Effective collision strengths with inclusion of resonance for hyperfine-structure transitions in H- and Li-like ions     

Hong Lin Zhang  Douglas H. Sampson 《Monthly notices of the Royal Astronomical Society》2001,322(3):433-437

Calculations are made of the resonance contribution to electron-impact excitation of H-like ¹³C and Li-like ²³Na, ²⁵Mg, ²⁷Al and ²⁹Si to the upper hyperfine levels that produce millimetre (mm) lines of likely astrophysical interest. The resonance contribution is found to be very important for these Li-like ions, considerably more important than for Li-like ⁵⁷Fe considered previously. However, resonances are found to be rather unimportant for H-like ¹³C. The effect of radiative decay on the resonance contribution is found to be insignificant in all of the present calculations.  相似文献   

A comparison of artificial solar granules with real solar granules     

H. Wöhl  Å. Nordlund 《Solar physics》1985,97(2):213-221

The lifetimes, characteristics of the shapes as well as lengths and perimeters of artificial solar granules (Nordlund, 1982, 1984a) are compared with data from the literature and parameters determined from two different sets of observed granules. No significant differences of the parameters for these sets of granules are detectable.Mitteilungen aus dem Kiepenheuer-Institut Nr. 251.  相似文献   

Systematic uncertainties in the analysis of star cluster parameters based on broad-band imaging observations     

R. de Grijs  P. Anders  H. J. G. L. M. Lamers  N. Bastian  U. Fritze-v. Alvensleben  G. Parmentier †  M. E. Sharina  S. Yi 《Monthly notices of the Royal Astronomical Society》2005,359(3):874-894

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The onset of shock wave in an electrically conducting and radiating gas     

A. Kumar  L. P. Singh  R. Shyam 《Astrophysics and Space Science》1985,111(1):131-137

The present work applies the method of characteristics to study the behaviour of planar and cylindrical wave-heads propagating through a perfectly electrically conducting and thermally radiating inviscid gas under the optically thin limit in the presence of a transverse magnetic field. The true nonlinear progress of the flow variable gradients at the wavefront is predicted and the critical distance at which the characteristics pile up at the wavefront to form a shock wave is obtained. It is investigated as to how the effects of radiative flux, the magnetic field strength and the specific heat ratio influence the process of steepening or flattening of the characteristic wavefront.  相似文献   

UV Leo: The Binary with the Two Suns     

G. Djurašević  P. Rovithis  H. Rovithis-Livaniou  E. Fragoulopoulou 《Astrophysics and Space Science》2005,296(1-4):311-314

BV light curves of the eclipsing binary UV Leo obtained at the Kryonerion Astronomical Station of the National Observatory of Athens, Greece, are analyzed. The analysis is based on a Roche configuration with two spots on the secondary surface. The elements of the two components of the system are calculated and the spot characteristics are given.  相似文献   

Chronology and evolution of the northern Iceland Plateau     

J. CAMPSIE  M. H. RASMUSSEN  L. C. KOVACS  F. DITTMER  J. C. BAILEY  N. O. HANSEN  J. LAURSEN  L. JOHNSON 《Polar research》1990,8(2):237-243

New aeromagnetic data, K-Ar age determinations of dredged marine igneous rocks, as well as other geophysical evidence have shed light on the chronology, nature and evolution of the northern Iceland Plateau. Correspondence between seismic refraction profiles taken on the Jan Mayen Ridge and westward through Jan Mayen Island, suppressed aeromagnetic anomalies, earthquake surface wave studies, and ages of dredged igneous rocks suggest these strata may form an extended region of thickened crust, possibly of Caledonian age, extending westward toward the Kolbeinsey Ridge and northwest to the south wall of the Jan Mayen Fracture Zone.  相似文献   

Some aspects related to the asymptotic solutions of the laminar boundary-layer equations with heat flux     

Anil Kumar  B. B. Singh 《Astrophysics and Space Science》1990,165(1):41-49

The oscillatory, conjugate and asymptotic behaviours of the principal and non-principal solutions of the Blasius and corresponding heat transfer equations governing the compressible laminar boundary-layer flow over a semi-infinite flat plate with heat flux have been studied; the results of the discussion being based on the asymptotic integrations of second-order linear differential equations.  相似文献   

Modeling X-Ray Photoionized Plasmas Produced at the Sandia Z-Facility     

P. A. M. Van Hoof  M. E. Foord  R. F. Heeter  J. E. Bailey  H.-K. Chung  M. E. Cuneo  W. H. Goldstein  V. Jonauskas  F. P. Keenan  R. Kisielius  D. A. Liedahl  C. Ramsbottom  S. J. Rose  P. T. Springer  R. S. Thoe 《Astrophysics and Space Science》2005,298(1-2):147-153

In experiments at the high-power Z-facility at Sandia National Laboratory in Albuquerque, New Mexico, we have been able to produce a low density photoionized laboratory plasma of Fe mixed with NaF. The conditions in the experiment allow a meaningful comparison with X-ray emission from astrophysical sources. The charge state distributions of Fe, Na and F are determined in this plasma using high resolution X-ray spectroscopy. Independent measurements of the density and radiation flux indicate unprecedented values for the ionization parameter ξ = 20–25 erg cm s⁻¹ under nearly steady-state conditions. First comparisons of the measured charge state distributions with X-ray photoionization models show reasonable agreement, although many questions remain.  相似文献   

The nature of parallax microlensing events towards the Galactic bulge     

Martin C. Smith  Vasily Belokurov  N. Wyn Evans  Shude Mao  Jin H. An 《Monthly notices of the Royal Astronomical Society》2005,361(1):128-140

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Microboudin structures of piemontite along the Sambagawa metamorphic belt, Japan: implications for lateral variation of differential stress during regional metamorphism     

T. Masuda  T. Shibutani  T. Ochiai  S. Akagi  H. Yamaguchi  Y. Kugimiya  N. Kimura  T. Miyake 《Journal of Metamorphic Geology》2004,22(3):199-205

Evidence is presented of a lateral variation in differential stress during metamorphism along a regional metamorphic belt on the basis of the proportion of microboudinaged piemontite grains (p) in a quartz matrix in metacherts. It is proposed that p is a practical indicator of relative differential stress. Analysis of 123 metacherts from the 800 km long Sambagawa metamorphic belt, Japan, reveals that p‐values range from < 0.01 to 0.7 in this region. Most samples from Wakayama in the mid‐belt area have p‐values of 0.4–0.6, whereas those from western Shikoku have p‐values of < 0.1. This difference cannot be explained by variations in metamorphic temperature, and is instead attributed to a regional, lateral variation in differential stress during metamorphism.  相似文献