Contribution to the search for binaries among Am stars – V. Orbital elements of eight short-period spectroscopic binaries     

J.-M. Carquillat  N. Ginestet  J.-L. Prieur  Y. Debernardi 《Monthly notices of the Royal Astronomical Society》2003,346(2):555-564

We present the results of a radial-velocity study of eight Am stars (HD 341, 55822, 61250, 67317, 93991, 162950, 224890 and 225137) observed at Observatoire de Haute-Provence with the CORAVEL instrument. We find that these systems are single-line spectroscopic binaries whose orbital elements are determined for the first time.  相似文献   

γ射线暴研究概况   总被引：1，自引：0，他引：1  

黎卓  戴子高  陆埮 《天文学进展》2003,21(4):334-369

γ射线暴(简称γ暴)的研究自1997年以来由于余辉的发现而有了很大的突破。在此，对γ暴的观测作了简要的概述，而对γ暴的理论进展和存在问题进行了较为全面的评述，内容包括γ暴本身、余辉、能源机制、寄主星系、暴周环境、高能粒子和引力波辐射、宇宙学意义等。  相似文献   

DISASTER ANALYSIS AND COUNTERMEASURES OF LAND SUBSIDENCE CAUSED BY COAL CUTTING IN CHINA     

YANGYong-liang SHITong-guang JLANGLU-guang LIYue 《中国地理科学(英文版)》2003,13(2):130-133

In recent years, many coal-producing countries have paid great attention to the land subsidence causedby coal cutting. In China, because of the dense population in coalfield areas, the land subsidence hazard is more seri-ous. After a brief analysis on the mechanism of land subsidence, this paper gives a comprehensive and systematical ac-count on all kinds of hazards caused by the land subsidence in China. The study shows that land subsidence has endan-gered land, buildings, traffic and communication lines, dykes and dams. It also causes damage to ecological and socialenvironment. In order to lessen the hazard of land subsidence, preventive measures should be taken to reduce the col-lapse amount, such as extraction with stowing, banded mining system, succession and coordination mining system, orhigh-pressure mudflow between rock strata. Measures of reinforcing or moving certain buildings should also be taken toreduce the destructive degree. In order to harness the subsidence land and bring them under control for fanning, mea-sures should be taken such as filling with spoil or fine breeze, excavating the deeper and covering the shallower land.  相似文献   

Doublet craters on Venus     

Cheryl M Cook  William F Bottke Jr. 《Icarus》2003,165(1):90-100

Of the impact craters on Earth larger than 20 km in diameter, 10-15% (3 out of 28) are doublets, having been formed by the simultaneous impact of two well-separated projectiles. The most likely scenario for their formation is the impact of well-separated binary asteroids. If a population of binary asteroids is capable of striking the Earth, it should also be able to hit the other terrestrial planets as well. Venus is a promising planet to search for doublet craters because its surface is young, erosion is nearly nonexistent, and its crater population is significantly larger than the Earth's. After a detailed investigation of single craters separated by less than 150 km and “multiple” craters having diameters greater than 10 km, we found that the proportion of doublet craters on Venus is at most 2.2%, significantly smaller than Earth's, although several nearly incontrovertible doublets were recognized. We believe this apparent deficit relative to the Earth's doublet population is a consequence of atmospheric screening of small projectiles on Venus rather than a real difference in the population of impacting bodies. We also examined “splotches,” circular radar reflectance features in the Magellan data. Projectiles that are too small to form craters probably formed these features. After a careful study of these patterns, we believe that the proportion of doublet splotches on Venus (14%) is comparable to the proportion of doublet craters found on Earth (10-15%). Thus, given the uncertainties of interpretation and the statistics of small numbers, it appears that the doublet crater population on Venus is consistent with that of the Earth.  相似文献   

The Orion nebula (M42) Herbig–Haro object, HH 201, within the tip of a molecular finger     

M. F. Graham  J. Meaburn  M. P. Redman 《Monthly notices of the Royal Astronomical Society》2003,343(2):419-426

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The efficiency of the spiral-in of a black hole to the Galactic Centre     

Piero F. Spinnato  Michael Fellhauer  Simon F. Portegies Zwart 《Monthly notices of the Royal Astronomical Society》2003,344(1):22-32

We study the efficiency at which a black hole or dense star cluster spirals in to the Galactic Centre. This process takes place on a dynamical friction time-scale, which depends on the value of the Coulomb logarithm (ln Λ). We determine the accurate value of this parameter using the direct N -body method, a tree algorithm and a particle-mesh technique with up to two million plus one particles. The three different techniques are in excellent agreement. Our measurement for the Coulomb logarithm appears to be independent of the number of particles. We conclude that  ln Λ= 6.6 ± 0.6  for a massive point particle in the inner few parsec of the Galactic bulge. For an extended object, such as a dense star cluster, ln Λ is smaller, with a value of the logarithm argument Λ inversely proportional to the object size.  相似文献   

The young cluster in the CB34 globule: the clumps and the outflows     

C. Codella  F. Scappini 《Monthly notices of the Royal Astronomical Society》2003,344(4):1257-1263

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Storm Damage Assessment Using Digitised Aerial Photographs: Eltham, New Zealand, 24–25 February 1986     

C. F. PAIN  P. R. STEPHENS 《New Zealand geographer》1990,46(1):21-25

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DEVELOPMENT STRATEGIES OF WATER AND LAND RESOURCES IN THE HEXI REGION,CHINA     

肖洪浪  高前兆  李福兴 《中国地理科学(英文版)》1996,(1)

ＤＥＶＥＬＯＰＭＥＮＴＳＴＲＡＴＥＧＩＥＳＯＦＷＡＴＥＲＡＮＤＬＡＮＤＲＥＳＯＵＲＣＥＳＩＮＴＨＥＨＥＸＩＲＥＧＩＯＮ，ＣＨＩＮＡ肖洪浪，高前兆，李福兴ＤＥＶＥＬＯＰＭＥＮＴＳＴＲＡＴＥＧＩＥＳＯＦＷＡＴＥＲＡＮＤＬＡＮＤＲＥＳＯＵＲＣＥＳＩＮＴＨＥ...  相似文献   

A deep Chandra survey of the Groth Strip – I. The X-ray data     

K. Nandra  E. S. Laird  K. Adelberger  Jonathan P. Gardner  R. F. Mushotzky  J. Rhodes  C. C. Steidel  H. I. Teplitz  K. A. Arnaud 《Monthly notices of the Royal Astronomical Society》2005,356(2):568-586

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