即将发射的"雨燕"天文观测卫星

2004年11月，“雨燕”(Swift)卫星计划由德尔他-2火箭发射升空，进入到低地球轨道(LEO)。Swift是观测γ射线暴(GRB)快速反应的天文卫星，用于对GRB进行研究。它可观测GRB及其在γ射线、X射线、紫外线和可见光波段中的余辉。     

日本天文-H卫星升空后不久失联

1 项目背景 日本自20世纪70年代中期开始,就以日本宇宙航空研究开发机构下属的宇宙科学研究所(ISAS,原文部省宇宙科学研究所)为核心开始研发和应用以X射线天文卫星为主的天文卫星.1976-2005年,日本共发射了7颗X射线天文卫星,其中5颗发射成功,按预定计划执行了一系列观测任务,取得了不斐的成绩.如:利用天文-D于1993年4月5日成功捕获到了刚发现的M81银河系的超新星SN1993放射出的X射线;利用2005年发射的天文-E2卫星配备的软X射线望远镜(SXT)所进行的一系列观测活动,不仅大幅拓展了观测范围(从原来的软X射线拓展到软γ射线),而且发现了距地球较近(8000万光年)处的黑洞,对人类了解宇宙结构、掌握宇宙全貌、厘清宇宙进化发挥了重要作用.     

法国、苏联联合研制天文观测平台

1984年2月,法国与苏联完成了联合设计 x 射线和γ射线观测装置的任务,该装置拟定安装在苏联改进的金星飞行器上,以进行天文观测飞行。法国负责提供γ射线望远镜,苏联负责研制 x 射线探测装置。     

宇宙探索简史 观测天文学的诞生

正天文学发展遵循"观测-理论-观测"的途径,不断把人类的视野伸展到宇宙的新的深处。所以观测手段是探索宇宙奥秘的重要手段,由此逐渐形成了观测天文学。观测天文学是天文学的一个分支,常用于取得数据以与天文物理学的理论比对,或以测量所得的物理量解释模型的含义。在实物上,通过望远镜或其它天文仪器的使用来观测目标。伽利略被人们称为"现代观测天文学之父"。     

未来的天文卫星

1989年,美国研制的,价值12亿美元的哈勃空间望远镜将进入太空,开始它历时15年的探测使命。哈勃望远镜能使用可见光、近紫外线/红外线(1200～11000埃)进行观测,能为理论宇宙学家、行星际专家等所有的天文学家提供极为丰富的数据。哈勃望远镜的发射将标志天文卫星发展到一个崭新阶段。今后10年,人们将发射各种类型的自由飞行天文卫星,采用各种观测技术,探测宇宙中大量的γ射线,x射线、紫外线、红外线、微波以及无线电波,因此天文科学将会有新的发展。     

大气中子感生的γ射线本底

大气中子同探测器物质相互作用产生的γ射线,往往成为一些X、γ射线探测器本底计数的重要组成部分。如何减少这部分本底的强度以增加探测器的观测灵敏度,是空间天文实测工作中一个重要课题。本文介绍一个附有中子屏蔽物质的小型背附探测器系统及其在气球上的飞行观测结果。结果表明,3cm厚的纯石蜡屏蔽层不仅不能减少本底,而且可能有相反的效果。      

美国发射高能天文观测卫星—3

9月20日,美国航宇局的HEAO-3科学卫星(高能天文观测卫星)在肯尼迪空间中心成功地用宇宙神-人马座运载火箭发射入轨。这是高能天文观测卫星系列中的最后一颗星。 HEAO-3的任务与它的两个先驱星稍有不同。HEAO-3和HEAO-2用以测量X-射线和寻找X-射线源,而HEAO-3将用来探测X-射线     

美国发射“γ射线大面积空间望远镜”

2008年6月,美国用德尔他-2火箭成功发射“γ射线大面积空间望远镜”(GLAST)。GLAST高为2.8m,直径为2.5m,发射质量为4277kg,运行在高550km、倾角为28.5°、周期为95min的圆轨道上。它是新一代γ射线天文探测卫星,其性能比在1991-1999年运行的“康普顿”γ射线观测台(CGRO)有很大     

多头锗空间γ谱仪探测效率的提高

在γ谱线天文观测中采用多头锗晶体作为γ谱仪中的中心探测器,以提高探测器的观测灵敏度。本文以一个九头高纯锗探测器系统为实例,用蒙特卡洛模拟方法,分析了入射光子在各晶体中的能损分配和各类效率的比例,给出在几种晶体输出幅度组合相加情况下,探测的全能峰效率可提高的份额。并用较完整的模型对单个晶体的模拟结果与实测结果进行了详细讨论。      

"赫歇尔"和"普朗克"天文卫星将揭开宇宙秘密

1 引言 2008年7月,阿里安-5火箭将从法属圭亚那库鲁发射场,发射欧洲航天局2个先进的空间天文观测台--"赫歇尔"(Herschel,见图1)和"普朗克"(Planck,见图2).     

Gamma rays from giant-molecular clouds

An examination of the evidence favouring the detection of gamma rays from the irradiation of giant molecular clouds by cosmic rays is given. Data relevant to specific nearby clouds are studied in some detail and the evidence favouring some of the so-called gamma ray sources being due to the irradiation of these and more distant clouds is critically assessed. The need for enhancement of cosmic ray intensity in some clouds is discussed. The relevance of this work to interpretation of current and planned X-ray measurements as well as future gamma-ray space missions is discussed.     

Multiwavelength spectral models for SNR G347.3-0.5 from non-linear shock acceleration

The remnant G347.3-0.5 exhibits strong shell emission in the radio and X-ray bands, and has a purported detection in the TeV gamma-ray band by the CANGAROO-II telescope. The CANGAROO results were touted as evidence for the production of cosmic ray ions, a claim that has proven controversial due to constraining fluxes associated with a proximate unidentified EGRET source 3EG J1714-3857. HESS has now seen this source in the TeV band. The complex environment of the remnant renders modeling of its broadband spectrum sensitive to assumptions concerning the nature and parameters of the circumremnant medium. This paper explores a sampling of reasonable possibilities for multiwavelength spectral predictions from this source, using a non-linear model of diffusive particle acceleration at the shocked shell. The magnetic field strength, shell size and degree of particle cross-field diffusion act as variables to which the radio to X-ray to gamma-ray signal is sensitive. The modeling of the extant data constrains these variables, and the potential impact of the recent HESS detection on such parameters is addressed. Putative pion decay signals in hard gamma-rays resulting from hadronic interactions in dense molecular clouds are briefly discussed; the requisite suppression of the GeV component needed to accommodate the 3EG J1714-3857 EGRET data provides potential bounds on the diffusive distance from the shell to the proximate clouds.     

Very high energy gamma-ray sources

A brief review of very high energy gamma-ray astronomy achievements is presented. The results of observations of the Crab nebula, the Cygnus X-3, Vela pulsar, radiogalaxy Centaurus A and 2CG 195+4 show that all these objects are the sources of very high energy gamma-quanta. The most powerfull source is Cygnus X-3. Its gamma-ray luminosity is no less than 3·10³⁷ erg.s⁻¹. The upper limit of quanta energy is no less than 10¹⁶eV. All sources are variable in different time scales, from milliseconds up to years. The nature of all these sources is not known yet, but known ones are pulsars.     

Organic molecules in the gas phase of dense interstellar clouds.

Since a previous COSPAR review on this subject, the number of molecular species identified by astronomers in dense interstellar clouds or in the envelopes expelled by evolved stars has grown from about eighty to approximately one hundred. Recent detections in stellar envelopes include the radical CP, the second phosphorus-containing astronomical molecule; SiN, the first astronomical molecule with a Si-N bond; and the HCCN radical. In the dense interstellar clouds recent detections or verifications of previous possible identifications include the H3O+ ion, which is a critical intermediary in the production of H2O and O2; the CCO radical, which is isoelectronic with HCCN; the SO+ ion, which appears to be diagnostic of shock chemistry; two new isomers of cyanoacetylene, HCCNC and CCCNH; and the two cumulenes H2C3 and H2C4. Some recent work is also described on the mapping of interstellar clouds in multiple molecular transitions in order to separate variations in chemical abundance from gradients in physical parameters.     

Large scale distribution of the [CII] fine structure line in the galaxy — ISAS/UA galactic plane survey by balloon

An extensive survey of [CII] line emission has been made by using balloon borne telescopes incorporated with a liquid helium cooled Fabry-Perot spectrometer. The observations cover major part of the galactic plane in the first and fourth quadrants as well as some typical HII regions/molecular clouds complexes and a dark cloud. The observed [CII] emission is very strong and ubiquitously distributed throughout the galactic plane. The emission should be generated mostly in photo-dissociation region(PDR), but the ionizing and heating UV sources should be well mixed with the molecular clouds, presumably due to clumpy or filamentally structure of the molecular clouds. Some part of the emission may be originated from ELD HII regions which are illuminated by isolated O- and B-stars rather uniformly distributed in interstellar space.     

Low and medium energy gamma-ray astronomy — present status and future aspects

During the last few years quite some progress has been achieved in the field of low and medium energy gamma-ray astronomy below about 30 MeV. Gamma rays from the galactic center and anti-center region have been detected, which require a high interstellar electron flux in the 100 MeV range, if they are predominantly diffuse in nature. Though the Crab pulsar and its nebula are still the only galactic gamma-ray sources which definitely have been detected, some recently determined upper limits to the gamma-ray fluxes of other radio pulsars are close to the theoretically expected values. Active galaxies seem to have a maximum of luminosity in the range between several 100 keV and a few MeV and, therefore, are of special interest. First observational results have been reported on the Seyfert galaxies NGC 4151 and MCG 8-11-11, and the radio galaxy CenA. The nature of the diffuse cosmic gamma-ray component at low gamma-ray energies is not yet solved. Unresolved active galaxies are good candidates for its origin.Considering the present status of gamma ray astronomy the study of galactic sources like radio pulsars and the unidentified high energy gamma-ray sources, the Milky Way as a whole, active galaxies and the diffuse cosmic sky seem to be the prime targets for broad band observations below 30 MeV in the GRO area. An unexplored field like that of low energy gamma-ray astronomy, however, is always open for surprises.     

Constraints on a hadronic model for unidentified off-plane galactic gamma-ray sources

Recently the H.E.S.S. collaboration announced the detection of an unidentified gamma-ray source with an off-set from the galactic plane of 3.5°: HESS J1507-622. If the distance of the object is larger than about one kpc it would be physically located outside the galactic disk. The density profile of the ISM perpendicular to the galactic plane, which acts as target material for hadronic gamma-ray production, drops quite fast with increasing distance. This fact places distance dependent constraints on the energetics and properties of off-plane gamma-ray sources like HESS J1507-622 if a hadronic origin of the gamma-ray emission is assumed. For the case of this source it is found that there seems to be no simple way to link this object to the remnant of a stellar explosions.     

Neutral clouds in a pervasive X-ray gas between the sun and northern HVCs

We present evidence that the soft X-ray distribution observed with the ROSAT PSPC instrument is not adequately explained by the standard Local Hot Bubble model (/1/). We discuss the X-ray absorbing cloud LVC 88 + 36 − 2 embedded in the hot plasma of the Local Hot Bubble, the X-ray shadow of the Draco nebula and other clouds inside and outside the galactic disk, and the X-ray emission associated with halo type objects like the HVC's M I and M II. They populate the distance range from about 60 pc to more than a few kpc and imply the presence of X-ray emitting plasma between the sun and and the outer galactic halo. These observations are consistent with a pervasive X-ray emitting plasma in which neutral clouds are embedded. However, the volume filling factor of this plasma is not known. A model which adequately describes the observed features has been developed and published by Hirth et al. (/28/).

For the first time in the literature we present results of a correlation analysis of X-ray shadows and H I or IR images of a molecular cloud. This is a new technique for the determination of the total column density of hydrogen nuclei for molecular clouds.     

Resolving electrons from protons in ATIC

The Advanced Thin Ionization Calorimeter (ATIC) experiment is designed for high energy cosmic ray ion detection. The possibility to identify high energy primary cosmic ray electrons in the presence of the ‘background’ of cosmic ray protons has been studied by simulating nuclear-electromagnetic cascade showers using the FLUKA Monte Carlo simulation code. The ATIC design, consisting of a graphite target and an energy detection device, a totally active calorimeter built up of 2.5 cm × 2.5 cm × 25.0 cm BGO scintillator bars, gives sufficient information to distinguish electrons from protons. While identifying about 80% of electrons as such, only about 2 in 10,000 protons (@ 150 GeV) will mimic electrons. In September of 1999 ATIC was exposed to high-energy electron and proton beams at the CERN H2 beam line, and this data confirmed the electron detection capabilities of ATIC. From 2000-12-28 to 2001-01-13 ATIC was flown as a long duration balloon test flight from McMurdo, Antarctica, recording over 360 h of data and allowing electron separation to be confirmed in the flight data. In addition, ATIC electron detection capabilities can be checked by atmospheric gamma-ray observations.     

Results from the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Observatory

The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory covers the high energy gamma ray energy range, approximately 30 MeV to 30 GeV, with a sensitivity considerably greater than earlier high energy gamma-ray satellites. Thus far, 4 pulsars have been detected and their properties measured, including in 3 cases the energy spectrum as a function of phase. The details of the galactic plane are being mapped and a spectra of the center region has been obtained in good agreement with that expected from cosmic ray interactions. The Magellanic clouds have been examined with the Large Magellanic Cloud having been detected at a level consistent with it having a cosmic ray density compatible with quasi-stable equilibrium. Sixteen Active Galactic Nuclei (AGN's) have been seen thus far with a high degree of certainty including 12 quasars and 4 BL Lac objects, but no Seyferts. Time variation has been detected in some of these AGN's.