太阳射电频谱仪数据采集与自理自相关频谱仪原理与应用）

本文论述了０．７～１．４ＧＨz太阳射电频谱仪数据采集与处理系统是如何实现的。正在 研制的此仪器采用了多通道频谱仪与自相关频谱仪结合使用的方案。首先,本文详细讨论了自相关频谱仪的原理,并介绍了北京大学研制的自相关频谱仪的结构。在此基础上着重讨论了多通道频谱仪与自相关频谱仪的同步控制的解放方案,以及大容量数据采集实时存盘的解决方案。最后,介绍了我们为数据预处理采用的一些方案。     

数字声光频谱仪时间分辨率的测定

本文报告了对新近研制的太阳米波数字声光频谱仪数据采集系统时间分辨率的测定,并讨论了该仪器以不同方式工作时可能达到的最高时间分辨率。     

数字声光频谱仪性能改进

本文介绍了数字声光频谱仪通过鉴定之后所进行的一系列改进。对电系统和声光系统频率响应进行了综合补偿,改善了整机频率响应。提高了时间分辨率。软件改进增加了频谱仪数据采集功能,并使它操作更加简便。     

全数字化自相关射电频谱仪观测分子谱线成功

鉴于分子天文学对研究银河系结构、恒星诞生和演化、宇宙化学及宇宙生命等方面有极其重要的意义,近年来国内不仅在这个领域的理论研究有迅速发展,而且积极进行着实测手段的建设.其中,用于谱线观测的射电频谱仪先后确定采用的数种技术方案,均已进行研制并已在实验室调测.然而因种种技术上的考虑,原来并没有打算采用国外已广泛使用的全数字化自相关射电频谱仪.     

CFR—256—1型多通道滤波式频谱仪

本文扼要介绍紫台13.7米毫米波射电望远镜的多通道滤波式频谱仪之原理、组成及取得的初步结果。     

云台射电频谱仪预研

简要介绍了用于研究分子夭文学的各种射电频谱仪及国内外发展状况,讨论了各种频谱仪的优缺点,最后提出了云台建立射电频谱仪的型式。     

用于分子谱线观测的512路数字式自相关频谱仪

本文简要介绍了采用一比特自相关技术实现的５１２路数字式自相关频谱仪的工作原理及系统的硬件和软件构成。该频谱仪主要用于分米及ｃｍ波段分子谱线观测。频谱仪系统时钟可在６２５ＫＨｚ和２０ＭＨｚ之间按２的倍率选择，最大分析带宽为１０ＭＨｚ。最高频率分辨率为０．６１ＫＨｚ，相应于１８ｃｍ波段的速度分辨率为０．１ｋｍ／ｓ。文章最后给出了利用上海天文台２５ｍ射电望远镜观测ＯＨ脉泽源的结果。     

基于IBOB的射电望远镜宽带数字频谱仪系统的设计与测试

简述了基于IBOB和Xilinx System Generator平台的射电望远镜宽带数字频谱仪系统的设计与应用;给出了双路400MHz、2048通道、16IP输出数字频谱仪系统的具体设计方案,并对该数字频谱仪器的性能指标进行了分析和测试,验证了方案的可行性;最后初步讨论了滤波器设备对后端系统的影响。     

太阳米波射电声光频谱仪实验方案

本文提出了一个声光型太阳米波射电爆发动态频谱仪的实验方案。采用PbM_0O_4声光调制器,频带70—130MHz,预期频率分辨率好于0.3MHz。天线使用宽频带菱形天线。     

1-2GHz太阳射电动态频谱仪

本文描述了北京天文台研制的１－２ＧＨｚ太阳射电动态频谱仪的性能、结构、初步观测结果及进一步改进计划．     

Instructions for authors

正Research in Astronomy and Astrophysics publishes original research papers and reviews on all branches of astronomy and astrophysics.Reviews are by invitation only.Important new results that require rapid publication can be submitted as a Letter(Letters must be restricted in length to 6 printed pages).Authors who submit a paper are expected to be able to certify that the paper is original work,     

Research in Astronomy and Astrophysics CONTENTS

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Alkali and halogen chemistry in volcanic gases on Io

We use chemical equilibrium calculations to model the speciation of alkalis and halogens in volcanic gases emitted on Io. The calculations cover wide temperature (500-2000 K) and pressure (10⁻⁶ to 10⁺¹ bars) ranges, which overlap the nominal conditions at Pele (T=1760 K, P=0.01 bars). About 230 compounds of 11 elements (O, S, Li, Na, K, Rb, Cs, F, Cl, Br, I) are considered. The elemental abundances for O, S, Na, K, and Cl are based upon observations. CI chondritic elemental abundances relative to sulfur are used for the other alkalis and halogens (as yet unobserved on Io). We predict the major alkali species in Pele-like volcanic gases and the percentage distribution of each alkali are LiCl (73%), LiF (27%); NaCl (81%), Na (16%), NaF (3%); KCl (91%), K (5%), KF (4%); RbCl (93%), Rb (4%), RbF (3%); CsCl (92%), CsF (6%), Cs (2%). Likewise the major halogen species and the percentage distribution of each halogen are NaF (88%), KF (10%), LiF (2%); NaCl (89%), KCl (11%); NaBr (89%), KBr (10%), Br (1%); NaI (61%), I (30%), KI (9%). We predict the major halogen condensates and their condensation temperatures at P=0.01 bar are NaF (1115 K), LiF (970 K); NaCl (1050 K), KCl (950 K); KBr (750 K), RbBr (730 K), CsBr (645 K); and solid I₂ (200 K). We also model disequilibrium chemistry of the alkalis and halogens in the volcanic plume. Based on this work and our prior modeling for Na, K, and Cl in a volcanic plume, we predict the major loss processes for the alkali halide gases are photolysis and/or condensation onto grains. Their estimated photochemical lifetimes range from a few minutes for alkali iodides to a few hours for alkali fluorides. Condensation is apparently the only loss process for elemental iodine. On the basis of elemental abundances and photochemical lifetimes, we recommend searching for gaseous KCl, NaF, LiF, LiCl, RbF, RbCl, CsF, and CsCl around volcanic vents during eruptions. Based on abundance considerations and observations of brown dwarfs we also recommend a search of Io's extended atmosphere and the Io plasma torus for neutral and ionized Li, Cs, Rb, and F.     

Instructions for authors

正Research in Astronomy and Astrophysics publishes original research papers and reviews 011 all liranchcs of astronoiriy and astrophysics.Reviews arc by invitation only.Important new results that require rapid publication can be submitted as a Letter(Letters must be restricted in length     

The climatic and physiographic controls of the eastern Mediterranean over the late Pleistocene climates in the southern Levant and its neighboring deserts

Modern-day synoptic-scale eastern Mediterranean climatology provides a useful context to synthesize the diverse late Pleistocene (60–12 ka) paleohydrologic and paleoenvironmental indicators of past climatic conditions in the Levant and the deserts to its south and east. We first critically evaluate, extract, and summarize paleoenvironmental and paleohydrologic records. Then, we propose a framework of eastern Mediterranean atmospheric circulation features interacting with the morphology and location of the southeast Mediterranean coast. Together they strongly control the spatial distribution of rainfall and wind pattern. This cyclone–physiography interaction enforces the observed rainfall patterns by hampering rainfall generation south and southeast of the latitude of the north Sinai coast, currently at 31°15′.The proposed framework explains the much-increased rains in Lebanon and northern Israel and Jordan as deduced from pollen, rise and maintenance of Lake Lisan, and speleothem formation in areas currently arid and semiarid. The proposed framework also accounts for the southward and eastward transition into semiarid, arid, and hyperarid deserts as expressed in thick loess accumulation at the deserts' margins, dune migration from west to east in the Sinai and the western Negev, and the formation of hyperarid (< 80 mm yr^− 1) gypsic–salic soils in the southern Negev and Sinai. Our climatic synthesis explains the hyperarid condition in the southern Negev, located only 200–250 km south of the much-increased rains in the north, probably reflecting a steeper rainfall gradient than the present-day gradient from the wetter Levant into its bordering southern and eastern deserts.At present, the rainiest winter seasons in Lebanon and northern and central Israel are associated with more frequent (+ 20%), deeper Cyprus Lows traversing the eastern Mediterranean at approximately the latitude of southern Turkey. Even these wettest years in northern Israel do not yield above average annual rainfall amounts in the hyperarid southern Negev. This region is mainly influenced by the Active Red Sea Troughs that produce only localized rains. The eastern Mediterranean Cyprus Lows also produce more dust storms and transport higher amounts of suspended dust to the loess area than any other atmospheric pattern. Concurrent rainfall and dust are essential to the late Pleistocene formation of the elongated thick loess zone along the desert northern margin. Even with existing dust storms, the lack of rain and very sparse vegetation account for the absence of late Pleistocene loess sequences from the southern Negev and the formation of hyperarid soils.When the north Sinai coast shifted 30–70 km northwest due to last glacial global sea level lowering, the newly exposed coastal areas supplied the sand and dust to these active eastern Mediterranean cyclones. This enforced the latitude of the northern boundary of the loess zone to be directly due east of the LGM shoreline. This shift of coast to the northwest inhibited rainfall in the southern Levant deserts and maintained their hyperaridity. Concurrently, frequent deep eastern Mediterranean Cyprus Lows were funneled along the northern Mediterranean increasing (probably doubling) the rains in central and northern Israel, Lebanon, southwestern Syria and northern Jordan. These storms and rains formed lakes, forests, and speleothems only a short distance north of the deserts in the southern Levant.     

Active hot star shells

Interferometry in the visible provides milliarcsecond spatial resolution and thus has been used for studying the circumstellar environment of active hot stars. In this paper I will illustrate how the visibility modulus and phase can be used to better constrain the physics of Be disks through results from the VLA, the MkII and the GI2T interferometers. I will insist on the importance and the potential of coupling high angular resolution with high spectral resolution to the study of Be shells. Finally I will present a possible study of the circumstellar disk of Be stars using the VLTI. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study on the Stressed Mirror Polishing with a Continuous Polishing Machine for Large Aperture Off-axis Aspheric Mirrors

A special stressed annular polishing technique is proposed to mill the off-axis aspheric sub-mirrors of a large segmented mirror with an annular polishing machine. Based on the basic principle of stressed annular polishing technique, a set of special stressing mechanisms are designed to convert milling the aspheric surfaces of sub-mirrors with different off-axis distances into milling the spherical surfaces with identical radii of curvature, so that they can be pol- ished simultaneously on a continuous polishing machine. It took about contin- uous 40 hours to polish a scaled-down mirror of the planning Chinese Future Giant Telescope (CFGT) using this technique. This mirror has the 330 mm di- ameter, 3.6 m off-axis distance, and the 21.6 m radius of curvature, and its max- imum asphericity is 16 micron. The experiment shows that this method has a high effciency, suits batch manufacturing, especially the batch manufacturing of aspheric sub-mirrors of the segmented primary mirror of an extremely large aperture telescope.     

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.     

我国新一代VLBI数字基带转换器研制进展

数字化是目前设备研制发展的趋势,介绍了中国科学院上海天文台利用超大规模集成电路结合软件无线电技术,自主研发的我国新一代VLBI数字基带转换器(Chinese Data Acquisition System,简称CDAS).文中描述了设备的工作原理及其组成,并以VLBI观测实验数据证明其可行性.与原有的模拟设备(Anal...