Orbital periods of 22 subdwarf B stars     

L. Morales-Rueda  P. F. L. Maxted  T. R. Marsh  R. C. North  U. Heber 《Monthly notices of the Royal Astronomical Society》2003,338(3):752-764

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Measuring shapes of galaxy images – I. Ellipticity and orientation     

Nurur Rahman  Sergei F. Shandarin 《Monthly notices of the Royal Astronomical Society》2003,343(3):933-948

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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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Longitudinal dispersion compensation for the Very Large Telescope Interferometer     

Samuel Lévêque  Bertrand Koehler  Oskar von der Lühe 《Astrophysics and Space Science》1996,239(2):305-314

The Very Large Telescope Interferometer [1,13] will be operated in air which will introduce small optical path fluctuations due to internal turbulence [4,6] and dispersion effects. Both may contribute to fringe contrast decrease. Longitudinal dispersion effects can be corrected by inserting an appropriate glass of variable thickness in one arm of the interferometer [3,5,11,12]. This paper presents a new method applied to VLTI in order to select the optimum glass, according to both the observing wavelength and the spectral bandpath, and to calculate its thickness. Results are presented in terms of improvement on the fringe contrast.  相似文献   

Is dark matter created in the gravitation field of galaxies?     

V. Majerník 《Astrophysics and Space Science》1996,240(1):133-139

Using the heuristic arguments of quantum physics we describe a new mechanism of the creation of short-living particles from the virtual ones in a stationary gravitation field. The mass of these particles is a function of the intensity of gravitation field. We suppose that the particles created in the gravitation field form a part of the non-baryonic dark matter. Having the intensity of gravitation field in a galaxy we can calculate the density of dark matter created in it by the vacuum quantum fluctuation. We calculate the distribution of this dark matter in a model galaxy and show that its total mass is comparable with the visible mass of the galaxy.  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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