On the relation between orbital structure and observed bar morphology     

P. A. Patsis 《Monthly notices of the Royal Astronomical Society》2005,358(2):305-315

We investigate the morphological relation between the orbits of the central family of periodic orbits ( x ₁ family) and the bar itself using models of test particles moving in a barred potential. We show that different bar morphologies may have as a backbone the same set of x ₁ periodic orbits. We point out that by populating initially axisymmetric stellar discs exponentially with test particles in circular, or almost circular motion, we may end up with a response bar which reveals a shape different in crucial details from that of the individual stable x ₁ orbits. For example, a bar model in which the x ₁ orbits are pure ellipses may have a much more complicated response morphology. This depends on the particular invariant curves around x ₁, which are populated in each model.  相似文献   

LAMOST总控系统程序设计     

徐灵哲  徐欣圻 《天文学进展》2005,23(3):287-292

国家重大科学工程项目LAMOST总控系统的程序设计是一个庞大的软件工程．其总控系统下共包括8个既相互独立又互有关联的子系统．如何通过良好的软件设计方法来处理好这8个子系统之间的关系使其协调运转，以及如何确保软件开发的可维护性、可持续性是研究重点．  相似文献   

The dependence of protoplanet migration rates on co-orbital torques     

G. D'Angelo  M. R. Bate  S. H. Lubow 《Monthly notices of the Royal Astronomical Society》2005,358(2):316-332

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The old open cluster Trumpler 5: a reddened, metal-poor anticentre cluster     

Andrés E. Piatti  Juan J. Clariá  Andrea V. Ahumada 《Monthly notices of the Royal Astronomical Society》2004,349(2):641-648

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Stellar models and Hyades: the Hipparcos test     

V. Castellani  S. Degl'Innocenti  P. G. Prada Moroni 《Monthly notices of the Royal Astronomical Society》2001,320(1):66-72

We compare theoretical stellar models for main sequence (MS) stars with the Hipparcos data base for the Hyades cluster to give a warning against the uncritical use of available theoretical scenarios and to show how formal MS fittings can be fortuitous if not fictitious. Moreover, we find that none of the current theoretical scenarios appears able to account for an observed mismatch between theoretical predictions and observations of the coolest Hyades MS stars. Finally, we show that current theoretical models probably give too faint He burning luminosities unlike the case of less massive He burning models, with degenerate progenitors, which have been suggested to suffer the opposite discrepancy.  相似文献   

UBV RI CCD photometric study of the open clusters Basel 4 and NGC 7067     

R. K. S. Yadav  Ram Sagar 《Monthly notices of the Royal Astronomical Society》2004,349(4):1481-1492

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A Chandra X-ray survey of nearby dwarf starburst galaxies – II. Starburst properties and outflows     

Jürgen Ott †  Fabian Walter  Elias Brinks † 《Monthly notices of the Royal Astronomical Society》2005,358(4):1453-1471

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On salinity regimes and the vertical structure of residual flows in narrow tidal estuaries     

D. Prandle 《Estuarine, Coastal and Shelf Science》1985,20(5):615-635

An examination is made of the circulation in narrow estuaries subject to a predominant tidal forcing. Velocity structures are derived separately for residual flow components associated with (a) river flow, (b) wind stress, (c) a well-mixed longitudinal density gradient and (d) a fully stratified saline wedge. Dimensionless parameters are introduced to indicate the magnitude of each component and these parameters are evaluated for 9 major estuaries, thereby revealing their sensitivity to each component.For a channel of constant breadth and depth, formulae are deduced for the length of saline intrusion, L. Comparisons with observed data show that such formulae may be used with confidence to predict changes in L arising from variations in river flow, tidal range or channel depths.The level of stratification is shown to be related to a product of two parameters, one associated with velocity structure and a second involving the square of the ‘flow ratio’ $\text{u}\text{u}\text{?}$ (i.e. residual velocity/amplitude of the tidal velocity). This relationship provides a simple classification system for estuarine stratification which can be used to indicate the sensitivity of any particular estuary to changing conditions.  相似文献   

Spectral variations of DY Cen     

Sunetra Giridhar  N. Kameswara Rao  David L. Lambert 《Journal of Astrophysics and Astronomy》1996,17(1-2):23-40

Two high resolution spectra of the hot RCrB star DY Cen in the red region are compared. The photospheric absorption lines show a radial velocity variation of 12 kms-1 between 1989 July and 1992 May. Emission components to some CII lines present in 1989 are almost entirely absent in 1992. Nebular forbidden lines of [OI], [NII] and [SII] appear unchanged from 1989 to 1992  相似文献   

Prediction of lateral variability in fracture intensity using multicomponent shear-wave surface seismic as a precursor to horizontal drilling in the Austin Chalk   总被引：1，自引：0，他引：1  

Michael C. Mueller 《Geophysical Journal International》1991,107(3):409-415

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