高精度测定外行星位置-可行性及实验

大行星位置的测量是天体测量学中的一项长期而重要的任务。如何在当前形势下高精度测定行星的位置是本文研究方向的最终目标。鉴于太阳系内行星和木星都有新技术进行高精度的位置观测,作者探讨了如何用光学手段高精度测定外行星（土星,天王星和海王星）的位置,提出了用长焦距望远镜ＣＣＤ观测行星卫星和用中天望远镜ＣＣＤ观测暗恒星相配合的思路。因此,对长焦距望远镜ＣＣＤ观测外行星卫星和中天望远镜ＣＣＤ相对观测恒星进行了系统调研,同时也对外行星卫星的理论从观测验证的角度进行了介绍。本文重点介绍了在长焦距望远镜上相对于天王星卫星高精度测定暗恒星的位置。结果表明,相对于天王星卫星确实可以精确测定同一ＣＣＤ视场中暗恒星的位置,位置测量的精度和国外最好的天王星卫星位置测量的精度相当或更高。还介绍了与观测资料的归算有关的天王星和卫星的位置历算。最后,分析了我国从事高精度大行星位置测量的可行性     

天王星卫星CCD观测的初步分析

１９９５ 年８ 月在上海天文台利用安装在１ ．５６ 米望远镜上的ＣＣＤ 探测器对天王星五颗主要卫星进行了定位试观测。将观测所得的位置资料与其理论值做了比较。结果表明：ＣＣＤ观测的位置精度优于照相观测的结果。这些资料对于卫星轨道的研究是有价值的。     

天王星卫星的CCD观测与分析解的比对

本文给出了处理天王星卫星ＣＣＤ图象位置资料的新方法,并将我们在１９９５年取得的重要资料与两种理论模型位置进行了比较计算,结果表明经处理后的天王星五颗主要卫星ＣＣＤ观测精度有了较大提高。     

高精度测定外行星位置—可行性及实验

大行星位置的测量是天体测量学中的一项长期而重要的任务,如何在当前形势下高精度测定行星的位置是本文研究方向的最终目标,鉴于太阳系内行星和木星都有新技术进行高精度的位置观测,作者探讨了如何用光学手段高精度测量外行星（土星,天王星和海王星）的位置。提出了长焦距望远镜ＣＣＤ观测行星卫星和用中天望远镜ＣＣＤ观测暗恒星相配合的思路,因此,对长焦距望远镜ＣＣＤ观测外行星卫星和中天望远镜ＣＣＤ相对观测恒星进行了系     

天王星卫星CCD（SRT）位置测量的数字图象处理

天然卫星的位置测量在天体测量和天体力学中都有重要意义。国外有人对天王星卫星位置测量应用新的图象处理方法得到了高精度的卫星观测资料。利用云南天文台１米望远镜上获得的两颗卫星的ＳＲＴ的ＣＣＤ观测资料进行了新老图象处理方法的比较研究。当用两颗卫星直接作定标测量ＣＣＤ的比例尺和指向时表明：主星晕的处理对卫星位置的测量非常重要。去晕处理后,测得的比例尺和指向的弥散将大为减少。     

依巴谷星(104297)相对于伽里略卫星Callisto的CCD位置测量

１９９７年１１月１４日晚，在中国科学院云南天文台１米望远镜上用新安装的１０２４２ＣＣＤ观测到了木星的两颗伽里略卫星；Ｅｕｒｏｐａ和Ｃａｌｌｉｓｔｏ及一颗依巴谷星（星号为 １０４２９７）．当采用新的 ＪＰＬ ＤＥ４０５和 Ｓａｍｐｓｏｎ－Ｌｉｅｓｋｅ理论（Ｇ５）计算卫星的理论位置并相对于Ｃａｌｌｉｓｔｏ测量恒星位置时，视位置的观测值与计算值之差的平均值在赤经和赤纬方向分别为△α＝－０″０２９±０．″０１２，△δ＝０．″００５± ０．″０１１．这对应于平均观测历元（ＵＴ）：１９９７年１１月１４日１３时４３分５０秒．这一试验结果与 Ｃａｓａｓ等在同一时期内ＣＣＤ观测的结果有着很好的一致性 它反映了依巴谷星表体现的光学参考系与ＤＥ４０５体现的动力学参考系在观测历元具有较好的一致性．单次位置测定的标准误差在赤经赤纬方向分别为±０．″０５２和０．″０４７．这一精度明显优于 Ｃａｓａｓ等人发表的 Ｃａｌｌｉｓｔｏ的处理精度，并与目前国际上最好的伽里略卫星观测精度相当     

观测所获得的土星卫星1988年坐标及其与理论值比较

本文发表我们于1988年在云南天文台1m望远镜通过对土星卫星照像观测所归算出的土星卫星的位置,并与理论计算值进行比较分析。     

用M15进行CCD视场的校准

用1996年10月所获得的球状星团M15和大距离双星61Cygni的CCD观测资料,分别求解了上海天文台1.56m天体测量望远镜上安装的CCD探测器视场的位置角改正δp和尺度因子ρ。通过对土星主要卫星观测资料0－C的计算分析表明,经球状星团校准视场后所得结果较双星校准后结果的精度要高。该结论为进一步提高计算大行星卫星的位置测量精度打下良好的基础。     

射电源0716 714和0839 187的光学定位

利用北京天文台具有ＣＣＤ终端的６０ｃｍ光学望远镜（Ｖ波段）观测射电源的光学对应体，得到了０７１６＋７１４和０８３９＋１８７精确的光学位置。参考星表采用拉帕尔玛（ＬａＰａｌｍａ）的１８ｃｍ全自动子午环观测资料编制的ＣＡＭＣ星表，该星表是ＦＫ５星表系统。两颗源位置的内符精度约为０．″１９，与其他作者给出的光学和射电位置观测结果分别进行了比较     

HD 104237,εCha和HD 100546的演化状态

根据Ｈｉｐｐａｒｃｏｓ的资料和ＴＤ－１对εＣｈａ和ＨＤ１００５４６的紫外观测资料讨论了εＣｈａ、ＨＤ１０４２３７和ＨＤ１００５４６在赫罗图上的位置以及它们的演化状态．     

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     

A thermodynamic model of high temperature lava vaporization on Io

We modified the MAGMA chemical equilibrium code developed by Fegley and Cameron (1987, Earth Planet. Sci. Lett. 82, 207-222) and used it to model vaporization of high temperature silicate lavas on Io. The MAGMA code computes chemical equilibria in a melt, between melt and its equilibrium vapor, and in the gas phase. The good agreement of MAGMA code results with experimental data and with other computer codes is demonstrated. The temperature-dependent pressure and composition of vapor in equilibrium with lava is calculated from 1700 to 2400 K for 109 different silicate lavas in the ONaKFeSiMgCaAlTi system. Results for five lavas (tholeiitic basalt, alkali basalt, Barberton komatiite, dunite, and a molten type B1 Ca, Al-rich inclusion) are discussed in detail. The effects of continuous fractional vaporization on chemistry of these lavas and their equilibrium vapor are presented. The predicted abundances (relative to Na) of K, Fe, Si, Al, Ca, and Ti in the vapor equilibrated with lavas at 1900 K are lower than published upper limits for Io's atmosphere (which do not include Mg). We predict evaporative loss of alkalis, Fe, and Si during volcanic eruptions. Sodium is more volatile than K, and the Na/K ratio in the gas is decreased by fractional vaporization. This process can match Io's atmospheric Na/K ratio of 10±3 reported by Brown (2001, Icarus 151, 190-195). Silicon monoxide is an abundant species in the vapor above lavas. Spectroscopic searches are recommended for SiO at IR and mm wavelengths. Reactions of metallic vapors with S- and Cl-bearing volcanic gases may form other unusual gases including MgCl₂, MgS, MgCl, FeCl₂, FeS, FeCl, and SiS.     

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.     

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.     

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.