、高时间分辨的 3台船载仪器组成 ,并能够相互联合、同步触发观测 .其中 ,超软Ｘ射线探测器的探测能段为 0 .2～ 2ｋｅＶ ,Ｘ射…     

一种低噪声硅微条探测器读出电子学系统的设计

硅微条探测器空间分辨率高、工作性能稳定, 广泛地应用于空间高能粒子探测领域. 如费米gamma射线空间望远镜(Fermi Gamma-ray Space Telescope, FGST)以及阿尔法磁谱仪(Alpha Magnetic Spectrometer 2, AMS-02)的径迹探测器中都采用了高位置分辨率的硅微条探测器. 基于硅微条探测器在空间观测领域的应用前景, 针对硅微条探测器单元设计了一套低噪声的电子学读出系统. 整个电子学系统分为前端电子学、数据获取电路和上位机软件. 前端电子学为提高集成度, 采用了一款电荷读出芯片VATAGP8, 实现了多通道、低噪声的电荷信号测量; 数据获取电路使用现场可编程门阵列(Field Programmable Gate Array, FPGA)实现了对前端电子学的时序控制以及对测量信号的采集控制; 上位机用来接收、处理数据获取电路采集的信号数据. 在对电子学通道的线性、基线、噪声等性能进行测试之后, 得到系统在0--200fC电荷输入范围内的线性增益约为13.41bin/fC, 积分非线性小于1%, 噪声小于0.093fC. 为了验证电子学读出系统对硅微条探测器单元的读出能力, 将两者集成在一起并测试了宇宙线缪子的能量沉积, 得到读出电子学系统的信噪比大于32, 缪子的电离损失能谱与Landau-Gaussian分布符合较好, 能够满足硅微条探测器单元读出电子学的设计要求.     

我国4300 m高度上的高能宇宙线研究

随着γ射线天文学的兴起，10年前在西藏高原海拔4300m的羊八井谷地，出现并成长着一个国际知名的宇宙线实验站。其中日合作的ASγ阵列在国际同类实验中，首先观测到了蟹状星云的Multi-TeV稳定γ射线发射及活动星系核Mrk 501在1997年、Mrk 421在2000年的Multi-TeVγ射线强爆发，独家测出了反映太阳和行星际磁场状态的宇宙线太阳阴影的偏移并将之用于太阳活动变化的监测，利用高海拔优势及乳胶室和Burst，探测器与阵列的联合实验进行了超高能宇宙线能谱和成分的研究。以高阻板探测器(RPC)地毯式阵列迈入≈100GeV空白能区的中意合作ARGO(Astroparticle physics Researchat Ground-based Observatory)计划，已进入大规模安装调试阶段。欲牢固占领Multi-GeV-TeV能区和满足对高可变、大峰流、短时标河外γ源的观测所需的高海拔巨型大气契仑可夫光成像望远镜计划5@YorG，也正在酝酿之中。     

暗物质粒子探测卫星的能量重建和宇宙线质子能谱的分析

宇宙线的观测研究和暗物质粒子的间接探测是高能天体物理领域两个重大研究课题. 自1912年V. Hess发现宇宙线开始, 人类对宇宙线的观测历史已经超过了一个世纪, 传统理论模型预言``膝''区以下能段的宇宙线能谱应服从单一幂率分布, 而近些年的空间和高空气球实验表明10 GeV--100 TeV的宇宙线质子能谱可能存在偏离单一幂律谱分布的重要结构, 这对研究银河系内宇宙线的起源、传播和加速机制具有重要意义. 另一方面, 得益于宇宙线和伽马射线观测精度的提高和观测能段的拓宽, 暗物质粒子的间接探测在国际上受到越来越多的关注, 暗物质粒子可能会发生湮灭或衰变产生稳定的普通高能粒子, 包括正负电子对、正反质子对、伽马射线和中微子等, 进而在宇宙线或伽马射线留下可探测的信号.     

基于暗物质粒子探测卫星的宇宙线直接探测研究

高能宇宙线的起源、加速和传播是重大的前沿科学问题,回答该问题需要对宇宙线的能谱、各向异性以及各类高能天体电磁辐射进行精确观测.通过空间粒子探测器对宇宙线各成分能谱的直接测量是研究宇宙线物理问题的重要手段.中国于2015年底发射并持续运行至今的暗物质粒子探测卫星以其大接受度、高能量分辨率等特点,在宇宙线直接探测方面取得了系列重要成果,揭示出质子、氦核、硼碳和硼氧比例等宇宙线能谱的新结构,为理解宇宙线起源等科学问题提供了新的依据.介绍了暗物质粒子探测卫星的仪器设置、运行状况、科学成果及其物理意义.     

来自天体的X射线——伦琴X射线天文卫星的一些重要发现

１９９８年９月２０日,伦琴Ｘ射线天文卫星（ＲＯＳＡＴ）在指向转换过程中扫过太阳附近,结果来自太阳的强烈Ｘ射线烧毁了其上的高分辨成像仪（ＨＲＩ）。此后,在１９９８年１２月,ＲＯＳＡＴ上的另一个主要探测器位置灵敏正比计数器（ＰＳＰＣ）利用剩余的少量气体进...     

A study of secondary cosmic ray flux variation during the annular eclipse of 15 January 2010 at Rameswaram, India

The gamma ray flux was measured during the annular solar eclipse on January 15, 2010 at Rameswaram, India using NaI (Tl) scintillator detectors and the variation in charged particles and gamma rays was monitored using Geiger Mu¨ller (GM) counters. The gamma ray flux variation was studied in energy range of 0.1–3.5 MeV. Weather parameters (temperature and humidity) were continuously recorded throughout the duration of the eclipse at the site and correlation between gamma ray flux and weather parameters was examined. Analysis of the secondary cosmic ray flux using Fast Fourier Transform (FFT) was carried out to study the impact of the eclipse on the flux modulation. An overall decrease in flux was observed by both GM counters and scintillator detectors. A relative enhancement observed for short time during the eclipse which could be associated with the presence of counter electrojet observed at Rameswaram. This is suggestive of an increase in secondary cosmic ray flux at the geomagnetic equator during every counter electrojet due to decrease in geomagnetic rigidity.     

The global structure of the interstellar medium

In the context of a review of work on the global structure of the interstellar medium, supernova remnant evolution, flows in multiphase media, cosmic ray moderation of flows, theories of the Galactic halo gas, and the nature of the local superbubble are considered. Speculations about the nature of a one parameter fully self-consistent model of the interstellar medium-supernova-radiation and cosmic ray background system are offered.     

The composition of the cosmic radiation and the atomic properties of the elements

The composition of the primordial cosmic radiation has been compared with the solar system composition and that of interstellar matter. It is found that the overabundance of an element in the radiation is approximately proportional to the cross-section for the ionization of neutral atoms of that element through fast charged particle impacts. The results strongly support the assumption that the selection of cosmic ray particles is governed by the atomic properties of the elements.     

Measurement of the absolute intensity of cosmic X-rays

The intensity of the diffuse component of cosmic X-rays was measured with use of a rotating collimator system borne on a sounding rocket. A part of background counts proportional to the field of view of proportional counters enabled us to determine the intensity of the diffuse component to be 0.66±0.07 photons cm^–2 sec^–1 keV^–1 in the energy range between 3.6 and 9.0 keV. The spectrum in this energy range was found to be comparatively flat. The intensity of Sco X-1 was also measured and its time variation was investigated.     

On the Relationship of the 27-day Variations of the Solar Wind Velocity and Galactic Cosmic Ray Intensity in Minimum Epoch of Solar Activity

We study the relationship of the 27-day variations of the galactic cosmic ray intensity with similar variations of the solar wind velocity and the interplanetary magnetic field based on observational data for the Bartels rotation period # 2379 of 23 November 2007 – 19 December 2007. We develop a three-dimensional (3-D) model of the 27-day variation of galactic cosmic ray intensity based on the heliolongitudinally dependent solar wind velocity. A consistent, divergence-free interplanetary magnetic field is derived by solving Maxwell’s equations with a heliolongitudinally dependent 27-day variation of the solar wind velocity reproducing in situ observations. We consider two types of 3-D models of the 27-day variation of galactic cosmic ray intensity, i) with a plane heliospheric neutral sheet, and ii) with the sector structure of the interplanetary magnetic field. The theoretical calculations show that the sector structure does not significantly influence the 27-day variation of galactic cosmic ray intensity, as had been shown before, based on observational data. Furthermore, good agreement is found between the time profiles of the theoretically expected and experimentally obtained first harmonic waves of the 27-day variation of the galactic cosmic ray intensity (with a correlation coefficient of 0.98±0.02). The expected 27-day variation of the galactic cosmic ray intensity is inversely correlated with the modulation parameter ζ (with a correlation coefficient of −0.91±0.05), which is proportional to the product of the solar wind velocity V and the strength of the interplanetary magnetic field B (ζ∼VB). The high anticorrelation between these quantities indicates that the predicted 27-day variation of the galactic cosmic ray intensity mainly is caused by this basic modulation effect.     

Gamma-ray probe of cosmic ray pressure in galaxy clusters and cosmological implications

Cosmic rays produced in cluster accretion and merger shocks provide pressure to the intracluster medium (ICM) and affect the mass estimates of galaxy clusters. Although direct evidence for cosmic ray ions in the ICM is still lacking, they produce γ-ray emission through the decay of neutral pions produced in their collisions with ICM nucleons. We investigate the capability of the Gamma-ray Large Area Space Telescope ( GLAST ) and imaging atmospheric Čerenkov telescopes (IACTs) for constraining the cosmic ray pressure contribution to the ICM. We show that GLAST can be used to place stringent upper limits, a few per cent for individual nearby rich clusters, on the ratio of pressures of the cosmic rays and thermal gas. We further show that it is possible to place tight (≲10 per cent) constraints for distant  ( z ≲ 0.25)  clusters in the case of hard spectrum, by stacking signals from samples of known clusters. The GLAST limits could be made more precise with the constraint on the cosmic ray spectrum potentially provided by IACTs. Future γ-ray observations of clusters can constrain the evolution of cosmic ray energy density, which would have important implications for cosmological tests with upcoming X-ray and Sunyaev–Zel'dovich effect cluster surveys.     

高海拔宇宙线观测站LHAASO概况

宇宙线发现百年以来,宇宙线起源仍然是一个谜.研究宇宙线起源主要在甚高能(VHE)伽马射线天文学和宇宙线物理学两个领域交叉展开.新一代高海拔宇宙线观测站(LHAASO)拥有高海拔、全天候和大规模优势,利用多种探测手段对宇宙线开展联合观测,大幅提升对伽马射线和宇宙线的鉴别能力. LHAASO将开展全天区伽马源扫描搜索以大量发现新伽马源,将获得30 TeV以上伽马射线探测的最高灵敏度,将在宽达5个数量级的能量范围内精确测量宇宙线分成份能谱,为揭开宇宙线起源谜团给出重要判据.系统介绍了LHAASO的探测器结构、性能优势和科学目标.     

Lyman-α production by suprathermal protons

At sufficiently low energies, cosmic ray protons capture electrons from interstellar Hi and become neutral. In the subsequent cascade to the ground state a Doppler-shifted Ly- photon may be emitted. The neutral cosmic ray will be excited collisionally by further encounters with the ambient interstellar gas, emitting additional Doppler-shifted Ly- photons. We give the form of the cosmic ray spectrum down to 10 keV, assuming that there is no cosmic ray injection below 1 MeV. The neutral fraction is evaluated as a function of energy, and the diffuse ultraviolet flux is calculated. Comparison is made with observations in the range 1225–1340 Å. We conclude that far more stringent limits on the flux of subcosmic rays may be obtained by consideration of the heating and ionization of Hi regions.     

Investigation of the relative abundance of one-fold neutrons in an incident flux of the cosmic rays from neutron monitors data

The behaviour of relative content of one-fold neutrons in the incident flux of cosmic rays during Forbush-decreases and solar cosmic ray flares is considered based on the network of cosmic ray stations. The barometric dependence of this value on the network of cosmic ray stations. The barometric dependence of this value on the latitude and see level altitude of a cosmic ray station is obtained.     

Production spectrum of gamma rays in interstellar space through neutral pion decay

We have obtained a simple representation to the observed invariant cross-section for the production of neutral pions in proton-proton collisions. Making use of this representation, we have calculated the differential and integral production spectra of gamma rays in the Galaxy from interactions of cosmic ray nuclei with interstellar gas. It is shown that the uncertainties in deducing interstellar proton spectrum by demodulating the observed spectrum do not affect very much the gamma ray spectrum. We have also determined the gamma ray production spectrum through bremsstrahlung process for a typical interstellar electron spectrum derived from the radio spectrum in the Galaxy. From these, the total gamma ray production spectrum resulting from the interaction of cosmic rays with interstellar matter is compared with the observed gamma ray spectrum in the Galaxy and some inferences have been obtained. We also point out the possible uncertainty in the present calculation and suggest the improvements needed.