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31.
Electron impact excitation rates for transitions in the S v ion, calculated with theR-matrix code, are used to derive the electron temperature sensitive emission line ratiosR
1 =I(854.8 Å)/I(786.9 Å),R
2 =I(852.2 Å)/I(786.9 Å),R
3 =I(849.2 Å)/I(786.9 Å), andR
4 =I(1199.1 Å)/I(786.9 Å), which are found to be significantly different from previous estimates. A comparison of the present results with observational data for a sunspot obtained with the Harvard S-055 spectrometer on boardSkylab reveals generally good agreement between theory and experiment, except in the case ofR
1, which is probably due to blending in the 854.8 Å feature. The possible effects of Lyman continuum absorption on the observed line ratios is briefly discussed. 相似文献
32.
M.S. Hanner E. Tedesco A.T. Tokunaga G.J. Veeder D.F. Lester F.C. Witteborn J.D. Bregman J. Gradie L. Lebofsky 《Icarus》1985,64(1):11-19
The dust coma of Comet P/Churyumov-Gerasimenko was monitored in the infrared (1–20 μm) from September 1982 to March 1983. Maximum dust production rate of ~2 × 105 g/sec occured in December, 1 month postperihelion. The ratio of dust/gas production was higher than that in other short-period comets. No silicate feature was visible in the 8- to 13-μm spectrum on 23 October. The mean geometric albedo of the grains was ~0.04 at 1.25 μm and ~0.05 at 2.2 μm. 相似文献
33.
34.
D. Montes M. C. Gálvez M. J. Fernández-Figueroa I. Crespo-Chacón 《Astrophysics and Space Science》2006,304(1-4):367-369
High resolution echelle spectroscopic observations taken with the FEROS spectrograph at the 2.2 m telescope ESO confirm the binary nature of the flare M3.5V star LU Vel (GJ 375, RE J0958-462) previously reported by Christian and Mathioudakis (2002). Emission of similar intensity from both components is detected in the Balmer, Na i D1&D2, He i D3, Ca ii H&K, and Ca ii IRT lines. We have determined precise radial velocities by cross correlation with radial velocity standard stars, which have allowed us to obtain for the first time the orbital solution of the system. The binary consists of two near-equal M3.5V components with an orbital period shorter than 2 days. We have analyzed the behaviour of the chromospheric activity indicators (variability and possible flares). In addition, we have determined its rotational velocity and kinematics. 相似文献
35.
A radiative seasonal model which incorporates a multilayer radiative transfer treatment at wave-lengths longward of 7 μm is presented and applied to Saturn's stratosphere. Opacities due to H2-He, CH4, C2H2, and C2H6 are included. Season-dependent insolation is shown to produce a strong hemispheric asymmetry decreasing with depth at the Voyager encounter times, and seasonal amplitudes of 30°K at the poles are predicted in the high stratosphere. The ring-modulated dependence of the insolation and the orbital eccentricity are shown to have a significant effect. Calculations agree closely with the Voyager 1 and 2 radio occultation ingress profiles recorded at 76°S and 36.5°S for CH4/H2 = 3.5 + 1.4/? 1.0 × 10?3;the estimated errors include modeling systematic errors and uncertainties in the occultations profiles. The possible role of aerosols in the stratospheric heating is analyzed. The Voyager 2 egress profile recorded at 31°S cannot be reproduced by calculations. Some constraints on the C2H2 and C2H6 abundances are derived. The upper portion of the occultation profiles (p < 3mbar) can be matched for C2H2/H2 = 1.0 + 1.3/?0.6 × 10?7, C2H6/H2 = 1.5 + 1.8/?0.9 × 10?6 at 76°S and C2H2/H2 = 4 + 6/?4 × 10?8, C2H6/H2 = 6 + 9/?6 × 10?7 at 36.5°N. At the northern occultation latitude, the discrepancy with the concentrations derived from analysis of IRIS spectra by R. Courtin, D. Gautier, A. Marten, B. Bézard, and R. Hanel (1984, Astrophys. J.287) can be explained by a sharp variation of the mixing ratios of these gases with altitude in the upper stratosphere. Other interpretations are discussed. 相似文献
36.
In this paper we analyse error-removing techniques used without sufficient theoretical support in a previous paper, where Chandrasekhar's higher-order perturbation theories were developed for either uniformly or differentially-rotating polytropic stars. 相似文献
37.
38.
A new procedure to separate the instrumental and atmospheric components of stray light is presented. It is based on the dependence of the aureole's atmospheric component on the air mass and is applied to measurements taken with the Vacuum Newton Telescope (VNT) at the Observatorio del Teide (Tenerife). The resulting instrumental part is independent of the air mass.The variation of both components with wavelength is also studied. The instrumental component shows no dependence on wavelength, in contrast to the atmospheric one which is greater in the blue than in the red.It is concluded that observations with air masses larger than two will probably be strongly affected by stray light. 相似文献
39.
40.
An updated Lagrangian finite-element formulation has been developed for time-dependent problems of soil consolidation involving finite deformations. Large plastic strains as well as rotations occur in such problems and nominal stress measures are introduced in the formulation to redefine stresses. This leads to corrective terms for equilibrium and yield violations in addition to geometric stiffening terms in the governing integral equations. The soil is considered to be either a linear elastic or an elastoplastic, critical-state material. Some simple numerical examples are studied to validate the formulation, followed by a detailed analysis of the problem of penetration of a pile into soil. The results of this problem are viewed with emphasis on the physical interpretation and practical significance. 相似文献